plug reading ....

[x-bird]

Been dealing with the carb/fuel issues on the 250 and finally seem to have it pretty close to beaten.

After i added the fuel pump, it's running much better, but completely dies out if i try and run up a small steep incline. bogs out to the point of stalling. i'm thinking float level on that problem.

other issue is getting a good read on the plugs. the last one looked really rich after i added the pump; prior to that it had decent color. only change i've made so far is to drop the needle back down two notches to lean it out.

for test reads, i can't go WOT then cut it with the auto clutch, so my plug pics are pretty much from running about 10 minutes and show idle start, run and idle/shut down.

first two pics are prior to needle change and without pump.

3rd/4th pic is with needle moved and pump installed.
seems to have a strange pattern to it as far as only getting color on the front and it's kind of dull powdery looking.

also getting more off throttle backfiring.

right now, i have plenty of jets to take it leaner, have to get more if i need to go fatter.

i'm almost inclined to go fatter with it, but not too sure. ????

[Miamieddie]

Adjust ur float higher. Leaner on ur pilot jet. Bring ur needle back to factory setting. And try the wot test. Start there and maybe play with air/fuel screw.... maybe.

[x-bird]

particular carb is an oem suzuki mikuni. they set it up as a 3 circuit carb with idle, low throttle then main (1/4 throttle-up). Most of the parts are no longer available--including bowl gasket!

didn't get a chance at it yesterday, but yes the float is off.

Needle is at factory position on the last run.

the air and pilot adjustment screws aren't giving me the idle rev increase they should, so i know the pilot's off for the setup. between the float needle and seat, more jets and a couple of pilot jets, i'm going to be into it for 1/2 the cost of a new flat slide carb that has all the parts available.

right now, i'm just trying to get the float and the main dialed in and wondering what everyone thinks about the color and pattern in the last two pics.

Flat slide is in the works as a "christmas present"

If i'm correct in my thinking, truly correct WOT tests are just about impossible with this. when i kill it at WOT, the engine continues to dead cycle through engine braking, pulling idle level fuel in as i come to a stop. if i downshift with it shut off, there is no neutral without running down through the gears to the neutral position and it's pretty rough on the trans and the rears lock up. I just run the snot out of it in 3rd (highest gear i can max the revs out going around my house) and drive it into the garage.

[Masteryota]

3rd and 4th plug don't look terrible, but a tad on the rich side. You may not be able to get a good reading on the plug, but I would rather a bit rich than lean, but I also like power(insert Tim Taylor grunt here).

I had not thought about the WOT test like you have, I figured in 2nd gear WTFO and then kill the ignition and coast, any fuel let in won't be burned, and should evaporate rather quickly. As long as the throttle is closed, the needle should prevent much, if any, fuel from exiting the bowl. Correct me if I am wrong, please. Clean and clear test results, probly not, but probly as close as we are going to get, given the circumstances.

I think you should get the float figured out, and then drop one or two main sizes, and hold out till the man in red delivers a new carb.

[SYCARMS]

The slide carbs are much tougher to dial in as compared to the CV carb. With the CV carb all your going to change are the jets. On the slide carb not only the jets but the needle, needle orifice, and slide have to be in sink. If your using the carb that come with the engine then it should be within specs but if not you can be looking at any one of the combinations. I have been messing with CV carbs and on occasion the slide carbs that come on the 110cc and below.( nothing like the Mikuni) When I decided to go with a Mikuni on the 150cc I entered into a whole new world. I had to consult with the guy's at Carb Parts Warehouse who are the distributors in the US for Mikuni. Once I was put on track all I had to do was tweek it. Now once I got the carb dialed in OMG what a difference from the CV carb. From a dead stop without foot on brake, when I nail the throttle I no longer have the slight hesitation and will leave 2 40' black marks in the grass. Several had told me for a few years to go with the Mikuni but I was hard headed and decided I would prove to them I could run the CV carb successfully. It run great with the CV carb but little did I know how much more performance I would get with the slide carb.

[x-bird]

I'll just be changing from a round slide to flat slide. the whole "in sync" is what i'm dealing with. the changes in intake and exhaust components from the old quad made enough of a difference to negate the stock setup. It being an oem carb with no parts available, common sense (and the advice of the guys at Sudco LOL) says go to the flat slide and pick up better throttle response and more bottom end power. --may be able to re-gear a bit and actually gain on the top end to boot.

[Masteryota]

I had wondered about the difference in flat vs round slide carbs, and had the opportunity to research them when looking a replacement for my RM80. Same deal, carb parts only available through dealer, and would be more to get the 4 parts I need than to replace with new after market unit. Only difference is original is flat, replacement is round.

Round slide carbs seem to offer similar results to the flat, but are easier to tune and keep tuned. The flats have a little better low-mid response, but can drive a man to drink trying to get them dialed in, and then the season changes, and start all over again. I had already bought the carb for the ATC engine before this, and it made me curious about what I had done, and if I made a mistake. The other issue I saw was in severe dust, the rounds stick a lot easier than the flatties. More surface area for debris to get lodged in, I guess. Either way you go, make sure you have more than one source for parts, or snag something off a common engine.

[x-bird]

i'll be going new mikuni TM-24 out of the box with a 1.5 needle and 130 main. Not goign to mess with anything used for this.

tweaked the float a bit and dropped from a 125 jet down to a 122.5. pretty much ran as weak as it was before adding the pump, seemed to take a while to pull any midrange power, then it'd kind of wake up at 3/4. didn't have the grunt to pull 3rd/4th strong from a slow roll. Plug is clean as a whistle.

I'm wondering if the sort of weird look to plug pics 3-4 (kind of powdery) is burned up anti-seize. I try not to get it on the base or upper two threads, but you know how that stuff is ...

Think I'll leave everything alone over the weekend and toss a 127.5 in it. good surprise was that my 125 is right in the middle of about 10 jets i have, so i can go both ways in 2.5 increments. Guess I forgot about the one batch i ordered.

[x-bird]

sudco's mikuni tech commented that all the "problems" i described come back to float needle and seat for the most part (aside from the lack of a fuel pump and float level).

Given that even with the vacuum pump in place, i'm still getting fuel out the overflow vent after it sits a couple days (garage is our smoking lounge, nothing like walking in there for a butt and smelling gas) top of the trans is wet with it from it dripping out. Float should actually have the level in the bowl down, i think the tech's right about the needle/seat.

Santa's coming early, going to do a scrapyard run to scrape up enough for the new carb and quit fueling around with this one.

[Masteryota]

and quit fueling around with this one.

Funny

[Miamieddie]

Ur right on the float I said it wrong DOWN not higher.

[x-bird]

of course i can't leave it be.

day off today, so i did my scrapyard run, scored another $40 on a scratcher and dumped exactly enough for the carb into the bank ... will it be there when i pull the trigger????? LOL ....


Threw a 130 main in it, factory float height ... couldn't get out of it's own way ....

got to staring at my plug collection and noticed the base shows rich on the 125 and 130 even though the porcelein shows decent.

so i jetted smaller (120) and it was an improvement but still some erratic running, sometimes it'd be fine and other times it'd just not be firing off right.... Then i notice what looks like a crack around the intake flange where the machine screw is. RTV'd it. no real change .... check my pos. terminal wire on the coil and realize that the TT tach wire stuffed up in there is pushing/lifting one side of the female plug off of the spade. moved the TT wire back to the plug lead, squeezed the connector shut and things got much better. Plug is pretty much clean again, no soot on the base. i think I need stock heat range plugs .... (it had a 1-up in it and that's all the parts store had in stock)

also ran into the idle just running up out of nowhere and holding steady at 2500 rpm, which isn't good to dump the clutch into. wouldn't come back down.

Murphy has taken up residence in this carb i think, time to bring in the new one ... and see if i can find a new intake ... screws on the old one are buggered--i've never gotten it off. going to have to take the Impact driver to it. (KD handheld hammer type)

[Masteryota]

I still don't understand why manufacturers put phillips screws in crucial areas. Toyota still does it, and they account for 100% of my mucked up and replaced fasteners. Too bad you don't know any machinists close by, an aluminum intake would be a nice addition and may allow mounting the carb more level. I know I would like to have one made, if affordable, to be able to mount my carb at a more level position so my filter doesn't stand out like a red flag.

[x-bird]

i think it was sudco that had intakes in their catalog ... i have quite a few machinists close by; (about 3 shops within 1 mile, 20-30 within 10 miles) either i can't afford them, or i've called in my fair share of favors (parts or advice) with them and don't want to press them for anything more unless it's crucial.

As far as phillips go, that's been a sore subject with me for decades--in my years working in the auto body and resto biz i must have impact hammered out hundreds of them in door latches and hinges in cars from the 50s through the 90s --almost always ended up with deformed door shells and a and b pillars.

[x-bird]

i hate it when my brain starts kicking into overdrive ... got to wondering last night after "fixing" the coil terminal if I also don't have an ignition issue added into the mix. I'm using a an ooollllldddd used LT250 coil/plug wire and the original CDI.

when i first started reviving the engine, I was using the original CDI and a gy6 coil/plug wire. Can't remember when i swapped coils. What's getting to me is that even without the fuel pump I wasn't having quite as many "erratic" problems back when i first got this going.

So now that's got me trying to figure out how to wire a gy6 cdi in. original 250 cdi has an orange wire and a green wire that loop to each other through what looks sort of like a light bulb filament image on the schematic. I'm thinking that's the reverse or neutral safety kill loop. Otherwise the 250's cdi seems pretty basic, black to +coil, black/yellow to kill side of ignition switch, black/red to the magneto and black/white to ground.

to match the GY6 cdi, --with suzuki wires in parentheses, i'm thinking green to ground (b/w), green to - coil (ground lug), b/w to + coil (B), blue/white to magneto (B/R), black to ignition (B/Y) and first leaving the orange green open, if no fire, then connecting them . i have about 4 spare gy6 cdis, so if i cook a couple, no big deal LOL ...

[Masteryota]

Thats what I did. Plus they are about $6 of ebay. I assume the 250 is AC fired? Mine was fairly simple to wire in, stator wire to the supply voltage pin, ignition advance to the trigger pin, coil and the rest are straight forward. I found these for the 2 plug type CDI's. There are other plugs out there, but they can get expensive, the quality of the pig tails I posted are pretty good considering the price.

[x-bird]

From what i can tell, it appears to be AC fired. only real difference is that the old coil used the winding frame lug as the ground.for now i'm just going to dismantle a square block plug i have to use the female terminals from it. really just a test to see if it makes a difference.

Was just chatting with some friends that run a motorcycle/quad shop and they dangled an injected 4-stroke 450 bike engine in front of me for next to nothing. tempting, but i don't want to have to create reverse.

[x-bird]

Well, so much for that plan ... looks to be DC based. copied the configurations from an installed working gy6 (have an engine on the test stand at the moment) and i end up with the 250 CDI having a 12 volt feed into it and a single ground coming out. (vs no 12v+ input and two grounds out of the gy6) the orange and green are the Neutral/reverse safety switch so that leaves it as a 3 wire output with 12v coming in. No Spark. end result of playing with lots of old tape and two bowls of spaghetti is that i have a gy6 col in place of the 250's for now.

[Masteryota]

All the diagrams I found appear to have AC fired CDI for your engine. Let me give this a whirl. Red/Black wire to CDI power, Blue wire from pulse coil/exciter, Yellow/Black to kill switch, Black/White to ground, and Black to the coil. Unless I am looking at the wrong diagram, and be sure the power comes straight from the stator, before the regulator. Your green wire is the main power wire, that may be why you have 12V there. You should be getting over 20V AC at the CDI power wire, I was getting well over 35V with the pull start.

If the wire colors are different at the CDI plug, then I may have the wrong year diagram.

Many of the guys on the trike site reported much better fuel burn and hotter spark with the GY6 unit installed, I have a feeling the 80's CDI's are feeling their age. Some reported having to rejet a few stages leaner due to adjusting fuel to compensate for weak spark.

[x-bird]

diagram from the 250 manual--dk what you found online, but pretty much nothing exists in print for this engine without buying it.

I have the gy6 CDI (separate 2 wire and 4 wire plugs into it) wired as follows--looking at cdi from the back with the plugs on the bottom, first wire colors are based on my gy6 harness. parentheses are the 250 harness/cdi

bottom right corner pin , blue/white to stator (black/red)

bottom middle pin, black/white to coil+ (black)

top right corner pin green to ground

middle top pin green to ground

the above two are tapped together and connected to chassis ground with a lead going from that going to the - terminal on the coil

top left pin black to (black/yellow)


what i'm left with is a black/white wire on the 250 harness (just a ground wire for the cdi) that originally plugged into a cdi black/white lead and the Green and Orange loop from the reverse switch. Tried that open and closed, made no difference.

GY6 cdi and coil tested and work on the gy6.

[x-bird]

can you say "bass ackwards"? LOL

Think i have it figured. GY6 harness and electrical on the test stand is from an 07 carter talon. pretty sure it's a DC system.

The baja reaction i have appears to be an AC system.

The 250 i'm pretty sure is also AC

I have 6 (no, now 5) CDIs floating about. Some of these came with the baja, some came with a crossfire engine i picked up (no harness for it) and some came with a Sunl engine (no harness for it.) They are all the small body type. searched a bit and found that there are small body DC CDIs. indicator is the circuit only uses 1 wire in the 2 wire plug. that's the setup i'm running on the test stand.

While testing one of the cdis on the gy6 it blew while cranking (popped a chunk off the back).

I'm thinking i have a mixed bag of CDI's with no real way of telling which are which. the reaction has an aftermarket cdi in it and uses both wires on the 2 wire plug. I'm thinking i should copy that configuration over to the 250 along with the cdi and see what happens.

[Masteryota]

The green and orange wire are for the pulse generator/exciter for the pulse/fire signal, according to the diagram you posted. It is an AC fired unit, but you have me thoroughly confused on the CDI pinout. I will attempt to replicate the position of the CDI, but bear with me.

bottom r/h corner should be kill switch- blk/yellow
bottom center is coil- blk
bottom l/h is pulse- orange or green, this part stumps me....
top r/h is AC power- blk/rd
other 2 pins are grounds

The pulse coil confuses me, it looks to me the CDI supplies the ground for the pulse, might try grounding the green wire to frame first and see if you have fire, then switch. I am confident you can make this thing run on a GY6 CDI. I would be willing to say you could hook up the ground side of the pulse coil to the other side of the CDI, but wait till you get it figured, at the risk of popping another CDI.

[x-bird]

you're right about the orange and green wires, they go into the case along with the neutral safety wire and i made a wrong assumption as to where they went. now i remember having this thing opened up and checking the stator coils when i was first trying to get it to fire last year. the orange and green do go to the "pickup" as i always call them LOL ... one definitely grounds from what i remember when checking it, pretty sure it's the green. Hooking green to ground doesn't bother me, it's where to put the orange that's the kicker. if i fry the pickup, it's just about game over for the engine. It should be sending out the spark signal to the cdi. other question then becomes which cdi do i pull from my pile?

Picture one shows the CDI pinout i've been working from/matching.
I'm thinking this is DC. This works, was the setup when i ran the 150 and is now the "test stand" setup. Harness and components came from the '07 Carter. This blew a cdi just about instantly this morning. I have another identical cdi to the one that blew (manufacturer and #s on it).

Picture two is the pinout on the baja. Note that both pins are used on the two wire plug and there's only one ground out.
Thinking this is AC. Haven't traced it all out yet nor tried replicating this on the 250, but it's the cdi i want to use. hate to cook it.

[Masteryota]

Originally Posted by x-bird

Hooking green to ground doesn't bother me, it's where to put the orange that's the kicker. if i fry the pickup, it's just about game over for the engine. It should be sending out the spark signal to the cdi. other question then becomes which cdi do i pull from my pile?

Picture two is the pinout on the baja. Note that both pins are used on the two wire plug and there's only one ground out.
Thinking this is AC. Haven't traced it all out yet nor tried replicating this on the 250, but it's the cdi i want to use. hate to cook it.

I would advise against using a 'performance' CDI, due to the integrated ignition advance. The orange wire from the pickup goes to the trigger pin, and yes, it tells the CDI when to fire the coil. I am curious though, about the pickup coil, and if it advances the spark timing at all.

As far as which CDI, try the basic ones first, at least you can replace them cheaper than the better or DC units. Since you have bypassed the reverse engine stop switch, the second ground wire for the AC unit probably isn't needed.

Mine runs with just one ground wire attached, but that ground wire goes into the harness and is bolted to the head. I will add the other ground wire once I finalize the harness construction, cause I'm kinda anal about stuff like that.

[SYCARMS]

The trigger has no capability to advance timing. It is all done within the CDI.

[Masteryota]

Originally Posted by SYCARMS

The trigger has no capability to advance timing. It is all done within the CDI.

Ahh, then a GY6 CDI won't work properly. I was thinking that way since the trigger was located so close to the stator, that it was just a sensor. I guess I got lucky with the mechanical advance.

[x-bird]

since were on the CDI subject, just came across the best manual that i've yet seen in terms of pdf reproduction clarity showing a wiring harness and the guts of a cdi - for a crossfire 150. also the same wiring as the reaction and definitely much different from the carter harness/cdi wiring .... I think i'm going to take the cdi that's a match to the one that blew on the carter harness and match it to the baja config and give that a try on the 250.

master, the pinout you have in the thumbnail only differs from what i've done where the 2-pin plug is concerned. where your pic shows the ac power, that's where the lead to the ignition kill switch is on my setup, with nothing attached to the other.


http://buggynews.com/resources/file/12081

as far as advancing timing with the trigger, it could only be done with an offset flywheel key or by physically moving the coil. But the way it's mounted in the 250 leaves no room to move it and not enough "meat" on the mount tabs to elongate the holes to move it a degree or two.

and thanks for the reminder about the built in advance on that cdi, forgot about that!

[x-bird]

sooo ... I walked away from the electrical system other than leaving the gy6 coil. went back to the carb, pulled the 120 main and went drastic and put in a 107.5. let the needle sitting in the middle position where i last had it and dropped the float about 2mm. Haven't pulled the plug yet, but i'm sure it's gong to show lean, was having a lot of off throttle backfiring, even when easing off the gas slowly ... but of course, when it seems lean or really lean---it runs like stink LOL

flaoat adjustment is probably about as deep as i can run it. a carb is a carb when it comes to steep inclines for the most part and from a dead stop with it pointed uphill, it did the best it has done yet with it ...

http://youtu.be/8bwij_EBJNc

oh yeah, yard for some strange reason seems to be morphing into something looking like a track. )))

injected RMZ450 anyone? I passed as tempting as it was. no stator, tb or electrics and needing a countershaft bearing and maybe more inside ...

now if i can find an ltz 400 cheap enough, i'll pull the trigger.

[x-bird]

man this thing has my number ...

finally figured i don't have any jets in the range i need, which is going to land somewhere in the 110-115 area. Also need to get some pilot jets for it (just cannot get the idle and needle dialed in correctly and a needle valve and seat.

All told, it's going to eat up another $60 or so, half the price of a new flat slide that will in turn need pilot and main jetting done ....

I'm at that point where i just can't make up my mind ..save money and toss more new parts at the old carb, or buy a new carb, spend more $s on it and run it for a season then sell the used "new" carb off when the time comes.

I figure i'm going to push the 250 for one more year in it (going to save any dollars I can scrape together for shocks by spring) before converting up to something in the 400-450 cc range.

What would you do????

[351mustanger]

I have not seen anyone mention this on the forum yet. I was tought that the reading on the pocelain should be taken at the base, not the tip. Most times, when doing a chop test, the tip reading is quite lean compared to the base.

Here is some good info.
http://www.braigasen.com/howtoread.htm

[Miamieddie]

Thats very good info 351..... but I dou t anyone will be chopin up there plugs on wot test till they get it right. just sayin. You can get a good sense of knowledge by checking ur plug the way most of us do. Reading the outside without choping. But good info.

[351mustanger]

You are right eddie. There is no law that says you have to take good advice. It is never crowded along the extra mile.

[Miamieddie]

And that is definitely damn good advise you gave 351.

[SYCARMS]

Originally Posted by 351mustanger

I have not seen anyone mention this on the forum yet. I was tought that the reading on the pocelain should be taken at the base, not the tip. Most times, when doing a chop test, the tip reading is quite lean compared to the base.

Here is some good info.
http://www.braigasen.com/howtoread.htm

That is good info, however my belief is if you are all out racing your buggy such as long circle track or drag racing where you are at full throttle the majority of the time this is a necessity to do a chop test. Most of the members do the normal riding without reaching top speed that much. In this case a simple read of the plug is more than sufficient but still a necessity.

[x-bird]

Ditto the above ....

Anyway, bit the bullet and went for a new carb. Just too many concerns as to whether the slide is too worn, dialing correct setup of all parts without a good performing baseline to match off of and lack of "stock" size parts to work with etc. ...

To add the final insult to injury --all in 1 shot) I decided to tweak the pilot a little larger, as it was definitely too small. did that, rejetted to a 120, dropped the needle to full lean. Fired right up idled ok, shut it off to check something, then wouldn't refire unless at WOT ... running real rich (i figured it would) walked away from it for a few hours, came back to a flooded carb and air filter, leaking all over. (i think at full lean the jet needle may hit the float needle.) Kill the fuel, clean up the mess. yank that sorry old carb off.

this am, pull the wet plug, put a rag over the hole and go to blow it out ... hit the button, look back and it blows the rag off and gets me right in the face. Don't think i have leakdown issue LOL ..... Good riddance! ouch! Just glad i completely removed the plug.

[x-bird]

finally cooking with gas ....

Overlooked the obvious, the mikuni vacuum pump (smallest) is too strong for the float needle, which is also the smallest size, so no change can be made to fix it in regards to needle and seat. time for an adjustable fuel pressure regulator. way past time actually. Weird that it didn't flood out as bad as it has lately when i first put it in the system.

santa came early, 24mm TM flatslide is installed after having to fab up a redneck style adapter between the intake and carb spigot. (about 2 inches narrow style hard plastic vacuum cleaner pipe did the trick) the extra length should help enhance the bottom end, but i will hav eto make a support for the air filter end of the carb. the tm28 carb was a match dimensionally to the old VM, but would have been worse on the bottom end than the old VM was.

Took it out in the snow today (after flooding the heck out of it with the pump i went back to gravity fed for the time being). out of the box it came 115 pilot and 130 main.. Jumped right up to a 120 pilot and it still wants more--still don't have the correct adjustment levels at the air and idle screws. Main i left be, have some larger ones coming. Feels good enough down low to be thinking about doing a final gear ratio change to get some top speed back.

Ran pretty decently but i can tell its still lean across the board.

shot some vid, but both my computers had major malfunctions this past week, so i cobbled two into one and the resulting frankenrig is not happy messing with hd video. LOL

[SYCARMS]

After many years of running the CV carbs on my 150, I decided to go with a Mikuni VM-32. Never messing with a slide carb except for the ones used on the 50-110 buggies I had a new learning curve. To tune a CV carb, a main and pilot jet is the extent for tunning. The Mikuni as well the main jet and the pilot but also the needle jet, jet needle, throttle valve, main air jet, , needle valve and slide all play a part in tunning. The carb I chose was not setup at all for my 150 and I almost pulled my hair out getting the engine to first idle then run without the backfire then the fine tunning. I was fortunate enough to have the guy from Carb Parts Warehouse which is the main distributor for Mikuni in the US, help me to tune it to a baseline so that main jet and needle was all I needed to mess with to fine tune it. Man what a difference as compared to the CV carb. Now when I hit the gas there is no more lag but instant go. With the 32mm CV carb when I nailed it in the grass the tires would spin for a few feet then hook up but with the Mikuni when I nail it I now leave 2( 30' tracks before the tires hook up with lots of fishtail. It takes a lot more time to get a baseline then final tune but it is well worth it for the performance you gain. It will really wake a performance engine. I guess thats why all the sport atv and dirt bikes use them. Sounds like your close to dialing it in. The only thing I wonder is if the fuel will eventually eat away at your vacume tubing. Many plastics won't hold up to fuel especially if ethanol is in the fuel you use.

[Miamieddie]

A word of advise for all northern boys and gals... once you get your buggy stunned for the winter and for the summer(2 different tunning) make a record of it, everything thing and size jets etc you've done to it. It will save you all a bunch of headaches. Its only a suggestion not telling you all what to do. I don't do that cause I live in Florida but I would if I lived were it snowed.

[x-bird]

^^good advice--already have a log going ... My 'bird's had me in that habit for years.

Can you say "understeer" ? LOL

http://youtu.be/yNeDvMThHJc

[SYCARMS]

Kool video

[x-bird]

Thanks Tom. i was pretty well frosted after 20 minutes of riding around. My "good" computer has an issue with either temp or fans and the mobo keeps dumping off on start. had the video nearly done in 20 minutes when that happened. Reassembled my old rig with it's half shot vid card and redoing the vid took all of yesterday afternoon, evening and this morning and turned out "meh" compared to what i had ready to go. I just keep watching it to listen to the dead. (one of my fav songs) used the gopro editing software. It's nice with a good computer.

[Miamieddie]

I've never seen snow must be nice.. I'm moving up to dunnellon fl. North Florida where the temp at night is 20 degrees colder than Miami. Im hoping it doesn't affect my jetting. Example if its 55 at night in Miami its 35 in north fl. So I'm hoping I won't have to mess with my jets... will have to see.then again if its colder than 45 that's just too cold for me to ride.

[Masteryota]

Originally Posted by Miamieddie

I've never seen snow must be nice.. I'm moving up to dunnellon fl. North Florida where the temp at night is 20 degrees colder than Miami. Im hoping it doesn't affect my jetting. Example if its 55 at night in Miami its 35 in north fl. So I'm hoping I won't have to mess with my jets... will have to see.then again if its colder than 45 that's just too cold for me to ride.

Dunellon isn't as north as I would have though, try living up here for a bit, last week it was 78 degrees in the morning and by sunset it had dropped to below 40. No wonder everyone stays sick.

I don't see it making a difference enough for you to change. Maybe a touch more fuel from the mixture screw when it really drops. I know what you mean, I used to jump on the bike at near freezing temps in my younger years, now anything less than 60 and I'm staying home, lol.

[x-bird]

relative humidity and altitude typically play more into the need to rejet than does moderate temperature change. I know all 3 are interrelated, but a lot of people tend to look only at one and draw conclusions based on a single aspect. A barometer is your best friend for jetting. With my bird in the summer, i can start at the track in the morning and run into the night and not need to rejet if i start a little fat. helps that Island dragway is 15 minutes away with only 100 foot elevation drop. if i go to E-town or Atco, lower altitude and it needs more. Maple Grove runs the same setup as Island. Other times of the year, then it's just a guessing game throughout the day anticipating how much faster the car will go--i'll come down nearly a 1/2 to 3/4 second in my ETs sometimes. in the spring or fall, at any of the tracks it'll need at least one, possibly two rejets because the change in temps and air density is large enough to warrant it.

setting up the buggy here at home then racing it 800 feet higher, 30 miles north in a totally different geographical terrain with a different weather system is a real head scratcher. add to it that you're not allowed to do any prerunning/driving of race vehicles on the property other than firing up the engine to warm it up/work on it on trailer or campsite and it becomes a total crapshoot.

If you've every heard the term "cold crisp air" that's the point where you can have colder air (below 32 degrees) that is less dense because it's very dry air. around 33-35+ degrees, you have air that you can nearly drink and you know snow or rain is coming. big difference between the two which will actually require the opposite jetting than just basing it on temp ... I prefer to jet at this time of year to get a baseline setup that's about as rich as i'll ever need.

good morning .... just rambling ...

[SYCARMS]

Here in Mississippi it ranges 100 deg. to 20 deg sometimes lower. I don't have to rejet. In higher altitudes the air is thinner so jetting is necessary. If your into rscing then temp and watergrains will make a difference but not for normal ridding. After all you don't do this for your car or truck even if a 1960 model.

[Masteryota]

Originally Posted by SYCARMS

Here in Mississippi it ranges 100 deg. to 20 deg sometimes lower. I don't have to rejet. In higher altitudes the air is thinner so jetting is necessary. If your into rscing then temp and watergrains will make a difference but not for normal ridding. After all you don't do this for your car or truck even if a 1960 model.

I know Mississippi can be just as volatile as here. In-laws live near Meridian, and half the time we go, its 20 degrees hotter than here, and no sea breeze. I love the lower humidity though, and nights in the 20's in october. Now that I think about it, every time we leave there, it has been during a tropical storm.

[x-bird]

more snow fun, this time it's about a foot deep and crusted on the top.

Ran out of gas after tracking in the loop, then killed the battery trying to refire it (didn't realize i was running on empty)

27.5 pilot, 160 main. finally getting a little color on the plug, base ring is showing rich though. not going to change anything until i get the fuel pressure regulator installed. should be here any day.

http://youtu.be/zX2WZ94ZB8k

[Miamieddie]

If I remember correctly base ring measures your idle . and the porcelain measures wot (main jet). Make sure that your base ring color goes completely around the ring. Not half way. It sounds like your getting close to getting it OK.

[351mustanger]

The base ring is a general idea of your overall jetting. It does not give an indication of any certain jet.

[Miamieddie]

This may help I can't post anything . I'm on my phone.... Google this : plug reading guide. Then click on the one that says 4 seconds flat. That will show you pics of what I'm talking about. If you can capture the pic of the plug I mentioned and place it here would be great. I don't have a computer.

[x-bird]

I had several sites plug pics and reading info (including doing cutaways) bookmarked, and use probably one of the same ones you're talking about. my computer is on life support at the moment, (really, you should see what i have cobbled together on my desk superfrankenjunkrig!) user profiles dump every time i shut down --- lost my bookmarks and email and am not resetting all that til i get the new computer and plug in the old drives to salvage my pics, vids etc.

Anyway, plug pic. I think it's going to get richer with the pump and regulator in place with no other changes. i may also be sucking air at the carb's fuel input, my hose is a little loose even though it's clamped.
What i've been doing until i get the above finished is working without a fuel feed baseline.


Pilot may be too large right now by a size or two. I've matched the TM jets to what Chad at Sudco had told me was the rough equal of the VM carb/jets i was running.

As with the VM, the one area that seems to be the hardest part to get right is the idle setting. the old standard of 1.5 turns out then work to the highest rpm with 1/2 turn doesn't work for me. It keeps wanting turned way in, which should point to the pilot being too small. However, initial throttle (idle to 1/4) response has always been great. That's my head scratcher. This may need a different slide cutaway.

Once i get into the larger main sizes, even when it shows lean, it pulls through all the rev range strong until i hit the upper gears. With yesterday's setup, upper gears were still pulling--the snow just prevent any real running in those. when i did get into 3rd-5th, chain judder was hitting (they're all too loose--you see it in the vid when i'm by my spruce trees) and the engine wasn't dying down.


Hardest part is the lack of TM info. I have the VM supertuning manual, but nothing was ever put out for the flatslides.

[x-bird]

well, after a lot of work, i'm finally getting this thing into range.

came to the conclusion that at "idle", (which is non-existent) no matter what pilot i'm running, it's not getting enough air unless i open the throttle, which then starts dumping in fuel from the needle feed.

Even with the needle in the hole all the way, I could get it to run that way, but it was a full bypass of the idle range and more than half of the pilot circuit (still had fuel coming up past the needle) and it just ran way too rich. it left me always dumping too much fuel for the amount of air at idle.

That situation left me with no alternative but to modify the carb.
Nothing like hacking on a brand new one!

The choices were to enlarge the air feed to and through the pilot circuit or to modify the throttle slide with a cutaway on the backside to feed air across the pilot circuit's feed hole.

Given that i knew how much i was lifting the slide to achieve idle, i went with choice B. (also cheaper to replace a slide than the whole casting if it didn't work)

Interestingly enough, the slide's backside had a depression matching the front cutout as if there was another application that used a slide with front and back cutouts. So i carefully dremel sanded out a match to the front (3.0 mm slide).

Installed, i get idle with the slide fully closed (idle screw all the way out) and the main feed not adding fuel. Drive test is still giving me a soot-ringed base and clean to grey porcelein. I think the pilot jet is a touch rich and the main is lean. needle is on center.

Pulls good and strong down low, gets soggy/stuttery up top.
Time for some more jet testing now.

[Masteryota]

I'm not trying to call anyone out here, but didn't you special order that carb specifically for THAT engine?

I would have thought that it should have been right in the middle of the spectrum for a 250cc with or without engine/bolt on mods. Modding a new carb is not acceptable to me, particularly a new custom picked/designed unit.

All said and done, I am happy you are finally getting the engine dialed in. Even though you are getting there, you still looking for something bigger? Or will running at full strength be enough?

[x-bird]

I chose not to pay the extra for a "tuned" version and picked up the lowest priced box stock one off e-bay. That's one reason i haven't bothered sudco or carb warehouse's techs much on this other than some initial input. T

These particular 250s were never supported, modded or raced, so i didn't trust that a "250" tune based on experience with another 250 engine would plug-n-play.

It is undersized for the application in some ways, but it is doing exactly what i want it to do, which is enhance the powerband at the bottom end. Chad at sudco indicated that the next size up in the flat slide series, a TM28, would be worse on the bottom end than the stock round slide, and i think he was correct in that assessment.

Seat of the pants run today says i can definite re-gear by .3 to .5 on the final ratio for more top end. While it's not spinning the tires, it definitely has a lot more power down low and throughout than before. Latest plug read (since my last post) says a little more main jet and maybe 1 more pilot size down. soot is lighter, ceramic has a nice light tan just starting to show. electrode is fine as are the ignition timing marks on the strap.

I've only been into this carb about 40 (no joke) times since i got it. Working up a vid of today's final session.

[x-bird]

ground is slicker than snot since it's frozen ...

I was running quite a bit in 5th looking for 6th ))))

http://youtu.be/TU95A3nTt_Y

[Masteryota]

Sounds pretty good. I am assuming the abrupt engine RPM change is tire slip, and not clutch slip? I know you were fighting that for a bit, and now with the engine almost dialed in, I would be listening closely for it again.

[Miamieddie]

The modifications your doing to your carb is beyond my knowledge. I'm just a simple guy. Lol. With that said I'm glad to see your working it out.