yerf dog 3206 internal gearing??

[jmansracerocket]

ok im going nuts spending hrs of research for gearing the yerf with the new mods top end is greatly improved!! and with that i lost a decent amount of low end and want some of the low end back. Theres a bunch of things i know i can do such, rollers, sliders, axle sprocket, and internal gears!. The biggest one that caught my eye is the internal gear swap i would really like to change that to get some low end back rather then have to change the axle sprocket and lose some clearance and have to buy a different chain. The problem is i cant seem to find a place that sells the internal gears with mixing and matching combos that has the pressed on gear already. I was thinking change the stock rollers which are 14 gram to a 12 gram slider, or just throw in the 10gram rollers i have in box, and then with that change the internal gearing so i can get more low end back. Throw your input at me.

[xlint89]

What did you change?

The Yerf's with the Howhit engine are geared pretty low already.

To be honest, I'm considering changing my gears to go up with the power mods I added. Plenty of low end TQ with the stock gearing as it is.

I do like the 12g sliders though.


This might help

http://buggymasters.com/forum/showthread.php?t=2670

[jmansracerocket]

I put the a-11 cam in have 22inch rear tires, and ported intake. Top end picked up big time, but the low end suffered, I would like to get that low end grunt back nothing better then coming out of a turn and being to hit the gas and feel that pull but i don't really have that right now so trying to decide what I can do. I think even a 35 tooth axle sprocket will help.

[Johnny 5]

I took the gears out of our first engine howhitt 150 that is no longer running, and they were 40/13=3.07. The sprocket size stock 16/31 for the dune 150 with reverse.
I wanted to see how hard it was to press it off before I bought gears. I was not worried about breaking this set so I took it to work on our 20 ton press and it came off without any effort.
So pressing the gears is not hard at all, if you dont have a press any machine shop could do it, or automotive shop.
I did change our rear sprocket to 39t and it climbs and has take off but top end is about 33 mph revving beyond what is healthy, so crusing speed is about 25mph.
Both our buggies have 22/10/10 cst ambush tires with 10 gram sliders and a Dr pulley variator on the blue dune , 8/9 gram rollers Dr2 variator on the red dune.
I did order 2 35t sprockets this summer from buyatvsonline and they sent me 2 31t sprockets because the 35t is not in stock. Sucks when they advertise in stock and send you what you already have.
I am probally going to put them on because the 39t kills the pull and top speed.
I have found out that with a 150cc engine you give and take.
The challange is to find a happy medium.
That is why these buggies are so fun, low cost to modify and fun to ride.
I would try lighter sliders or rollers first because you already have them.
Sorry for the long reply just trying to help if I can.

[x-bird]

I've been pleasantly surprised with what came stock in the 2-bolt SYM/ Carter Talon engine i put in mine. I'm pretty sure its 14/41 (40?) with 16-31 sprockets and 22x12.50 tires. Still haven't changed the spring or rollers (14G) and it has plenty of pull and seems to have decent top-end. (don't have a way to accurately measure top speed) Sometimes I wonder why the internal gearing isn't the first mod people look at. Then again, this orphan 2-bolt is usually referred to being one of the better built clones, maybe its cyl. head/valve config. provides it with more bottom end than most.

[xlint89]

Originally Posted by jmansracerocket

I put the a-11 cam in have 22inch rear tires, and ported intake. Top end picked up big time, but the low end suffered, I would like to get that low end grunt back nothing better then coming out of a turn and being to hit the gas and feel that pull but i don't really have that right now so trying to decide what I can do. I think even a 35 tooth axle sprocket will help.

Interesting....

I too have those same mods, but they improved my acceleration as you can see in my results.

Are you sure you're not starving for fuel down low now?

Have you rejetted the carb since the cam swap?

Does your carb have an adjustable needle? My Ebay carb did, maybe you can raise the needle a notch or 2 and see what happens if so?

[jmansracerocket]

for some reason it likes 35 pilot jet and a stock main ! and screams on top end i did mess with that screw that has the spring in it off to the side of the carb if thats the one your talking about. I could try the 40 pilot and maybe back out that screw a turn and see what happens but its a little slugish off the start compared to the stock stuff but on top end not even close to the same thing.

Originally Posted by xlint89

Interesting....

I too have those same mods, but they improved my acceleration as you can see in my results.

Are you sure you're not starving for fuel down low now?

Have you rejetted the carb since the cam swap?

Does your carb have an adjustable needle? My Ebay carb did, maybe you can raise the needle a notch or 2 and see what happens if so?

[xlint89]

No, the needle i speak of is on the actual slide inside the carb. Need to remove the top cover to access it. (some don't have the adjustable needle, some do)

The idle mixture screw is what you're talking about.

Best way to adjust that is to use a tachometer.

Turn your idle up a couple hundred RPM over normal. I usually set it around 1000 RPM.

Then turn the idle screw IN or OUT 1/4 turn and see if the RPM goes up or down.

You will be about perfect when you get your maximum RPM reading.

NOTE: Wait a few seconds between turning the screw to allow the change to take affect.

Ideally you want to be around 1 - 1.5 turns out from a seated (closed) position.


If it runs best with it almost closed, you're too lean and need to jet up on the pilot.

If you're like 2.5 - 3 turns out, you're too rich and should jet down.

Hopefully this works out for you.


What exhaust are you using right now?

[jmansracerocket]

right now i threw the stock exhaust on, i still have the hammerhead sitting here, this weekend i will be tinkering with it il put the hammerhead exhaust back on, il put the yellow clutch spring in, and il try the 10 gram rollers since i have them and see how it goes from there.

[SLESTAK75]

Originally Posted by xlint89

Interesting....

I too have those same mods, but they improved my acceleration as you can see in my results.

Are you sure you're not starving for fuel down low now?

Have you rejetted the carb since the cam swap?

Does your carb have an adjustable needle? My Ebay carb did, maybe you can raise the needle a notch or 2 and see what happens if so?

Hey xlint. Could you explain a bit more on this needle adjustment? I noticed after putting the A12 cam in mine that is sputters a bit on takeoff and then evens out and goes just fine. My a/f mixture screw seems to be set okay at around 1-1.5 turns out and at WOT my plug read a nice tan (used to be terribly rich before cam) . Just trying to narrow down this sputter. I'm about to send my head to Tom for p&p and .025 mill so it would be nice to know all possible adjustments when tuning in. Thanks.

[xlint89]

Remove the top of your carb carefullly so you don't lose the spring. Lift the rubber diaphragm out with the needle and slide assembly. There should be some sort of needle retaining screw down inside the assembly. Remove it and push the needle out. Does it have an "E" clip and notches cut into the needle? If so, it's adjustable just like aftermarket carbs. You can then adjust the amount of fuel delivered by moving the needle up and down by installing the E clip on different motches of the needle.

Clip on the highest notch puts the needle deeper into the main jet and reducing the amount of fuel.

Clip on the lowest notch raises the needle and allows more fuel to escape from the main jet.

This does slightly affect your take off, but it's generally the mid to upper RPM that this affects.

It's normally your air mixture screw and pilot jet that affects low RPM and take off, but the needle can affect it some.

This is actually a decent explanation of what is going on.

http://forum.highlifter.com/Basic-CV...-m1872049.aspx

[bear]

Now u got me curious 'bout my carb!

[SLESTAK75]

This makes sense to me. Similar to the way the old rochester 4 barrels worked. Thanks X.

[xlint89]

Please remember that these stock CV carbs do have a slight hesitation as the carb reacts to the engine vacuum at sudden throttle opening. That's the reason you see the aftermarket CV "pumper" carbs. They have an accelerator pump in order to combat the hesitation, and the reason why slide type carbs have an instant throttle response feeling as compared to the stock carb.

[SLESTAK75]

Thanks for that info x. I did not know that. That makes sense. I never noticed it before the a12 cam but it ran super rich too so maybe that's why I never noticed.

[bear]

Thanks for the heads up on that "Xman"!

[ckau]

Originally Posted by xlint89

Please remember that these stock CV carbs do have a slight hesitation as the carb reacts to the engine vacuum at sudden throttle opening. .

Thats because the carb has to reach a certain vacuum level before the slide reacts . You can reduce that hesitation or reaction time by cutting one turn, one turn only! out of the long spring found under the slide diaphragm. This enables the slide to open at a lower vacuum level by lessening spring tension. Throttle response is more crisp. Don't be tempted to cut any more than one turn! Cutting too much removes too much spring tension and the slide bounces up and down with the slightest vacuum. This cause erratic unstable idle and/or the buggy instantly revs up engaging the clutch as soon as the motor starts.

[xlint89]

Very nice trick. Did not know that......

[SLESTAK75]

I'm glad you said that because I had actually thought about this. I did this to the vacuum secondary on my old corolla's 2 barrel years ago. Sweet tip. Thanks.

[bear]

Hmmm, now that's worth looking into! us poor b-stards are alway's looking for a performance freeby!

[Johnny 5]

I am going to try this on my wifes blue buggy, when we hit a hard bump or rough terrain the carb bogs and cuts out from the slide closing due to the impact. And if it dosnt work I have a spare parts carb.

[ckau]

Originally Posted by Johnny 5

I am going to try this on my wifes blue buggy, when we hit a hard bump or rough terrain the carb bogs and cuts out from the slide closing due to the impact. And if it dosnt work I have a spare parts carb.

This trick won't cure that problem . If anything it may make it worse. If you got slide bounce now, cutting the spring lessons tension in turn may contribute to more bounce. I'd take a look at the vacuum source. Weak vacuum can't hold the slide steady. You may have a leak in the diaphram or a hose.

[xlint89]

Wasn't there a fuel delivery problem with the CV's on bumpy terrain?

I know mine would aslmost stall out when I backed my kart out of the garage and over a 2 X 4 mounted on the ground to keep critters out.

[Johnny 5]

I also have the fuel float set high and am going to adjust it down a bit, may also be part of the problem. I did check the diaphram and vacume line and they are good.
I do remeber that at 3/4 throttle it wont cut out over big bumps as much as it does wot.

Now that I think of it when I am ridding the blue buggy by myself it cuts out more on bumps because the suspension is set up stiff for two riders. When my son is with me it is alot better.

The only time I notice it is when trying to get top speed with my hand me down garmin from my dad that has a battery life of two minuets when not pluged in. So I try to get four runs in as fast as possible and kind of drive it like a rental car.

This is a scooter engine being pushed to the limit and probably wasnt designed for rough operation so it works pretty good overall.

It is kind of a speed limiter that slows you down on rough terrain so you dont crack your frame.

The rear swing arm has broken only 5 times and the main frame behind the driver and passenger seat broke clean off at the weld. So maybe the speed limiter idea isnt working
so good. That is why I bought the hobart ez125 welder, got tired of paying 50 bucks for repairs every time it broke. It has paid off and goes on every trip with us to the desert.

Sorry for getting of subject, has anybody tried the 28mm flat slide carb with good results?

[xlint89]

Running the Mikuni 28mm flat slide presently. Still trying to get the bottom end tuned correctly. Slight hesitation at take off, and using choke is too rich at start up.

Once I get the motor up to temp, and past the hesitation, it runs great. Has a really strong pull from mid to upper RPM range.

Still trying to get a GPS WOT run on the current set up. I got a feeling it should be pretty good.

Mikuni 28mm, A10 cam, 14g rollers, 16T drive gear with the 36T axle sprocket.

I think it's Jersey devil on the other site is also running one and likes it alot.

Tom from Syc Powersports has tried to convince me that a 26mm is still too big to use for most of the "built" GY6's. He feels (and is probably right) the stock 24mm carb is more than enough for these small engines. I'm hard headed and have to learn for myself sometimes.

[bear]

Hey, someones gotta push the envelopes, right!?

[ckau]

Originally Posted by xlint89

Tom from Syc Powersports has tried to convince me that a 26mm is still too big to use for most of the "built" GY6's. He feels (and is probably right) the stock 24mm carb is more than enough for these small engines. I'm hard headed and have to learn for myself sometimes.

I agree with him, The 24, properly set up and jetted does fine for most motors out there. The intake and exhaust tracts have got to be punched out to handle the flow of anything larger or you'll create a bottleneck which can hurt more than it helps.
I've always felt the tract sizes should match the flow capabilities of the carb, (24mm carb-24mm tracts), etc. but I could be off- base with that logic.

[SYCARMS]

What makes this confusing is in the automobile field one chooses the correct carb using cfm. The motorcycle world does not go by cfm but rates their carbs in mm's. The mm's don't tell the flow rate.

[x-bird]

Originally Posted by SYCARMS

What makes this confusing is in the automobile field one chooses the correct carb using cfm. The motorcycle world does not go by cfm but rates their carbs in mm's. The mm's don't tell the flow rate.

And of course, every knucklehead out there still dumps a 4100 or larger series double-pumper on their stock sbc and says it runs in the 10s ...

I think it really boils down to the way these3 particular carbs function. the draw-through is a venturi designed to up the velocity. you'd have to have a smaller carb than tract sizes on both ends to make it work effectively. if the carb is too big the velocity will drop too fast feeding into tracts that don't pull enough volume to take advantage of the pressure differential created.

sort of like the issues the big three had with the tunnel port heads developed in the late 60s for trans am and nascar ---just too much tract volume needing to stay in way too high of a rev range to sustain the necessary rate to make them work effectively.

[bear]

Is there a way to monitor the volume on these carbs and if so would the data be of any value? could you possibly change the volume to maximize what you could and maybe waste gate the overflow? I dont know if its possible but could you force vortex the intake and flute the exhaust?

[SYCARMS]

A dyno

[bear]

That just goes to show my ignorance on these little engines, I had no idea you could dyno them! thanks Tom, I've got a local bike shop with a dyno, so once everything is done on both buggy's I might take them up to see what it says about them!

[SLESTAK75]

Sorry Bear. If you take your buggy to this shop to have it tested, the only thing that dyno will tell you is ..............P O S. P O S. P O S. P O S.

[bear]

Oh well, I'll just have to be happy knowing, they take me where I want to go!!!

[SLESTAK75]

It would be interesting to see what a dyno test said.

[SYCARMS]

I would have dyno'ed mine if I had access to one. The closest ones are for cycles and will not acomodate a buggy, closest one I found is 500 miles away. I could have bought a homemade one from old man Lunati of Lunati Cams but it was an engine dyno only and had no provisions for computer readout. This thing was crude using a Blower for the load on engine, with a lot of math being applied. He made it in the early 60's for his sons go kart engines he used to race. One like I would need is an easy 10G.

[bear]

Wow you have met Mr. Lunati!!! thats legendary stuff!

[Johnny 5]

By P.O.S. you mean power of a scooter?

[SYCARMS]

He is an interesting guy to say the least. I met him couple years ago when I brought my head and cam to Ultridine Cams to figure a custom cam for my GY6 motor. As Don and I were talking cams I brought up dyno's asking if he knew anyone selling one for a reasonable price. Thats when he told me to talk to old man Lunaiti next door. He was there checking out 1 of the 4 huge buildings he just had built. I went over there and he dropped what he was doing and we talked. He took me to another building and showed me the home made dyno and explained how he used it for his son's gokart which he had won over 100 first place trophies. He explained that although it had no computer capabilities but said it was just as accurate. He then explained how I could use it and how to calculate the HP to within +1 to -1% of a new dyno. After explaining I looked at him and said Huh! he looked at me and said Oh your one of those who napped during math class then laughed. He said when he and his son built it he
couldn't afford a dyno for his son's kart but that he wanted to teach his son how to tightly budget and still win. He is old but plenty sharp and a very interesting guy to talk to.

[bear]

I'll bet! can you imagine the knowledge inside that head! and I've alway heard he was a real down to earth guy too.

[SYCARMS]

He is very down to earth, as I said when I approached him it was obvious that he was in the middle of something but immediately acknowleged me. We talked for about 3 hours and it would have been longer but I had to be somewhere else.

[bear]

Those are the kinda life experiences you just cant buy!

[SLESTAK75]

I met Mr. A12 one time. I couldn't understand a word he said. He kept saying something about flied lice. I don't know. He was no where near as impressive as Mr. Lunati.