Carb frustrations

[Jtsarby]

It seems like the carb on my carbide needs cleaning every other week. I am now way to familiar with how to disassemble, clean, and reassemble the carb on my Kart. bow often is everyone cleaning their carb? I have an inline filter.

[xlint89]

I haven't had to clean my carb yet.

What kind of fuel are you running? I only use premium.

With an in line filter in place, what are you finding inside the carb?

I found corrosion sticking the needle on my motorcycle while running Sunoco 93 octane. I stopped running it and switched to Shell premium. Haven't had an issue again.

[Jtsarby]

I run 89 octane. I went out to start it tonight and it wouldn't start. Cranked for a few and then backfired. I jumped a mile high. Something is going on. This thing is a blast when running but this is getting frustrating.

[EVILWS6]

I always run 93 octane with sta-bil in all my small engines. Everytime I fill my gas cans,I immediately add sta-bil when I get home. I never really have had any fuel issues since I've been doing this for so long I can't remember when I started.

[liduno]

+1 on the sta bill. Make sure your tank is clean and not getting water.

[xlint89]

Originally Posted by Jtsarby

I run 89 octane. I went out to start it tonight and it wouldn't start. Cranked for a few and then backfired. I jumped a mile high. Something is going on. This thing is a blast when running but this is getting frustrating.

Have you checked your valve clearances at all?

[Jtsarby]

No I haven't. I bought the gauges to do it I haven't had the time. It's on my list.

[Jtsarby]

Checked the valve clearances today. Intake was great but the exhaust was way too tight. I set them both at .005. It fired up but is running poorly. Almost like the carb is dirty. I just cleaned the carb so I know it is clean. Any ideas?

[JERSEYDEVIL]

yeah , ive said this more than once. these carbs are disposable. some last years some months, some are junk out of the box new. but there is something that goes bad in them that even a rebuild kit wont fix that makes them run like they have a vacuum leak. when that happens toss them and get another.

[xlint89]

I can't comment on what JD has recommended as I have an aftermarket Mikuni installed on mine. It may be true.

Curious though, if you keep cleaning your carb, what are you finding inside it?

Lastly, I run .003 on the intake valve and .005 on the exhaust for valve clearances.

[JERSEYDEVIL]

Originally Posted by xlint89

I can't comment on what JD has recommended as I have an aftermarket Mikuni installed on mine. It may be true.

Curious though, if you keep cleaning your carb, what are you finding inside it?

Lastly, I run .003 on the intake valve and .005 on the exhaust for valve clearances.

ive been running a mikuni for six years on mine for that reason and the benefits. i just know from working on everyone else's stuff that if basically if you've chased a miss that sounds like a vacuum deal and everything else is straight....toss it!

[Jtsarby]

I have two carbs. They are both Mikuni. It was running perfect and just died one day. The only thing I noticed was the exhaust was a little loose. The nut worked itself loose. I tightened it and it would not restart. I cleaned the carb and it would not start. I switched it the the other carb and it wouldn't start. I then pulled the valve cover and adjusted the valves. The intake was .005. The exhaust was really tight. I set them both to .005 and it started but runs rough like the main jet is clogged. When I clean them there is nothing noticeable in there to make them run bad. I am now an expert at breaking down and cleaning a carb. I'm getting good spark. I'll adjust the valves again and see what that will do.

[jmansracerocket]

Check all ur ground connections, and try a different cdi box. I remember ckau saying sometimes a bad cdi box can cause those systems. The stock wiring on these buggies isnt the greatest.

[Jtsarby]

Readjusted the valves to .003 intake and .005 exhaust. It fires right up and idles fine but dies if I give it any gas. I'll check all the wires today. It has a brand new cdi from buggy depot. It is supposed to be the upgraded cdi but it is a black one. I was under the assumption the the upgraded ones were orange. It's acting like the main jet is clogged. My boys are driving me crazy to get this running again. At least I like working on stuff like this. I like riding it more though. Thanks for all the help. I love this forum!!!!!!!!

[Jtsarby]

One question. Could I have damaged anything by running it with the exhaust loose? I'm not sure how long it was that way.

[xlint89]

Most likely no damage occurred. You should be fine.

What mikuni carbs are you using?

What other "modifications" have you done to said buggy?

And just as Murphy's law moment, my needle was stuck in my bike carb again when i went to ride it today.... I replaced it early in the season. F'ing ethanol fuel!!!!

[Jtsarby]

The only mod I have done is to put a Uni filter on the cart. I changed the plug today and it fired right up and ran perfect for few minutes. Then Started bogging down again. It acts just like a clogged main jet. The old plug was pretty black.

Here it is


Here is the new plug after running it for a few minutes.

Here is a pic of the carb

[x-bird]

could be junk in the tank floating in the fuel and sucking onto the tank filter and stopping flow. also, check the gas cap vent. it could also be plugged and causing the tank to vacuum seal and stop the flow of gas. definitely sounds like an issue of fuel flow cut-off once a certain amount has moved thru the lines.

[liduno]

When you say you added a uni filter, did you keep the stock airbox? I only ask because if you eliminate the airbox there is a good chance you will need to re jet.

[xlint89]

Check what X bird suggested about the vent hole.

Liduno is spot on about the re-jetting of the main. How about a pic of the UNI you installed on the machine?

Lastly, that is NOT a Mikuni carb in that pic. It's a chinese clone of the Constant Velocity. (most likely a cheap replacement carb off Ebay)

Might want to try replacing the carb like JD suggested earlier if the vent checks out fine, and the main rejet doesn't solve the issue

[Jtsarby]

I'll get a pic of the uni. He has cap is brand new and is venting properly. I just got the carb from Buggy Depot. It was the more expensive "Japanese" carb. If it's a ch at knock off clone buggy Depot is passing them off a genuine.

[Jtsarby]

I went out to start it after church. It fired right up and purrs like a kitten while idling. I can rev the engine and it returns to idle. If I try and give it gas again it dies. Has to be fuel flow. It ran perfect for weeks with the same setup.

here is a pic of the filter.

[liduno]

Normally when you get rid of the airbox you would need to jet it, but if it ran good like that before then you're probably right about a fuel delivery issue.

[xlint89]

Looking at BD's website, I only saw 2 carb choices in the fuel category.

1. was the 30mm CV style carb for 175cc engine and larger. Said nothing about it's place of origin.

2. was the Mikuni 26 VM round slide carb.

There seems to be some sort of confusion on the carb in your pic. "Designed in Japan" normally means made in China.

Liduno is right about that UNI filter. With it being out in the open like that, it normally runs a bit lean and requires rejetting.

3 questions.

1. Have the air temperatures dropped in your area lately? You may have been running a little lean before when air was warmer, but now that's it's getting colder, the engine may require more fuel.

2. Are you sure you're not getting an air leak somewhere? Intake manifold leak, vacuum hoses in good shape and properly connected?

3. In all of your carb cleanings, have you ever messed with the float height? Have you ever checked your float height since the problems started?

Please post a good clear picture of your carb and vacuum hoses hooked up for us to see. Thanks

[Jtsarby]

As for the carb. It is item #400. They have two versions. One is the "china" version and the other is the "Japanese" version. The #400 is the Japanese version.
Here is a screen cap of the one I got.

1. Air temps have not changed.
2. I checked for leaks and cannot find any. I sprayed around the intake manifold and nothing changes.
3. Float height is good.
Here are pics of the carb

[Jtsarby]

Sorry about the image size. Trying to reduce that.
Here is a video.
https://youtu.be/pb2Yzr7TkcQ
I can give it throttle in rev it is long as I don't let t return to idl. if it returns to an idle and I touch the gas it dies just like in the video

[ckau]

If that Uni filter is mounted directly to the inlet on the carb, there's your problem. Too much air turbulence entering the carb causing erratic slide bouncing. You need a "velocity pipe". A 7 inch length of pipe between the carb and Uni to smooth out the air flow

[Jtsarby]

Any recommendations on what to use for the pipe?

[OLDKID]

Kitchen sink drain pipe plumbing . On my Yerf Dogs I used a section of chrome plated extension pipe , can't remember diameter but it slid snugly into the UNI . And a Fernco TC150 rubber/neoprene plumbing coupler to mate pipe to carb. Three hose clamps , done .

[Jtsarby]

I put a longer intake tube "velocity pipe" and it didn't change anything. I adjusted the air fuel screw per manual and it still dies. I the. Removed my CDI and put the old one on and it would not start at all. I put the new one back on and Viola! She runs. I have no idea what's going on and I'm not holding my breath but she is running again. Sounds like it may be electrical.

[liduno]

L o l

[xlint89]

So you're good now?

When my coil failed, it would cut out at high RPM and felt like a fuel starvation issue.

Interesting that the DENI carb didn't show up for me when I clicked on the fuel section of that site. I do like that OEM brand for CV style carb

[Jtsarby]

Well back to running poorly.

[Gy6buggy88]

I know you said you bought a new gas cap, but try this: remove the gas cap and try running the engine to see if if dies. Post your results.

Also if you look inside the tank you will see a screen tube sticking up. It has a fine mesh screen that could clog up easily. If memory serves me I think that screen comes out by unscrewing the fuel shutoff valve under the tank.

Sometimes these stupid simple little things make problems on these buggies.

[Gy6buggy88]

Something else I thought was, did you notice the problem after replacing the fuel filter or has it run fine using that same filter before? Maybe try flipping the filter around.

[Gy6buggy88]

When you removed the factory air box what did you do with the vent line hose that used to connect to the air box? Maybe you got a venting issue now.

[BuggyMaster]

Why did you get rid of the factory carb? American sportworks carbs are unique. Don't know why...I am guessing because of whoever their manufacturer is. They start with a 114 which is typically lean to begin with. Adding a uni (with the tube), an FMF slip on, and an A11 cam with a performance CDI required a whopping 150 main jet. Yep you read that right...a 150. BUT... this is nly with an American Sportworks factory carb. If you try to jet that much on just about any other catb I've used it would choke out.

So:

1.) Where's your factory carb at and why arent you still using it?
2.) What mods do you have?
3.) what jets came in the new carb and whats in it now?
4.) Remember that some of these buggies are pig headed untill they get off thenchoke. What happens if you let it idle and warm up for a solid 5 mins+? Can you work your way into the gas by feathering the gas?
5.) When it dies, if immediately afterwards you give it a shot of carb cleaner does it fire? (I.e. It was starving and you fed it)
6.) American Sportworks uses DC based CDI boxes where most others use AC. Is your new CDI box a DC CDI? Probably wouldn't run with AC based but figured I would ask.
7.) When it dies, immediately afterwards check for spark.
8.) Got a timing light? If so put it on it and hit thentrigger and see if you are losing spark just prior to it dying.

Report back your findings.