More carb problems but its a quad please help

[nb200x]

so I am working on a MOTO4 yfm350er about a 93 model. it was leaking fuel and running poorly barley running at all. prior to that it had been sitting (couple of years) but running well before that. So I rebuilt the carb soaked it new gasket and new jets. no it will idle great but the top end falls on its face and stutters I have adjusted the needle up and down no change. I cant find trouble shooting procedure for this thing anywhere. this carb is very popular it was on a warrior kodiak big bear moto4 from like 87 to 99. can you please help me.

[yaegerb]

Idles fine and runs through gears but stumbles at wide open?

[nb200x]

stumbles in neutrtal from 3/16 - wot

[yaegerb]

Have you tried putting the needle clip on the second or first groove from the top?

[barnett468]

Hello

Are you saying it ran perfectly at one time with this carb?

When you cleaned the carb did you spray carb cleaner with the nozzel in all the jets and watch the fluid come out inside the carb bore?

If it has points check them for proper adjustment and wear.

Did you install a new plug?

Does your plug look wet or black?

[nb200x]

it did run good whith this carb. I cleaned the carb yes saoked it and blew it out with carb cleaner and and compressed air. I have set the needle in all grooves, it runs best one notch down from top. new plug its a lil black but its dry. I know I am clueless

[yaegerb]

Have you checked for intake leaks?

[barnett468]

Hello

Good suggestion from yaegrb.

Look at the plug again after running. If it even remotely looks damp or has a very thin wet film on it it is burning oil. Try a compression test first before anything else.

Clean the black carbon off the plug lay it on cyl head kick it over and see if spark is pale yellow or a strong blue color.

What about the points I mentioned? If you do not check these things no one can help you.

If it has points and they are ok try a new condenser. If the points, carb float, intake leaks and condenser are ok it is probably your coil breaking doen under load and you need to get it tested at a local shop.

Does it work noticeably better when you first start it or after it gets warm?

[nb200x]

I dont think it has points...if it does where are they located. compression is good. does a coil, or points or cdi box go bad just from sitting.
it ran fine when it was parked....but that was a couple of years ago.

[muthey]

I can guarantee you don't have points, I suggest going back to the carb, check your primary jet again, there is a good chance that in the process of starting it and letting it idle dirt got in there from your fual lines, if you go through the carb again and nothing is wrong, while it is idling spray starting fluid around the intake if it idles up there is a leak some where. next have you cleaned or changed the air filter yet, also is it a wet filter or dry. Check the air filter outlet tube for rats nests, happens more than you think. Try it with the gas cap off and see if it runs right. Check the color of your spark, also look through your wiring for a loose or corroded ground. I also recommend a new spark plug. And last but not least check your main needle for wear. I my self would go back through the carb and make sure the pilot screw is correct, and that I didn't miss something in the carb.

[barnett468]

Hello

Before you do anything stick your carb drain hose in a narrow glass with the gas valve off. Loosen the drain screw on the bowl slightly until carb is empty and look at drained gas carefully. If your gas is not almost clear it will not run right, if it has water in it it will sink to the bottom and you can easily see it, if it has debris it will be obvious. Tell us what you see.


Xlnt tips from muthey. Since it ran fine before your needle and jet are not worn out. Your cdi can go bad if it was stored in a moist place like outside or near the beach or somewhere humid but otherwise no it is fine. Coils have been known to act like this.

Old gas turns bad and does all the things you mention is it old or new?

Your plug should not be black so soon. It is either rich, bad spark dirty air filter. Clean and check carb again, make sure sure

High float levels can contribute to this, sinking floats, bad needle and seat etc.

[Bungle]

Hi I had the same problem with a 225 moto 4 years ago. It turned out to be a blocked breather pipe from the carb. The one that is linked to the float bowl that allows air in or out when the chamber is filling or emptying. Disconnect all the breather
Pipes and give it a go

[nb200x]

I rebuilt the carb new jets new needle. when this started plug is new tried it with the air box disconnected. got good blue spark. I am going to c if the intake leaks

[barnett468]

Hello

Rule number one NEVER assume anything.

You do not have an air leak. If you did it would not idle and your plug would not be black from excess fuel as your description suggests it is. It is impossible!

If you did everything that everyone has asked you should have found your problem by now. Until you do more of these things there is no point in asking anymore questions.

Did you do everything?

Drain the carb like i suggested,

Install old needle it ran with that before.

Is the number on the new needle the exact same number as the orig?

[nb200x]

yes I have been at this things for weeks. To me its an air fuel mixture issue but the pilot screw does nothing to help or make it worse. I have done a lil research on this particular carb and the best i can figure its junk. i can get a brand new chinease carb for my 200x for 21 bucks its 175 for this one. and 400 for a good original. it has 2 throttle cables and no adjustments I think yamaha dropped the ball on this one.

[yaegerb]

i'll ask again...have you checked for intake leaks? Start it up and take carb cleaner or starting fluid and shoot it all over the intake boot. If it revs then there is a leak.

[barnett468]

Hello

My personal opinion is that after all i have read from you that you should just do the air leak test as suggested by yeagerb and if no results then give up and buy new chinese carb.

Most of us could figure it out in 30 minutes if we were there but were not and even though we try to describe the tests we suggest they can be difficult to understand exactly.

What are the results of the fuel bowl fuel inspection I suggested?

If you did this weeks ago it still should be done again, things change sometimes.