Hi, I'm new on here looking for a little help for my quad. It has a mikuni carb model L/M/N/P/R/S/T. When you run it all out, it runs fine. Once it gets hot if you putt around about half throttle, or it you just ride slow and easy, it will shut down and the plug will be wet and fouled. I took the carb apart and cleaned it out and installed a new needle and seat. Now, it is doing the same thing. If anyone has any ideas, let me know.

Thanks

 

Did you try a new spark plug? D7EA.

 

Yes, I had a D7EA and also went up one to a D8EA

 

Did you just get the quad? What's the history behind it?

How's the air filter? Is there any reason to believe its jetted wrong? I mean, did it run fine one day and then start this?

The carb is obviously not dirty or the plug wouldn't be wet and black.

 

Oh, stay with the D7EA. The 8 is a colder plug.

 

The quad is actually my neighbors. He has had it since it was new and has been struggling with this problem for years.

 

Did you try moving the needle clip around? I'd move the clip higher on the needle and that will restrict some gas at half throttle. That will probably solve your problem.

 

I'm glad you said that because that is what I was going to try this weekend. Do you think I should just go up one notch?

 

I think you should try all notches until it runs right. You should also inspect the needle for any wear. If it has significant wear, you really should replace the needle and the needle-jet.

I'm guessing you have the 1990 250S quadsport? If so, the correct needle is 5HN31 and the stock clip position is in the middle. The correct needle-jet is O-3.

Over time, the needle vibrates against the hole and wears the needle and hole.... And that lets too much gas thru.

If you can't find that needle, the mikuni 5L1 is the same thing.

This might be of use to you: http://www.alpha-sports.com/satv/1990/LT250S/04.htm

 

I really appreciate the help!