Carbon Fouling help

Hi guys, quick question, my bike 1999 wr 400 runs great with new plug but after a full day of riding it wont start or starts and instantly dies, if i put a clean plug in it fires up first kick, could this have anything to do with my valve clearances? if not im guessing fuel mixture problem, if fuel mixture what screws do i adjust to where?

Just sounds like it is jetted a bit rich.

Does it sputter or stumble at certain throttle openings or does it run well across the full range ?

thought it would be that, although it ran fine for months at a time and then all of a sudden it stuffs up after every ride, when its riding it runs great never bogs nor backfires.

Jetting does not change over time, so it can't be jetting.

Besides, jetting that rich would make it run terribly. 

 

More likely you have worn out valve guides, rings, etc and you are passing oil.

 

Time for a rebuild.

Was afraid of that :(, thanks for input guys

You might want to clean your air filter it may be dirty and causing a rich condition

I clean the filter every ride so its not that aha

I am sure it needs a rebuild but I didn't think tht affected the plug,while I'm on the topic can anyone tell me what can go bad I I kept riding the bike?

I am sure it needs a rebuild but I didn't think tht affected the plug,while I'm on the topic can anyone tell me what can go bad I I kept riding the bike?

 

If your valve guides are worn, most likely your cam chain, and cam tensioner are worn out too.

If that is the case, you will own a large paper weight if you do not follow the standard service in the service manual.

Valve guide wear is usually a sign of really bad air filter maintenance, extremely lean jetting,  or tons of hours on the motor.

Okay for starters I clean filter every ride I know for sure it isn't too lean, what is classified as ones of hours

Okay for starters I clean filter every ride I know for sure it isn't too lean, what is classified as ones of hours

 

300+

Okay I'm on about half that,could a bit of shit in a air intake cause "rich" jetting which lead to carbon fouling?

It can also be  blow by from worn or cracked rings on piston. Or scored cylinder walls from overheating. I would bet on one of those.

Okay I'm on about half that,could a bit of shit in a air intake cause "rich" jetting which lead to carbon fouling?

No.

Do a leak down test or tear it apart.

 

You are saying that your '99 motor has less than 300 hours?

It has roughly 150 hours on a complete rebuild of all internals

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