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total distortion

98 400 won't start (long version)

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I picked up a 98 yz 400 from this guy a little while back. He wasn't the type to keep up on maintenance on stuff. So after hours of kicking I finally got it started. It seemed to run ok. Next was to do some basics, oil change and spark plug. It runs a lot better. Then it sits for a couple of weeks. I go and start it and it runs fine at first, but then once it starts warming up, it dies. I start it again and it starts running really bad. I start it about 4 times more each time getting worse till it just wont start.

I did some tests and in had no to weak spark,so I got a new stator. I figure while I'm at it I'll check and adjust the valves,and clean the carb. Now it won't start at all. It starts for a half second and thats it.

Recap- New stator, plug, valves/ timing good, clean carb = No start!

What else should I check?

Thanks

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Check/clean the grounds (bolts) on your coil - sometimes, corrosion sets in.

how old is the gas in it?

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Did you flush out the tank ?

It may be a simple case of old fuel residue in the gas tank which has now been flushed down into the carburettor.

The fact that it started suggests spark etc is not the problem.

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Check/clean the grounds (bolts) on your coil - sometimes, corrosion sets in.

how old is the gas in it?

I tried that, but will check again.

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Did you flush out the tank ?

It may be a simple case of old fuel residue in the gas tank which has now been flushed down into the carburettor.

The fact that it started suggests spark etc is not the problem.

I'll flush the tank and make sure that it's clean.

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sure sounds like a carb problem... my old 400 gave me some issues like that and it was a partially plugged pilot jet / pilot circuit.

keep working on it.

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sure sounds like a carb problem... my old 400 gave me some issues like that and it was a partially plugged pilot jet / pilot circuit.

keep working on it.

That's what I'm leaning towards, although I did get it to start and run a little bit. I had to have my friend hold the choke(it won't stay open by itself) while I started it. Once it did start I had to hold the choke or it would die, even when it got warmed up. Now I'm back to having a hard time starting it again.

I'll pull the carb and do a proper cleaning. Hopefully that will solve the problem.

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dont feel bad... I had mine off a couple of times before i bit the bullet and completely dissasembled and soaked it. And mine had never set for any time at all. From what I have read the early fcr's are very finicky. Mine was, but once cleaned and set right, it was fine.

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