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Need Help - YZ250 Won't Start

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Hey guys - I need some help here. I bought a 2001 YZ250 a few months ago, which appeared to be in great condition when I inspected and gave it a test ride. However, once I got it home I literally rode it once and I could not get it to start again after that. here is what I tried:

- Did a compression test - read out about 130-150, which seemed a bit low so I put in a brand new piston, rings, gasket. compression still ready 150psi tops even after the new top end

- Tested all of the electrical connections - found that the spark plug cap was bad so I replaced it

Once I did these two things, the bike started right up after about 3-4 kicks. I let it warm up for 5-10 minutes and it was spewing smoke out of the exhaust. Also, the idle speed was off so I adjusted the pilot air screw and idle screw.

I thought my bike was ready to go, but now I cannot get it to start AGAIN (tried changing spark plugs and adjusting idle back, but no luck). I'm seriously frustrated so any thoughts would be much appreciated. 

- the bike had been sitting for about 3 months so could the 2 stroke oil have settled to the bottom of tank and damaged/clogged something after being run through the engine?

- I am using a BR8ES plug and the spec says to use B8EG - could that be it?

I'm running out of ideas, thanks for your help

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Oil separation in the gas tank is not an issue. BR8ES is fine just make sure it's brand-new and you have a lot of them. Check again for spark with a new plug.
Have you tried holding the throttle WFO and kicking quickly five times in a row with a new plug?
On an older bike that is new to you it wouldn't be a bad idea to replace reads and crank seals. That will keep all the air going in the direction you want it to.

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Thanks Kinger for the quick reply.

I meant to say I was using BR9ES (not 8) spark plug. Anyway, I picked up a BR8ES this afternoon and tried to start it after checking the spark (which was a nice blue). It would NOT start with just the choke on, so I tried your suggestion (choke off, throttle wide open, rapid kicks) and it started up on the 5th kick. I let it run for about 10 minutes to try to clear it out but I am still getting lot of smoke out of the exhaust.

Do you think the hard starting and the excessive smoke could both be symptoms of bad crank seals? Anything else that could be an issue? I did check the reeds when I did the top end and they look almost new.

 

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Get a full box of spark plugs next time you can. I would go with the 8s

You say you let it run for about 10 minutes does that mean you rode it or just let it run in neutral? I would ride it and when warm get it up on the pipe/power band good a few times and the smoke should all but go away. if it doesn't clear up and keeps belching smoke then it could be a right side crank seal. If it clears up I would clean the carb and reset the float height.

It could have just built up a lot of fuel in the base from riding it with a bad plug cap.

 

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Update: I pulled the carb and cleaned it thoroughly. The pilot jet was a little clogged so I thought for sure that was the issue. It started up after 4 kicks (with choke on) and I let it run in idle for a bit.  Turned it off and tried to start it back up and it would not start without the throttle wide open. This time I took it for a 5 minute spin up the street. Ran it hard through third gear and cleared out the smoke that I was describing earlier. Turned it off and it still took 5-6 kicks with throttle open to start it. Seems like when the float bowl is empty it starts up ok, but once it fills it has a hard time starting. I did check the float height when I pulled the carb and it was perfect.

Any thoughts???

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