think i may have bent a valve...

I have had this 01 YZ 250F for one year. Just after I got it, I had the valves re-shimed (they were.012in off). Even after I got that done it was real hard to start. Just before I put it up for the winter, the pilot jet screw vibrated out so I put it back in. When I started it back up it would die everytime I gave it gas so I continued to turn it out until it ran good (7-8 full turns). but then the exhaust header got real real red with in 5 minutes of idle. Like cherry red hot. I just put a new jet screw and spark plug in and cannot get it started. I don't think I have enough compression because i can kick it without using the decompression lever. so I think I may have bent a valve when the header was gettin red. Any tips or advice would be helpful. Thanks.

You piston and rings probably melted to each other and scored the cylinder.

Probably time for a new top end.

Get a compression tester for $10 or make one. Leak down tester would work better and tell you whats really wrong.

Matt

how much would that be for the parts? I'm pritty mechanically inclined so i think i might be able to do it myself with the clymer manual i have. are there any areas i need to look out for if i do it myself?

Confirm your valve clearances. If they are ok, replace your pilot jet and reset the fuel screw.

A red hot header on a bike just sitting there is normal, as is over-heating. You cannot let it just sit there without a lot of box fans running. Hopefully, you did not cook the engine.

You might not, maybe just a readjustment, and valve check.

This is if you need a rebuild.

You will need a Hone, ring spanner/pliers their worth it, piston ring compressor...

You have to take it apart and see what you have. If the cylinder looks fine just hone it at home. If its bad and has overheated bring it to a shop and they will bore it oversize for $40.

The piston, rings, gaskets- $150-200

Tools- $50

You also may have a warped head... You will have to have it checked at the shop. You may have toasted the head and valves.

Valve kit-$320

Best case is $300

worst $800

Idk what caused it their could be other problems.

Matt

Make sure when you put the fuel screw back in, you didn't also lose the spring/washer/o-ring that goes on it. If any of those are missing, your pilot circuit on the carb will be screwed up, and it won't start. Inspect the o-ring and replace it if it's not in PERFECT condition. '

Red glowing pipe is normal if you're not moving, but you just don't want it to keep it glowing read too long. You're probably OK if it was only a few minutes.

You should probably re-check your valve clearances too. If they've moved that far, they'll probably continue moving, and may be prone to break which is expensive.

Make sure when you put the fuel screw back in, you didn't also lose the spring/washer/o-ring that goes on it. If any of those are missing, your pilot circuit on the carb will be screwed up, and it won't start. Inspect the o-ring and replace it if it's not in PERFECT condition. '

Red glowing pipe is normal if you're not moving, but you just don't want it to keep it glowing read too long. You're probably OK if it was only a few minutes.

You should probably re-check your valve clearances too. If they've moved that far, they'll probably continue moving, and may be prone to break which is expensive.

:excuseme: +1 Those parts are pretty small and if you didn,t know they were there you would just put the screw back in and never know the difference.:smirk:

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