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okay, my dads crf250x just started working crappy. It some times now just dies when the rpms are low, and it started backfiring on deceleration.

What causes this? is it from valves or what? this is our first full size 4-stroke so my experience with them is very little.

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for sure its the valves. i had the same problem on my 04', and i had to go stainless steel. i did some research on the valves and i found out that honda got smart about the valves on the 06' bikes and newer so they will last longer. but still, they will need adjusting after a while.

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Checking your valves is not a bad Idea for a starting point.If it starts easy when cold it's most likely not your valves.You could have a plugged up pilot jet.stuck hotstart or exhaust leak.

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Theres a sticky up top that shows you with pictures how to shim.If you can't find it, someone will post the link for you.Shimming is only a band aid and doesn't last very long before they need to be shimmed again.When you do your valves talk to AgentSmith.

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Your gonna tell me that taking the carb out to clean it is easier than checking the valves?:moon:

are you saying its easier to cheack the valves than the carb??:thumbsup:

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Checking the valves is easier than taking the subframe,airbox up and shock out to pull the carb.If it's your first time it shouldn't take more than 30 mins.It is also a good baseline starting point specialy from the symptoms you describe.It's pretty easy to clean the main jet & pilot jet with the carb in the bike once you find the niche.But that is not taking the carb out to fully bust it down & clean it.If your valves check out fine I would just losen the carb boots and twist the carb so you can get to the main & pilot jets througth the float bowl.

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i cheacked the valves last night and there was no clearence. i could not even fit the smallest feeler guage i had in. :thumbsup:

Time to rebuild your head or buy a new one. I would run the Faction intakes and stock exhausts:thumbsup: That set up for me has been bulletproof. You can shim. I just would stay close to the truck and or never turn your bike off if you ride again after shimming. Is it just the intakes or all that are zeroed? I would find it strange that all of the valves are gone. The RI is usually the first one to go I think.

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wow, i took out the main and pilot jets and the pilot jet was filled shut. i cleaned it out and it should be running good in no time:thumbsup:

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Time for a valve job. Don't bother to re-shim if they went to zero. Call Dave at MXTime he does great work fast. He will fix you up with new stainless valves at a great price. There are some great threads on pulling the head. I recommend buying a service manual if you don't have one, you will need the torque specs when you put it all back together.

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i cheacked the valves last night and there was no clearence. i could not even fit the smallest feeler guage i had in. :bonk:

Sounds like the engine was not at TDC on the firing stroke.:bonk:

Andy.

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