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Valve issue

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My crf230f 05 was running great then it lost power and started clanking. I took the head off and noticed that the intake valve was hitting the piston. What would cause this? possibly chain strech. I need a new piston, so i was considering a big bore kit. which one is the best ect. thanks for any and all help.

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Almost certainly the cam chain jumped a couple of teeth putting valve timng out of sync with the piston stroke thereby allowing valves to hit the piston. Cam chain tensioner either broke or was just not adjusted. Doubt you need a new piston but if it hit hard enough that you do then you likely bent a valve also.

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My crf230f 05 was running great then it lost power and started clanking. I took the head off and noticed that the intake valve was hitting the piston. What would cause this? possibly chain strech. I need a new piston, so i was considering a big bore kit. which one is the best ect. thanks for any and all help.

Chain wore then jumped or tensioner failed, it is a piece of crap. Old worn Valves never stick, in fact check your guides they should be gone by now on an 05.

Valves hitting piston doesn't do any damage to piston but bends valves. Valve job, chain, & tensioner is all you need.

If your bore is good, I just put in a 12:1 piston and love it.

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Tensioner failed, I have a replasement on it's way. The 12:1 piston that Countdown mentioned; is there a brand I should buy?

Thank you, Shellshocked,wanawakeboard and countdown for all your help.

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Chain wore then jumped or tensioner failed, it is a piece of crap. Old worn Valves never stick, in fact check your guides they should be gone by now on an 05.

Valves hitting piston doesn't do any damage to piston but bends valves. Valve job, chain, & tensioner is all you need.

If your bore is good, I just put in a 12:1 piston and love it.

Just wondering why you think valves never stick?

I have seen many valves stick in the auto 4 stroke world, and read about valves sticking in the cycle world, what is it that makes you feel that valves "never stick" I know that in this case it was the tensioner but I am curious how you come to that conclusion. :thumbsup:

Im always open to others experience..

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Just wondering why you think valves never stick? I have seen many valves stick in the auto 4 stroke world, and read about valves sticking in the cycle world, what is it that makes you feel that valves "never stick" .

My auto experience ended in the 70's but I worked as a mechanic and in an engine rebuilding shop.

Frist, obviouisly I mean never in mormal use. Second, to "stick" is to sieze in the guide. Not the valve hitting the piston and bending the stem. Not installing new guides and failing to ream to proper clearance. Not a loss of top end lubrication. Not loss of liquid cooling.

I have seen many "stuck" valves over the years but never just "sticking" under normal use, it was always the result of some other failure. With normal use, they just keep getting more clearance and more lubrication as the seal ages. Bottom line there is no mechanizm to make them stick that is not something else that failed first.

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got ya... I was just thinking from the original post (clanking etc etc) perhaps he did lose oil pressure for some reason (blockage or some other failure) And since the valve did strike the piston I thought perhaps a stuck valve was possible due to the unknown factor...

thanks for the reply...

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got ya... I was just thinking from the original post (clanking etc etc) perhaps he did lose oil pressure for some reason (blockage or some other failure) And since the valve did strike the piston I thought perhaps a stuck valve was possible due to the unknown factor... thanks for the reply...

When you lose oil to the overhead, the first thing that goes are the cam lobes / rockers and valves quit opening.

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YOu guys really serious about sticking 12:1 pistons in a 230F? A 230F don't have knock sensors or 32bit parallel processors on board a computer to back off ignition timing to control predetonation.

Where are you going to get 98 octane gas to keep a 12:1 from predetonating?

The best gas available is only from the southern states, and that's 93 oct super unleaded. That's only good for 10.5:1 on a very good low humid day.

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YOu guys really serious about sticking 12:1 pistons in a 230F? A 230F don't have knock sensors or 32bit parallel processors on board a computer to back off ignition timing to control predetonation.

Where are you going to get 98 octane gas to keep a 12:1 from predetonating?

The best gas available is only from the southern states, and that's 93 oct super unleaded. That's only good for 10.5:1 on a very good low humid day.

Here's some good data. the Wiseco piston that is claimed to provide 11:1 compression is listed very generously. While the piston does have an increase with a small flat dome, it also sports very deep valve pockets that reduce much of what is gained from the raised section.

The piston also sits down in the bore .030", just like the OEM piston. Plus, the stock head gasket measures .040". A stock CRF230 is @ 8.7:1 compression ratio. A stock Gen1 CRF150 is even lower, closer to 8:1, even though both bikes are listed by Honda to sport 9:1 compression ratio.

I crunched the numbers long ago and can report that a 230 with a Wiseco and everything else stock is still under 10:1 compression. That is why they will run on pump premium in most instances with no detctable detonation, even with a stock cam. Add in a performance profile, and all is well on pump premium.

What I take from that is that running a "high compression" piston in a 230 really isn't too much compression.

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