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top end rebuild advice

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Hi guys , i just got a crf250x and i knew when i purchased it, it was looking for a top end pretty soon, but i also got a good deal on it. 

Basicly on a 100 mile trail ride it went from full to just the tip of the oil dipstick, soo im gonna go ahead and get the top end done now.

 

Should i get OEM parts? piston, rings, valve seals?or some other brand?

 

the bike hauls ass the way it is, i dont want any high compression piston stuff its fine stock.

 

any tips or advice? 

my mechanic told me to install stainless steel valve kit on the intake , since the head is gonna be off

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<<any tips or advice?>>

 

+1 on the SS intakes.  Will list much longer than stock TI's.

 

Make sure you send it to a good shop that can cut the seats on the three angles required to get the valves properly fitted.  Also, I would have the valve guides replaced.

 

OEM stuff for everything is fine.   Some consider using a TRX piston, which has a wider skirt and a 3rd ring for good oil control.  Personally, I think I'd stick with the stock piston, but that's me.

 

Jim.

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BTW, I'd also check the tranny oil level to make sure the oil burned rather than migrated.  If the right end crank seal is blown, oil will push over to the tranny side from the engine.

 

Jim.

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My bike was blowing smoke, OEM parts did the trick. I did some research here prior to the rebuild and it seems most people go with OEM, Wiseco, or JE. But since you don't want to go with high comp I would say OEM. Definitley replace the valve seals at this point too, they don't cost much.

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BTW, I'd also check the tranny oil level to make sure the oil burned rather than migrated.  If the right end crank seal is blown, oil will push over to the tranny side from the engine.

 

Jim.

well the bike does smoke soo i really didnt bother checking for oil migrating to the tranny side, because the smoke is visable under acceleration, its not embarissing but its there :p its enough to leave a black mark on the back fender after the ride

thanks for the advice i really appreciate it bro !

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<<any tips or advice?>>

 

+1 on the SS intakes.  Will list much longer than stock TI's.

 

Make sure you send it to a good shop that can cut the seats on the three angles required to get the valves properly fitted.  Also, I would have the valve guides replaced.

 

OEM stuff for everything is fine.   Some consider using a TRX piston, which has a wider skirt and a 3rd ring for good oil control.  Personally, I think I'd stick with the stock piston, but that's me.

 

Jim.

TRX piston? like the quad?

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 Yes.  It shares the same size bore as the CRF.   Many like to use that piston instead for longevity.   It has a wider skirt and a 3rd ring for better compression and oil control.

 

  Of course there is a loss in performance.  The whole idea of the "pan cake" or slipper piston was to reduce mass, which means faster rev's.  That's one of the reasons the CRF acts more like a 2T rather than a 4.  The primary goal in the design of the motor was for performance and every design decision was based on that.  Using TI valves for the intakes was another.   TI's are lighter than SS.  If they could get away with it, the exhaust would be TI as well.

 

  Many love the CRF, but hate the maintenance it requires, instead remembering their XR's with fond memories and the "ride it and forget it" attitude they had in regards to maintenance (because it would let you).  XR's were/are "Bullet proof" and last forever without doing any serious maintenance.

 

Jim.

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Yes

im not saying that i dont believe you guys!, but i searched and couldnt find anything about that trx piston used in a crf250x, i only found it used in a crf450x...  :ride:

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im not saying that i dont believe you guys!, but i searched and couldnt find anything about that trx piston used in a crf250x, i only found it used in a crf450x... :ride:

Agreed. Not heard of using a 250 quad engine piston in the 250X. Yes on the 450 but I don't see the advantage if the stock style piston is broken in well.

Side note, how are the valve clearances? You certainly need a piston ASAP but not necessarily a valve job. I replace the piston once a year but still on stock valves with my 05 CRF250R. Valve stem seals are easy enough to do with the head off, just need a valve spring tool.

A full valve job with SS valves, guides and seats is a bucket of $$$.

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Agreed. Not heard of using a 250 quad engine piston in the 250X. Yes on the 450 but I don't see the advantage if the stock style piston is broken in well.

Side note, how are the valve clearances? You certainly need a piston ASAP but not necessarily a valve job. I replace the piston once a year but still on stock valves with my 05 CRF250R. Valve stem seals are easy enough to do with the head off, just need a valve spring tool.

A full valve job with SS valves, guides and seats is a bucket of $$$.

yeah my mechanic told me, first he needs to tear into it - to know exactly whats goin on... and see how far the valves are from zero. im sure this motor has never been opened up before soo they should still have lots of life. i hope i can just do piston rings and valve guides and then braap

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 Your right...I let the fact that this was a 250 slip....it's the 450's that share the same bore size. I do believe however that a 3 ring piston is available after market (Wiseco?), but that may only be on a big bore (ie. 270).

 

Jim.

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yeah my mechanic told me, first he needs to tear into it - to know exactly whats goin on... and see how far the valves are from zero. im sure this motor has never been opened up before soo they should still have lots of life. i hope i can just do piston rings and valve guides and then braap

Do NOT just replace the rings. Replace the entire piston. Slipper pistons can and will flip in the bore with too much wear. Guys typically replace at 100 hours on a woods-ridden bike and 50 on a track bike. Honda recommends a new piston every 15 hours in competition.

I replace pistons once a year even though they are working fine. Compare a $150 piston kit to a complete engine replacement due to broken cases from a piston flip.

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Just got it done thanks guys !! for your time.

just changed Piston ring kit, + valve seals, 

 

cylinder was in perfect shape , clear crossetching all there, the piston looked great (mechanic said it was like new), and valves are excellent shape...

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