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throttlejokey

4Rt Engine

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hello can any one tell me how many hours before a piston change ?

I have run 4RT's since '05. My first one I did 18 months on and sold to a friend. He gave it a very hard time for the next 2 years before we stripped the motor. The piston wear was only just above the min manufacturing tolerance and no where near the replacement limits,bore wear was also well within limits. Ring gap was however close to the wear limit. My current motor has done 6 years with almost no missed events and still has good compression and uses no oil, however will be stripping soon.

Other threads have confirmed long life of the cylinder components, I think quite a bit will come down to air cleaner maintenance and oil and filter changes. How piston wear is so limited in an over square motor when the piston skirt is so short amazes me, it looks more like a tin lid than a piston !!

Reckon periodic compression check will give a good guide to service intervals as the motors do not seem to suffer catastrophic piston failures based on time.

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hello can any one tell me how many hours before a piston change ?

I've never heard of one, my old 4rt possibly did 3000 hours with no problems and is still going today although less hours. A one year old 4rt with 500+ hours is just about run in I'd say, there are so many 05 bikes still going strong.

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I've probably got 200 hours on my 14 now which I bought 6 months ago, still feels a little tight and is nowhere near run in yet. Swap the oil every month and the filter she'll go forever.

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I think they got the manual times when they were smashed on Sake.

You can bet Honda san is rubbing his little Japanese hands when people follow those cylinder / piston service times as they probably give him a financial erection !

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I think they got the manual times when they were smashed on Sake.

You can bet Honda san is rubbing his little Japanese hands when people follow those cylinder / piston service times as they probably give him a financial erection !

I believe the 4rt engine is based on the CRF MX engine which would be pretty stressed as a competition engine. The 4rt does not rev as much and is under little pressure most of the time, the piston intervals are probably based on the CRF rather than the 4rt. I know many riders with 4rt's, many of them 05 bikes will mega hours on them and tough lives, none have had any major issues let alone piston changes or slap.

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