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maintenance vs four stroke

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with my 2001 at 250 hours, wouldnt it need alot more work than just cam chain and rings? like what about the crank and gear box? where a i can do my own maintenance on a 2 stroke. i dont change heaps of parts just put it in the shop each year for valve adjustment and new rings and maybe next year a piston. i dont mind that two stroke are more frequent cos i like working on bike just worried about doing it on my four stroke and messing some thing up. i should of just bought a 2 stroke to start with

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As long as your valves are still within spec you'd just need the cam chain, and piston/ rings... and check for play in the rod. Your gear box (tranny) should need nothing. Learn to do the work yourself and you could pay for a new crank with the money your spending on labor. If you have a manual and can work on a 2 stroke you can do just about everything on the 4 stroke as well. The only thing I take my thumper to the shop for is to have the valve seats cut. Keep in mind where most catastrophic failures stem from in a 4 stroke... cam chain derailing or a valve dropping. In most cases that is directly related to lack of maintenance.

I was intimidated by the thumper as far as doing my own work for a long time... finally I just decided to tear into it and its no more difficult than wrenching on my smokers as long as its kept up with.

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ok thanks. how long can i get out of a crank? the bike amazingly still has great compression. does it really need a new piston and rings? why do the valves drop? what would i have to do to fix that? how much?

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ok thanks. how long can i get out of a crank? the bike amazingly still has great compression. does it really need a new piston and rings? why do the valves drop? what would i have to do to fix that? how much?

The crank in my old 450 had about 400 hrs on it and was still well within spec. I just replaced the main bearings every 100 hrs. Piston and rings is just a preventative maint. thing. Let it go too far past recommended intervals and your asking for trouble esp. on a 250f which most riders rev quite a bit higher than a 450. I race so my intervals will be different than most non racers. Ive never owned a 250f either so I cant comment on how long a piston and rings should last or when they should be replaced. Valves usually let go because they are worn past the service limit. Keep them within spec. and you should be good to go. I just recently learned that after they are shimmed they should probably be replaced and the need to shim should be used as a warning sign. Keep oil and filters clean and your chances of any catastrophic failures decrease dramatically.

Edited by ftball90

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sweet thanks. i might just put a new cam chain cos i reckon is ****ed. probably just leave piston and rings

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Really?!? Is it still the original piston and rings and timing chain?

If they are all original, you should replace them all. Just because you still have good compression doesn't tell the whole story. Micro-fractures don't affect the compression on the topend. But, they can cause the piston to come apart in rather spectacular (read expensive) fashion.

If that piston were to detonate, you will be replacing the crank, all bearings, splitting cases, sending the jug and head off for major work and big bucks.

Replacing the piston yearly for a thumper that is raced is just good preventive maintenance IMO.

Same for your '01 250F. Replace the piston, rings and timing chain annually, regular oil changes, and a good thorough inspection when doing the topend and those bikes will last almost forever.

Remember, Yamaha's thumpers are about the most reliable bikes out there. But you still need to do some scheduled maintenance to avoid the big repair bills.

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my 2010 only has 47 hours on it. is it worth rebuilding it yet? do you think it needs it yet? and the 01 with other 250 hours you reckon i could get away with only piston, rings and cam chain?

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If your on the rev limiter I would replace it but if not your probably good to go for a little longer. My buddy who rides 250 A class puts 50 hrs on his pistons and he's always all over the rev limiter. But hes sponsered by a shop so he replaces everything in the top end at once since he gets really really good deals on his parts and doesnt do his own labor. So Arnego is correct, it all depends on your riding style and how hard you ride the bike.

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