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How many hours on your 2-stroke top-end?

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With reasonable care using quality oil at no more than 40-1 and good air filter maintenance................IMHO 50 hours is very obtainable. Due to low cost of a top end job, I wouldn't go much past that even if the compression was still strong. Pistons tend to fatigue and break after 60-75 hours and they tend to make an expensive mess when they go! :thumbsup:

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My current bike is an '02 KX250. I typically get 35-40 hours on a top-end, the rings and piston will be right on the edge of still being in spec at that time. My first crank lasted approx. 200 hours before the lower rod bearing began developing play. The crank bearings were still tight, but of course it all got replaced while the engine was apart. The OEM plating was worn out after the first top-end. The US Chrome re-plate is still in good shape after 7 rebuilds. I get about the same life out of my clutch plates as I do my pistons, as I tend to abuse the clutch. I replaced the stock clutch basket when I replaced the crank, as it was starting to develop some mild grooving. It actually help up well considering how hard I am on clutches, it lasted much longer than my Suzi clutch basket did.

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2005 YZ250

I have 15 races on it and I figure about 80 hours total on it. Compression new was 260 psi, its now about 245 psi (94%). I use Maxima K2 at 40:1. I change my air filter religiously.

However, since

Pistons tend to fatigue and break after 60-75 hours and they tend to make an expensive mess when they go!
I plan on doing my top end this week.

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I Have a 95' yz250, unknown hours on bottom end but has no play. Have 14hours currently on top end. I usually change them out every 60-75 hours. Thats about right :thumbsup: considering i dont race and im not too hard on it.

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10year, you must ride inbetween races right? You cant get 80 hours from 15 races. Btw, my 125 went about 40 on the last piston. (32:1 mix, and jetted rich).

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10year, you must ride inbetween races right? You cant get 80 hours from 15 races.

Fourteen 2 hour races plus one 3 hour race = 31 hours.

Conservative estimate of 4 hours riding between races = 56 hours.

I'm way over do.

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I just did mine not to long ago (05 YZ250) it had atleast 50 hours on it...and by the the look of everything next time I'll give it another 10-20 hours before replacing the piston and such...

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I just did mine not to long ago (05 YZ250) it had atleast 50 hours on it...and by the the look of everything next time I'll give it another 10-20 hours before replacing the piston and such...

Yea a 250 should go for 60hours ATLEAST if it wasnt abused

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really depends what kinda of bike and how your ride it. Since my KDX is for trail riding and i'm mostly riding in 2nd and 3rd with the occasional low rpm cruise in 4th i hope to get 2 years out of it if not a little more. I'll become a little more cautious of the compression after a year. I was thinking about a YZ and almost got it but the thought of rebuilding probably twice a year just didn't appeal to me. If i would have raced i would have been a little more open to the rebuilding deal.

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gulley04 thats great, I just have 39 on my meter on my 06 yz, and it still runs like crazy. I run 40:1 Bel ray HR1, with 20% 110 race gas. Probably will tear down at about 45hrs and change top end. Looking thru the exhaust port I can see where cross hatching is gone in places around intake port. I hope to get your time 60hrs on next run.

06 YZ250V

03 YZ450F (parting out)

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I change my top end after every moto.

Honestly, I took my piston out of my 98 (wiseco) after 55 hours. It looked and measured brand new. I am fanatical about cleaning my airfilter.

the new bike is going to get the piston replaced at the end of the season. I have seen too many stock ART pistons break when they start to wear. I will probably replace it with the single ring wiseco.

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gulley04 thats great, I just have 39 on my meter on my 06 yz, and it still runs like crazy. I run 40:1 Bel ray HR1, with 20% 110 race gas. Probably will tear down at about 45hrs and change top end. Looking thru the exhaust port I can see where cross hatching is gone in places around intake port. I hope to get your time 60hrs on next run.

06 YZ250V

03 YZ450F (parting out)

Yea if you dont abuse it and clean the filter frequently it should go 60 hours easy :thumbsup:

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I did my top end at 60 hrs ....just "to be safe". I could have gotten away with slapping some new rings on it and buttoning it back up. HOWEVER...that doesn't make sense once your into it.

My point, I run HR1 at 32:1 and the bike was clean and had very little wear at 60hrs. If it weren't for the possible ring failure I would not have bothered.

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going on 1 year, ride it every sunday or every other sunday for 1 year straight. Still lights up 1st kick. Tons of power. Wins races. Going to go 1 oversize from stock. Screw aftermarket piston. Yamaha owns me....

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I have an '05 yz 125...I just put a brand new top and bottom end in my bike about 5 hrs. ago (riding time)...I have about 50 total hrs. on my bike...I change my top end about every 10 hrs. and my bottom end every 25-30...It keeps everything running right

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I did my top end at 60 hrs ....just "to be safe". I could have gotten away with slapping some new rings on it and buttoning it back up. HOWEVER...that doesn't make sense once your into it.

My point, I run HR1 at 32:1 and the bike was clean and had very little wear at 60hrs. If it weren't for the possible ring failure I would not have bothered.

60 hrs. huh?...Maybe you should read your owners manual...Lmao...You must ride 1st gear everyplace.

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