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I took a trip out the the Pismo Dunes in California and some of the other bikes that went along for the ride ended up having engine problems.

It has been a while since i did any maintenance to my 02 Honda CR250 so i decided to take my top end off to make sure i didnt have any major damage to the piston.

at this point i am not sure what to look for.

Could you please take a look at this pictures and give me some feedback as to why such a high amount of build up.

img00039201003292054.th.jpg

img00040201003292054.th.jpg

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What kind of running problems were you having? That's one dirty piston crown. This isn't necessarily a problem, it may just be a characteristic of the oil you burn. My piston crowns are usually just as clean on the day they come out as when I installed the piston new.

Anyways, do you ever have to top up the transmission oil? How does your air filter look? These are other sources of dirt to crud up a piston crown like that.

Finally, you can't see piston failures coming. You have to replace your piston before it happens. If you haven't done any maintenance on the bike a while, you're probably due. Pismo is hard on bikes, too.

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What kind of Oil do you run to keep your piston so clean?

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What kind of Oil do you run to keep your piston so clean?

👍 I'd like to know that too !

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My piston is usually clean, hasnt had a rebuild in months, (Over 20hours)

Stripped barrell of 2weeks ago and the piston seemed fairly clean, I use Putoline MX7 at a 32:1 ratio.

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My piston is usually clean, hasnt had a rebuild in months, (Over 20hours)

20 hours? Oh. What's it look like after 100 hours?

JayC

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just curious how often or how many hours typically should a piston last, say average trail riding, 1996 yz 250. or is a re-ring needed every so often.

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I get 20 hours trail riding. My rings never get a chance to wear out so compression is still high. I get no chances to re-ring. The skirts of my pistons wear out. For the most riders, I would say 20-40 hours in a 250 but no more than 40 for anybody.

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20 hours? Oh. What's it look like after 100 hours?

JayC

Im Not dumb enough to let my piston last that long, I know the consequences of a worn piston, Skirt Smashing and then loosing bits in the bottom end, Piston Slap, Scoring cylinder etc etc.

I had a 96' Which only ever had 1 rebuild in its life and that was in 98'. I owned it from 2002-2008 with 0 maintenance, not even a spark plug. It always started 1 or 2nd kick. Just goes to show what some of these things can put up with.

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I don't see anything wrong. Since you've already started taking it apart, go ahead and throw a new piston and set of rings in it.

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Thank for all the comments,

i do have some questions as to how to prevent this from happening again.

Is this caused by running rich?

Do any need to work on re-jetting the engine?

Are there any long term problems that can cause damage to the engine if i continue to run how it is and just replace the piston?

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When was the last time the power valve was serviced?

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ive seen worse

+1 on the power valve service

i think ur runnin fine personally. carbon buildup only increases your compression ratio! hahaha

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I got the bike used about 4 months ago, i really have no idea when it was serviced last.

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I got the bike used about 4 months ago, i really have no idea when it was serviced last.

That being said..... I would put in a new topend clean the cyl., head & powervalves. After you put it back together run some good stroke oil & rejet if needed. Overall the pics don't look to bad other than some carbon build up & the studs needing some lubrication.

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