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New piston?

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Hey guys so still new to the 2 stroke club but have been reading a ton about general maintenance, etc. So long story short, bought me a 94 cr250. not sure how many hours are on top end but starts on first kick always and runs like a champ, had some extra time today so decided to take a peek at the cylinder and piston as a general inspection. Does the piston look good enough for a couple more hours of riding or should I just do a top end now and not risk anything in the future, thanks.

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I agree with  Ayeecole, I also noticed some pitting on the top of the piston. But ya never know, she could be good through the entire summer; would be a fun winter project.

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Depending how reliable you want to make it or, how much you want to invest in this bike,

with the wear shown on the cylinder it's probably out of spec and needs re-plating.

(measuring it to see if it's out-of-round as well)

 

A new piston will simply wear out sooner if installed in that bore

and the ring won't seat/seal properly due to the lack of crosshatch.

Edited by mlatour
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damn, was not expecting this news haha. Im just trying to make it last for summer but also don't want any problems with it. Here is another angle of the cylinder, are you sure it would be replating? and with what you are saying about it being out of spec would it be better to just buy a 01 cylinder new for about a 100 more or so if I am going to get it replated?

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Your pics only show the cylinder, remove the exhaust and have a peak at the piston's skirt.

Depends how much you want to invest in this old bike, has the bottom end been rebuilt, suspension refurbished etc ?

 

Unless for sentimental value, IMO anyone should reconsider planning major investments in bikes that are older than 8-10 years,

not that they're not the latest technology or performance but, parts availabilty will eventually catch up with you.

By the time your done, you will have spent the same as buying a bike 10 years newer.

 

Having a 500$ bike with 2000$ of repairs sit in the garage because you can't locate a older / discontinued part in mind.

 

If you simply trail ride this old CR250, (no high track use)

if no deep gouges are felt, just clean up the cylinder with a green ScotchBrite pad. (don't attempt to hone it)

 

Edited by mlatour

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Thanks for your reply. I recently serviced the forks and rear shock, and bottom end is rock solid with about 50 hrs or so on it. I will scotchbrite the cylinder and will continue to ride it (trail ride is what I do). Only plan on putting a few more hours on her until the summertime when I can really ride. Once summertime hits I will send the cylinder off to millennium for a replate and match to a pro x piston kit, assuming nothing has grenaded haha.

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Your bikes sounds in overall decent shape (bottom end, suspension)

as mentioned trail riding isn't much of a strain versus MX track riding.

 

but still have a look at the piston's skirt thru the exhaust port,

that may decide if you keep riding it a bit or, preventatively tear it down / refurb it now

(preventing a 'grenade' to take out your bottom end with it)

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Look for deep scratches, or un-even wear / shiny spots.

You'll perhaps see some dark blow-by past the rings.

 

But from your first pic showing the exhaust side of the cylinder, it looks okay,

no erosion on the edge of the piston from running too lean, no un-usual wear marks etc.

 

The wear on the cylinder's intake side could be from debris / dust injestion, bad sealing air filter.

 

Edited by mlatour

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Actually not much blow-by at all but, unfortunately lots of wear.

Not sure how long I'd keep running it, especially if it's a cast piston.

 

Pretty clean exhaust port for a trail ridden engine, what premix / ratio ?

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