Just picked up a Hobbit and when stripping it down I found the piston like this. Comes from a DR kit and the barrel and other side of the piston look spotless. I can barely feel the marks with my finger and there is a slight chip by where the rings sit.
A replacement piston here in the UK is $60 so I'd rather save the money but of course don't want to create more harm than good. Should I just stick some new rings on it and go? What do you guys reckon?
In my opinion it can definitely be re-used, but I would take some very fine grit sandpaper to clean it up, and knock down the slight chip
Thought it would be ok, just reassuring to get another opinion. Will have a go at cleaning it up, thanks
It’s fine. Just smooth down any sharp edges
Edit: check if the pin is snug in the bore. Sometimes they get loose and then it’s time to replace (edited)
knock down any high spots, you can test by orienting the piston and dropping into empty cylinder. Drop test. Also, Make sure the rings are gapped and move freely.
Mix 40 to 1 and go slow. That piston will seize again.
would make a good paper weight . if the cylinder is good then grab a replacement piston , also inspect the crankcase for metal
I'd run it, I dont think it's gonna be the weakest link. However, it IS a weaker link. so maybe that's your next failure point.
My bigger concern is why - that's debris. If it was a piece of metal from the ring, your rings not OK, if it was a piece of the clip, or a ring pin, then it's not OK. maybe it was a piece of the reeds. did dirt get in? If you can't find where it came from it'd be pretty skeptical that there's not more debris, porobably skeptical enough to rebuild it and make sure theres no other grit in there that's just gonna wreck it a mile down the road
I ran a piston that was a lot worse than that for years .
It had seized , hard . I just smoothed it , cleaned it and ran it .
And , I am not an easy rider .
Decided to run it after cleaning it up a bit, got the new rings to sit nicely and I reckon it will work fine. I split the crankcase because I wanted to replace the crank bearing anyway, lo and behold I found two chunks of piston ring floating around in there, but nothing else and no signs of damage. Thanks for the advice.
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