neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Apr 3, 2020 6:14:44 GMT -5
Hey guys. Started rebuilding this chinarelli the other day after finally getting that stubborn engine long bolt out on my other post haha. . I’ve got the old stage6 streetrace 70cc cast iron cylinder. Piston was worn out with vertical scratches and some are deep enough. Have ordered a new piston kit(pin+bearing, rings, gaskets). Cleaned cylinder head. However when cleaning the cylinder barrel itself I noticed that there are some vertical scratches which doesn’t look deep but can feel it with my fingernail. Can this scratches still be fixed by honing? I am really tempted to scuff it with fine grit but i stopped myself as i might just ruin it for good. Will post pics of it. Thanks
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neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Apr 3, 2020 6:18:12 GMT -5
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neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Apr 3, 2020 6:19:31 GMT -5
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neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Apr 3, 2020 6:20:00 GMT -5
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Post by geoffh on Apr 3, 2020 9:33:15 GMT -5
Neogie,hold off until one of the more experienced guys helps out,but some info they will need.some pictures of the piston may help and how "worn out" and where will help.the diagonal lines in the cyl are there by design and should feel like a finger print the vertical lines are the problem,are they scratch able.What do you do with the scoot hobby? or lifeline transport,makes a difference on decisions.
Geoff
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Post by Zino on Apr 3, 2020 21:23:46 GMT -5
You might be able to lightly hone out those verical scratches if they are not to deep .
If they are real deep you would have to go up a size in piston becuase you would be moving from honing to boring .
If you are going to do that raise your exhaust port a mm or so and polish it and match it to your exhaust pipe .
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Post by Zino on Apr 3, 2020 21:34:22 GMT -5
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neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Apr 4, 2020 1:36:07 GMT -5
@zino18, it’s not deep but i could feel the scratch when i run my finger nails. Will try to buy some honing tool and see how it goes.
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Post by Zino on Apr 4, 2020 6:17:54 GMT -5
Groove equals blow by
It might be tolerable but if you are going go to all the work of reringing and a new piston .
Check with a small local machine shop .
A couple of 20 dollar bills or 12 packs of beer might also get it honed out .
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Post by 190mech on Apr 4, 2020 9:19:28 GMT -5
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neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Apr 6, 2020 0:46:00 GMT -5
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neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Apr 6, 2020 1:00:47 GMT -5
Have i hand honed it right?😂 Should be ready for a new piston and ring?haha. . i cleaned the cylinder with easyoff oven cleaner which worked really well and i managed to get rid of the aluminum sticking to the wall with a little help of scotchbrite. Can still see the vertical lines in the pic but it’s definitely smoother now and can’t feel my fingernail on it. Then hand honed it with a 240 grit sand paper which is what i have in hand. My greatest fear is making the diameter bigger on the cylinder with hand honing but it shouldn’t right and i should be safe?😆
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Post by 190mech on Apr 6, 2020 5:31:06 GMT -5
It looks like a runner to me,,Remember that a tight ring seal is only needed from TDC to the top edge of the exhaust port..Make sure its cleaned well of the sanding residue,an oiled white paper towel should come out clean when the bore is wiped,if not,clean some more..Good Job!
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Post by Zino on Apr 6, 2020 7:52:47 GMT -5
Nice work
Good pictures for the next guy to see the repair
Get her on the road .
Its scooter season .
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neogie
Scoot Enthusiast
Posts: 142
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Post by neogie on Apr 7, 2020 3:52:23 GMT -5
Thank you guys for guiding me with this rebuild👍🏻 Good learning experience for me. Just waiting for my new piston kit to arrive. Will update once it is running😊
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