Look at my Cylinder walls

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Moto

Moto

Member
Jan 7, 2012
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San Francisco, CA.
Well I took off my cylinder today. Ive been running a puch head and with an otherwise stock setup, needle bearing engine. I was a little disappointed with what I found. When I first got the engine it had a bunch of crap in the cylinder, metic shavings and such, so I cleaned them out. The piston had a bunch of little divits in it, same with the cylinder head mating surface. Anyway I probably have 200 miles on my engine now and I wanted to check out the cylinder. I was a little bummed out by the cylinder scoring but the rest of the engine look really good.

Here are some of the nicks of the edge of the piston: PS pics get big when you click them


That part is not so bad, heres what Im worried about:






These scores come out a little more exaggerated in the pics, but I can definitely
feel them with my fingernail. So what do you guys think-new cylinder? Dont worry? Motodnut
 
S

SpeedWizzard

New Member
Mar 9, 2012
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Those scores look pretty deep, you could keep using the current piston and cylinder, probably won't be nearly as powerful as it would be, you could re bore the cylinder and get a new piston or you could probably just go the cheapest route and buy a new piston and cylinder or even a complete engine and keep the bottom end for parting out. it's up to you but I would personally just go for the new engine.
 
biknut

biknut

Well-Known Member
Sep 28, 2010
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It's easy enough to change the cylinder and piston, if you can find the right ones.
 
Bikeguy Joe

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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SpeedWizzard said:
Those scores look pretty deep, you could keep using the current piston and cylinder, probably won't be nearly as powerful as it would be, you could re bore the cylinder and get a new piston or you could probably just go the cheapest route and buy a new piston and cylinder or even a complete engine and keep the bottom end for parting out. it's up to you but I would personally just go for the new engine.
Click to expand...
You can not "re-bore" these cylinders.

That looks like something got loose in there and made that damage. Is your piston alignment pin still in the piston?

If it runs, leave it alone for now, but that's pretty bad.
 
Moto

Moto

Member
Jan 7, 2012
403
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San Francisco, CA.
Thanks for the input, there was metal shavings and crap in the cylinder from manufacturing that made those markings on the piston, Im definitely getting a new cylinder. The needle bearing and wrist-pin are in really good condition, so nothing from that got into the cylinder. It still does 30mph. brnot
 
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skitchfish

Member
Oct 27, 2010
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Michigan
I had one about that nasty and it ran fairly well for along time. Not that it has anything to do with anything but i am interested to know what oil and ratio you are using. I just like comparing cylinder and piston top pics for my own knowledge.

Those are nice pics, wish i could see one of combustion chamber on puch head. Are the keeper pins in the ring groves on piston still intact? Is that a BGF engine? Thanks for the pics and good luck.
 
Greg58

Greg58

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May 1, 2011
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Chances are if you found debris in the cylinder you had more in the crank case that got drawn through the engine as you ran it. If and when you replace the piston and cylinder it might be a good idea to remove the crankcase and wash it out, we had to do that a lot when rebuilding engines for motocross bikes that were ran on as lean a mixture as possible.
 
Moto

Moto

Member
Jan 7, 2012
403
15
18
San Francisco, CA.
Hey skitchfish,
Im running echo power blend full synthetic at 26-1. It's a motovelo engine. The bike is back together, and running well.


Here is the combustion chamber:



can you say niiice?!?!

P.s here is the incredible P.O.S. low compression head that came with the kit with the same divits:





runs good! Not too worried but still gonna replace the cylinder.
 
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JonnyR

New Member
May 13, 2012
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i would replace the piston and also clean out the crank case since that's probably where it came from thats some bad damage. also what kind of power increase do you see from the head?
 
S

skitchfish

Member
Oct 27, 2010
222
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Michigan
Moto, Thank you for the excellent pics, Thought maybe she got reeally hot at some point from detonation but your awesome head is pristine. Thats cool your still rolling, not to jinx you but you can replace your top when you smoke your bottom.LOL
 
Greg58

Greg58

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May 1, 2011
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Mark you will need to have some measurements before ordering a piston, some members have had problems with piston pin placement. It would be a good idea to mic the distance from the top of the piston to the pin, having this info when ordering may save you from buying wrong parts.
 
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