> Kelikaku קוטין wrote:
> That image looks bad - but not the worst it could be. Lightly honing,
> and taking another photo will show if there are any imperfections in the
> bore. One section in your photo might be dirt or might be a
> crack/casting error. With only 400 miles on it your components should be
> fine, not impossible if the piston and rings are damaged but they look
> good in the photo.
> Light honing, and light sanding with a fine grit (#300 or higher) of the
> piston till you can see clean metal. You need to get that combustion
> chamber clean, put it back together, then see if the problem duplicates.
> When you hone it, you don't go crazy, just get the honing tool in there
> and make several passes, it just needs to look clean inside, being
> careful not to open up the bore any more than needed. When you hone it
> you're also wearing out the cylinder. EDIT: with only 400 miles on it
> you might get away without even honing, just using wet/dry sandpaper
> that you're using on the piston should also do the trick.
> If you have a wire wheel on the bench, that might be enough to clean up
> your piston, and a drill mounted wire wheel could do the trick for your
> cylinder. Probably before you start sanding, try using a wire wheel and
> take some photos. If you can get everything clean and you can see clean
> metal with a wire wheel it's possible that might be all you need. Start
> with a wire wheel before you start honing and sanding. Make sure
> everything is absolutely clean before you put it back together. If you
> do it take photos with similar views and post them, if you can.
> Also, did you check to see if the rings are loose on the cylinder? They
> should flop around slightly. If they're stuck or too tight, they need to
> be removed and the slots need to be cleaned out. You may want to do that
> anyway, and when the rings are out, you should lay them flat and take
> images of them. They should be of even width all around. If there are
> thin spots, they're worn out. With only 400 miles on them it's likely
> that they're almost new.
> If you pull the piston/cylinder and put in a 70cc kit, you have an
> entire project on your hands; changing the carburetion, the exhaust, and
> other stuff is going to come into play.
> Just doing some simple maintenance on a 400 mile engine should be both
> easier and all that you should have to do, but putting a bigger cylinder
> in will be a huge project comparatively. I'm just trying to give you
> some perspective. Comparing hours of work to weeks of work.
Ummm...I absolutely would not use a wire wheel on a piston or the bore. The wire wheel is steel and the piston is aluminum. It will chew up that shit so fast. Can you put the piston in the cylinder and push it through with no problem? I have a cylinder here that looks fine but when I push the piston through it gets hung up at a point and gets real tight.