lathe boring a cylinder

[Body Cast]

I want to get one more season out of my sons '94 PW80 before upgrading. I could really use the time to save $. The thing is, I hear some aweful piston slap (i think). It is a pretty loud rattly sound in the top end and has been that way for a while now. I am assuming that it will need to be bored for a next size up piston to fix. I will take it apart soon and check it all out. I am an experienced job-shop machinist(but not experienced with engine machining) with tools at my disposal and was wondering if I can bore and hone the cylinder myself on a lathe or if it would be more trouble than it is worth. I suppose I could do it on a mill as well but figuered a lathe be less work. I live in the boonies and don't know where there is a good shop locally for this...plus I don't want to spend a fortune on a worn out pw80.
Or, what are the chances that just a piston, rings, and hone would quiet it down enough for one more season.
Any experiences/tips/advice would be appreciated.

 

[Ol'89r]

Or, what are the chances that just a piston, rings, and hone would quiet it down enough for one more season.
Any experiences/tips/advice would be appreciated.

Body Cast.

You may want to check the piston against a new one first. Usually, most of the wear is on the piston. Mic it near the bottom of the skirt from front to rear. Also, mic the cylinder bore and check for taper in the bore. Check around the exhaust port since most of the wear in the cylinder will be in this area. Your service manual will give the proper specs.

IMO,If you have an automatic feed on the quill, I would use the mill with a boring bar. If you use the lathe, you would have to carve out a holding fixture for the cylinder rather than clamping the cylinder in the chuck. Don't clamp the cylinder skirt in the chuck even though this looks like the easiest way to do it. Or you may just want to ship it out to Eric Gorr. Check out his link on the left side of the page.

Good luck. :cool:

 

[Body Cast]

Thanks for the help. I will check it out and if I can get away with just a piston ect. then that is what I will do(hopefully). If the cylinder looks too worn, I think i will do the work myself. I can make a fixture plate no problem. If I take like an 1.5" thick round piece of aluminum(we have a bunch at the shop), and bore a center bore for the cylinder skirt, and put a 4 bolt pattern to hold it down, and face this in the lathe for perpendicularity before mounting and indicating the cylinder, then it should work ok then ..right? I would have just chucked it up with in a 6 soft jaw chuck if you hadn't told me not to. Is it too easy to compress? I could make a torque plate as well if it is neccesary. I would do what you said and bore it in the mill but our boring heads are ancient and suck. Seems to me, I would need to make some kind of fixture anyway. I can use the CNC lathe and get the precision easily.
Sending it to Eric Gorrs sounds tempting but I like projects like this, and really dont want to spend much on a bike that I won't own for long and I think I should be able to do it. Plus, I get the feeling he is real busy and I hate waiting. thx again

 

[Ol'89r]

Body Cast.

That will work fine. :cool:

A six jaw chuck would work in the lathe but, you would have to be very careful not to chuck it too tightly or it could distort the sleeve and give you a false reading. Making a fixture to bolt the cylinder to would be a better way to go IMO.