Setup: Holding Chainsaw Cylinder on Lathe?

[Chips O'Toole]

I got myself an Echo 501-P, which is a nice 50-cc chainsaw. I stuck a 16" full chisel bar on it, and I am planning to fiddle with it to increase the performance. I don't need to do this, but I thought it would be fun.

Sooner or later, I may want to put this cylinder, or one from another saw, on the lathe. I have seen people using shopmade aluminum mandrels for this. They shove them inside the cylinder.

I don't quite understand where they get the friction to turn the cylinders. If the mandrel slips inside the cylinder, I would expect the cylinder to remain stationary when the lathe is running because the parts would slip against each other. How are people getting cylinders to move with their mandrels?

 

[matthewsx]

Not sure if you’re going to be able to bore a cylinder with a mandrel inside. Maybe they’re cutting down the cylinder to increase compression.

Know this isn’t what you want to hear but my suggestion is taking your new oversized piston and the cylinder to a bike shop or one that works on snowmobiles and have them fit it.

I’ve built tons of small engines for paying customers so I’m not really guessing about this.

You could totally gear up to make this happen in your shop but it does take some specialized equipment to bore and hone for oversized pistons. If you decide to try it, find some trashed cylinders to learn on first.

JMHO,

John

 

[Chips O'Toole]

Thanks. The purpose is to work on the base, not the bore.

 

[matthewsx]

A shop made mandrel should give plenty of purchase for machining the bottom of the cylinder.

Are you planning on raising transfer ports?

John

 

[Chips O'Toole]

How does it grip the cylinder?

 

[Flyinfool]

You use an expanding mandrel it will grip very tight.

Or The cylinder could be attached to the mandrel by a screw thru the spark plug hole.

 

[RJSakowski]

Most of the small engine cylinders that I have seen have four bolt holes. Use them to mount the cylinder to a plate and mount the plate in the four jaw. Adjust for zero runout at the chuck and then check at the outbound surface, tapping lightly to get zero runout. Recheck at the chuck and adjust as necessary.

 

[Nigel123]

Most of the small engine cylinders that I have seen have four bolt holes. Use them to mount the cylinder to a plate and mount the plate in the four jaw. Adjust for zero runout at the chuck and then check at the outbound surface, tapping lightly to get zero runout. Recheck at the chuck and adjust as necessary

I got myself an Echo 501-P, which is a nice 50-cc chainsaw. I stuck a 16" full chisel bar on it, and I am planning to fiddle with it to increase the performance. I don't need to do this, but I thought it would be fun.

Sooner or later, I may want to put this cylinder, or one from another saw, on the lathe. I have seen people using shopmade aluminum mandrels for this. They shove them inside the cylinder.

I don't quite understand where they get the friction to turn the cylinders. If the mandrel slips inside the cylinder, I would expect the cylinder to remain stationary when the lathe is running because the parts would slip against each other. How are people getting cylinders to move with their mandrels?

Helping a friend out doing the same thing

Used a tailpipe expander to hold it and shim if necessary
made a plate with a bushing with set screws which fits in the tailstock to put a little pressure on the head
seems to work good taking small cuts feeding from the inside out

 

[RaisedByWolves]

How does it grip the cylinder?

I’ve done this on 1/4 scale race boat engines back when I had no idea what I was doing.

The cast aluminum is like chalk to cut so there’s not much pressure needed.

I was fortunate enough to have a cylinder with the plug parallel to the bore, so a bolt through the plug hole was sufficient.

This was for turning the fins off of the head for a water jacket and taking material off of the base.

You can lose height on the cylinder just by removing the gasket and using loctite 515 flange sealant.

Gets you .010-.015 depending.

 

[RaisedByWolves]

You use an expanding mandrel it will grip very tight.

Or The cylinder could be attached to the mandrel by a screw thru the spark plug hole.

This is best as the chrome in the combustion chamber is not as important as the chrome in the cylinder.

Scratch or chip that and you’re done.