Super Rat cylinder

[gilligan98]

One of the project bikes I just got had a seized up motor. The cylinder has a small gouge in the wall. Can this cylinder be sleeved or bored? It has a marking of .060 on the top of the cylinder.

Edit: Looks like this may be an Ace 100 motor. The left engine half number is 92-1001.

[olddogs]

A super rat cylinder has 4 intake studs, an ace cylinder has 2. I would have the cylinder measured, 50 mm would be stock. The oversize is usually stamped on the piston crown, not on the jug. You can get pistons as large as 80 over. An ace 100 cylinder is not rare and would not be worth any extra effort beyond a simple cylinder bore job. A super rat cylinder may be worth some extra machine work. They are becoming scarce. As far as the engine, a p code is ace, an m code super rat. It is stamped on the upper corner of the right case half.

[gilligan98]

It does have a 4 stud intake. There is no case marking on the right half. The pictures attached show the gouge and the cylinder marking.

[Bullfrog]

That looks like a pretty nasty gouge!

The marking does not indicate +.060". It is a "size class" mark which was stamped on the cylinder prior to engine assembly at the factory. The "size class" of the cylinder was used to aid a factory worker in selecting a proper "size class" of piston such that the proper piston/cylinder clearance would be achieved. These "size class" markings allowed the factory floor workers to assemble engines without having to take a time out to measure the bore and the piston.

Ed

[gilligan98]

Thanks Bullfrog. It does look like the gouge is deep. Can this cylinder be sleeved or should I just look for another?

[Bullfrog]

While it could be sleeved, it may not need to be sleeved. Only the person doing your boring work can answer that question. I surely can't answer it by looking at one photograph.

It could be that the cylinder is still standard bore -- not likely, but it could be. You won't know that till you accurately measure the bore diameter. If it should happen to be standard or .010" over, there is a lot of "meat" available for cleaning up that gouge.

So you need to develop a bit of precision information before you can reasonably decide what to do with the cylinder.

Ed

[kingdve]

Just for info I have seen and done useing JB Weld to fill gouges in cylinders , clean it good with some thinner and spread it in nice and smooth then a light hone ... know of a Polaris snowmobile cylinder done years ago its still in there

[Bullfrog]

Was the JB Weld in a portion of the cylinder swept by the ring(s)?

Ed

[racerclam]

Jb weld will soften in time from gasoline. There are better choices , BUT only use epoxy below exaust port . And if the gouging is below the top of the exaust port doneven worry about it as it wont affect compression.

Rich

[racerclam]

Ok I just went back to the picture , I guess its in the compression range noy good ! Rust pocket ?

Rich

[gilligan98]

The piston was rusted in the cylinder. I will be taking it to a local machine shop for evaluation.

[kingdve]

yes it was , the Polaris snowmobile was along narrow gouge far as I know its still n there and running fine , buddy of mine did it and peaked in with a small light a few times its since been sold ..