60 mm pistons?

[Carl Hill]

While sorting through my assortment of Penton pistons I came across 2 new 60mm pistons with extra rings. They have an "x" stamped under the crown.
For 152 possibly???
Any 152 experts out there?

[thrownchain]

Yes 152 cc motor.

[Carl Hill]

Anybody need one (or two)?

[KJDonovan]

Carl,

I may be interested - Can anyone tell me what cylinder I would need to mate one of these with 6B bottom end?

Thanks,

Kevin

[Larry Perkins]

It only was used with the old cast iron cylinder.  I am told it will not work with the alloy ones.

Larry P

[Paul Danik]

I had an alloy top end that was a 152, so it has been done.  I think the only determining factor in converting an alloy top end into a 152 is how much metal there is to work with on the liner. I can't think of any other issues as long as you don't use the Yamaha 305 piston that requires the base of the cylinder to be machined to make up for the wrist pin location on the Yamaha piston. Another issue is the wrist pin on the Yamaha piston has a larger diameter so the early aluminum rod with a top end bushing had to be used as the bushing could be reamed out to fit the wrist pin, obviously the steel rod had a needle bearing.

What make are your pistons Carl ?

I think one of you guys who works at boring cylinders over the years would be able to measure the outside of the liner and then determine how much meat would be left after boring it out to accept the 152 piston and give an educated guess if it would be to thin. Possibly you might not be able to get many over bores as it might get pretty thin, but that would probably never be a real problem.

I never used the one I had as it went to a new home on the west coast, if I remember correctly. I would be curious to hear what you experts have to say on this matter. Maybe it is a bad idea, maybe not. Might be a good way to use up a supply of standard size 152 pistons and worn out alloy cylinders.

Paul

[Larry Perkins]

Paul are the 60mm pistons that Carl is speaking of the Ymaha 305 pistons?  If so are you meaning one like them but smaller pin?  Just trying to follow and I am certainly not an engineer.

Larry P

[Paul Danik]

Penton eventually had pistons made up by Weisco that had the same size wrist pin and pin location as the Sachs piston which made the conversion much easier. I think they might have been labeled as Hi-Point at one time as well.

A little bit of info on finding an early conversion at swap meets and such is the fact that many of the early conversions that Penton did, and if I am not mistaken exchange conversions that they sold as well, would have the Sachs hi compression head on them, so...., when you find a cast iron cylinder engine topped by the Sachs hi-compression head, take a good look at the base of the cylinder to see if it has been machined thinner. You can usually tell by how little metal is below the cast in number on the cylinder base vs how much metal is above it. Found a good number of early 152s over the years that way.

I am not sure what pistons Carl has.  

Paul

[Larry Perkins]

Got it! Thanks!  Carl can you check and see if the pin size is the same as a Sachs piston?

Larry P

[Carl Hill]

I will check it out. Stay tuned...

[Carl Hill]

OK, here is what I found. The overall height and contour of the piston is the same as 125 Sachs. The wrist pin is 1mm larger. The distance from the pin to the piston crown in 3mm less. So... Yamaha? Was this a common mod back then?

[Carl Hill]

So I dug out an old Hi Point catalog and it shows the 152 kit for "Mudlark, cafe MX, and 68-69 Penton ". Also lists 2 different wiseco pistons for 152, "old style" and "new style".
With "2 thin compression rings" which my pistons have. So I am thinking now I may have the "old style "  wiseco pistons.

[KJDonovan]

Carl,

I may be interested - Can anyone tell me what cylinder I would need to mate one of these with 6B bottom end?

Thanks,

Kevin

[Larry Perkins]

It only was used with the old cast iron cylinder.  I am told it will not work with the alloy ones.

Larry P

[Paul Danik]

I had an alloy top end that was a 152, so it has been done.  I think the only determining factor in converting an alloy top end into a 152 is how much metal there is to work with on the liner. I can't think of any other issues as long as you don't use the Yamaha 305 piston that requires the base of the cylinder to be machined to make up for the wrist pin location on the Yamaha piston. Another issue is the wrist pin on the Yamaha piston has a larger diameter so the early aluminum rod with a top end bushing had to be used as the bushing could be reamed out to fit the wrist pin, obviously the steel rod had a needle bearing.

What make are your pistons Carl ?

I think one of you guys who works at boring cylinders over the years would be able to measure the outside of the liner and then determine how much meat would be left after boring it out to accept the 152 piston and give an educated guess if it would be to thin. Possibly you might not be able to get many over bores as it might get pretty thin, but that would probably never be a real problem.

I never used the one I had as it went to a new home on the west coast, if I remember correctly. I would be curious to hear what you experts have to say on this matter. Maybe it is a bad idea, maybe not. Might be a good way to use up a supply of standard size 152 pistons and worn out alloy cylinders.

Paul