wanted: cast iron 125 cyl

[Lew Mayer]

I'm looking for a used, even worn out,cast iron 125 cylinder suitable for boring out to a 152. I got one and when I had it bored we found a casting flaw right between two ports.
Ouch!
Lew

Lewis A Mayer

[john durrill]

Lew ,
 I think from what Doug has told me you need a 100 cc  cylinder to do the 152 kit.
 i believe he said that a 125 cylinder would go through the transfer ports if you bored it out for the 152 piston.
 Drop him an email amd make sure.
John

 

[Lew Mayer]

John,
I know you can use the 125 cylinder for sure.I just had the bad luck of finding a casting flaw. I'm not sure why they used the 100's later on. It may be they had more of them in stock. Doug says I can use either since there is no change in the ports for the 100's. So I guess I'm looking for either one. My machine shop just may not be happy to have to bore more out of a 100. Thanks for the help.
Lew

Lewis A Mayer

[Doug Wilford]

Lew;
I said if you are lucky you could use either one, and the ports are the same. but the 100 is cast larger and will leave more  thickness than the 125.   I do remember that there was more than one reason that we did not use the 125 cylinders for the 152 conversion.

 

[Paul Danik]

I was moving some NOS cast iron cylinders and decided to measure the outside of the cylinder that extends into the cases.  Both the 125 and 100 measure 64mm. It seems that if you bored either one to fit the 152 the remaining material would be the same on either one. The difference that causes the problem seems to be the angle that the skirt of the cylinder is cut on the 125 to blend into the transfer port.  It has a much sharper angle flowing into the transfer area than the 100 cylinder has. Hence when you bore the 125 cylinder you have a sliver of material left on the skirt in the area of the transfer port.  The 100 cylinder has  much less of an angle and also a smaller opening to the transfer, this would translate into having more consistant material thickness remaining after boring it out to the 152 specs. You need to have both cylinders to see the difference, but I would conclude that the 100 cylinder is better for your project. Hope this helps.

 

[Lew Mayer]

Paul,
 Thanks for that info. I know now a 100 is the preferred cylinder to get but I could use either.
Lew

Lewis A Mayer

[LINDEMAN]

Lew,I have a 100 cylinder,but I already bored it to std. 125 ready to install.I could get a piston for another 125 aluminum cylinder I have  to use on my project.I dont know how to calculate the expense.I would have a std. piston left over and would have to bore the other one.Might not be practical? I will check my piston/cylinder stock and keep in touch.Probably will be weekend.

 

[john durrill]

Lew,
 can you describe what gets the thin knife edge when you bore out the 125 cylinder?
 thin edges and not a good thing. Just curious about your project. chamfering any thin edges back to keep them away from the piston and the rings would sound like a way to get around that. that is if you have the room and enough material left.
John

 

[Dennis Jones]

Hi Guys

I have stock a 125 iron cylinder and one bored to 152 (not sure how it stared life). They look to be identical except for the bore. Where the transfer ports meet the bore on the 152 it is knife edge thin. Toward the front of the cylinder the bore actually moons into the transfer port. I had this cylinder on a trials bike that had other problems and when I had it rebuilt I had another 152 kit that was ready to go so I used it. I don't know if this info wil help or just make it more confussing.

Dennis Jones