152cc with Alloy?

[Frenfroe]

Is it possible to do a 152cc Six Days with an alloy cylinder? What is necessary? I have a 6A that needs a new topend, might as well make her a lot bigger while I'm at it.
thanks,
Frank

[Doug Wilford]

Anything is possible, but you are on a very expensive project to do so.   The present 125 liner could not be used, or overboared enough to fit the 152 piston ( 62.0 mm I think,someone please correct this if I am wrong.)  I am not sure there is even enough cylinder to take a larger sleeve.  At one time Wiseco made 60 over pistons that would work in the standard sleeve, but you are taking the risk of the lower rear part of the sleeve cracking or breaking off.  Best to buy a new sleeve and piston from Donny Smith and have Forest Stahl do the work.

[Frenfroe]

Thanks Dr. Doug! I didn't know if there were 152 sleeves ever available. But I could use a early iron cylinder, I think a 100cc was recomended, and mill an alloy head, couldn't I? The 6A is salvagable with just a new 55mm bore and piston. Looking for maximium low-end, figured a 152cc was the way to go for that.
Thanks,
Frank

[TGTech]

Frank,

   I also believe that you wouldn't be able to use any of the present liners, but I'm wondering if you couldn't employ some modern technology and have the cylinder casting itself hardcoated like today's cylinders? After all, that is all they are, is aluminum castings with a hard coat on them. You'd have to work on making sure that the port faces were chamfered properly though.

   If I were in your shoes, I think I'd contact one of the coaters and ask them about it. There is Millenium Technologies and Langcourt Ltd. that I am familiar with, but I'm sure that there must be other companies. There is also the issue of the size of the bore without the liner in it.

Dane

[Frenfroe]

I've never pulled a Sachs sleeve, others that I have had the outer sleeve as the inner wall of the transfers. The transfers were only grooves once the liner was pulled out. If the Sachs is the same, some liner would have to be fitted. The wall thickness of the liner is important to prevent breaking at the spigot. I've opened the throat on a TL125 before to accept an XR200 cylinder to make a 168cc bigbore trials motor. A lot of people use a stepped down sleeve and a CB750 piston, the thin spigot will often crack, even at 145cc.

I've never used one but the new ceramic coatings are supposed to never wear. One of those companies has their US location not too far from me. That would be a possibility.

Could it be done with an iron barrel? Any problems with heat? Is the porting similar to the alloy "A" barrel?

Frank

[Paul Danik]

I bought a 152 Sachs alloy topend at VMD a few years back.  The unit had been completed many years back by a machine/motorcycle shop for a customer and had never been picked up. The cylinder had also been fitted with a reed kit. A larger sleeve appeared to have been installed to be able to get the proper bore.  So to answer if it is possible I would have to say yes. I no longer own that topend kit so I really can't help you much further.
Paul