View Single Post
Old 05-03-2011, 05:44 AM
DaveC's Avatar
DaveC DaveC is online now
Motorized Bicycle Elite Member
Join Date: Jul 2010
Location: Boise, ID
Posts: 967
Default Re: engine spitting oil

Anyway, My Boy Go Fast motor called for 12.5 lb/ Others here have said as much as 18 which is high. I went to 15 lbs when I put on the Hi Compression Puch head on SBP studs. Plus I tapped the block to make sure the threads bottomed.

When I torqued to 12.5 lbs I went up in 2.5 lbs stages, 2.5 to 5, 5 to 7.5, and so on until 12.5 was reached, rode for 100 then re-torqued to 15 cold.

I'll be pulling the head today to put it on a new 49cc. I really want to look at the mating surface. Stock there's a raised ring around the combustion chamber that crushes when torqued due to the fact it's made from "dead soft" aluminum. It's very soft so it does crush but the ring feature does not exist on the Puch head, it's just flat surface to flat surface. Plus that will give me the chance to get out my combustion chamber measuring stuff and find out for sure the volume of the chamber so an accurate compression ratio can be determined. I've been running under the assumption that the C/R is around 13:1, pretty high . On the 49cc motor it's supposed to run at 11:1 or so but I really want to know.

I'll be rebuilding the 66cc with guidance from Daniel Maia's and jaguar's threads on rebuilding and porting, including epoxy intake product MADE for intakes to change transfer port angles. You can look a Puch and Morini bottom cylinder gaskets and see the port angle is different than the HT one.

oops, it's early and I ramble
Reply With Quote