The transfer ports in large (90cc) horizontal Minarelli/clone engines, and even smaller high revving versions, have been mentioned as a point of restriction by 190mech for years and he has been kind enough to provide some photos that help to show why.
For a little background info, a few of us have tried to build 90cc+ engines using "standard" parts. By standard, I mean typical generic cylinder kits. Not the high end racing kits. These generally seem to make peak output no higher than 10,000 to 10,500RPM, while smaller engines may be able to rev beyond that with similar cylinder kit designs. I did have a 103cc for a while that would reach 12,000RPM regularly to achieve it's top speed, but that was only with near original sized pulleys in the CVT. Once I used an over range CVT, it was apparent that it peaked by 10,500RPM and the previous higher revs were needed by the more standard CVT parts to reach high speeds, but were not where peak output was made.
Here are a few pics of the transfer tunnels I sectioned on a 52mm Mina jug,note the tiny 50cc opening then it expands in hope for flow,but alas the tunnels have hardly any curve(vision a tea cup handle),so the mixture is badly restricted and improperly directed into the cylinder;
Here are some pics showing Minarelli cylinders and MX cylinders. It's pretty eye-opening. I believe John posted more somewhere, and if I ever find them I will post them as well.
Senna1Rossi: Thanks renagade281!
May 23, 2016 14:59:12 GMT -5
Fox: I don't really know how to say this but straight. I am Dave's Girlfriend Kellilee and bluntly and VERY SADLY he passed away early Tuesday morning. I know he would want ya all to know this. Thank You Brent for befriending my love he was very happy on here!
Jun 18, 2016 16:26:04 GMT -5
Fox: www.gofundme.com/29mgf6b8 I hope it is ok to pass on his gofundme page link. If not you will un-post it I'm sure. Thanks again all!!
Jun 18, 2016 16:31:18 GMT -5