Minarelli Transfer Port Cutaways & More Info
Dec 3, 2017 8:45:31 GMT -5
ryan_ott, aeroxbud, and 6 more like this
Post by 90GTVert on Dec 3, 2017 8:45:31 GMT -5
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.
Now, some high end racing cylinder kits use a base spacer and adapt more MX-like cylinders to standard Minarelli cases to help with this problem. Here's one example :
scootertuning.ca/en/cylinders-high-end-77-100cc/17065-cylinder-kit-stage6-r-t-95cc-14mm.html
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.
Here are a few pics of a 90cc case and YZ80 interface puzzle;
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.
Now, some high end racing cylinder kits use a base spacer and adapt more MX-like cylinders to standard Minarelli cases to help with this problem. Here's one example :
scootertuning.ca/en/cylinders-high-end-77-100cc/17065-cylinder-kit-stage6-r-t-95cc-14mm.html
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.
