Thought I'd make a thread about this build as many questions have been asked about it..It started with my desire to build a better Minarelli race engine.After trying to mod the existing design it was clear the basic engine would never achieve my goals.The Minarelli scooter engine is a 'utility' engine designed to move people and not much more..No extra material is built into these light and fragile engines..My "Dud pile" grew bigger as my failures increased.An earlier build was a BWS 100 52mm crank wedged into a Mina case with an aluminum plate welded to the cut down case flange to accept an RM125 cylinder..It ran strong till the thin cases split from the increased power,(more stuff in the "Dud pile).After that I decided an alternate method would be to graft an existing proven MX racing engine to a scooter CVT system..After all a Harley among many others have a separate engine and tranny..Sooo,a new quest was on!Find an engine with a right hand ignition system with good parts availability,,The European MX ers were RH mag in the 80's,but after much searching I found Honda and Yamaha switched to RH mag for several years in the 80's too!I found a complete 1983 YZ125 engine on Ebay for a good price and that started the project,,Now I had to figure just how to make this idea work..Here is the YZ motor split for inspection;
Gearbox had to go,had to be CVT;
Drive side machined ;
Sawed the Mina crankcase off;
Mockup of final configuration;
More to follow..
Last Edit: Sept 22, 2013 15:54:26 GMT -5 by 190mech
Next steps,,Had to center the new crank in the exact same position as the Mina crank in order to use stock CVT parts.Fabed up a quick and dirty plate using another old Mina longblock I had,then I bolted it to the CVT cover on the project engine;
Then I had to simulate my 1/4" aluminum plate that was to be welded so I used a piece of 1/4" plexiglass which allowed me to see all areas that might cause problems and locating mount points were easy to find;
Fabed a matching plate from 6061T6 and TIG welded it on,then started to find good mounting areas;
Thanks for posting up some pics and info for everyone John. Way too badass to not share. You know you're making some power when a stretched out sprinter with a forward lying riding position needs a wheelie bar while piloted by a dude that likes wheelies.
Post by dennis5150 on Sept 21, 2013 19:00:13 GMT -5
This is what you do when you can't find what you want ! I've done this kind of thing many times, I have huge respect for people who think outside the box and make an Idea happen. Go ahead say it can't be done !
Last Edit: Sept 21, 2013 19:01:43 GMT -5 by dennis5150
Thanks Guys!Its all just a big experiment so if it blows tomorrow,off to the "Dud Pile"!After getting it running and doing some test runs ,the thought of using a stock 1983 MX cylinder(30 years ago!!),how strong it runs,I just wonder what a 2010 cylinder would run like??Maybe next year.. Can post more build details if you all are interested..
Post by kevin55950 on Sept 21, 2013 19:16:49 GMT -5
For sure we want details
John, your fabricating skills are just crazy! That's the first build like this I've seen, and it's very well made. It's not just fitting example a mina hori cylinder on a minarelli vertical block, it's something totally unique! I hope for you it will last, and that it will run stronger and stronger. There's so much time invested in your build. Can't wait to see it race
Scootertuning.ca official seller!
103cc (in parts) 2004 Bw'S sport with custom made body
2000 Yamaha Jog, trench cut zuma case with 90cc MVT engine kit & more.