Post by aeroxbud on Aug 30, 2021 13:04:41 GMT -5
Parts are hard to find and pricey, but are available for the Keeway 4t scoots like F-Act 50. I've been able to find some here in the US and mostly Europe. Here's a link en.50factory.com/XNUMX-engine-crankcases-XNUMXqmb
Forwarding...If you need a crankshaft be prepared to pay $400 US!! I need crank bearings but have to get a new crank to get them.
The 137qmb has a 46mm stroke and 37mm bore where a 139qmb has a 41mm stroke and 39mm bore. You can get a 44mm stroker crank for the 139qmb which with a 52mm bore (same bore as 125cc) will give you 95cc's. I'm going to try to take a 137qmb connecting rod, because it's longer, and install it on a 44mm stroker crank for a 139qmb and use a piston with a shorter compression height. This would decrease the rod angle, increase the rpm range and spin up quicker. I'm a motorcycle mechanic and I've been racing all my life. Making horsepower is what I do best. I have a couple 50cc scoots that I've built up and they are fast. Matter of fact I'm on vacation this week and I'm about to tear down my 52.4mm bbk engine and install a 44mm crank. I was riding last week and the crank broke sending the flywheel across a ditch! It was turning over 12,000 rpm and running over 60 mph when it broke and tore the ignition pick up and blower cover off the engine!!
If I can answer questions or help anyone feel free to ask. I look forward to helping out when I can.
Welcome to the forum.
That sounds like an interesting project a lot of people would like to read about.
Please start a build thread, and post your progress.