Kitted A3 Update

Heres an update of my newly kitted 1991 Tomos Golden Bullet A3 with 64cc Airsal reed kit, vm20 carb, 17.5 idle jet, 180 main (soon to downjet to somewhere around 140-155), needle on richest (bottom notch for now its still winter), estoril sidebleed pipe. Bike still has stock gearing (26/22). All I can say is wow what a difference. Bike accelerates like mad off the line and riiiips from 0 to 45mph. First gear is just insane. Stays in first until 20-22mph and power shifts (literally jumps forward into 2nd) and keeps on pulling hard all the way to 45mph. Fastest and most fun moped off the line I've owned. Can't wait until spring to see how she pulls after getting the jetting dialed in. Still has the 180 jet the vm20 came with but I've picked up an assortment of Mikuni jets (140-155) to tune it in.

Re: Kitted A3 Update

Nice! Sounds great. A3 are really underrated motors. Once you get it dialed in you might want to bump up the gearing a little to keep the rpm down and keep that bushing alive but 45 is pretty damn good for that setup.

You can use marty's gear calculator to figure out your rpm, I would say keep it under 9k, usually that kit doesn't really make much power above 9k so gear to go your top speed at about 8500 and it should be safe.

Re: Kitted A3 Update

Thomas Peffer /

I used Marty's gearing calculator and yes from here on I will keep the rpms under 9k which translates to actual speeds of 40mph or less. Most of the time my riding is between 20-35mph during break-in of the new kit. Also I'm running a good premix of 40:1 to protect that bushing

Re: Kitted A3 Update

But he is saying if you regear you can keep your speed while keeping the RPM's manageable.

Also practice controlling your shift. If you let it jump into the second gear real hard all the time it will start breaking things quick. And it is difficult to find replacement parts for those engines. Which is why they are not as popular as an a35 which you can buy OEM parts to rebuild from the ground up. You will start learning the feel of it just before it shifts. Just turn off the throttle while it shifts then gun it again as soon as it has made the move to second. You will not lose any speed doing this but will save life on your engine.

Thanks for posting an update!

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account