Gearing for Triped Microcar V1 with Polini Kit

I have a 10:60 gearing right now, the Polini 80cc kit, stubby MLM Proma style pipe, VM20 carb, B8HS spark. Stock points ignition and timing. Stock clutch and springs. Previous owner made all the motor mods for the exception of the pipe.

Went around the block topping out 20mph with temps in 360s and climbing, motor over revving, crazy vibration. Maybe 10:60 gearing was okay for the stock 49cc setup. I need to re gear for the Polini and can get pretty much any size rear sprocket from 27 to 72. What would be a middle of the road gearing setup for acceptable acceleration and top speed? The V1 gearing chart floating around here won't apply to the Tri-Ped.

Re: Gearing for Triped Microcar V1 with Polini Kit

Overpriced Parts /

Need 50% more gearing to get 30 mph! So maybe 11x 42-45 gears as well as better springs in the clutch,

I love when people say stock timing? That phrase means nothing,

What what they really mean is untouched timing/untouched magneto not timing set to stock specifications in manual,

And with a kit timing has to be set to the low end of the stock timing specifications!

Lower timing, maybe a bit Richer jetting to get cooler temps though 360F if it was sustained temperature on long full throttle runs would be great!

I had kitted v1 general that I worked on (The guy just slapped a kit on it then seized it got another kit and he was seizing again so he finally brought it to me to tune)

Man that thing shot to 390 head temps on full throttle runs quick so I had to lower the timing (as well as richen the jetting a bit) to get to sustained 375-380 F head temps for mile long full throttle runs,

Initial timing measured well passed 22° before top dead center timing for it was unchecked and the points were jumping all over the place due to a rusted rough point cam,

V1’s kinda suck to service the magneto and Time/tune it because they have fan shroud and fan that you have to remove before you Service/set/reset/tune the timing that can take several times to do so to get a perfect balance of good power yet cool temps,

If I were you I would service the magneto, points, smooth and grease point cam and everything and lower the timing at least a few degrees if it’s in the 20° range to start,

But be prepared to remove shroud and everything a few times so you could have good power as well as good temperatures

Re: Gearing for Triped Microcar V1 with Polini Kit

yeah the polini kits are pretty good about staying cool with the fan shroud and everything, but on the micro car it has a lot more load on it than a moped so you gotta figure that into the equation.

they get really hairy/unstable above 35 mph or so... well i shouldn't say that, our gang has one but its pretty jacked up, wobbly forks, untrue rims, etc. either way just about any triped gets real hairy by 40, and they tear up clutches if you try to slip them, so don't plan on crazy high gears.

the other thing i noticed is that some of those tripeds have like home-made style gears that have a weird profile and mounting, you might not be able to find a replacement rear gear.

Re: Gearing for Triped Microcar V1 with Polini Kit

I converted mine to differential axle and have lots of rear sprocket options for the Peerless model 100 differential. My drive train is the least home made looking part on the trike.

It's a heavy tri-ped so I'll need a somewhat taller gearing ratio than the "ideal" one in the gearing chart (3.4 gearing ratio wouldn't be applicable) to get up and going quicker. With existing 10:60 setup it's crazy quick off the line but stalls at 20mph and starts overheating.

So you say go ahead and order up a few rear sprockets in the 40-45 tooth range and experiment?

I'm going to start a separate thread on timing. Putting the Ducati CDI in there. You can see from the photo my 6v existing wiring is held together with alligator clips for testing.

IMG_20190923_211022730.jpg

Re: Gearing for Triped Microcar V1 with Polini Kit

yeah! thats cool i remember seeing your build thread but i don't remember the peerless axle thing.

i just cannibalized a rear engine rider for the trans and a couple other parts and i was lookin' at that axle, perfect for a triped. Great ideer.

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