I've rebuilt an old Kazuma Meerkat 48cc from what turned out to be little more than a skeleton I bought on a whim. Engine seems to be a KZM139FMB?

It runs great now, on the bench & I'm nearly ready to let my lad loose on it.

I'm a bit confused by the gearing though, can anyone tell me how the gears on these quads work?

Looking into the hole above the engine's drive sprocket, at the gear position indicator contact, with the plastic cap off, clicking the gear pedal 'down' repeatedly on the bench results in the indicator contact rotating clockwise through all 5 of it's positions continuously. i.e. 1-2-3-4-5-1-2-3-4-5-1-2-3 etc

Before I actually removed the rubber blanking bung from the gear position indicator hole, I'd expected to see the contact stop rotating a full circle at some point, and only be able to be shifted back the way it came. Like, 1-2-3-4-5-4-3-2-1-2-3-4 etc. Not keep going round and round endless full circles on every press of the gear pedal.

I'm sort of worried that this would allow the rider to cycle continually through the gears in this fashion... neutral, 1st, 2nd, 3rd, reverse, neutral, 1st, etc..

I'm imagining all sorts of trouble when the 3rd to reverse transition happens!

(Is there a reverse on these, or is it just 4 forward and neutral?)

Either something's broken in the transmission or I'm not understanding how it works.. I suspect the latter..

Did these quads come without any form of gear position indicator? There never appears to have been a switch fitted in the hole although it's hard to tell. Just that everything seems pretty undisturbed, no chewed up screw heads or other evidence of anyone ever having removed a switch in the past. I've managed to find and order a 5-contact rotary switch insert that should allow me to build a little indicator panel with a few LEDs or something to help my test pilot along, once I've figured out how the gearshift actually operates.

I guess the obvious thing would be 'try it and see' but I'm a bit nervous about taking it off the safety of the bench until I really understand what's going on with the gears.

[edit] This is a link to a schematic of a honda 50's gearbox - I think it's similar to what's inside the Kazuma 139 engine? can anyone confirm, or even help me understand how it works if it's the right diagram? Honda C50 1982 Gearbox

 

Just checked a Kazuma Falcon workshop manual and it does show a shift drum (6) and selector forks (1.2 and 1.3) that look like the ones pictured above. Seems to be close in design to the bigger Hondas I work on and, if so, the shift drum should come to a stop and have to go round the other way. those wiggly tracks in the drum come to an end and the drive pins (4) go into them, so should not go further than the end of the tracks. The Falcon manual indicates 4 speed for 100cc or 3 speed plus reverse on 90cc and 110cc models.

 

Thanks Merryman. I was looking at those drum tracks and thinking the same thing, which is why I thought something was maybe broken inside.

I double checked the quad with the wheels off the ground, and the neutral switch contact does definitely keep rotating all the way round. It seems there's no reverse and the pattern is neutral-1-2-3-4 all down, and then round to neutral again.

I did come across a 3-speed to 4-speed conversion kit on Ebay though for the Honda C50. It contains a full gearshift including all new shafts, cogs, drum, forks, the lot.. and they direct you to just replace the whole geartrain & mechanism when converting from 3-speed to 4-speed. Their drum has continuous tracks and the pattern is neutral-1-2-3-4-neutral-1 etc.

So, something that acts like my Meerkat 50 transmission does seem to exist, it turns out.

The seller of the kit notes "you can't shift into neutral unless the vehicle is at complete rest" so that would tend to put my mind at rest regards suddenly slamming 4th-neutral-1st

I figure this is what's going on, whether my Meerkat has been modified with a different geartrain or they just come like this from the factory, I don't know.

 

Have the same one my little guy started on.

NO reverse… all forward gears.

Grandpa bought it well used, given to a cousin who’s rather large dad would get drunk with his buddies and run the hell out of it, then sat for 6+ years, and was resurrected with a replacement carb, and an oil change, and my son got ahold of it as his learner and has run the hell out of it too. That little Kazuma has an UNGODLY amount of hours on it and purrs like a kitten with little more than oil changes, chain lubes, and one valve adjustment.

Single handedly made me a believer in Chinese stuff….