50cc Tuning

[redhenracing2]

So my newly acquired wheels have a few issues, aside from a few obvious aesthetic details.

It will not go over about 25, I know it's only a 50 but it should be able to do better than that.

It smokes very badly, aspecially at idle.

It won't idle.

(not by itself anyway)

At full throttle, it bogs down as if it's not getting gas.

Sound like I need a good carb cleaning?

[Big Rich]

Im no 2 stroke expert by any means, but a carb cleaning would do wonders.

[yamahonkawazuki]

yup my 50cc bicycles would do 35 ish. so a carb cleaning first off, tehn change plug, then try it

[redhenracing2]

Shouldn't take long to get the carb out and cleaned, it's smaller than my fist. I guess we'll try that first. I found a BRAND NEW carb for $20, may snatch that up just in case. It needs tires really bad too, I found some Dunlop race tires  (not)

[Big Rich]

Redhen, do you have a compression tester? Good spot to start out with as well on an older motor.

With a proper expansion chamber, reeds, and some tlc, I bet that little motor could scare you. If you are really ambitious/  daring, look for an early cr60 or cr80 motor to shoe horn in there.

Just kidding. Don't do that.

[noworries]

Small 2-strokes like a clean, non clogged up exhaust box as well. Worth checking that out as well as a carb clean. Compression important, and it's cheap and easy to shove in a new set of rings. Older motor designs with points rather than electronic ignition set-ups benefit from playing with the gap and timing positions. And a new plug is always a good investment on a stroker. With an auto clutch, playing with the rollers and springs at both ends of the belt can be/and bring a lot of fun. Enjoy.

[redhenracing2]

Well, after some research, it seems that I may actually have an 80. It has wheels, plastics, and seat from an 80, which are notably different from the 50. The thing is, he also has spares of all these parts that all appear to be from a 50.

How big an effect does jetting have on these engines? The exhaust has to be one of the most restrictive systems I've ever seen, would opening it up help? Apparently even a 50 in good running shape should be able to do 35-40.

[paulc86]

Carb cleaning!  Also, check all the gaskets sealing the carb to the engine, and the exhaust to the engine.  2 Strokes are kinda picky in that regard.

Also, if its smoking badly and bogs, I'd be temped to say its running rich, without really hearing it.  What's the plug look like?

Thats all I can think of before I head to work.

[Big Rich]

Depends what you mean by opening it up. Probably the best solution would be to get a pre made expansion chamber from another bike (similar or slightly larger cc's preferably) and "make" it fit. There's a huge amount of science that goes into 2 stroke exhaust though, and I've never looked into it.

Every little thing you can do to that motor will make a world of difference. It's one thing adding a K&N to a GS500 with it's plentiful horsepower (in comparison). But if you can squeeze out even 1/2hp out of small bike, it's worth it. For example: my old CL175 had a hacked exhaust with 2-2 pipes and small baffles for mufflers. Ran like crap.....all the time. By making a 2-1 muffler and smoothing out the exhaust, it ran like a champ. Well, a 175cc champ.

[tt_four]

A lot of scooters and mopeds were designed to only go 25mph. In a lot of states, including mine, part of the legal definition of a moped is that it doesn't go over 25mph, so manufactures keep it that way with jetting and gearing. You'd be surprised what you can find for those little engines. You could clean and rejet the carb, new air filter, find a little exhaust for it. Not sure if it has an oil injector, but I'd recommend ditching it and pre-mixing your oil. If the injector fails it's just burn up your motor. Some people even get into porting the motors so they run more efficient. Mine was made to go 25. After I put the 70cc cylinder on it the top speed is pretty much double plus accelerates way better. Try to find a scooter forum and you can definitely find some info on them.

[redhenracing2]

A lot of scooters and mopeds were designed to only go 25mph. In a lot of states, including mine, part of the legal definition of a moped is that it doesn't go over 25mph, so manufactures keep it that way with jetting and gearing. 

In GA the limit is 30. But today I found something interesting while playing around with the carb . . . .

The engine case is stamped 79cc.

I'm still calling it 50, and when I repaint it I'm gonna put some '49RR' (in the CBR font) logos I found on it. I saw those and thought it was hilarious for some reason. It must be a 50 frame, because I ran the vin at the dmv and it came up as never having been tagged before. If it was sold new as an 80 it would have been tagged and titled (I assume, correct me if I'm wrong).

According to the specs for this engine, it should be able to break low 40's stock. A carb clean is definitely in order.

I found a good forum (complete with original service manual downloads), but apparently they have a major problem with spamming and have temporarily shut down self-registration while they clear out spam and lurker accounts. Whenever they open back up I will be getting somewhere with it a little faster.

[tt_four]

I wouldn't be surprised if all of those old frames were the same between the 50 and 80cc models, so it was probably common for people to buy a bigger motor and swap it in. I always thought it would be awesome to get a small dirtbike motor, reweld the mounts on my moped and bolt a real motor in there. Is the 80cc motor still a 2 stroke? I'd assume an 80cc 4 stroke and a 50cc 2 stroke would be pretty similar in top speed, but 80cc will be better for getting around. Maybe take the VIN number to the DMV and see if they'll run it and tell you what it is. That way if they happen to know it's an 80 you'll save your trouble of trying to pass it off as a 50. I bet somewhere on the internet you could find a VIN number decoder that'll tell you the year and model.

Hopefully the forum helps you out. When Heather got me that moped I joined one of the moped forums, and even though some of the kids knew their stuff, it turned out that a huge portion of kids that are into tuning mopeds are huge asses, and are completely unwilling to give you an answer. They'll harrass you for days, and then finally give you a partial answer in the most condescending way they can. All the while you're just trying to figure out how someone's head got so over inflated because they managed to 'tune' their machine to go 50-55mph, which is clearly one of the qualifications of considering yourself godlike. Heaven forbid someone with a scooter try to join the forum and accidentally call their bike a moped. They got chased out of there so fast. It kinda ruined the whole experience for me. It really makes you appreciate a forum like this where you can ask any question no matter how dumb, and people will be happy to help. You would picture that a group of kids fixing up 30 year old bikes would have a bit of personality and be fun to hang around, but there's definitely something I'm missing in the equasion.

In the mean time, if you get bored while you're waiting for your scooter forum to open back up, head over to mopedarmy.com, join the forum, post up telling them you just picked up a new moped as a project and post some pictures, haha 

[yamahonkawazuki]

best way to do it TT. best way ive seen thusfar