Agility City 50 won't speed up

[ams_nsl]

Hi yall,

I can't seem to figure out why my scooter won't speed up more then 55kmh (35 miles at most).
I just spent 288 euros in a retarded service and no result. They upgraded to a racing CDI though then reverted everything I had on the scooter to stock, saying it's better.
I had my clutch glazed and because I already had 9000km with it I bought a Malossi Clutch and bell, put it back together and it didn't go over 35kmh (20mph), so I gave up.
Service guys said it's my stock CDI at fault, so they replaced it with the racing one and said the problem is fixed but now I think I have more revs and same speed as the initial stock CDI.

Anyway, it's not about that. I'm now running:
Polini Speed Control with 8 grams
Racing CDI
RMS Clutch with sport springs, Malossi Speed Bell (I also have a Fly Clutch but I feel the RMS pulling a bit better after testing both)
Malossi White Contra Spring (1000)
Malossi Kevlar Belt

Sometimes after I run it for 2-3 km at max speed 55kmh (35 mils) and it loses power, almost shuts down, like there's no more gas in the carb.
After a few seconds it starts right up and everything is ok again.

The 8 grams I feel a bit heavy when driving, it goes up in revs along with the speed. I bet they're good for consumption, but that's not what I"m looking for.

With the stock CDI it used to go 55kmh (35 miles) with just the Polini Variator and 6.9 grams, everything else stock.

I would expect a bit more from a racing CDI.

I'm planning to try lighter rollers over the weeked, I have some 6.9 and some 3grams and I'm going to combine 6.9 and 3. I tried the 6.9 and it wasn't much of a difference.
With just the 3, the engine revved a lot but it didn't pull much, max speed 10mph, something like that.

Also after the service, I've noticed the idle is a little bit higher. If I rev it quickly, the revs go down a lot and then up again and I don't see a difference in revs when cold and warm. I would blame the electric choke. Not sure how to test that.

What do you guys think?

[zombie]

First off the problem is the rollers. DON'T combine them. Get a set of 5 or 5.5 gram and you will be hitting 40-45 mph.

The malossi white spring is actually lighter than the OEM spring so I would lean toward the 5 gram rollers.

The changing rpm may be one of three things... An air leak under the intake manifold, a crack in the manifold coupler, or a tear in the carbs vacuum diaphragm.
Pull off the intake manifold, and replace the rubber "O" rings. While you have that off, inspect the coupler for cracks. They ALL crack eventually. If so replace that. Pull the cap off the carb, and look CLOSELY at the diaphragm. If it's torn/replace it.

To test the auto choke... Turn on the bike, and check for +12 volts on the connector. If that is good then pull out the choke, and make sure the pinn moves at least 4mm.


Be careful of the tiny "O" ring on the choke. It's easy to tear it.

Also w/ all the parts you installed you should have at least an 85-87 main jet in the carb. I'm guessing you have a 78-82

[ams_nsl]

Thank for your help, I'll order the 5 grams and the jets today and also inspect the carb.
I'll post my findings as soon as I make the changes.

I'm not sure what size jet I'm running, probably too small because the plug is always shiny clean, so it's running too lean.

I've read about people running 102 in their 50cc but with an open air filter. Not sure what the performance gain is from doing that but I'll try the 87 first.
If I remove the air filter and start the engine, it's not running very happy with the current jet.

[zombie]

I'm surprised it runs at all without the air box. I was running a 147 main/open filter on a 70cc Malossi kit at one point.

Jetting is subjective, and differs from engine to engine. Keep us updated, and we are all happy to help[.

[blue]

First off the problem is the rollers. DON'T combine them. Get a set of 5 or 5.5 gram and you will be hitting 40-45 mph.

The malossi white spring is actually lighter than the OEM spring so I would lean toward the 5 gram rollers.

The changing rpm may be one of three things... An air leak under the intake manifold, a crack in the manifold coupler, or a tear in the carbs vacuum diaphragm.
Pull off the intake manifold, and replace the rubber "O" rings. While you have that off, inspect the coupler for cracks. They ALL crack eventually. If so replace that. Pull the cap off the carb, and look CLOSELY at the diaphragm. If it's torn/replace it.

To test the auto choke... Turn on the bike, and check for +12 volts on the connector. If that is good then pull out the choke, and make sure the pinn moves at least 4mm.


Be careful of the tiny "O" ring on the choke. It's easy to tear it.

Also w/ all the parts you installed you should have at least an 85-87 main jet in the carb. I'm guessing you have a 78-82

   x 2 he is right 5.5 rollers worked the best for me.along with a 82 main jet.

[JJJoseph]

You can't expect much more than 55kph from a 50cc.  There simply isn't enough hp to do what you're expecting, and never will be.  The basic 50cc model is rpm restricted by the CDI, and speed-restricted by the gearing/variator.  It's likely more cost effective to upgrade to a 100cc model.

Don't get me wrong: you can indeed upgrade a 50cc model with a series of mods, enough to get 80kph but the cost will be at least as much as upgrading to a larger model.   Trying to boost your 50cc will be a series of expensive frustrations as you gain 3kph, then lose 2 kph, and so on.

[zombie]

Never heard it said better.

Actually you can build up a 4t 50cc for 2-300.00 to run 60mph but you really have to know what you are doing, and prepare everything correctly. It's all in the little details/prep of the parts.

I'm closing in on 4 years w/ a 50mm kit, 24mm carb, shorty 1" exhaust. 60 mph

My 2t has close to 5 grand invested, and has perhaps 40 miles on it... in the past year.  80mph

For that same 5k, I am building a 650 triumph that will most likely last another 40 years. (it's a 1967 engine)