Carb problem?

327ren said:
And what does it mean that bottom end throttle response is better with the NT? Gotta know these things.
Click to expand...

The NT carb is sized right for a 50cc motor. That means, at low rpm, if you snap open the throttle, it will still fuel the motor well enough to accelerate smoothly.

OTOH, with a carb that's a little too big, when you try the same thing, it might stumble at low speed, or have flat acceleration until it gets going a little higher rpm. The trade off is, the bigger carb will probably have a little more power in the upper rpm range.

NT carbs were the original carbs. The CNS was only installed with the goal of passing epa rules. If you're a factory trying to sell legal motors that meet epa rules you have little choice, but to use a carb that's too lean running for the motor to run well.

I think secretly they figure most people will end of changing to a NT after they buy a motor that comes with a CNS. Even though that's kind of a crappy solution, it's better than not being able to get a motor at all.

I made one bike for a friend with a SkyHawk 80 that came with a CNS. Out of the box it only went about 10 mph, but it started and idled fine. After a lot of tuning I got it to run about 25 mph.

A year later she brought it back to me for service, and some repairs. The plastic spacer on the intake manifold was broken. I decided to replace her CNS with a NT. A week later she sent me a email saying she got it up to 35 mph, and she felt like it was a new bike lol. I didn't do any tuning to the NT at all, except move the needle to the next to the leanest position.
 
I adjusted everything, and the motor will not turn over. I adjusted so that the carb was actually flooding. The float made no difference. I had the same problem. It sputters, then dies. Anyone have any clue?
 
Hmmm... Now it is being a PITA.
Check the spark plug for a good strong spark.
The weird running symptoms could have been related to a failing spark plug, CDI or mag coil, but they typically fail like a light bulb, good one moment and bad the next, except for the spark plug. They can operate poorly for a while. A weak or sporadic spark will cause the engine to run very poorly and give very similar symptoms to a carburetor with a bad state of tune.
 
327ren said:
I adjusted everything, and the motor will not turn over. I adjusted so that the carb was actually flooding. The float made no difference. I had the same problem. It sputters, then dies. Anyone have any clue?
Click to expand...

From reading your original post it sounds like your initial condition was too rich due to float allowing too much fuel into the bowl. From reading the above post which says your carb over flows fuel after you made the float adjustment means you either bent the float tab in the wrong direction or you put the needle into the valve upside down. The pointed end of the needle has to go up into the valve. Whatever the cause, you went from too much fuel to WAY too much fuel, you need to be moving in the opposite direction.

If you read the second post in my "CNS carb working great" thread it will give you all the hints I have about adjusting the float, so check that thread over there for more tips on that.
 
OK, I replaced the CNS high performance carb with an NT. I still have the sputtering motor. Can't blame it on the carb now. What is the problem?
 
Is the NT carb tuned up good?
How healthy is the ignition system?
Are the crankshaft seals good/ not leaking air in or out?
Is the cylinder base or head gasket leaking?
Is there an air leak somewhere in the case center gasket? The trickiest one to find is where the flywheel cavity abuts up to the transmission cavity. Yes, it can leak there, but it is really not that common.
 
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