Motor chokes when +20mph, tried multiple things, need more ideas

[dmopedMA]

Thank you guys a lot!

I remembered that my back mount block is cracked (it was my fault...) so I'm sure that this is making the motor to vibrate more than it should, so I just ordered a new one to replace it. I'm gonna play a little bit with the float level and see if that helps meanwhile the replacement arrives.

 

[KCvale]

Just give your engine the Shove Test.
Put one hand on the engine head, the other on the top bar above it.
Now shove the engine back and forth as hard as you can.
If it moves AT ALL that is a Fail.

 

[Frankenstein]

Just give your engine the Shove Test.
Put one hand on the engine head, the other on the top bar above it.
Now shove the engine back and forth as hard as you can.
If it moves AT ALL that is a Fail.

... and to add to that, if it moves tighten the bolts evenly a bit at a time and recheck engine movement, don't just tighten the s**t out of the bolts, you only need them snug enough to be solid, not stripped, and upgrading bolts is a good idea.

 

[dmopedMA]

... and to add to that, if it moves tighten the bolts evenly a bit at a time and recheck engine movement, don't just tighten the sh*t out of the bolts, you only need them snug enough to be solid, not stripped, and upgrading bolts is a good idea.

Ok, good to know, won't be the first set of bolts that I strip...

 

[dmopedMA]

Hello everyone, here I am with the updates:

Yesterday as @Frankenstein told me, I lowered the float level and now it chokes, but in a different way. Before when I reached the 20mph spot, it chocked until it got around 12mph (around 3-5 seconds), coming back to live there, but now after lowering the gas level, when it reaches the problematic speed, it chokes, but just for a second and comes back for an other second or two and chokes again, giving the feeling that your "riding a horse".
I believe that we are close to where the problem is... my question now is: Did I lower it too much and now it doesn't have enough gas? Is this the best I can get with the vibration I have?

Regarding vibrations, the replacement for the mount block is on it's way.
As @KCvale told me, I tried to move the motor with the "Shove Test" and it didn't move at all.

One idea that I got and I would like to discuss with you guys, is having an extended intake for the carby made out of rubber (picture attached from here: http://www.dragonfly75.com/bicimoto/index2.html) and then attach the carby to the byke frame, I believe it will reduce the vibration in the carby by a lot, what do you think?

 

[gary55]

It might isolate vibration some. You should try a smaller jet to see if that is the prob. Sickbikeparts has them for the nt carb. Droping to a #68 might be the cure. If it works great if it shows improvement then you know it's a step in the right direction. Jets are cheap so you might want to order two. A#68 and a #66 to save in shipping. Try the 68 first.

 

[dmopedMA]

It might isolate vibration some. You should try a smaller jet to see if that is the prob. Sickbikeparts has them for the nt carb. Droping to a #68 might be the cure. If it works great if it shows improvement then you know it's a step in the right direction. Jets are cheap so you might want to order two. A#68 and a #66 to save in shipping. Try the 68 first.

Thanks for your reply.

I'm gonna try to see if reducing the vibrations by changing the mount block helps, I may try the extension to confirm if the problem is due to vibrations, if it doesn't then I'll go for the jets, thanks for the info!
BTW, what is the default jet installed in the stock NT carb?

 

[gary55]

Thanks for your reply.

I'm gonna try to see if reducing the vibrations by changing the mount block helps, I may try the extension to confirm if the problem is due to vibrations, if it doesn't then I'll go for the jets, thanks for the info!
BTW, what is the default jet installed in the stock NT carb?

#70

 

[Frankenstein]

Thanks for your reply.

I'm gonna try to see if reducing the vibrations by changing the mount block helps, I may try the extension to confirm if the problem is due to vibrations, if it doesn't then I'll go for the jets, thanks for the info!
BTW, what is the default jet installed in the stock NT carb?

Then it would have to be the vibration (less fuel foams quicker than more,) you may want to just get a rubber hose to act as part of the intake so at least the engine vibration won't be so hard on the carburetor... Nothing else other than altering the crankshaft flywheels

 

[dmopedMA]

Here I am with the updates:

So, I changed the mount block and I took the chance to level the motor (carburator wasn't perfectly parallel to the floor), after that I went for a spin ant man, looks like something changed, still got a little bit chocking when getting speed, but if you wait two or tree "chockes" it went throug... not bad!

Just for testing, I changed the configuration of the carby nail to one point upper, and I believe that I got the sweet spot, it goes fine, almost no chocking, and if there is any, just removing a little bit of throttle, it goes away, oh boy, it IS fast! such a nice feeling passing a moped scooter and watching the guy's face

I still have to do some more testing, but if it keeps going as it went today I won't tune it up more.

Thank you guys! a lot! if there is any change in behavior, I'll update here.