Howdy From Greenville, NC

[mdschurtz]

Hi guys, I just built my first bike and its alot of fun to ride when the motor decides to run right. I'm running into a problem where it revs all the way to the top with the clutch in, but when it's under load and i'm riding it doesn't want to go over what seems half throttle.

Specs:
Frame: old huffy good vibrations
Engine: Chinese 80cc 2 stroke Everything is stock except the briggs and stratton fuel filter (motor did the same thing before i changed the filter)

here are some pics:

Plans for it are: (in no particular order)
1) rear mounted cylindrical tank
2) occ chopper fork
3) expansion chamber
4) 36 tooth rear sprocket

 

[xseler]

Howdy and welcome!!

Sounds like you've got an air leak or an overly lean condition.

Good luck in your search for the solution!

 

[mdschurtz]

thanks i will check and make sure the cab is on the intake pipe all the way and tighten everything up. also what is the best way to adjust Air to Fuel Ratio? via the idler screw on the carb or something else. Thanks for the advice

 

[[email protected]]

Sounds like your clutch is to tight. mine used to rev high when my clutch was tight.

 

[mdschurtz]

Sounds like your clutch is to tight. mine used to rev high when my clutch was tight.

ok thanks. that's a high possibility

 

[Greg58]

Welcome to the forum. As was said above it sounds like either a air leak or a cable that is not letting the barrel in the carb close all the way. If the intake to cylinder gasket seal is good and the carb is sealed to the intake check the cable. First remove the air filter and twist the throttle and watch the barrel as it moves, do this with the handle bars in different positions to make sure the cable is not binding. As for the mixture you can't adjust it without modifying the main jet size. The best thing to do is get it running correctly as is then after break in do the fine tuning. Ever one of these ive dealt with the miixture was fairly close.

 

[mdschurtz]

ok So I have semi fixed the issue. I adjusted the throttle and clutch cable and made sure there was no air leaks in the carb to intake. now the bike will go full throttle but when it starts getting into the higher RPMs it just kind of dies off. like it's too rich or too lean, the problem is my adjuster screw on the outside of the carb really doesn't do anything for me. should I adjust the jet? if so do I just need to remove the bowl to access the jet?

 

[Greg58]

The screw is the idle speed adjustment if it only has one. Like I recommended. You need to break it in before modifying the jet because once it broken in you probably will need to fine tune it. About 300 miles on both of my bikes is where the power improvement started.

 

[mdschurtz]

so I should just keep riding it how it is until it breaks in and it might fix itself?

 

[Greg58]

The more you run the engine the better it will get, if the spark plug color is light brown on the insulator I would ride it. In the classic thread section you will find spark plug color charts and recomendations how to do a plug chop.

 

[mdschurtz]

ok thanks Greg

 

[mdschurtz]

good news! I changed to an NGK spark plug and adjusted the carb and the problem is way better now. i think now i just need to work with the mixture a little and figure out where the screw needs to be

 

[mdschurtz]

ok so slight update. Today the issue was more noticable again so I did a little more research on the CNS carbs. I never checked the screws on it before installing and some of them were not as snug as I would like so I fixed that. I also took the slide out and adjusted the clip on the needle to the 2nd from the top. Should the slotted washer go on top or underneath? i put it underneath

 

[Greg58]

The washer goes on top of the e-clip then the spring holds the pin in place.

 

[mdschurtz]

awesome, I will fix that when i get the bike out. Thanks for the help Greg