possible air leak

socialdistortionkid

socialdistortionkid

New Member
I got my engine kit running well then all of a sudden my engine wouldnt keep a steady idle so i assumed it was my carburetor, swapped it out for my NT without any difference.

It can ride it to Wot without bogging but will not stay running without me keeping it at 1/4 throttle with the clutch lever pulled in it the engine wont keep a steady idle it revs high then low like an air leak.

Im getting so pissed off i wanna throw this bike in the trash
 
Last edited:
Did you lift rear wheel off ground with motor running ? If when the wheel is up it turns and engine runs ok it's prob clutch adjustment. Most air leaks tend to cause runaway idle.
Not bog and kill? Just a thought...
 
The leak, if that is actually what you are fighting against, could be coming from where the carb attaches to the intake manifold, where the manifold attaches to the cylinder, the cylinder base gasket, the cylinder head gasket, the crankshaft seal behind the mag rotor, the crankshaft seal behind the small gear in the transmission, or the gasket between the crank case halves.
There are many places for a leak to occur. They are also easy to test for by using a little WD40, carb cleaner or brake cleaner.
With the engine running at the throttle position where it runs the worst, spray around the possible places for a leak to occur and if the engine runs better for a second, you have found the leak.
Warning! All the suggested sprays are highly flammable (they need to be) so be careful and don't accidentally light a fire where you don't want one.
 
fixed the killswitch problem now it turns off. my wheel spins with the clutch lever pulled in so im going to fix that and get back to you on that.


Basically i ride along at a steady speed for 5 seconds then it goes baaaaaaaah for about 3 seconds gets to about 4mph and repeats itself its pissing me off and it wont idle right
 
socialdistortionkid said:
fixed the killswitch problem now it turns off. my wheel spins with the clutch lever pulled in so im going to fix that and get back to you on that.


Basically i ride along at a steady speed for 5 seconds then it goes baaaaaaaah for about 3 seconds gets to about 4mph and repeats itself its pissing me off
sounds like a fuel delivery problem from the fuel tank to the carburetor, or the float mechanism inside the carburetor is adjusted too low or it is partially clogged at the float valve
and it wont idle right.
Check out the fuel delivery problem first to be positive that all is good, then try tuning the idle speed and fuel mixture
Click to expand...
_________________________________
 
Update: fixed the clutch flower nut and the wheel does not spin with the lever pulled in.

It is not a fuel delivery problem it defiantly is getting fuel in the float bowl and the spark plug is wet. When i touch the idle screw it doesnt do anything.

I am going to try my CNS carburetor again because that is advice i got. I think its an air leak to be honest.
 
It sounds like you are on the right track.
An air leak typically does not cause a repetitive loss of power though. Usually they cause hard starts, a high idle speed, a hot running engine and a flat (gutless) power band at higher RPM's.

Also, try using a little RTV black silicone when installing the carb to be sure that there are no air leaks there.
 
AHHH! It Will not start with the CNS carb I dont want to take it to the shop but im out of ideas =( I put gasket sealer on the intake manifold that connects to the cylinder. I can pedal down a hill and it doesnt do anything but if i get about 3mph it starts backfiring and etc (smoke coming out the air filter?) and firing with smoke coming out of the exhaust but it dies because i get tired of pedaling, this engine has so much compression its hard to keep pedaling with the lever disengaged.


Ran terrible yesterday with a NT now wont start but i have to consider that it is cold outside, it still should start though
 
Last edited:
A backfiring 2-stroke is usually an ignition problem. Unless you are actually hearing and seeing explosive force coming out of the carburetor, it isn't really backfiring. Smoke coming out of the air cleaner just means something is wrong. What type of spark plug are you using? NGK B7HS I hope.
What you are describing sounds like a plugged up exhaust. Just to rule that out, remove the exhaust only long enough to see if it will start. If you leave it off forever, you will do serious damage to the piston and cylinder.
I am getting frustrated too trying to diagnose it through a computer screen. This one is being a real bugger! It is so much easier when you can diagnose it in person.
 
Ya its a brand new engine kit, brand new CDI, killswitch disconnected. The exhaust is new.... shouldnt be plugged up i am running 20:1 non synthetic for break in (too rich?) and i am using a bp6hs spark plug, runs the same with the chinese plug.


It starts up with my nt carburetor and barely starts up at 3mph with a cns so i think its an air leak.
 
socialdistortionkid said:
Ya its a brand new engine kit, brand new CDI, killswitch disconnected. The exhaust is new.... shouldnt be plugged up i am running 20:1 non synthetic for break in (too rich?) and i am using a bp6hs spark plug, runs the same with the chinese plug.


It starts up with my nt carburetor and barely starts up at 3mph with a cns so i think its an air leak.
Click to expand...

Well if it starts with the NT carb, then that does rule out a plugged up exhaust.
Brand new mufflers have been known to be all fubar'd internally from the factory and barely flow better than a soda straw though.
have you tried any of the CNS tricks that other folks have been working out?
http://motorbicycling.com/f34/omg-i-have-tune-cns-help-30169-8.html
 
Youre the man Gearnut! problem solved dance1 . New intake gasket because it was slightly leaking and base gasket fixed the problem. :-|| Base gasket was ripped up from the factory! Pretty stupid that they would install a ripped up gasket with a new engine, after taking apart everything the mechanic was out of ideas so i told him to check the gaskets and i watched him take the head off and the base gasket was ripped up in about 10 places.

Now to mess with the cns carb.....
 
Last edited:
I'm glad to hear that you got it all worked out!
At least you had one to find all torn up. They are known for leaving out a random gasket from time to time.
 
I've been kinda pushing the whole mentor thing lately , but see ,it can work . The whole point of this forum is to share info and exp. And help each other out.
Glad your figureing it out ,gear nut perfect mentor ;)
 
You must log in or register to reply here.
Back
Top