No Gas to engine

Watts · Jun 21, 2014

Another post this year, 3 yrs trying to get this bike going and no luck/answers. I had a a few mechanic guys come down to look at the 80cc chopper with chinese engine kit installed.

Again it seems that just as in previous 3 years, everytime I try to start the bike the engine wont get any gas. I have tried cleaning carb, float bowl, looking for cracks, making sure seal is tight, mixing right mixture of oil / gas, adjusting float pin, priming. etc etc etc. The gas just doesnt want to get into the engine, it just leaks out the float bowl.

I have tried putting gas directly into the engine and it trys to start as you can hear the popping of the msall amount of gas igniting. Spark plug is fine, CDI has to be fine if its giving a spark.

I replaced the fuel line with a new one and removed the fuel line filter, nothing will get the gas into the engine, the spark always is dry after. I even tried making sure there was good air flow through the exhaust pipe and there is.

Seems it might be an airflow problem but that makes no sense as everything has been checked, why does the gas just sit in the carb and leak out and not go into the engine????

PLEASE PLEASE HELP, this is the last year I am going to try and fix this...If I cant im trashing it and going electric and will curse gas bikes for life. :-||

Greg58 · Jun 21, 2014

Gas leaking out of the carb means the float level is too high, it should not leak at all. Which carb do you have? The nt has the choke lever on the carb the CNS has a thumb lever on the handle bar. The only thing that comes to mind is the main jet is blocked , this jet is what the needle goes into when it slides up and down.

2door · Jun 21, 2014

Have you checked to see if the jet is there? It will be a brass tube that threads into the carburetor body. There have been many reports of finding the jet was not screwed in but laying in the bowl/float.

The carburetor works on a siphon system. Air drawn in by the engine passes over the emulsion tube that the jet is part of. It essentially 'sucks' the fuel up from the bowl, mixes it with air and that fuel/air charge is then introduced to the engine via the intake manifold.

This might seem like a stupid question but it has happened. Did you replace the gasket between the intake manifold and the cylinder? If so did you make a hole in the gasket?
I had a builder make a new gasket but it was a full face thing that completely blocked the intake from the cylinder.

You're positive fuel is flowing to the carburetor from the tank? You've disconnected the fuel line at the carb, opened the fuel petcock and confirmed flow? The kit tanks are notorious for having dirt, rust and scale that will quickly clog the in-tank screen preventing fuel from flowing.

I'm also assuming the fuel tank outlet fitting is higher than the carburetor inlet. It must be. Fuel, or any liquid won't flow uphill. It is a gravity flow system. The tank has to be high enough to allow that.

Tom

crassius · Jun 21, 2014

I once had an engine come from the factory with an intake gasket that had not had the hole punched out in the center - you might want to check that.

If you take the air filter off and feel it suck air when you turn the motor and still get no fuel to the cylinder, then I"d try a new carb.

CTripps · Jun 22, 2014

Since you mentioned you've asked about this before, I was just going over your previous posts/threads.. Have you followed through on the suggestions given there? Just have to ask before we go over the same ground too many times.

I see from those posts you've replaced the magneto a few times.. If you're convinced it's the carb, for about $5 more you could simply replace the stock carb, or for $10 grab a slight upgrade.

http://www.speeddemon.ca/stock-carburetor-mb-49-66-80.html

http://www.speeddemon.ca/speed-carburetor-49-66-80cc-39-99.html

Dave31 · Jun 22, 2014

When I have experienced something similar I determined it was too low compression. Maybe this is what is going on with your motor?

Watts · Jun 23, 2014

Greg58 I have the nt carb based on your description. 2Door yes main jet and brass tube intact and thoroughly cleaned a bazillion times..lol. Never replaced gasket and there is a small "air hole" in the neck just after the carb. Fuel is definetly getting from tank to carb, as carb is always flooded with fuel. Fuel tank is quite a bit higher than the carb intake yes. Really really seems like an airflow or compression issue maybe???! Thanks for everyones input and 2Door for the better workings of the carburator and airflow! 2 Weeks from selling this beautiful but broken baby =( Hands are blackened with grease and still movement is deceased, removal of the lingering pain may be the only way not to go insane.

GearNut · Jun 23, 2014

"Air hole in the neck"? This sounds like you have an intake manifold that has been fitted for the ill conceived "boost bottle". Plug that hole! It should not be there.

As for the carburetor leaking fuel, it should never, ever do that.
Either there is crap stuck inside the float valve or the float needs adjustment to slightly lower the fuel level inside the carburetor.

Greg58 · Jun 24, 2014

Gearnut is right, you shouldn't have any leaks between the carb and the cylinder. Since the engine relies on vacume from the piston moving to draw the fuel mixture through the carb.

CTripps · Jun 24, 2014

Definately plug that hole, and/or replace the intake manifold. That's probably less than $10 (http://www.speeddemon.ca/intake-manifold-mb.html) to your door. I suppose you could probably wrap the stem of the manifold in tape like a hockey stick until it comes in, but you're better off replacing it, in my opinion.

By the way, I reference that website because they're Canadian (no exchange or other hassles) and they ship quickly - I ordered motors on a Monday, they shipped the next day for delivery the following Tuesday/Wednesday (not bad) and they arrived on the Friday of the week I ordered them, so in 4 days.

2door · Jun 24, 2014

Ditto on the intake manifold situation. If there is any opening downstream of the carburetor, even just a leaky gasket, it will adversely effect the way the engine runs, or keep it from running if that opening, hole, is large enough.

As was suggested by CTripps, you could try wrapping the intake with tape just to test our theory. It will be a very temporary fix but it would tell you if that is the problem. Whatever, I'd replace the manifold with one without holes in it.

Tom

CTripps · Jun 25, 2014

Yeah, the tape wrap would be simply to test the theory. In my opinion, it'll be far easier to simply replace the manifold than it would be to attempt to fill in that hole considering the cost of a new one. I've probably got one I could send you, but it would probably cost as much in shipping as it would for you to buy a new one.

Watts · Jul 8, 2014

Thanks to everyone who offered their input and help in regards to this bike over the years of being on this forum, the insight and knowledge shared by all is truly a gift and will be forever cherished.

I have reliinquished the bike to other hands in their pursuits of getting it running I will keep all posted on the results. Sad news I do miss that beautiful chopper, but I just did not have the ability to love her properly I guess......

So I traded her in for a Viza V2 40CC Scooter!!!! Sure not as fast, a little safer, but way better engine build and components by my understanding. Pull start, starts everytime no problems. I am loving it, and reloving gas engines!!! I will post some picks of the Viza V2 soon.

Thanks again to everyone, and the utmost respect to all!!!

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