Chattering and stalling

Fengist

Fengist

New Member
Ok, so I've built my first bike, I'm in the middle of breaking in a Chinese 2 stroke. (I'm sure everyone but me follows the rules during break-in) and I'm having one issue and one concern.

Issue: At higher speeds with the throttle wide open, it stalls out. It's like it's getting no fuel. Once it slows down, it will speed back up, then stall out again. If I keep backing off the throttle I can find a spot where it runs 'normally' without stalling.

Concern: At higher speeds, when the throttle is in the spot where the engine rpm matches the road speed (it's neither making power nor engine braking) I get this LOUD metallic chattering noise. Is this normal for Chinese 2 stroke engines?

Some things to consider:

E85. I live in Iowa and ethanol mix is all we can get. I am running the 'premium' grade in it.
I've read that E85 should be mixed with ester based 2 cycle oil. This will be something I'll have to order order off the internet. In my small town, they've never even heard of such. For now, I'm just using the stuff I find locally.
I permatex'd the carb onto the intake. Like I guess most people I was getting a lot of extra air in there so that issue is fixed (I hope).
I'm running whatever the stock jets are. I have this innate fear of putting my carburetor parts under the drill press. I've also read that E85 doesn't produce the same power as non booze flavored gas. I've also read that it runs hotter. This would seem to explain why my spark plug boot has started to... oh... melt.

Thanks in advance.
 
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Update:

Just got back from riding it to work and it's still stalling out. But, I noticed something on the frame of the bike, a trail of dark grey oil below the intake for the carb. I took the cover off the carb and the filter was soaked with gas. I may have done this myself as I was playing around with the choke while riding it to see if it was an issue of too much air. I did keep a watch on the fuel filter while riding and it seems to keep gas in it but it built up a lot of foam.

Any ideas?
 
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surging like that means you're shaking the carb too much - fuel is foaming in the bowl

most comom cause is loose motor mounts
 
crassius said:
surging like that means you're shaking the carb too much - fuel is foaming in the bowl

most comom cause is loose motor mounts
Click to expand...

Now that makes perfect sense. It's foaming in the filter. It never occurred to me it was foaming in the bowl too.

I've checked all the mounts and they're tight. Because it's an Onex I had to use the universal adapter and I bolted everything directly to the frame. There's no cushion or padding in there.

I read where one guy described riding a bike with these engines is like sitting on an orbital sander. Mine qualifies for that description. I'm having to wear gloves to keep the vibrations from stinging my hands.

Could it just be that I've got a really unbalanced motor?
 
the pre-2012 motors may still be selling cheap on ebay - they were called bone-shakers for a reason, but they ran OK if they were bolted down properly

holding top of motor and frame near gas tank, one should not be able to even budge the motor by pulling on it - also good to check frame for cracks
 
Yea... bone... teeth... nuts... bolts... and lots of other stuff. My bike is now down because of vibrations. The pin that holds the clutch cam in place... broke in half, I assume, as a result of the cam vibrating up and down. My clutch cam then vibrated out, banged up against the chain and made a nice mess of the clutch cable and arm. In the same trip, a stud holding the intake vibrated out so I limped home with one bolt holding the carb on... and the mount for my headlight vibrated to the point that it snapped in half and fell off.

Vibration? Ummm no. It's a built-in self-destruct mechanism. You've heard of planned obsolesce? I'm thinking the Chinese plan on these things lasting 2 weeks.
 
Oh, and that's after the front fender vibrated itself to the point that it's attachment to the fork broke and it promptly wrapped itself under the font tire... while I was riding it. Ever tried to drive a bike using a fender for a tire?

I've read what everyone.. and mean EVERYONE has said about not using rubber between the motor mounts. But, I'm at the point that if I don't find some way to stop these massive vibrations soon, I'm not gonna have a bike left.
 
on old motors, vib usually doesn't start till you're faster than about 20mph or so - if there all the time, then you've got a problem in the build

if you can't find the reason for that vib, and no one with more experience is in your area, you might want to buy another kit from a diff seller, build another bike, and see if same thing happens again

if 2nd bike does not vibrate, then swap motors to see what's diff between the 2 bikes
 
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