Full primer bulb, popping, and backfires

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J

joecon321

Well-Known Member
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49
Location
Virginia
The engine is has barely 1 tank thru it and noticed full primer bulb after running. it has a lot of popping sound out the exhaust and the engine shuts down a lot and backfires. already checked for kinks in fuel line. going to look at spark plug tonight and clean it. anyone else experience or have any ideas on what may be going on?
 
would try again with a new plug as a start mate maybe breaking down inside ive had same problem before clean it or replace it and try if that don't work we can try something else but sounds like the plug but thats only a ruff guess
 
Thanks man, took out the spark plug and it was solid black like it had been burn up. So as soon as I find a replacement, I know I have one around here somewhere I'll update the progress.
 
still cutting off, popping, and backfires.

Changed the plug. Still shutting down, popping, and backfiring. now I'm think bad batch of gas so my next step is get rid of the gas in it and start a new. If anyone else has any ideas or suggestions please share. still sort of new to 1/5 scale and need all the help I can get and so far the people here have been awesome!
 
Thanks Al, I got the tuning set to factory and even lean it out a little and richin it a little then back to factory and still shutting down, popping, and backfiring. its a walbro 668 carb brandnew. brandnew engine also. It is really sad i'm having this much problems with my first 1/5 scale it is kind of discouraging me from continuing with 1/5 scale:( This is the second engine besides the first that came with the buggy I am having problems with.
 
This may be a stupid question but someone suggested to me that my engine problem may also be a air leak and I should make sure that the intake screws and bolts from carb to manifold including the head bolts are tight and secure. So my question is where are the head bolts located and how do I get to them?
 
For those still interested in this thread here's an update: put different mid grade gas in it. Got rid of the old. tightened up the carb screws and let her rip. Ran well only died once when bringing it in to give it a rest, fired right back up afterwards with less popping and no backfires.
 
Hi

Normally a full prime bulb means to much fuel go through the carb,try adjusting the low screw in by a fraction of a turn, check the screws and gasket are ok on the carb you can do this by removing the air filter and you will see 2 screws check remove them and check gaskets, check head bolts by removing the plastic case on top of the engine which is done by the 2 top screws on pull start side of the engine, hope any of this helps you mate

Also one time I had trouble with prima bulb full right up, I replaced all the carb gaskets,head gasket and still was the same, in the end I replaced the crank seals and it cured it...

Shaun
 
Last edited:
General rule of thumb after a good thrash use the oddified/goldy locks principle

Full bubble = too rich

Empty bubble = too lean

half bubble = Mmmmm just right
 
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