back fire through carb help

I hope it works tho, if not im gonna have to admit defeat and shes going to the shop

well guys i appreciate everyones help, Ive eliminated everything we've talked about and unfortantly its beyond me now, shes got a date with a shop mechanic now the real shitty thing is you know its gonna be something really simple and dumb and its prolly gonna cost a fortune lol i guess thats the price of learning though. still open to suggestions since im not going to take it next week or so. but to recap we know its not a carb problem now since i switched carbs with one off my working mower and it does the same thing, almost positive its not a valve clearence problem. soooo that leaves.........possesed possily? haha btw we cured the back firing through the carb problem but still fighting it only running on choke. Also compression is great, great spark and great fuel flow not only out the fuel line but also out the bottom of the float bowl....I also went to the extreme of putting a new battery in it just to eliminate all we talked about.

wait, when timing one of these small motors, Ive noticed something.....when i turn that motor to TDC, sometimes theres no valve clearence at all but i can rotate the motor over a cycle back to TDC agian and i have perfect clearence...is that normal??? is it possible Ive timed it on the wrong stroke of the cycle????

Yes its possible to time the wrong stroke of an engine. If it was it wouldn't run at all

I still say its carb related. Generally as a rule, backfiring is caused by a lean condition. If it was backfiring every stroke, then it could be valves, but if it only pops occasionally, its a fuel system issue.

Don't assume that the carb off your running engine is good for this engine either.. ALL engines are different when it comes to fine tuning. even between engines of the same make model and size.

If it makes you feel any better, the carbs on my bike had to be gone through several times before I found the problem.

It was a olugged passage I couldn't even see with the naked eye. I've seen this problem on many dozens of motors over the last 30 years or so.

yeah chopper that makes since now that you mention it, the good carb is off a 14 hp and the one im workin on is a 16.5 hp. for kicks i stuck the carb off my broken mower on the good one and it did the same thing the broke one did b4 it died, it missed and carried on at full throttle...so i guess its a day of cleaning carbs...what is the carb " dip " everyone talks about....is that something you can do at home???

PROGRESS!!!!!!! i took a guitar string and used it to clean the high flow jet out and sprayed it out and the thing actually ran on full throttle for a few seconds b4 sputtering out and dying.....I gotta go out and buy a blow tip for my air compressor since mine has mysterously went MIA lol

Well that's good news that you may have found some of the problem. Good thing is cleaning is a cheap fix .

carb dip is available from parts stores. It comes in several names and formulas.

try to avoid using steel wire or anything hard. brass jets are soft and can scratch easily, changing the metering. A piece of straw from a broom works, or something similar. I only use my mini drills if I know the exact size the jet is supposed to be.

Check out old motorcycle resto forums to see what they do. You'd be surprised what works.

Ive got one heck of a clog in the passage for the fuel, sometimes the carb cleaner will go through it, other times it wont, theres a 90 degree bend inside there im having problems reaching with my wire.....i guess its a long night of carb cleaner, probing and compressed air blowing...yay!

jaymz wrote:

Ive got one heck of a clog in the passage for the fuel, sometimes the carb cleaner will go through it, other times it wont, theres a 90 degree bend inside there im having problems reaching with my wire.....i guess its a long night of carb cleaner, probing and compressed air blowing...yay!

I hope you get it all working right.

good news! she now purrs like a kitten in heat! runs great...actually better!

So what happened? Did you take it in to be fixed? What did they do...what did they charge yah?

believe it or not i sea foamed the hell outta it after blowing the heck outta the carb with my air compressor.....runs great now.....must have been a tiny clog somewhere

if the carb is sucking air out that in than it is the timing. i just had a gocart in with the same problem. could also be spark.