hi guys. boy brought me an old 83 sporty today. said it started back firing thru the car all at once. sprayed sone wd40 in around the o-rings and the rubber where carb slides in. didn't seem to slow the motor. about 1/4 of throttle it back fires alot. took the carb apart and everything looked ok. has origanal carb and exhaust,new plugs and lots of spark. any suggestions?
Deleted. I had the wrong carb setup.
Check the spark timing on both cylinders?
If it is popping regularly/repeatedly maybe an intake valve not fully closing?
Quote from: roadkingdresser on July 05, 2019, 02:04:19 PM
hi guys. boy brought me an old 83 sporty today. said it started back firing thru the car all at once. sprayed sone wd40 in around the o-rings and the rubber where carb slides in. didn't seem to slow the motor. about 1/4 of throttle it back fires alot. took the carb apart and everything looked ok. has origanal carb and exhaust,new plugs and lots of spark. any suggestions?
Take a close look at the diaphragm at the top of the carb. If it has a tear in it, it will do as you describe.
Quote from: Tynker on July 05, 2019, 07:22:28 PM
Quote from: roadkingdresser on July 05, 2019, 02:04:19 PM
hi guys. boy brought me an old 83 sporty today. said it started back firing thru the car all at once. sprayed sone wd40 in around the o-rings and the rubber where carb slides in. didn't seem to slow the motor. about 1/4 of throttle it back fires alot. took the carb apart and everything looked ok. has origanal carb and exhaust,new plugs and lots of spark. any suggestions?
Take a close look at the diaphragm at the top of the carb. If it has a tear in it, it will do as you describe.
I thought of that too, but are these a CV carb on the old ironheads?
He said stock carb, meaning Keihin butterfly. But then says "rubber where carb slides in", meaning CV. I think some more detail is needed about the carb, as in what kind is it?
-JW
A punctured diaphram on a CV will not make it pop.
The slide just wont open and it won't make any power (probably rich too)
I assume the OP has already replaced the spark plugs with original heat range and not too big of a gap....
Good chance the plugs are black and furry.
It is a keihan carb and it does have rubber adaptor bolted to the intake. Good news is i found the problem,bad news took almost 10 hrs. put the plug testor for twin cam in and found out the coil was intermittently loosing power. one of the breakers under the seat a nut came loose. put a new nut on and O.K.
That's a though one to find!
That will make some serious exhaust reports and other bad behavior.
Tell me about it.I'm sure I woke the neighbors up this morn. :gob:
:hyst: :hyst: