dwaynemcfarlane
XS650 Enthusiast
What could it be?
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Troubleshooting for Backfiring?
- Thread starter dwaynemcfarlane
- Start date
Have you adjusted your fuel screws? Mine would backfire on the right side until I backed out the fuel screw a bit.
dwaynemcfarlane
XS650 Enthusiast
That is one possibility. Gotta test that when i hit the garage! 
Confirm the timing with a timing light. Timing too far advanced can result in back firing too.
-R
-R
dwaynemcfarlane
XS650 Enthusiast
Ill try that also !
!
A little more context would be helpful? backfiring out both cylinders or one, which one? BFing on acceleration or decell? BFing under load or no load? BFing with the choke on or off or both? Airfilters? Points? TCI? exhaust?
dwaynemcfarlane
XS650 Enthusiast
Im just trying to make myself a little troubleshooting list.
But first upstart today after 5 months of winter. backfiring idle on right cylinder it seems.
But damn nice to hear the engine
But first upstart today after 5 months of winter. backfiring idle on right cylinder it seems.
But damn nice to hear the engine
Somewhere during the process of a full and thorough tune up the backfiring will disappear and the odds of unplanned roadside thrashing will go down dramatically.
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My bike backfired from the day I got it in 1976. Didn't notice it much with the stock mufflers intil they rattled apart on the inside. With the shorty megaphones it's noticable. I've tried everything xcept replace the butterfly end seals. Timing at the more retarded fire mark is better, but your low speed, or air screw should be set to factory, then backed out slightly. I mean like a 1/4 to a 1/2 turn. Good luck!
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Yes, I agree with Gary. And as Gary once pointed out, (and it is very true), even just removing and reinstalling the tank will change things, particularly the throttle cable tensions. I have also found that the air screws have moved over many miles of time.
BFing on the right cylinder after a long period of sitting isn't totally unheard-of. Mine does it occasionally but usually clears up after 20-30 seconds. If it is sustained and only on one cylinder I would check my valve lash, verify spark on that cylinder, and change my plugs. If its a points bike, I would check my breaker timing and service my points.
Also forgot to mention that you should check your head pipe, a loose pipe or damaged exhaust gasket can cause popping as well.
Im just trying to make myself a little troubleshooting list.
But first upstart today after 5 months of winter. backfiring idle on right cylinder it seems.
But damn nice to hear the engine
If it is a upstart after the winter .. And it ran fine going in I Would wait a while ...
1 or 2 tanks perhaps 3 if it gets better gradually
Battery charged ?
The float valves at least can need some exercise time .
And the sparks plugs getting a heat up and so on.
Checking the bolts is a normal spring service.
In my view nothing strange or abnormal if some things offer a little resistance.
In the spring.
Some years even at lot of resistance.
But again if it ran going in usually nothing major has happened .. And it will go away.
I empty the tank going in And run the gas in the carburetors .. dry
and oil tank so that can cause a little smoke
if that is not done there can be Condensed water. Making substandard ignition.
Stay " Cool Under pressure " and it will go away mostly.
Use judgment ..
dwaynemcfarlane
XS650 Enthusiast
To be honest i did open the carbs and changed the diaphragms
To be honest i did open the carbs and changed the diaphragms
OK that changes the 1-2-3 tank Plan
Must be careful not to overheat .. But I would still suspect a spring upstart issue
What diaphragms ... And nothing else changed ?
Here are experienced people .than knows about what can happen after diaphragms are changed.
dwaynemcfarlane
XS650 Enthusiast
Steve C
XS650 Addict
I am not good at carburetors so i might best avoid talking to much about this
But i Know that the Throttle slide can be removed for this job leaving the carburetor in place .
Or as in the pictures taking the Carbs out
If So there is the possibility something needs to be tightened.
And some chemical can be sprayed on the outside looking for Leaks like
Starting fluid
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Diaphrams! That's a horse of a different color! Please don't take this the wrong way, but if it ran fine last fall, then why did you change the diaphrams?
Don't answer that, I'm sure you have a good answer! I would start by yankin the carbs again and blowing out all the holes, jets and journals. Measure the float levels, just in case. And be sure to gently tighten down the top caps evenly and slowly. Maybe a little grease around the sealing part of the diaphram and the top of the carb to allow for proper shifting and sealing of the new rubber.
Good luck!
Don't answer that, I'm sure you have a good answer! I would start by yankin the carbs again and blowing out all the holes, jets and journals. Measure the float levels, just in case. And be sure to gently tighten down the top caps evenly and slowly. Maybe a little grease around the sealing part of the diaphram and the top of the carb to allow for proper shifting and sealing of the new rubber.
Good luck!
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