FJ 1100 Backfiring

[FJ Bob]

Hi Everyone

I am getting my bike ready for spring after some clutch mods and the install of a new choke cable over the winter.

The choke cable seems to work and the bike starts right up.  However I get some popping and no the smooth idle I'm used to and when I start to give it some throttle the bike backfires right up through about 3000 rpm.   I used some Seafoam to see if it was a fuel issue although I did stabilize the gas in the fall. No luck.

So having not done anything in that area other than the choke cable I'm going start with the plugs to ensure they are fine.  If that reveals nothing then I guess I'll move to the carbs to see if I can find anything.

It ran perfect last year so this was not expected.

It is still around 0 Celsius up here so temp could be an issue and the popping /backfire seems to be reduced as the bike warms up but I'm not convinced that even at 30 Celsius the problem would be resolved.

Would appreciate if anyone  has any suggestions or can shed any light on other things which I should look at.

Thanks


Bob

[FJ_Hooligan]

If you have ethanol poisoned fuel in it, then one or more idle circuits may be clogged or partially obstructed.

[FJ Bob]

Sorry I posted this in the wrong section. 

Hopefully Admin can move it to FJ1100 / FJ1200 Running Problems or delete and I'll repost

Thanks

Bob

[FJmonkey]

Moved

[fj1289]

If you have ethanol poisoned fuel in it, then one or more idle circuits may be clogged or partially obstructed.

This - most likely idle circuits

Another possibility is a weak battery.  Bad battery can lead to weak spark - carbs can get blamed for ignition issues.   

[FJ Bob]

Hi Everyone

Problem solved and I must admit it was my fault.

When I was installing the new choke cable it appears that the vacuum hose pulled off of the petcock. 

I've reconnected it and returned the petcock to the on position and all is fine.

Thanks for your help and suggestions.

Bob

[red]

Hi Everyone
Problem solved and I must admit it was my fault.  When I was installing the new choke cable it appears that the vacuum hose pulled off of the petcock.  I've reconnected it and returned the petcock to the on position and all is fine.  Thanks for your help and suggestions.
Bob

Bob,

Happy that you found the problem. 

Hate to say, though, the bike should not run one minute with no vacuum to the petcock.  That gadget is a safety feature; in case the engine quits for any reason, the fuel flow is shut off.  Without that, if you have a leaky needle-and-seat in any carburetor, gasoline can flow through the carb into the crankcase.  Gas+oil there usually means a totally ruined engine, if you try to run it like that.  Then overnight, gas can also empty from the crankcase onto the ground and endanger any structure or people nearby, in the worst case.  RPM has what you need, for a bad petcock.  I would not consider a bad petcock to be a trivial matter, for the bike or what may be around it.

You can test the working of the vacuum petcock using mouth suction (or any small vacuum pump) on the vacuum hose, to turn the flow of fuel ON or OFF at the petcock.
.

[FJ Bob]

Red

I agree and it didn't run with the petcock in the "on" position.   The other issue was that the petcock was in the "prime" position which allowed the bike to run although not well.  So with the petcock back in the "on" position and the vacuum hose installed properly all is back to normal.

Regards


Bob