Backfire on idle issues

[Jferchal95]

Hi all,

As the title suggests, i appear to have some issue with the bike backfiring while at idle and sometimes even at low revs on decel (2000 or lower).

Its bugging the hell out of me especially sitting at traffic lights :|

The bike is a ‘99 curvy with a stock air filter, delkevic stubby slip on and 142.5 main jets on both carbs...

Any info would be appreciated, cheers!

[R1ffR4ff]

First thing is to look for air-leaks around the Carb inlets and also any leaks in the Exhaust system.

[Jferchal95]

Plugs are only 1500 miles old if that, no leaks in the exhaust system that i can tell, i’d like to think the problem arose around the time i changed the jets in the carbs, but it doesnt always do it only every other day sort of thing so it is a strange one.

Will whip the tank off next weekend and see if theres anything going on around the carbs and go from there, cheers!

[R1ffR4ff]

Plugs are only 1500 miles old if that, no leaks in the exhaust system that i can tell, i’d like to think the problem arose around the time i changed the jets in the carbs, but it doesnt always do it only every other day sort of thing so it is a strange one.

Will whip the tank off next weekend and see if theres anything going on around the carbs and go from there, cheers!

Also do searches for SV choke plunger problems as that seems to be quite common especially when the bikes have been left unused.

[johnnyrod]

Yep, sounds like it's running too rich, which at low revs is likely to be sticky choke(s)

[maviczap]

I'll also say sticky choke plunger having just cured mine of similar backfiring problem.

Might not be the plunger itself, but the choke cable, as I'd taken my plungers out a while back. When I unclipped the plunger from the cable it was quite clear how gritty the cable was.

I squirted some GT85 down the cable which has cured the back fire by allowing the plunger to fully withdraw when you push the choke lever back. I think a new cable is the answer.

Top tip, the plunger retaining screws are very soft, and easy to chew up, so I replaced them with stainless Allen bolts of the same thread size.