Odd tick over issues

1999 sv650s. Std down pipes with beowulf race can, std air filter, not sure if carbs have been rejetted to match race can.

Had the bike since July and ran fine for 550 miles. Its always back fired when ya shut the throttle off which sounded nice so didnt worry about until...........
5 mile ride to work the other week, got to work shut throttle off no backfire and revs sit at 4.5k rpm. Park it up, twiddle idle adjuster and it happily goes back down to 1.7k rpm. Switch off, rad fan runs on for 5 mins which has never come on before.
12 hours later, starts up first time and idle speed normal so start to ride home. No back firing at all and feels a lil wooly at top end of rev range. Pull in home and revs again up at 4k and rad fan running when I switch off 😕

Anyone got any ideas plz?

[TamSV]

Tank up, airbox off.

Did you use the choke to start? Choke plungers can get sticky on the curvy - definitely worth a look. If that's not it then worth checking throttle cables are properly adjusted or if somethings sticking. Also check for air leaks.

Thanks for reply. Choke I think is fine as when u let go the lever returns and revs drop. Had tank off and found front carb rubber to airbox wasnt tight at all which would explain the back firing when I got the bike. Also both rubbers to the airbox were not seated correctly inside the box. Bike only does it when warm so I'm a lil confused.

Pulled it apart again today. Front plug was whiter than casper the friendly ghost and rear one was black. Cleaned em up & re-fitted. Adjusted the throttle cables at the carb, double checked all pipework for cracks then headed out for a spin.

Now theres a tiny wee back fire on idle every 2 ish seconds, but the idle doesnt wander anymore which is nice. Power delivery sub 4k rpm is spluttery but go over that and its lovely and smooth and far improved from when I first got the bike.

So looks like it'll be off to a local bike shop to have carbs balanced and set up correctly. Also tried to adjust the clutch, but the cable is on max at both ends so I'll need to order a new un and quite possibly a clutch kit as well (35k miles).
Tempted to tackle clutch change myself while its off the road over winter along with a service.

[Bibio]

white front black rear tells me the rear choke plunger is sticking.

[TamSV]

Originally Posted by Bibio

white front black rear tells me the rear choke plunger is sticking.

+1 Very common and doesn't necessarily show up as a problem at the lever.

Originally Posted by Tdi90

Also tried to adjust the clutch, but the cable is on max at both ends so I'll need to order a new un and quite possibly a clutch kit as well (35k miles).

Are you sure about the clutch? 35k is nowt really.


Did you adjust the clutch at the worm gear? The cable adjusters only adjust the cable slack. The actual adjustment is at the worm gear (it's under the sprocket cover and sits in front of the sprocket).


If it hasn't been done for a while, it's well worth taking out the worm gear/lifting mechanism and dismantling it for cleaning and regreasing. It's something you'll want to do as part of your winter service anyway, costs nothing and might just solve your problems.


I'll be doing mine in the next couple of days while changing chain and sprockets so if you want I can post up pics of the whole process.

Could it be a spark plug lead is breaking down and making it fire sporadically!?

[Bibio]

good call nutz as its a known issue but usually the front.

worth a try, just thinking is it popping back through the carb? that's normally a sign of an ignition problem.

Didnt adjust clutch at worm gear but will give it a go in a couple of days.

Choke plungers; while I had the airbox off I operated the choke a few times while hovering my ears over the carbs and could very clearly hear the plungers operating ( a zoooooop click kinda noise from each carb)

The back firing on tick over isnt lound. Can you post video clips on here?

A local guy has offered to ultrasonic clean then balance the carbs, does that sound a decent price?