Backfiring / popping at low revs - carbed standard setup - SV650.org

05-08-06, 12:07 AM

I've got a pretty standard road curvey road SV.

Since I got it second hand it's 'back'fired a bit at low revs.

Seems to be fine higher up, but especially from the front cylinder it seems to pop a bit below 3-4k.
I stuck some new (well new to this bike, were in my minitwin) plugs in and the old ones looked like both cylinders are running rich.

Taking the air box of and starting it up, it was actually properly bike firing a little at low revs (through the front carb at least - didn't play too much though!)

The air filter looks ok.

Exhaust is standard as everything else seems to be.
Exhaust seems to be secure without leaks.

Any ideas what's likely to cause this?
I was thinking maybe float height set too high, but I still don't have a great understanding of carbs

.

05-08-06, 07:23 AM

no probs the sv is a backifiring machien

05-08-06, 08:59 AM

Bit embaressing when you're filtering through London behind a courier and your bike mikes a shotgun sound - the courier then pulls over and you feel obliged to bugger off even faster, than look even more of a twonk

.

It backfires a whole load more than my race SV with full M4 system does.

13-08-06, 12:01 PM

My 02 did the same thing and when I was checking the valves I noticed that the front carb intake did not look right. When the Suzuki employee put the carb into the intake it did not get pushed into it,instead the intake rolled and and it was left that way. I ordered an intake for it and I hope that it will cure the problem.

NedSVS · 13-08-06, 07:17 PM

Don't want to be alarmist, but backfiring through the air box is sometimes related to the inlet valve not being shut properly on the firing stroke. Two possible reasons for this: bent valve or no valve clearance. The valve clearances are usually good till way past the recomended checking mileage on the SV motors, so a bent valve would be more likely.

23-08-06, 11:33 PM

Meant to post, sorted this - so incase others have the same problem...

Turned out I was not being very observant.

The cover for the vacuum tube on the front carb wasn't on.
Put it back on and it runs fine.

Passed MOT and did a day being followed by a police man (bike safe) no problems!
Also only needs a tiny bit of choke when first started.

05-08-06, 12:07 AM	#1
G - renamed Guest Posts: n/a	Backfiring / popping at low revs - carbed standard setup I've got a pretty standard road curvey road SV. Since I got it second hand it's 'back'fired a bit at low revs. Seems to be fine higher up, but especially from the front cylinder it seems to pop a bit below 3-4k. I stuck some new (well new to this bike, were in my minitwin) plugs in and the old ones looked like both cylinders are running rich. Taking the air box of and starting it up, it was actually properly bike firing a little at low revs (through the front carb at least - didn't play too much though!) The air filter looks ok. Exhaust is standard as everything else seems to be. Exhaust seems to be secure without leaks. Any ideas what's likely to cause this? I was thinking maybe float height set too high, but I still don't have a great understanding of carbs .

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Backfiring.	Jay1	SV Talk, Tuning & Tweaking	5	11-03-08 03:54 PM
Pointy K3> twin can setup for 650, does 1000 setup fit?	aposegil	Stuff Wanted	3	26-10-06 03:41 PM
update on my 2000 sv650 backfiring/popping problems	klohiq	SV Talk, Tuning & Tweaking	8	17-08-06 09:36 PM
Backfiring	Avtjr64	SV Talk, Tuning & Tweaking	18	10-09-05 08:20 PM
backfiring.	echomadman	SV Talk, Tuning & Tweaking	5	27-05-05 12:11 PM

05-08-06, 07:23 AM	#2
Blazingsvbiker Guest Posts: n/a	no probs the sv is a backifiring machien

05-08-06, 08:59 AM	#3
G - renamed Guest Posts: n/a	Bit embaressing when you're filtering through London behind a courier and your bike mikes a shotgun sound - the courier then pulls over and you feel obliged to bugger off even faster, than look even more of a twonk . It backfires a whole load more than my race SV with full M4 system does.

13-08-06, 12:01 PM	#4
william t. Guest Posts: n/a	My 02 did the same thing and when I was checking the valves I noticed that the front carb intake did not look right. When the Suzuki employee put the carb into the intake it did not get pushed into it,instead the intake rolled and and it was left that way. I ordered an intake for it and I hope that it will cure the problem.

13-08-06, 07:17 PM	#5
NedSVS Member Join Date: Mar 2005 Posts: 572	Don't want to be alarmist, but backfiring through the air box is sometimes related to the inlet valve not being shut properly on the firing stroke. Two possible reasons for this: bent valve or no valve clearance. The valve clearances are usually good till way past the recomended checking mileage on the SV motors, so a bent valve would be more likely.

23-08-06, 11:33 PM	#6
G - renamed Guest Posts: n/a	Meant to post, sorted this - so incase others have the same problem... Turned out I was not being very observant. The cover for the vacuum tube on the front carb wasn't on. Put it back on and it runs fine. Passed MOT and did a day being followed by a police man (bike safe) no problems! Also only needs a tiny bit of choke when first started.