carb slide flutter - SV650.org

25-03-06, 11:25 PM

I just bought a 2000 SV650. When I open the throttle suddenly, the acceleration is uneven - it pulls, then hesitates, and then pulls again. Sadly, I rode rather gently during the test ride, and didn't notice the problem before I bought it. The previous owner says he had the bike in storage for a while, and then had a Suzuki shop clean the carbs before he sold it to me. I've checked the pilot jets - they're clean.

I tried removing the air filter so that I could watch the carb slides. I put the bike on a stand so the back wheel is off the ground, and I put the bike in a high gear, so that the engine doesn't rev quite so quickly when I open the throttle. What I see is that when I open the throttle, both carb slides flutter up and down like crazy. The fluttering lasts for maybe half a second, and the slides go from all the way down to all the way up, and then back down (or pretty close to it), several times during the half second. It's happening too fast for me to count how many times they go up and down, but I'm guessing it's maybe 5 times in that half second.

Any idea whether this is normal? It's hard for me to imagine that the carbs could be designed to operate this way - how is the carb going to provide a precisely metered amount of fuel to the air stream when the slide is fluttering around like a flag in a 20-knot wind? If it's not normal, any thoughts on what's causing it?

26-03-06, 12:36 AM

Some ’flutter’ is quite normal, remember the engine/valves opening and shutting means that the airspeed is not constant. Also remember that there is a spring holding the slider down.

If your ‘flutter’ is excessive, then this would suggest that perhaps vacuum is being lost. This could be due to things like split/leaking diaphragm, blocked orifice in the slider, inlet manifold leak, loose carb clamps, split fuel tap vacuum pipe etc etc.

On slightly different tack, you might want to test your throttle position sensor!?

27-03-06, 07:37 AM

Are there any modifications to the bike, exhaust etc?

Because you didn't notice the problem on a gentle test ride I would suggest that the bike is running lean in the midrange and you need to adjust your needle position.

The flutter of the slide is normal, as stated. The carbs rely on vacuum pressure to pull the slide back and allow air through, picking up fuel on the way. As was also stated, check for loose fittings and leaks but I'd start on the needles.

johnnyrod · 27-03-06, 11:27 AM

I'd check the carb balance I think, and I think Peter is probably right, it may be running lean. Is it all stock?

25-03-06, 11:25 PM	#1
mregehr Guest Posts: n/a	carb slide flutter I just bought a 2000 SV650. When I open the throttle suddenly, the acceleration is uneven - it pulls, then hesitates, and then pulls again. Sadly, I rode rather gently during the test ride, and didn't notice the problem before I bought it. The previous owner says he had the bike in storage for a while, and then had a Suzuki shop clean the carbs before he sold it to me. I've checked the pilot jets - they're clean. I tried removing the air filter so that I could watch the carb slides. I put the bike on a stand so the back wheel is off the ground, and I put the bike in a high gear, so that the engine doesn't rev quite so quickly when I open the throttle. What I see is that when I open the throttle, both carb slides flutter up and down like crazy. The fluttering lasts for maybe half a second, and the slides go from all the way down to all the way up, and then back down (or pretty close to it), several times during the half second. It's happening too fast for me to count how many times they go up and down, but I'm guessing it's maybe 5 times in that half second. Any idea whether this is normal? It's hard for me to imagine that the carbs could be designed to operate this way - how is the carb going to provide a precisely metered amount of fuel to the air stream when the slide is fluttering around like a flag in a 20-knot wind? If it's not normal, any thoughts on what's causing it?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Restrictor slide/washers	benjyman	Stuff Wanted	0	18-09-08 10:48 PM
wanted nokia 6500 Slide (or simerler)	hovis	Idle Banter	14	02-09-08 07:31 PM
Unbelievable Slide!	lukemillar	Racing and Paddock Chat	10	20-08-08 05:40 PM
samsung sgh-g600 slide mobile for sale	ging6996	Idle Banter	0	27-07-08 05:52 PM
Flutter flutter beep beep...	Baph	Idle Banter	3	01-03-07 01:43 PM

26-03-06, 12:36 AM	#2
Blue_SV650S Guest Posts: n/a	Some ’flutter’ is quite normal, remember the engine/valves opening and shutting means that the airspeed is not constant. Also remember that there is a spring holding the slider down. If your ‘flutter’ is excessive, then this would suggest that perhaps vacuum is being lost. This could be due to things like split/leaking diaphragm, blocked orifice in the slider, inlet manifold leak, loose carb clamps, split fuel tap vacuum pipe etc etc. On slightly different tack, you might want to test your throttle position sensor!?

27-03-06, 07:37 AM	#3
PeterM Guest Posts: n/a	Are there any modifications to the bike, exhaust etc? Because you didn't notice the problem on a gentle test ride I would suggest that the bike is running lean in the midrange and you need to adjust your needle position. The flutter of the slide is normal, as stated. The carbs rely on vacuum pressure to pull the slide back and allow air through, picking up fuel on the way. As was also stated, check for loose fittings and leaks but I'd start on the needles.

27-03-06, 11:27 AM	#4
johnnyrod Member Mega Poster Join Date: Jul 2003 Location: Doncaster, oop norf Posts: 2,128	I'd check the carb balance I think, and I think Peter is probably right, it may be running lean. Is it all stock?