So yesterday while riding my bike shot up to 7,000 rpm while idling at a light and wouldn't go below 4k. Choke, throttle, idle adjustments all did nothing.
Last night, I pulled the carbs out, cleaned them installed new gaskets in the float bowls. I put every back together today tightened the throttle cables (there was always a lot of play before it did anything) set the idle screw to nothing, and then started feeding the bike gas until it was warmed up. Again, it shot up to 4k and would not come back down. I then turned the carb sync screw to the right and boom, idle dropped. I turned it 2 whole turns then adjusted the idle screw some and took this video. I do not have a manometer so I took this video to get your guys opinion on if the carbs sound synced OK, etc.
Did I fix the problem or band-aid it poorly? The bike sounds better than it ever has, I think. The throttle was nice and responsive and the bike dropped back to idle quickly and didn't seem to be spiking for once, it was hovering quite nicely.
Quote from: zephyr_bike on December 20, 2013, 07:47:40 PM
So yesterday while riding my bike shot up to 7,000 rpm while idling at a light and wouldn't go below 4k. Choke, throttle, idle adjustments all did nothing.
Last night, I pulled the carbs out, cleaned them installed new gaskets in the float bowls. I put every back together today tightened the throttle cables (there was always a lot of play before it did anything) set the idle screw to nothing, and then started feeding the bike gas until it was warmed up. Again, it shot up to 4k and would not come back down. I then turned the carb sync screw to the right and boom, idle dropped. I turned it 2 whole turns then adjusted the idle screw some and took this video. I do not have a manometer so I took this video to get your guys opinion on if the carbs sound synced OK, etc.
Did I fix the problem or band-aid it poorly? The bike sounds better than it ever has, I think. The throttle was nice and responsive and the bike dropped back to idle quickly and didn't seem to be spiking for once, it was hovering quite nicely.
Sounds good to me!
When you said this:
QuoteI then turned the carb sync screw to the right and boom, idle dropped. I turned it 2 whole turns then adjusted the idle screw some and took this video
Makes me think you have a vacuum leak? If the idle adjustment screw is bottmed out, the throttle butterflies will be at nearly 90* vertical. In other words, no room for air to get in, but if the idle was hanging at 4k, then air is still getting in or the engine would have died immediately.
As is suggested by others here, you can check for vacuum leaks by spraying some starting fluid in the general area of the leak while the engine is idle. If the RPMS shoot up, you've got a leak.
One cylinder....sounds just like mine did when cdi needed replacing..new plug was sparkling..never used lolol
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So 1 vote for sounds good but possible vacuum leak and 1 vote for sounds like it's only running on one cylinder.
I'll test vacuum and spark after some coffee. Spark plugs were replaced for a starting issue a few months ago though.
It sounds badass. I love the gauges. What kind are they? It does sound like it has a miss though but sounds good. What kind of exhaust do you have?
Quote from: zephyr_bike on December 21, 2013, 08:41:00 AM
So 1 vote for sounds good but possible vacuum leak and 1 vote for sounds like it's only running on one cylinder.
I'll test vacuum and spark after some coffee. Spark plugs were replaced for a starting issue a few months ago though.
I've had my bike run on one cylinder and it would absolutely NOT STAY RUNNING. It was a total pain to even get started, and would sound absolutely horrible when revved up and backfire.
I think you're safe. The easy way to check if feel near the headers after the bike has idled for a minute. If one side is not running, the header will feel cold.
Quote from: ron freeman on December 21, 2013, 03:54:05 PM
It sounds badass. I love the gauges. What kind are they? It does sound like it has a miss though but sounds good. What kind of exhaust do you have?
I replaced all of the lights on the bike (other than the headlight and brakelight) with LEDs. So the gauges are just stock with red LEDs. The exhaust is stock too.
Thanks!
Quote from: zephyr_bike on December 22, 2013, 01:20:37 PM
Quote from: ron freeman on December 21, 2013, 03:54:05 PM
It sounds badass. I love the gauges. What kind are they? It does sound like it has a miss though but sounds good. What kind of exhaust do you have?
I replaced all of the lights on the bike (other than the headlight and brakelight) with LEDs. So the gauges are just stock with red LEDs. The exhaust is stock too.
Thanks!
Did you use plug and play LEDs or something custom? I've wanted to replace all of mine, but the information here is not well put together about which specific LED to use.
I bought these from superbrightleds:
1 74-GHP Green 2.49
1 74-RHP Red 2.49
1 74-BHP Blue 2.49
2 WLED-R5 Red 2.99
1 WLED-A4-90 Amber Wide 1.59
The colors weren't necessary for the instrument panel since you're replacing white LEDs but it made them very vibrant. The amber is a direct replacement that works for the turn signal indicator. Lowered the power drain on the battery too.
Another quick and dirty sync test is to remove the spark plug lead from the spark plug for a few seconds, first one side, then the other side. if the bike dies on one of them you have found your problem.
It will run on a single cylinder but not very well.
Try not to unplug it for too long as it may damage the ignition circuit, I've had mine off for about 10 seconds at a time with no problems.
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I rode my 02 GS home about 10 miles on one cylinder and never gave it a thought about possibly causing any damage doing it. Was a loose plug wire in one coil causing the problem. Only one big hill and I got up as much speed as possible and just made it over the crest.
Previously I rode a Nighthawk 650 home on 2 of 4 cylinders about 30 miles. Was a loose primary wire on one of the 2 coils. The Nighthawk ran a little better on 2 than the GS did on one and didn't have a problem on that same hill.
If not too far from home I'd rather fix it there than along side the road.
I'll put up another vote on vacuum leak. Even in the video, it almost seems there is a slight delay when you release the throttle, or as though the rpms aren't dropping evenly and as fast as they should. I also find it hard to believe your carb screws turned two full rotations while riding all of the sudden, so it just makes me question why that would actually 'fix' the problem when the screw position was fine previously. The symptoms you describe when it happened are tell tale of a vacuum leak. :cheers:
- Bboy
Edit: I reread that first post and now notice that you did set the idle screw to zero first when setting the carbs back up. You may be okay now that you have been through the carbs and buttoned everything up... I do still think it was a vacuum leak that initially caused the issue, though taking carbs on and off may have fixed the issue. But depending on how warm your bike is in the video, I do still notice it almost seems to drop more slowly in rpm at 4k revs when you release the throttle... don't know if its worth looking into, but id say how it is right now, your bike is worth riding for sure!