Vibration under load
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Vibration under load
Hey guys, my bike has a vibration when it is under load, if i pull the clutch in it seems to go away. Mostly noticeable around 50 and 80 km's per hour. I initally thought it was the front wheel out of balance as there is no wheel weight on it. I would think if it was the front wheel it wouldn't go away when i disengaged the clutch. Any ideas? It's a 99 superglide.
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Joined: Oct 2007
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From: Palm Harbor fl.
yeah air fuel ratio. you notice this at a specific speed. does the vibration occur as bad at different rpm's at those given speeds. like in 3rd instead of fourth. Here's what I had happening to me. at RPM's just off idle my bike vibrated more than the rest of the time. BASICALLY IT VIBRATED TOO MUCH WHILE IN A CRUISING GEAR FORCING ME TO KEEP THE RPMS TOO HIGH TO AVOID THE VIBRATION. I had the dynojet kit in there. I replaced my dyno jet kit with an 88 sporty needle and 46 low 195 high. Now no more vibration.
With the throttle from about 1/8-1/4 open the bike relies on the width of the straight part of the needle to determine the AFR. Stock, the needle is too wide for a stage1 kit and you are very lean there. The dynojet kit is probably about the same width or more and I had problems with it. The sporty needle is thinner allowing for a richer AFR ratio at 1/8 to 1/4 throttle openings. Now heres the thing, most will just add bigger jets instead of changing the needle. The result is the bike runs too rich except for 1/8 to 1/4 throttle position. You get a rich running bike that vibrates too much while cruising at lower rpm ranges.
I tried new mounts, alignment, other possibilities, but the above is what caused my problem. Of course you could be experiencing something different. a good way to check this is to get the bike warm, and while parked, hold the throttle open a bit(just off idle)and see if your bike starts to vibrate more heavily. If so a rejet with the 88 sporty needle could be what you need.
With the throttle from about 1/8-1/4 open the bike relies on the width of the straight part of the needle to determine the AFR. Stock, the needle is too wide for a stage1 kit and you are very lean there. The dynojet kit is probably about the same width or more and I had problems with it. The sporty needle is thinner allowing for a richer AFR ratio at 1/8 to 1/4 throttle openings. Now heres the thing, most will just add bigger jets instead of changing the needle. The result is the bike runs too rich except for 1/8 to 1/4 throttle position. You get a rich running bike that vibrates too much while cruising at lower rpm ranges.
I tried new mounts, alignment, other possibilities, but the above is what caused my problem. Of course you could be experiencing something different. a good way to check this is to get the bike warm, and while parked, hold the throttle open a bit(just off idle)and see if your bike starts to vibrate more heavily. If so a rejet with the 88 sporty needle could be what you need.
Last edited by rounder; Mar 29, 2009 at 08:01 PM.
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It happens more at higher RPM's. Lower RPM's it seems to go away. If i'm in 3rd gear at high RPM's it will vibrate and when i shift into forth and the RPM's lower it will go away. It feels like the front wheel is out of balance. This is my first bike so i can only compare it to a car. It's like driving a car with a wheel out of balance. I have plans at taking it to the dealrship and have them set up my carb cause i think the guy i bought it from had it messed up. I bought it in the winter so could not road test it. It had a brand new set of plugs in it so when he brought it to me it started and sounded fine cold but when it ghot warmed up it doesn't run quite right. I had the ca
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carb off and cleaned it up but it didn't make any difference. I'm hoping its just a carb issue. I set the idle air/fuel mixture at 2 1/4 turns out but i can adjust it in all the way or out and it does not make a difference. I am a licenced automotive tech but never worked on bikes.
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My ohms are reading low on my plug wires and i can't seem to get a good reading on my coil. If i go by what my service manual tells me my coil is bad. Can anyone direct me in how to check the coil properly. Maybe a web sight. Thanks to all.