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Why does my 97 suzuki gs500e make a bellowing vibration at/and only at about 5200rpm in any gear?
A little after I bought this motorcycle I noticed a very deep and bellowing vibration coming from the engine whenever I would reach about 5200 rpm. This vibration occurred in any gear and was particularly annoying in 6th gear because at 5200 rpm is about 60 mph (highway speed). I took it to a local motorcycle mechanic (con-artist) and told me it could have to do with the dual carbs not being synced or something with the cam timing. He was about to charge me over 200 bucks for a shot in the dark so I took it upon myself to try to troubleshoot. Online I found directions for timing the cams for my exact bike. After I had done everything to spec the vibration still occurred. Not wanting to pay for a carb sync, I found on youtube how to make a somewhat accurate carb sync tool and after I had done all of that the vibration still occurred. I'm not a dumbass and I can accurately say I'm mechanically inclined so I knew what I was doing through both of these troubleshoots. I'm now wondering if there is any other possibilities of what the vibration could be coming from. Please help!!! And remember, cheapest solution is the winning solution on my budget of a father/student. Thanks.
And with the dual carb sync, I did a carb rebuild too- gaskets, O-rings and jets. No main or pilot jets though.
Crash:
The engine has dual overhead cams with a chain running from the driveshaft to the first camshaft then to the next camshaft. I timed the cams based on a specified position of the driveshaft while also have a certain number of links between the certain markings on each cam. This procedure was done by the book and correct. The camshafts, only about 8 inches long and an inch and a half wide each, looked in perfect condition and the chance of them bending seems implausible since they are so rigid.
Hopefully this next statement will make things a little more clear too. Acceleration and performance before 5200 rpm acts as normal, at 5200 rpm the vibration occurs and feels as if there is a loss of power and acceleration, after 5200 rpm the acceleration and performance returns to normal.
James:
How might I go about changing my final gearing? Transmission gearing or sprocket gearing? I actually was thinking about changing my sprocket ratio so that I get more speed and less torque to improve my mileage.
Tom:
In the example that you gave me, if I were to power through 5200 rpm there wouldnt be any hesitation or momentary deceleration, only a very quick increase and decrease in the vibration. It could just be my imagination that when I'm cruising at 5200 rpm the vibration causes a lack of power, but I only say that because the vibration is so strong that any normal person would hesitate when they felt it. When I intentionally cruise at this rpm and listen to the noise, it sounds like the vibration travels on a sine wave of getting stronger and softer with a frequency of roughly 1 wave a second. It's actually fairly rough to feel the vibration for an extended amount of time because its almost mesmerizing to the point where you feel like getting speed wobbles.
But
3 Answers
- Anonymous9 years agoFavorite Answer
It sounds to me like the motor is fine, but just has a "rough spot" at that speed, where harmonics may happen to create a buzz. You could try changing your final gearing to move it to a road speed that you use less. You might want to also loosen and re-torque the engine-mounting bolts.
Bent camshafts? Not likely!
- Anonymous9 years ago
So it returns to normal when you go through 5200 rpm?
At 5200 rpm your engine should just be starting to get really happy, and ready to go.
If you really dip the throttle (in say, 3rd gear) does the bike pull right through 5200? I mean does it pull through FAST? Does it in any way hesitate at 5200?
I'm thinking that the motor might just be coming into the power band, and is telling you that it is ready to rock!
The carb synch was probably a bs call, that is much more significant at LOW speeds. You know the cams are timed, if it pulls right through and otherwise runs ok, I'd think maybe it is just normal behavior. That's only a guess, you realize.
- CrashLv 79 years ago
Sounds like you're looking in the right area, your bike might come on the cam at 5200, so that's where the problem is. Any chance the camshaft might have gotten bent or out of alignment? Any work done in that area? I'd ignore the carbs. Other than tearing down the engine and maybe replacing the camshaft I can't think of what else you might try.
