rear end shake over 55

[Anonymous]

ok, i've got an 82 650G and this year its got 2 new tires (installed maybe 4 montsh ago) and just had a carb clean & synch.

now that i've got decent rubber etc i've been pushing a little harder and i started to notice a rough bounce/shake whenever i started to decelerate from around 85.. it started to become more frequent at lower speeds but smooths out when i accelerated....

when i pulled over nothing seemed loose....

i took it home on city streets (ie slower) and it seemed ok however at the same time it went to reserve so i'm thinking maybe its related...also i have a very slow leak on the rear tire (they reused the valve...need to fix sometime) so today after a full tank of gas and tire pressure checked (rear was down a few pounds) took it on freeway and felt it as soon as i hit 55....

so any thoughts..could the rear tire have become unbalanced ?
all the fluids incluuding the shart were replaced last summer...

thanks for any help...

[redliner1973]

back off the rubber boot thingy and see if the U-Joint itself or the mounting bolts are loose.

[Anonymous]

rubber boot thingy....u-joints/mounting bolts..

are we talking the shaft, the frame....i'm by no means an expert but i can figure stuff out with a little help..

thanks for the response, just a few more details...

Phil

[redliner1973]

On the lower left part of bike, by the kickstand, there is a rubber booty thingy that comes out of the back of the engine (tranny area) held on by a either a clamp or a rolled spring. Another way to find it is to follow the drive shaft, starting at the differential, and working forward. it is at the swingarm. pull the booty back and you will see inside, the U-joint and 4 bolts that hold it onto the tranny. Check to see if the bolts have worked there way loose.

[Anonymous]

thanks for the excellent description....

assuming their loose do i need to torque to x lbs or can i dab some red/blue ?? locktite and give it hell ?

[Anonymous]

thanks for the excellent description....

assuming their loose do i need to torque to x lbs

Yes

or can i dab some red/blue ?? locktite

Yes

and give it hell ?

Oh please no. I *THINK* they're in the low 30's but can't remember. If I hadn't sold my bike this past week, I'd have the torque values. Someone will have them. Nick??

[Dark Jedi]

I'll look this up tonight. Fer dog's sake, don't torque the hell out of em!

Loctite is your friend in there. I use red on my bike, and it hasn't shaken loose.

Also, check the fluid level of the shaft. Check it on the center stand, oil should come up to the fill hole, like the pumpkin on a car. Now is a good time to change that oil (90W gear oil) too. Like as not it has the factory oil in it. People forget to check and change it more often than not on these.

Good bike, two up it will still pull your helmet back when you lay on the throttle.

[Anonymous]

i replaced the shaft oil last year but it doesn't hurt to check the level...

according to the manual (and if i'm reading correctly) this is the process that involes removing the gear shift, engine cover & getting ot the clip that way.....right ?

[Anonymous]

well i took a quick look and they didn't seem loose....should i expect them to be finger loose or is it just a couple of pounds in torque difference ??

[Planecrazy]

Back to a different track, Phil ... you asked if the wheel could have become unbalanced. Yes, it's possible that one or more of the balance weights could have come loose and fallen off. Joe Nardy has a nice homebuilt balancing jig at his place ... if you ask really nice I'll bet he'll make time for you to ride out and re-check / re-balance the wheel, although depending on the distance you might want to break down and have your local shop do it.

Good Luck,
Steve 8)

[bwringer]

Are the steering stem bearings reasonably tight and fresh?

It's hard to tell from this computer chair a couple hundred miles away if this could be a handling problem or a drivetrain problem.

Loose engine mount bolts? Play in the swingarm bearings?

Missing or overly squashed axle spacers?

Bad wheel bearings?

Are the tires still round and the beads properly seated?

Any flat sealer goop in the tires that may have become less goopy and more solid than it should?

Just some things to consider.

And at least replace that leaky valve core. They're three for a buck or so.

[Joe Nardy]

Re: rear end shake over 55

also i have a very slow leak on the rear tire (they reused the valve...need to fix sometime)

Phil,

The time to fix the slow leak is NOW! It will not get any better and the consequences of it getting worse can be rather severe.

Try to determine if the problem is at the front or the rear of the bike. You say it occurs on deceleration. If you pull in the clutch does the problem stop, get better or worse, or stay the same? I'm thinking that since it is just on deceleration (it is just on deceleration, isn't it?) it is probably a drivetrain issue on deceleration load. Another possibility could be something in the front end due to forward weight transfer during deceleration.

Other than that, lots of good suggestions have been posted. It is very hard to diagnose something like this without seeing, hearing, and feeling the problem. If you think it would be okay to ride to Chicago we could check it out at my house. At the very least we could unmount the rear tire, replace the valve stem, and balance it.

As a quick drivetrain check you can set the bike on the centerstand and rotate the rear wheel in both directions. See how much free play there is when you reverse direction. There should probably be a small amount of free play but it shouldn't be enough to make any bad noises.

Joe

[Anonymous]

did some more diagnosis....

first off...is there a good way to find leaks on bike tires.....its a little big for the sink....i tried dawn around the base of the valve with no results...i did a visual inspectoin and nothing seems out of place...

regarding the banging/thudding type noise....
it now appears constantly over 55 on both accel & decel....pulling the clutch does appear to make it go away...

i did the rear tire rotation and it rotated freely forwards & backwards with no abnormal noises (not sure what you mean by free play joe)

drive train sounds expensive....

[Anonymous]

Shaking your tail at 55 is dangerous. You could break a hip!

[Joe Nardy]

did some more diagnosis....

first off...is there a good way to find leaks on bike tires.....its a little big for the sink....i tried dawn around the base of the valve with no results...i did a visual inspectoin and nothing seems out of place...

Use some soapy, sudsy water. Splash it on with a rag. Check the valve stem where it meets the rim, check the inside of the top of the valve stem (it could be that the valve core is not screwed in tightly), check the beads where the tire meets the rim, check the tread area. Take your time and look carefully. If it's leaking there has to be bubbles. However they might be tiny. Did this wheel have a tubeless tire previously? If not there is the possibility you have a leaky rim. I've never seen this but it is a possibility.

regarding the banging/thudding type noise....
it now appears constantly over 55 on both accel & decel....pulling the clutch does appear to make it go away...

i did the rear tire rotation and it rotated freely forwards & backwards with no abnormal noises (not sure what you mean by free play joe)

drive train sounds expensive....

Phil,

The fact that the clutch in makes the noise go away makes me think drive train. Whether you are accelerating or decelerating with the clutch out, there is a load on the drivetrain, either from acceleration or engine braking. Pulling in the clutch makes the drivetrain mostly freewheel. If your problem did not exist before the tire change and started immediately after the tire change I would think something got assembled improperly. As someone previously suggested, check all spacers, washers, etc. to see that they are assembled in the proper order. Also make sure nothing (such as spacers, washers, etc.) is missing.

Good Luck,
Joe