1978 R1007 vibration in rear end

[DBROWNSEY]

Good morning , My bike as developed a vibration in the rear end . I've started taking apart the bike , and was looking for advice on what to look out for ... Thanks Doug

[kentuvman]

Doug,

It could be the splines are stripped from the driveshaft to the final drive or possibly your wheel bearings going out - have you put bike on center stand and spun rear wheel and moved it from side to side? You may need a couple boards under center stand to get rear wheel off the ground.

Let us know what you find out.

[DBROWNSEY]

Doug, Thanks Will try tonight .

It could be the splines are stripped from the driveshaft to the final drive or possibly your wheel bearings going out - have you put bike on center stand and spun rear wheel and moved it from side to side? You may need a couple boards under center stand to get rear wheel off the ground.

Let us know what you find out.

Will take a look tonight . Thanks doug

[James.A]

Depending on what kind of vibration you are experiencing, you should look at the gusset on the rear subframe. The one under the seat with 2 bolts for the fender where the back of the tool tray would rest. Typically, the weld opposite the chrome handle will crack. Most of these welds that I have seen are what is known in the trade as "under-cut" and are weak. All dual shock bikes except /5 are susceptible.

[20774]

I think it would be helpful if you could describe the vibration in a bit more detail. Does it happen when you first start out, all all speeds? Maybe it appears at only one speed or is worse at other speeds. Have you had any rear wheel service lately? Is there any slop in the rear wheel bearings...if you grab the tire at the 9am-3pm (or thereabouts) positions and try and rock the wheel, is it solid or does it walk a bit on the axle? Before tearing it apart, you should investigate these kinds of things.

[DBROWNSEY]

Depending on what kind of vibration you are experiencing, you should look at the gusset on the rear subframe. The one under the seat with 2 bolts for the fender where the back of the tool tray would rest. Typically, the weld opposite the chrome handle will crack. Most of these welds that I have seen are what is known in the trade as "under-cut" and are weak. All dual shock bikes except /5 are susceptible.

I'll check it out tonight .

[DBROWNSEY]

I think it would be helpful if you could describe the vibration in a bit more detail. Does it happen when you first start out, all all speeds? Maybe it appears at only one speed or is worse at other speeds. Have you had any rear wheel service lately? Is there any slop in the rear wheel bearings...if you grab the tire at the 9am-3pm (or thereabouts) positions and try and rock the wheel, is it solid or does it walk a bit on the axle? Before tearing it apart, you should investigate these kinds of things.

I took a cloose look at the rear wheel first, and all looks tight.. could it be in the spokes? Vibration is worst 1st - 3 rd gear up to approx 65mph . mirrors shakes , seat shakes ect . It seems to follow RPM s . I'll be into it more this week end . freezin in NY and whats better than working on your bike. Thanks and I'll keep updating Doug

[20774]

Check the motor mounts. Have you balanced the carbs?

[30064]

Doug,

In addition to the previous replies; a number of things come to mind. It may be a good idea to check the transmission output shaft and driveshaft universal joint connection. Slide the shaft boot back from the transmission by removing the large circular boot clamp. Use a small pan to catch any escaping hypoid oil. Check the condition of the four bolts that secure the flange while slowly rotating the wheel back and forth looking for any visual slop. Then check the tightness (torque) of the four bolts.

Transmission in good shape? Have you changed the hypoid lately and inspected the magnetic drain plug?

Another check may be to simply check the roundness of your rear rear tire and rim by rotating the wheel and visually checking an offset or runout with a stable object.

Did you have a close look at the hub to wheel rivets and their conditions while the wheel was off?

[helmut_head]

Not sure how you diagnose that vibration as rear end, but I had high speed vibration, sort of like yours. Grabbed my eleven year old had him hold one engine mount bolt while I torqued the other side. We did both front and rear. They were previously snug, but not real tight. Problem solved.

The way the engine mounts to the frame, it actually all bolts together on the lower half and stiffens the entire frame structure. I am convinced I was having a frame resonance causing my discomfort, excited by the 1st order firing or imbalance, of course.

[cycleman2]

Yep I second checking the driveshaft, if everything in the rear drive is fine.

[DBROWNSEY]

I think it would be helpful if you could describe the vibration in a bit more detail. Does it happen when you first start out, all all speeds? Maybe it appears at only one speed or is worse at other speeds. Have you had any rear wheel service lately? Is there any slop in the rear wheel bearings...if you grab the tire at the 9am-3pm (or thereabouts) positions and try and rock the wheel, is it solid or does it walk a bit on the axle? Before tearing it apart, you should investigate these kinds of things.

Morning. removed the 4 final Drive bolts and found that the large nut/washer on the final drive was almost off. Finall drive is shot ! The bike has 45000 orig miles . Bummer! Rebuild/Buy new? any thoughts ? Thanks Doug

[20774]

Which 4 bolts? There are 4 that are under the rubber boot at the connection between the tranny and the driveshaft. There are 4 fasteners that hold the final drive onto the driveshaft housing. Sounds like you're talking about the fasteners in the rear.

Why do you say that the final drive is shot?

[bpeckm]

Morning. removed the 4 final Drive bolts and found that the large nut/washer on the final drive was almost off. Finall drive is shot ! The bike has 45000 orig miles . Bummer! Rebuild/Buy new? any thoughts ? Thanks Doug

Sounds like you are talking about this guy....

P1020724-M.jpg

If that nut were loose, yes your bearings are probably toast... but it may be worth playing with it by tightening and turning by hand etc.... Worst case, you can find a used one pretty cheap. Check the flea market here, and try the IBMWR fleamarket... there is usally a lot of stuff on there, with some good folks. I would use eBay as a last resort for something like this, though there are a couple of good bike-breakers who know their BMS stuff...you can try to contact them to see if they have anything that isn't posted.

[moosehead]

Morning. removed the 4 final Drive bolts and found that the large nut/washer on the final drive was almost off. Finall drive is shot ! The bike has 45000 orig miles . Bummer! Rebuild/Buy new? any thoughts ? Thanks Doug

Think your're referring to the pinion gear collar nut (#1 in diagram below)...



They rarely loosen off ( about 150 nm + tourque)(115 + ft/lbs) but they can (usually when work done on final drive and not tightened the collar nut up sufficiently). I know , had 2 loosen off on me on 78 100/7 and a 77 R100S.

All's not lost yet for the FD. Was this vibration ocurring for a long time or just start recently?? Mine was noticed immediatly on the 78 after going through similar problem on the 77 S. Both bikes, opened FD and checked all bearings, seals, gears etc by my buddy (whose an airhead mechanic)..resealed and reshimmed FD and tightened up collar nut to correct torque (with air ratchet driver). Have had no problems at all with either of them. But then again I caught it fairly early.

So I think you'll be OK if get FD checked over. Hopefully crown/pinion gears OK as well as other bearings

Of not OK used FD's are fairly easy to find - check out www.IBMWR.com and e-bay and also flea market here.

Good luck...they're pretty tough back there