Drivetrain Backlash

[salty_monk]

Well reading some of the bumpf that Sharpy kindly sent me (thanks mate!) it describes the shafty transmission as feeling like a "well oiled tight chain".....

Well thinking about it that doesn't exactly describe mine... there is more lash than my friends Honda CB750 Nighthawk although his bike is newer (94 or so).

I saw a thread on here a little while back that suggested the most likely culprit is the 6 rubber dampers in the rear hub, I'm guessing this is probably also the cheapest & easiest cure too.

The backlash is most pronounced in 2nd but you can feel it in all the gears but it's affect is lesser as you move up through the box.

So I have two questions... Who agrees with my diagnosis or if not then?

Also what is the special grease I read about for reassembling the rear wheel Molybedenum or something but I remember hearing something about the concentration or something.

Advice appreciated as ever, (got to get the bike up to scratch for the road trip in July.... \\/ )

Regards,

Dan

[salty_monk]

Well a bit more exploration today with the bike on centre stand. You can move the wheel by hand back & forwards around 5 degrees (about 2" movement at the rim) in every gear from 1 to five.

Is this normal?

Cheers,

Dan

[tomcat24551]

Here's a little info that may help.

I measured rear wheel free play in 1st gear on my '79 850 to be about 33mm on the tire sidewall, just below the point where the tread turns into sidewall--some 60mm further out from the rim (where you measured). This is roughly 1/2 of what you measured, even though it is further out, where the measurement should be greater anyway.

Does it look like anyone has ever been into the final drive? In September 1980, Suzuki increased the final drive gear backlash tolerances, allowing almost 4 times the maximum backlash from the previous specification. Evidently, it was too hard to get the backlash correct with the early specs, so they just made the acceptable range much greater in the revised specs.

(Early specs: 0.10mm - 0.17mm) (Revised specs: 0.03mm - 0.64mm)

Maybe someone had the rear drive apart and put it back together, setting backlash near the high limit. Or maybe the factory was using the revised specs for initial assembly and yours ended up at the high end.

I have an '83 850 also, and there is a noticeable increase in driveline play in the '83 vs the '79. It came that way. I was the 1st owner.

One other thing: Backlash has to be set correctly in the secondary, too, where the power turns the corner to go to the driveshaft. Somebody might have worked on that and botched the job.

I'm sorry, I didn't get to measure the rear wheel travel on the '83, but it was not convenient to do so tonight. Maybe later.

Tomcat

[tconroy]

Have you tried shifting at a higher rpm? Mine is not that bad but I had a dealer check it out when they put on a new back tire and they said it was fine.

[salty_monk]

Well after getting your figs I went out to meaure accurately as mine were just a guess.

At the same point on the tyre as you in 1st gear I have 40mm of movement (in a straight line, not around the radius) in 2nd this jumps up to 52mm then back down in 3rd to around 38mm, up to 48mm in 4th & down to 35 ish in 5th.

It doesn't look like anyone has ever had it apart but who knows... I don't have the service history. I don't think TPO would have.

The main time I notice it is changing up in 2nd coming back on the power quickly & changing down to 2nd then coming back on the power for a slow corner. I can compensate with the clutch if I think about it in time. My clutch is a bit "on / off" due to weak springs at the moment so maybe that's not helping.

Hopefully mine is one of the "looser spec" ones. It's an 80 model but it wasn't bought & registered until 81 so it's a late one.

If your 83 is noticeably different to the one measured above then it seems I might still be within spec.

Thanks for the help.

Cheers,

Dan

[duaneage]

The backlash is normal and designed into the shafty. If you look in the clymers manual or the factory manual you will see a mechanism in the transmission output shaft that allows for play in the driveline. this simulates the feel of a chain so that it is not too "connected". Gretly improves shifting performance and feel.

If I had a scanner i would upload the picture from the factory manual that clearly shows it.