Gearbox questions

Wreford Miles

Wreford Miles

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Is the gearbox on my R80G/S normal?

When offroading (after I've worked it a bit) it will stick in 1st when I come to a stop... as soon as i take load off when I move away it snicks up the box fine.

At the same time it can be difficult to find netural

When it's cold it'll not go into gear with out a lot of noise, once it's warm it's fine'ish with a clonk when it goes into gear.

Around 70mph i hear a whine when i put the power on... at first I thought it may be the tyres but i don't think so

I had run the bike with the oil in a bad state due to unnoticed water ingress on the last two oil changes since there has been a few fine fillings on the magnetic sump plug...

What are your thoughts.... typical BMW or plan a rebuild?

Cheers

Wreford
 
Mmmm, gearbox bearing gone perhaps!!!
Mine did something similar to this, the noise especially. Thought it was tyres or something else
rubbing somewhere. Turned out to be a brg on the output shaft. Replaced it and its fine now (cant belive it ran at all seeing the state of the knackered brg !!)
 
Could be gearbox bearings, but check your clutch first. Make sure it is disengaging fully and that the thrust bearing is in good condition.

The gearbox can be stripped at home, but it is not a job for the ham fisted. It is reasonably straightforward however and with a bit of care and knowledge it can be done successfully. There are a couple of things that can cause major issues if you are not prepared. Remember to take the speedo drive out of the housing. The output flange is on a tapered shaft and locked down with 120 lb ft of torque. This can take quite a bit of removing. Make sure you have a tool that will do the job or a handy machine shop that can do the job for you. You need to heat the end plate well prior to removal as the bearings are an interference fit on the inside. Also take care when removing it as all the bearings are shimmed for a correct fit and you need to know how to shim the replacements.

If I had gone to all the trouble of stripping a gearbox and I knew there had been oil contamination and metal filings, I would replace all the bearings as a matter of course. I would also replace the detente spring (I think it's called) on the selector as these have a habit of breaking.

If you do decide to strip the box and all the shafts, be extremely careful and methodical as an error in the rebuild process can result in the gearbox locking up thereby locking the back wheel. Not good.

As I say, it can be done and I know this because I have done it, but I would not recommend it if you are unsure of what you are doing. Much better to pay the few bob and have some peace of mind by having it done by a professional.

Doubtless there are more informed folk on the site who can provide a better insight. This is simply my 2p worth FWIW.

Best of luck
 
TheWarlock said:
Could be gearbox bearings, but check your clutch first. Make sure it is disengaging fully and that the thrust bearing is in good condition.
Click to expand...

I did wonder if it was the clutch dragging... when re engaging it does feel as though the lever travels a bit first so I assumed it's OK. Is theres ome other kind of adjustment I should do other than at the lever?

Havings said all that... i suppose fillings in the oild is not good
 
Clutch adjustment should be done in two places. One is at the handlebar and the other is at the back of the gearbox.

AFAIK this is normally done by releasing all adjustment at the handlebar and working at the back of the gearbox first. The general rule is that the clutch actuating arm on the back of the box should be parallel with the gearbox end plate when at rest. There is an adjuster screw and locknut on the arm to enable you to accomplish this task. Once the arm is correctly positioned, you should then adjust the handlebar lever to the correct tolerance ( I can't remember at the moment what the freeplay is but it is about a couple of mil. The owners manual or workshop manual contain the correct setting).

All of the above require the clutch, thrust bearing, thrust rod, cable etc to be in good condition. If the clutch cannot be set up within the required parameters, it is worth checking the components as they may be worn or broken. If you are stripping the clutch components remember that there is a tiny hole in the bottom of the thrust bearing tunnel that allows small amounts of gearbox oil to be splashed onto the bearing. On most bikes I have ever worked on, this hole is blocked with gunge and grit. It should be kept clean and clear.

HTH
 
Wreford,

I'd get it looked at if I was you. I left my R100 gearbox a little too long and found this when I stripped it a couple of weeks ago. A new layshaft is £249 and you need to upgrade gears on the output and input shafts to fit a new one.

:tears
 

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With the extra power you are putting through the box the chances are that fifth gear as worn making the whining. They tend to skew on the output shaft.

You will be surprised how good they feel and work after a proper rebuild.


This is a side on view of the selector mechanism. Theres very little space between the selector forks and cams - if anything as worn in there it could be binding.
 

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The 'box was fullt rebuilt on that bike less than 5000 miles ago, with the HPN gears and all bearings

You should have a copy of work done in the paperwork I gave you

I thought the 'box was sweet on that one and only had to blip the throttle on downshifts
 
You have also probably lost the dampener on the driveshaft when it was extended...That will increase the stresses on the gearbox a lot and reduce it's life no end :blast
 
Thanks guys... I have spoken with guy called Andrew Sexton, he seems to know his stuff. I'm planning to have him strip the box, help me rid some of the electrical gremlins and discuss large tank options which may also improve the steering lock.

I understand his knolwedge also extends to building airhead dakar bikes

Has anybody had any exsperiance of his work?
 
Wreford Miles said:
Thanks guys... I have spoken with guy called Andrew Sexton, he seems to know his stuff.

Has anybody had any exsperiance of his work?
Click to expand...

I know a few people who he has done work for
His work is fine...But he will charge you a fortune for his expertise
 
Rob Farmer said:
I see you're in a well paid profession...That will help :D
Click to expand...

hmmmmm... I'm a bit stuffed on options I want to know the bike is sorted because being a well paid profession also means I have no time time to fettle the bike myself, high out goings (failed marriage) and time off is valuable so when I plan a trip I have no room for breakdowns.

I do like the fact he's built some specials... what other options are there (other than do it myself, which is not)

In hindsight buying Jeremy's HP2 may have been cheaper in the long ron ;-)

But it's not an airhead and I think it's the nuts and if I have to sell my 1150 to help fund it then I'm ready for the WASPS!!
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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