www.boxertrix.com

Well after 55k my s has finally gone wrong and stranded me on the M25. There I was on my way to work doing about 70 mph when I started to notice what at first felt like light surging. ½ a mile further on and I went to accelerate, there was a clunk and all drive was gone. Pulled over to find the engine still running perfectly but pulling in the clutch just produced a loud whine.

I’ve got her back home and stripped down as far as the gear box the shaft seems ok (no worn splines etc) . The bevel box was a bitch to get off as the bearing on the adjustable pivot was stuck solid, I had to cut the pivot with a pad saw through the gap between the swing-arm and the bevel box nearly two hours later I was not best pleased

As I ran out of time I will remove the gearbox/clutch at the weekend. Any advice, things to watch out for would be appreciated.

Also a couple of questions, are the BMW guide pins necessary for removing the gearbox? (I suspect they’re not)

Isn’t the shaft supposed to be in 2 pieces? Should it come apart where the thin part enters the thick part (highly technical discription) as mine doesn’t?

Thanks for your input in advance

Cheers

Paul.

Paul - sorry to hear about that.

I'm not techie, but it sounds like the clutch has given out to me.

I don't quite understand why/where you had to saw the shaft (or didn't you?) The shaft SHOULD be in two sections, but people have had them seize before - Tony had his seize and could't split it for love nor money.

As for the splines - probably (hopefully as I'm going to do my clutch as soon as I can clear enough room in the garage) you don't need them and it can be manhandled into and out of position - don't suppose it's that heavy. I know others here have changed the clutch recently so they might be able to help.

Good luck anyway - and I hope it's something simple like the clutch rather than a terminal gearbox failure!

Jason

Ahhhh... the paralever bearing.. I understand. That was probably covered in loctite! I usually give it a bit of heat to move it - could be something else of course though

Cheers Jason, yes the heat gun was in full use and had no effect at all.

As to the clutch....... do they go that instantly? I'm new to the wonders of a dry clutch (having only ever owned rice rockets) but wouldn't it slip first?

If the engine run sweetly and the bike could be freewheeled whether in gear or not, the problem must be in either the clutch or gearbox. Its entirely possible that the splined centre of the clutch plate has parted company form the rest of the clutch. Given that the release bearing bears against this splined centre, that could explain the squeeling when pulling the clutch in.

I'd be inclined to replace all the clutch parts regardless given the bother you've gone to stripping it all down. Resist the temptation to skimp, even if pressure plate/bearing appear serviceable.

NO you don't need the gearbox mounting pins a couple of long bolts with the heads sawn off will od the trick nicely, though to be honest I didn't even use them I just slipped it on.

CLutch is easy peasy lemon squeezy to replace once you've split the bike, your problem is going to come with the exhuast bolts I'd bet I'd order all new fittings for the complete exhaust before starting, it'll just make your life so much easier..

The swing arm/ bevel bearings are loctited in and need a bit of heat, I split the bevel box a couple of weeks ago to regrease the drive shaft splines. Trust me, buy a BFO breaker bar and it'll come out first time ( ask me how I know this one ) the swing arm bearings came out okay when I replaced my clutch at Christmas, but the Bevel Box needed the BFO breaker bar to shift them.

AFAIK the actual shaft itself is 1 piece, but obvisouly you have the split for the CV joint ( I do stand to be corrected here ) and then the splined mounting collar for the gearbox output shaft, so I guess that makes it 2 piece.

Definately replace the friction & pressure plate, personally I'd inspect the rest and if needed replace them, but they're probably going to be okay. DO however use new bolts for the housing and cover as these stretch when tourqed correctly and as such should not be re-used !!!

Take your time, be thorough and you'll be fine, have fun.

******* Do make sure that the snap ring has fully engaged locking the drive shaft to the gearbox output shaft ( rubber mallet to seat it )**********
Give it a damn good pull to make sure that you have it locked in place

******* Also coat the gearbox output shaft splines with grease NOT the drive shaft splines as it'll then make an air seal and it'll be bloody hard to get the shaft on and the ring seated

Good luck

There have been reports in the past of the gearbox output shaft splines stripping for no apparent reason so maybe this has happened to yours. Apparently the factory were a bit tight with the grease when they assembled them.

Sounds like gearbox input shaft splines to me.It's just down to poor alignment at the factory.You will need to split the gearbox to change the shaft.Personally I'd just buy a secondhand unit from Motorworks...see if they've got a decent full clutch too.
Gis a shout if you need a hand or owt.
Bailey.

Thanks for the advice chaps, the bike is already stripped down to the gearbox, just got to undo the bolts and pop it off.

Bailey, thanks for the offer. If nothing else it's given me the chance to have the small crack in the frame welded. Looks like you got a go just in time

Cheers

Paul.

Unfortunately Mr Bailey was right. My gearbox input shaft is damaged

If anyone knows of a second hand gearbox for sale, I'm yer man.

Paul.

It's done and I'm back on the road

I can't believe how sloppy the old gearbox was, the new one (6500 miler off a BCR) is very smooth and positive. I replaced the clutch, gearbox, swing arm bearings and bevel box bearings and the only special tools needed were a piece of 3"x 2" timber with 2 x M8 bolts to bolt the engine to (so the frame can be removed) and a small flat piece of ally with two holes drilled in it to lock the clutch.

TBH it's all pretty easy to do, if a little time consuming.

Does this now mean I can charge £75 an hour as a BMW technician

crucial wrote:It's done and I'm back on the road

I can't believe how sloppy the old gearbox was, the new one (6500 miler off a BCR) is very smooth and positive. I replaced the clutch, gearbox, swing arm bearings and bevel box bearings and the only special tools needed were a piece of 3"x 2" timber with 2 x M8 bolts to bolt the engine to (so the frame can be removed) and a small flat piece of ally with two holes drilled in it to lock the clutch.

TBH it's all pretty easy to do, if a little time consuming.

Does this now mean I can charge £75 an hour as a BMW technician

Excellent news - and you're clearly pretty practical. I love taking things to peices, but putting them back together is another story

BTW - by "bevel box bearings", do you mean the crown wheel bearing and tapered roller bearing inside the bevel box, or the para lever bearings?

Jason

That'll be the paralever bearings, thankfully the bevel box apears to be ok

Has your bike got ABS? Reading the manual it reccomends you disconnect part of the ABS system but I'd rather not... I'm sure you could work round it but would be interested to know if you had any such problems

ta

No Abs on my bike, but like you say I'm sure it's not as difficult as BMW would have you believe. Like most of these things it seems a bit daunting until you do it and you realise it's pretty straight forward.