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More sprag quesstions - help needed!

BollocksBollocksBollocksBollocksBollocksBollocksBollocks
BollocksBollocksBollocksBollocksBollocksBollocks.

All back together, 50-odd quids worth of Silkolene and new filter, no leaks, looking great.
Fully charged battery, push outside, ignition on, prime pump, no throttle, cold running to max, deep breath, hit button and ... just the sound of a merrily spinning starter motor not driving anything.
Anyone got a gas axe?

So, if the casing is on flush, the various gears have got to be in place right? That BMW sprag seemed to lock up OK.
So is that sprag just no good (despite Royston's recommendation) or have I done something else wrong?
The sprag can only go in one way (flange between flywheel and housing right? So ... ?
Or does the BM sprag operate the other way?
Whatever. No option but to tear it down again. I'm running out of money and time here.:angry:angry:angry
 
Don't know how the BMW part vairies but the direction of rotation is marked on the flywheel usually.

didn't leave the woodruf key out did you ?
 
oh ****, I was hoping you found a cheap alternative.

Hope it is something simple and easy to fix
 
I'd managed to glue the large drive gear to the crank with over-enthusiastic use of loctite. Should I be loctiting the taper as well as the bolt?
 
I wouldn't have thought so, just the bolt.
Royston really seems to know Aprilias inside out (there was a race bike there when I was there 2 weeks ago) and seems to know just about every trick in the book with them.
 
A303 said:
BollocksBollocksBollocksBollocksBollocksBollocksBollocks
BollocksBollocksBollocksBollocksBollocksBollocks.

All back together, 50-odd quids worth of Silkolene and new filter, no leaks, looking great.
Fully charged battery, push outside, ignition on, prime pump, no throttle, cold running to max, deep breath, hit button and ... just the sound of a merrily spinning starter motor not driving anything.
Anyone got a gas axe?

So, if the casing is on flush, the various gears have got to be in place right? That BMW sprag seemed to lock up OK.
So is that sprag just no good (despite Royston's recommendation) or have I done something else wrong?
The sprag can only go in one way (flange between flywheel and housing right? So ... ?
Or does the BM sprag operate the other way?
Whatever. No option but to tear it down again. I'm running out of money and time here.:angry:angry:angry
Click to expand...

****, sorry to hear it was a no go.

So if the gears are all meshed correctly and the woodruff key is in place then it can only be the sprag clutch not operating correctly.

From the images you posted they looked to be of very similar dimensions albeit of a slightly different design.

When you mounted the sprag assy. on to the gear did you spin it by hand to aid mounting it? Did it lock up if spun one way and freewheel the other? I suspect if it just slipped on with ease then it may be of the wrong size.

May be that the dimensions are slightly different and that it won't engage. Shame cause it would have been really handy to have had an alternative sprag part.

Let us know what you find when you strip it down.
 
amb67 said:
****, sorry to hear it was a no go.

So if the gears are all meshed correctly and the woodruff key is in place then it can only be the sprag clutch not operating correctly.

From the images you posted they looked to be of very similar dimensions albeit of a slightly different design.

When you mounted the sprag assy. on to the gear did you spin it by hand to aid mounting it? Did it lock up if spun one way and freewheel the other? I suspect if it just slipped on with ease then it may be of the wrong size.

May be that the dimensions are slightly different and that it won't engage. Shame cause it would have been really handy to have had an alternative sprag part.

Let us know what you find when you strip it down.
Click to expand...

see above amb
 
Only thing to do is to strip it down and see what's gone wrong, it may well be something simple but without actually being there it's gonna be hard to diagnose from a distance.

Let us know what you find.

Don't anyone on here lend him a gas axe, Spoonz do you hear that??
 
Apparently it is not unheard of for the sprag housing to be mounted back on to the flywheel the wrong way round.

Thus causing loss of drive upon start up.
 
amb67 said:
Apparently it is not unheard of for the sprag housing to be mounted back on to the flywheel the wrong way round.
Thus causing loss of drive upon start up.
Click to expand...

You're being tactful amb, I realise but I put it on the way it came off (I'm pretty sure). Can you confirm that the flange on the bearing cage should be trapped between the flywheel and the outer bearing race when you bolt them together? The flange fits into the recess milled in the back of the race - and if you put it in the other way then it's just the pressure of the housing against the large gear which keeps it in place which doesn't look right to me.
When I stripped it I found that the clutch IS locking the wrong way. If you confirm that the mounting of the bearing cage is correct then there's only one fix at 6:40pm on a Sunday night - and engineering purists ain't going to like it!.
 
****...thats bad news Simon :-(

So it looks like the BMW part was too good to be true ?, oh well that will mean mine wont get fixed now till the new year - ho hum
 
Sorry to say but it does sound like you have built it all correctly.

The manual does show that the sprag is assembled so that the flange is trapped between the flywheel and the housing.

Perhaps the BMW engine rotates in the opposite direction to ours?

That's the only explanation I can give at this stage.

Do you have a copy of the sprag replacement guide, if not PM me your email address and I'll ping a copy across?
 
Last edited:
Just for a laugh I cut the spring back about 35mm on my old sprag , but put the little ball bits in round the wrong way.....it locks up beautifully , backwards !!.
It does sound reasonable that it locks the other way round though , isnt the BMW a parrallel twin ?
 
The taper that the flywheel locates on should be loctited as well.

The flange should go against the flywheel. Most Aprilia clutches and the housing have a reference mark to help but not sure if the bmw part will
 
Well, it's 11:40 PM (sorry neighbours!) and my baby has just given me three, strong, sharp, instant, graunchless starts.:doug
I'll give her a better testing tomorrow but things look encouraging.
The BM clutch was engaging the wrong way. I'd just assumed it would be right but when I sat down and worked it out having stripped it again (and given a clue by the merrily whirring starter motor) it was definitely wrong.
I'll give Royston a ring tomorrow – he sounds like he knows his stuff so maybe I ordered the wrong part (he just told me F650) or he fits it the other way round.
So don't completely give up on the fabled BM cheap sprag yet!
Kiwi was joking about turning his rollers round – but that's exactly what I've (very carefully) done and it seems to work fine. Yes I've probably shortened the life of the retaining spring by stretching it a little to get them out but I'll live with that.
I even managed to salvage the 50-quid oil using the wife's best jam making pan (the only thing clean and large enough to get it all in) – good job she was out. I cleaned it as best I could but those old biddies down the WI are in for a flavoursome treat next time she enters the preserve of the year contest. “And first prize goes to Mrs Reeve's Damson and Silkolene Marmalade, with its subtle hint of oil seal and overtones of instant gasket.”:puke
Thanks a million to all of your who have offered help and advice (Kiwi, AMB, Spoonz et al) – hope I won't have to ask you anything else for a while!:thumbup
I'll post up any more info on the BM part if I get it, plus a couple of tips and stuff I learnt along the way.
 
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