who makes high-performance pre-81 airhead clutch?

[spartanman]

Originally Posted by pommie john

Motobins do a heavy duty clutch spring.

http://www.motobins.co.uk/bmw-parts....20valve%20Twin

Thank you. Good to know.

[spartanman]

Update: The clutch slipped again this morning under high loads in top gear. I have to remove the trans to fix a notchy shift cam roller and replace the pawl spring (pre-emptive maintenance).

Just ordered one of these from Motobins:

CLUTCH DIAPHRAGM SPRING-HEAVY DUTY TWINS 1955-80 *RECOMMENDED FOR ALL 1000cc*
(NOT R45/65 1978-80)
Part No. 32000

I'll let you all know how it works.

[supershaft]

Originally Posted by spartanman

Update: The clutch slipped again this morning under high loads in top gear. I have to remove the trans to fix a notchy shift cam roller and replace the pawl spring (pre-emptive maintenance).

Just ordered one of these from Motobins:

CLUTCH DIAPHRAGM SPRING-HEAVY DUTY TWINS 1955-80 *RECOMMENDED FOR ALL 1000cc*
(NOT R45/65 1978-80)
Part No. 32000

I'll let you all know how it works.

I have found that new pawl springs are just as likely to break as old ones. I don't change them unless someone insists and have never had any problems for it. I have seen a couple of rollers split but I don't remember ever seeing one get a flat spot. Personally, I don't like the feel of a metal roller. It makes my bike feel like a K bike. At least to my toes. IMO, even that is not good.

I have always adjusted clutches by the book and never had a problem for it. Normally, cable free play isn't reduced by the bike getting hot, it is reduced by revs. Centrifugal force somehow forces the spring out just a tad. Lightly take out the cable play with your fingers at the lever and rev the engine. You can feel the spring moving back and forth.

I forgot to add that shift quality can be effected by the one shifter cam coming loose from the cam's gear. Check and make sure there is no slop there. The setup works loose and makes for notchy shifting. I lot of people forget to check that.

[spartanman]

Originally Posted by supershaft

I have found that new pawl springs are just as likely to break as old ones. I don't change them unless someone insists and have never had any problems for it. I have seen a couple of rollers split but I don't remember ever seeing one get a flat spot. Personally, I don't like the feel of a metal roller. It makes my bike feel like a K bike. At least to my toes. IMO, even that is not good.

I have always adjusted clutches by the book and never had a problem for it. Normally, cable free play isn't reduced by the bike getting hot, it is reduced by revs. Centrifugal force somehow forces the spring out just a tad. Lightly take out the cable play with your fingers at the lever and rev the engine. You can feel the spring moving back and forth.

I forgot to add that shift quality can be effected by the one shifter cam coming loose from the cam's gear. Check and make sure there is no slop there. The setup works loose and makes for notchy shifting. I lot of people forget to check that.

Thanks for the tip on the shifter cam. Disagree on thermal effects. Consider how idle speed increases when the engine warms up if there is insufficient cable slack. Parts of different materials thermally grow at different rates. Agreed, a new spring can fail too, though statistically, the one with the more stress cycles will fail first, all other things equal. And blasmephous as it sounds, I'm replacing the plastic roller with a k-bike steel equivalent. I find the k-bike shifter action to be less vague than the airheads.

[wirewrkr]

Originally Posted by spartanman

Update: The clutch slipped again this morning under high loads in top gear. I have to remove the trans to fix a notchy shift cam roller and replace the pawl spring (pre-emptive maintenance).

Just ordered one of these from Motobins:

CLUTCH DIAPHRAGM SPRING-HEAVY DUTY TWINS 1955-80 *RECOMMENDED FOR ALL 1000cc*
(NOT R45/65 1978-80)
Part No. 32000

I'll let you all know how it works.

Just so you know that is no different than the BMW HD spring available at any US dealer for the same amount of money $58.87 U.S.
The spring was introduced on all big twins after the R100 debuted in late 1976.
(The /5 spring is still available and has a lighter clutch feel. part # 21211250288 same price.)

Part number for the R100 spring you just bought in ENGLAND is probably 21211234035, $58.87, same as here in the US.

Check in your home country first, it'll save some aggravation and shipping $$$

[spartanman]

Originally Posted by wirewrkr

Just so you know that is no different than the BMW HD spring available at any US dealer for the same amount of money $58.87 U.S.
The spring was introduced on all big twins after the R100 debuted in late 1976.
(The /5 spring is still available and has a lighter clutch feel. part # 21211250288 same price.)

Part number for the R100 spring you just bought in ENGLAND is probably 21211234035, $58.87, same as here in the US.

Check in your home country first, it'll save some aggravation and shipping $$$

Thanks for the history lesson. Where were you yesterday?

[pommie john]

Originally Posted by wirewrkr

Just so you know that is no different than the BMW HD spring available at any US dealer for the same amount of money $58.87 U.S.
The spring was introduced on all big twins after the R100 debuted in late 1976.
(The /5 spring is still available and has a lighter clutch feel. part # 21211250288 same price.)

Part number for the R100 spring you just bought in ENGLAND is probably 21211234035, $58.87, same as here in the US.

Check in your home country first, it'll save some aggravation and shipping $$$

If your local BM dealer is anything like mine here in Oz, you're better off going to Motobins.
My local dealer told me there was only one spring available, and when I fitted it, the clutch slipped. I called Motobins, told them the part number that was on it and they said it was the weaker spring, sent me the new one, bingo no more clutch slip. Well worth an international phone call.

[wirewrkr]

Originally Posted by spartanman

Thanks for the history lesson. Where were you yesterday?

I'm always here. Always watching.
Most of the time anyway.

[wirewrkr]

Originally Posted by pommie john

If your local BM dealer is anything like mine here in Oz, you're better off going to Motobins.
My local dealer told me there was only one spring available, and when I fitted it, the clutch slipped. I called Motobins, told them the part number that was on it and they said it was the weaker spring, sent me the new one, bingo no more clutch slip. Well worth an international phone call.

Wish it wasn't so bad for you blokes over/down under there!
Here in the states there are still a few dealers who know what the fuck they are talking about with airheads, (one less guy since I retired) but they are out there.
I do free consultations too.
Too old to give a flying fuck anymore. ( never did anyway, but now it seems more acceptable!)
Good on ya P.J. for piping up when ya did.
Robert

[crazydrummerdude]

I've got the heavy duty clutch spring in my R75/6. I never really noticed a difference with anything.

But, the spring came to me below the suggested minimum relaxed height in the Clymer. I was told that the Clymers number is for the lighter duty spring.

So, what's the service limit of the heavy duty spring?

[supershaft]

Originally Posted by spartanman

Thanks for the tip on the shifter cam. Disagree on thermal effects. Consider how idle speed increases when the engine warms up if there is insufficient cable slack. Parts of different materials thermally grow at different rates. Agreed, a new spring can fail too, though statistically, the one with the more stress cycles will fail first, all other things equal. And blasmephous as it sounds, I'm replacing the plastic roller with a k-bike steel equivalent. I find the k-bike shifter action to be less vague than the airheads.

Thermal effects on idle speed is almost entirely do to increased combustion efficiency, not a change in cable pull. You are mixing an entire different can of worms into pot. Nevertheless, adjusting the clutch cable by the book does work and centrifugal force does reduce clutch cable pull at the very least a lot more than differences in temp.

Since we are making up statistics, I think statistically speaking a spring with a metallurgical flaw is the spring that will fail first. I think a good way to test for such a flaw is to put it through many stress cycles. If it has survived thousands, chances are it will survive thousands more. I have seen too many recently installed springs fail to think that new ones are any better than ones that have lasted quite some time. They might even be worse. That has been my experience so far.

[Rob Farmer]

Originally Posted by pommie john

Motobins do a heavy duty clutch spring.

http://www.motobins.co.uk/bmw-parts....20valve%20Twin

+1 on that. I have one in my 78RS no problem with the clutch at all.

[spartanman]

Originally Posted by wirewrkr

Just so you know that is no different than the BMW HD spring available at any US dealer for the same amount of money $58.87 U.S.
The spring was introduced on all big twins after the R100 debuted in late 1976.
(The /5 spring is still available and has a lighter clutch feel. part # 21211250288 same price.)

Part number for the R100 spring you just bought in ENGLAND is probably 21211234035, $58.87, same as here in the US.

Check in your home country first, it'll save some aggravation and shipping $$$

I emailed Motobins. You're correct. Their heavy-duty spring is BMW 21211234035. I cancelled the order. Thank you.

[spartanman]

Originally Posted by mymindsok

If you want to throw your $$$ away, Motoren Israel can probably help. They manufacture good stuff for racers and the high performance crowd but the prices are insane. Look em up via Google and rest easy in the knowledge that they take credit cards.

You can easily shim your spring to get more pressure and then add an 'easy clutch' system but you'd better keep an eye of the ancillary parts.

The late model clutch is the way to go.

So I assume you shim behind the diaphragm spring? Any idea how thick?

Poked around on Snowbum's site as suggested above. Sounds like a .050" donut shim will do it.