Topic: Which Clutch in a Hi-Performance Motor?

[736cc]

 Its slipping at hi-RPM in upper gears and winter down-time is here, what brand of clutch plates should I use in my hot-rodded CB750 K1? Its got a Barnett from 1975 or so.

[MRieck]

I use a stock clutch with Barnett springs. Bead blasting the steel plates is a very good idea too. Extra plate clutch packs make it difficult to find nuetral.

[736cc]

 Coming from the top motor-man here, thats sounds like the ticket.

[eldar]

That combo has been used before with good reported results here.

[Sam Green Racing]

In our 836 motor (86bhp) we used new stock plates and springs and it seems fine upto now.

If need be, we have a set of Barnett springs that Mike sent to us.

Sam.

[RRRToolSolutions]

I went through this twice and finally listened to Mike and Buzz- stock fibers and stock steels + Barnett heavy springs. The CB750 clutch system is my absolute favorite of all I've ever seen, built, tried, or read about. I like the ball bearings in the tear-drop hub. Brilliant and I still believe Yamaha, Suzuki, and Kawasaki should have copied it. Just brilliant!

Oh, back the clutch - 1,200 miles and no clip - none. There is a noticable change in pull pressure once those Barnetts are installed. They make those plates stick like epoxy and the mechanism is plenty strong and well designed (as I rambled on above) to handle them.

Regards,
Gordon

 

[sbc1320]

Had stock clutch plates and Honda 305 springs 30 years back in my old 74. Worked very good.

[jaguar]

might be a dumb question but why blast the steel plates?

[MRieck]

might be a dumb question but why blast the steel plates?

It deglazes them and really purges junk off the plates. The blasted surface engages better too. Road race teams have done it for years. Honda used to bead blast Supersport brake rotors after every race for the same reason.

[Tower]

Stronger springs, extra plates, and glass peening will give you bragging rights at your local hangout.  You will also get less comfortable grip, harder shifting, faster fibre wear and more heat and overall extra stress on the transmission.

Glass peening creates micro dipples on the plate surface.  The dimples make for much better grip, but also wear the fibres faster.  If you're into rebuilding the clutch, then this is not an issue, otherwise the extra grip is unnecessary.  Combine this with harder springs and the shifts can be a bit jarring.  Combine all three and you could be fighting the clutch with most every shift. 

If you need that extra umph because immediate power to the rear wheel gives you a fraction of a second competitve advantage coming out of knee-down turns - then this combo is advisable.

For most of us, stock plates and springs will last longer and will be the most comfortable.

[754]

Jarring is right, like hand coming off the bar if you are not used to it!!

When I had a pretty fresh xtra plate Barnett & of course springs.. I can remember gpoing down a really steep hill, banging 2nd and getting the front end a bit!!




and that is with a 6 over swingarm and lowred a bit.

I might try APE xtraplate, if not it will be Barnett all the way..

I should mention I usually hold it at 7 or 8K off the line & slip the clutch for about 40 ft.. hundreds of times.. try that with stock plates..

[Big Jay]

When you never want it to ever slip again

http://cbrzone.com/clutches.html

[MRieck]

Stronger springs, extra plates, and glass peening will give you bragging rights at your local hangout.  You will also get less comfortable grip, harder shifting, faster fibre wear and more heat and overall extra stress on the transmission.

Glass peening creates micro dipples on the plate surface.  The dimples make for much better grip, but also wear the fibres faster.  If you're into rebuilding the clutch, then this is not an issue, otherwise the extra grip is unnecessary.  Combine this with harder springs and the shifts can be a bit jarring.  Combine all three and you could be fighting the clutch with most every shift. 

If you need that extra umph because immediate power to the rear wheel gives you a fraction of a second competitve advantage coming out of knee-down turns - then this combo is advisable.

For most of us, stock plates and springs will last longer and will be the most comfortable.

I think you need an undercut transmission for true bragging rights. I have never experienced "jarring" starts with beaded steel plates. If anything it gives a more progressive feel to the clutch. Many people...including several on this board ....have ridden my personal bike and never noted anything wierd with the clutch. The roadracers I've helped really like the feel when coming off the starting line. I don't like extra plate clutch packs as the height is off and then finding nuetral (at a stop) becomes almost impossible. If you have a 40 or 45 HP CB the stock springs will work OK but even Honda had stiffer OEM springs in early K's so what does that say?

[RRRToolSolutions]

Mine was an absolute waste above 8,000 rpm with new fibers, steels, and springs. I'm talking $300 nos new. Every fiber, every steel, and springs was factory Honda and it still slipped miserably when the tach reached 8,000 - not good for stock rods and certainly not what I had in mind when going to an 836 bore, cam, and ported head.

The addition of heavy springs will have absolutely nothing to do with shift quality or finding neutral. The clutch pack gets the same separation whether they are stock springs or coil-overs from an old Chevy. Extra plates and fibers will bring about sticking plates and have less free-play for the plates to spin freely when the clutch is pulled and the gaps are supposed to allow independant movement within the basket. I went with stock plates and steels to retain that buttery smooth shifting (not quite, but close) and the springs to make sure they got stuck together when released.

Works for me in a daily driver and mountain roads where hundreds of shifts are required on every ride.

Gordon

[Bodi]

For a daily rider, you will have trouble beating the stock clutch pack - with stronger springs only if you're getting slippage. Stronger springs means more lever effort and that can really be a pain (literally) in city traffic.
For racing, Barnett friction disks work great. You get a very strong hookup with lighter springs, and with the Barnett springs in a 750 you won't have slip with any practical motor. But... the material wears rapidly compared to stock, putting a fair bit of fibrous crap in the oil and the disks won't last as long under hard use. The greatest drawback to Barnett disks is that they stick to the plates - tight - when the motor cools down. With a race bike you free the clutch and it's good all day, not a big problem. On a street bike it's a pain in the a$$. Every morning you have to go through some ridiculous dance to free the clutch or you forget and the bike leaps forward (usually a big surprise) when you drop it into gear.

[754]

Everything is a sacrifice..

No pain No Gain....

[Jerry Rxman Griffin aka MuthaF'er]

I have no problems with my Barnett (yet) and stock springs. It's only a 812 Yoshi kit and does not have the head ported. It will very readily hit 10,000 rpm with power. No slippage that I can detect.