Hi,

I am starting to assemble the 570 engine I got from Pam and Greg. It appears to have non-stock clutch plates and springs. The springs are about 5 mm shorter than the stock ones, but have a larger wire size: 2.34 stock, these are 2.43 mm. The plates are thinner than the stock ones, but appear new.

Does anyone know what the spring length and friction plate thickness specs are for a Barnett clutch kit? I'm not sure these are Barnett parts, since they don't list springs.

I'd like to make sure these are OK before I get them installed.

Kevin,
I hope I can help you out with what I experienced.
When I first started racing my 555 GS I had problems with smoking the clutch.  This may have been partly due to an incorrectly adjusted clutch, but in my effort to figure out what was wrong I bought a lot of hardware & learned a few things.  I bought a Barnett clutch kit, with springs, and got nothing for it except more lever effort.  The springs are definitely stiffer than the OEM jobs, but they were shorter & didn't seem to make the clutch work any better.  I know that spring force is simply the spring rate times the compression & I reasoned that the Barnett springs just were not compressedd enough to give me any significant increase in force against the clutch plates.  I measured the spring rates on a spring tester & found that the rate is higher on the Barnett (of course) but the force they exert is similar to the OEM springs at the installed height, because the OEM springs are compressed more.  Anyway, what I ended up doing was to use the OEM springs & shim them so that they were pre-loaded as much as possible with the clutch engaged (lever let out) without coil-binding when the clutch was disengaged (lever pulled in).  It was a fiddly proccess to go through & I think if you run the experiment yourself you can demonstrate to yourself which springs will work best for you.  If you can shim up & get more spring pressure with the Barnetts while not shimming so much that they coil bind, use them.  If you get more pressure (with the clutch engaged) with the OEM jobs, then that's what you want.  My conclusion was that the Barnetts were a waste of money, but I'd suggest you do the same test & draw your own conclusion.
Best of luck.
Bob

I am no racer and have poor memory and have never split my motor to look at the clutch...
Here is what I remember from way back when (1999 or so) on the mailing list...With barnett clutch the guy used stock springs for better engagement and similar lever effort. No idea who either...
Cool.
Srinath.

Thanks Bob! Looks like they may be a Barnett kit then - they don't list springs anymore.

Yeah, shorter, stiffer springs aren't likely to buy much. The springs are a lot shorter. And then plates are all thinner too, so you end up with even less pre-load

Maybe I'll just swap the stock stuff from my other engine. I haven't had any clutch issues so far, even when my engine was at 55 hp.

I have never used anything other than a stock clutch. In fact, I have only ever replaced one clutch and I replaced it with another slightly used clutch pack from one of my parts motors.

I have heard from directly from people who have tried them that the Barnett clutch is not so good and most folks usually go back to the stock clutch.

I've used Barnett plates with the stock springs. Worked fine.
Lately I've been having issues with slipping clutches. They are all old clutches out of other motors though. I have a new stock clutch for my GSX500R motor. But I just picked up a complete Barnett kit for the SV650. The friction plates are .02 thicker and the springs are shorter and heavier.
The springs reach coil bind the same as the stock ones, using the vise method of measuring.
I have only trial fitted it in a basket, but looks good so far.
We'll see how it works when I get the motor running.

Although it may not apply to everyone's case & YMMV, etc., etc.  --  I have an Excel spreadsheet that I did a long time ago when I was having my clutch problems & I measured my springs on the spring tester.  I will try to dig up the file & if anyone is interested in posting it I can e-mail it to them.  The interesting thing is that the two spring lines cross because they start out with different lengths & different spring rates.  The chart just shows spring force as a function of spring height.  May be helpful may not.

Bob,

If you find it, I wouldn't mind seeing it. I can't fathom why the Barnett springs would be so short. As you said, they would have to be shimmed to get the same pre-load as the stock springs.

That is interesting that Bob B. says the friction plates are thicker on the Barnett, because mine are thinner than the stock.

Bob B., do the friction plates have small circular notches out of the outside tabs at 3 places? I'd like to confirm this is a Barnett set.

The friction plates don't have any notches. I've never seen any with notches. Not even for my Ducati.