Best guesses on RGS "clutch" issue?

Hi Paul. A clutch would be good news rather than a broken transmission problem. Save yourself some grief and use some new steels/frictions from Wolfgang and jump back on. I suspect your clutch was slipping and just smoked.
 
Red's racer uses Kevlar plates and it's making over 130bhp at the rear wheel.
I would try to get to the bottom of the issue before just bolting it all back together with new plates.
 
And yes..new clutch springs for sure too. Wolfgang used to have some very nice "performance" clutch springs in the store. I used them when my clutch began, almost imperceptibly, slipping at full honk. I might have been stuck at the side of the road too.
 
maurice turner said:
Hey Paul maybe the high engine revs you were experiencing was due to a huge amount of clutch slip? Possibly the springs didn't have enough tension allowing the clutch to slip at high engine speed, this would create huge amounts of heat destroying the friction plates and distorting the crap out of the steel driven plates you will find that they are most likely toast like the friction plates.
That amount of movement in the drive doesn't mean a lot as this will vary depending on what gear that the gearbox is in,  the lower the gear the more rotation of the clutch drum, its probably not slack but just the reduction in the gearbox.
Click to expand...

That happened on my old 3C, hammering down a motorway, looked down and it was at 9000 revs, it was a slipping clutch and new springs cured it. I never actually noticed until I looked at the rev counter.
 
Rusty Spokes said:
Hi Paul. A clutch would be good news rather than a broken transmission problem. Save yourself some grief and use some new steels/frictions from Wolfgang and jump back on. I suspect your clutch was slipping and just smoked.
Click to expand...
Agree with that and previous re slipping clutch. Years ago my brother in law took my other half's bike for a ride and came back with it screaming and barely moving - turns out he was an experienced moped rider and he'd forgotten in was a manual gearbox and left it in 4th or 5th and used the clutch to take off from a standstill - several times, by the look of the clutch (totally scorched). But exactly the same symptoms as your RGS Paul. If it's a hydro clutch I'd suspect there was some tension on the push rod, which may have been the start of the issue - would manifest itself once you started caning it and building up plenty of heat!!
 
The backlash you mention in post 47 is just the difference between the driven and driving gear dogs, I would think it pretty much normal. It does seem like there was insufficient press over the clutch plates. What oil are you using, just out of interest?
 
well, all sounds like great news, no need to take engine out! Thanks for all the replies. Feeling a little sheepish that is is "just" the clutch, I thought I had some sort of major failure, relieved that it is not.

I have ordered a new clutch pack (steels and fiber) and new clutch springs from Wolfgang, will be here on Monday.

for oil I am using  https://www.schaefferoil.com/vtwin-oil.html  I just checked its specs, it says it can be used with motorcycles with common crankcase/trans, "non metallic clutches only". I have been using it in my Harley and all three Laverda's for a very long time. Now I am wondering what a "non metallic clutch" is or isn't.

I agree with Grant I need to figure out why this happened. First thing to check, I think, is what the clutch push rod length is supposed to be on an RGS, in total, with the bearing in between the two halves, or just the length both halves are supposed to be. Does anyone know?
 
Kevlar plates cured my RGS of all its tendency to slip at higher rpm (>5000) without needing heavier springs. Highly recommended.
Pushrod lengths for a 120 engine (courtesy of info from DAM Classic Racing included in their extended operating arm kit) 133.5mm. Inner ball bearing 6mm. Outer 8mm
 
Checking the specs for clutch springs. the free length should be 47mm and anything shorter than 45.5 is time for replacement.

If you can measure the spring strength, the clutch springs should have 270 (27kp) kiloponds each @27mm compression. 

motorcycle-quad-clutch-springs-set-of-6-pieces-spring-clutch-reinforced-ebc-csk007~2.jpg


Your clutch pack (steels and frictions stacked) should be about 30mm

Your old spring free length is the best clue to the clutch mystery.
 
very useful info, Rusty and Rob. Thanks so much. Will measure when I can get to the garage, and report back.

Rob, when I substantially downsized house and garage two and half years ago, unfortunately a lot of my garage stuff/parts/tools had to go into extended storage. I am pretty sure I have at least one new set of Red's Kevlar lined clutch plates "in stock" so to speak, but finding them from storage is enough of a challenge I just ordered new from Wolfgang of whatever he stocks.

I have had the Kevlar clutch plates in my 79 1200 for some years now, so far so good.
 
Rusty Spokes said:
Checking the specs for clutch springs. the free length should be 47mm and anything shorter than 45.5 is time for replacement.

If you can measure the spring strength, the clutch springs should have 270 kiloponds each. 

motorcycle-quad-clutch-springs-set-of-6-pieces-spring-clutch-reinforced-ebc-csk007~2.jpg


Your clutch pack (steels and frictions stacked) should be about 30mm

Your old spring free length is the best clue to the clutch mystery.
Click to expand...

Is a kilopond something to do with roast duck?

Paul
 
If you have a engine valve spring tester that reads out in pound force (lbf/in) you can convert to Kiloponds.

1 kiloponds = 2.2046226294122 pounds-force.

270 Kiloponds (27kg) @27mm compression for the stock clutch springs, 370 (37kg) Kiloponds @27mm  for the "racing" or "SFC" clutch springs.

Wolfgang's performance clutch springs I received were stronger than stock and did not seem much heavier at the clutch lever, nice. I think he gets them made in Germany like his fork and valve springs. They might be from some other supplier though.

Overall spring length is the easiest test.

Ducks-1024x608-1024x585.png



 
My first dino run years ago and the operator commented on finding on ocasion one weak spring and that causing a fluter in the pack at high revs checking tension is a good idea
 
Rusty Spokes said:
the clutch springs should have 270 (27kp) kiloponds each @27mm compression. 
Click to expand...

270 kiloponds would be a bit excessive. 1 kilopond = 1 kg force, so that's 270 kg per spring. You'd need to be superman to pull the clutch lever!

27 kiloponds is the figure you're after (27kp)

Looks like the label on that picture of the spring testing gizmo is wrong. 27 kiloponds is about 270 Newtons. Perhaps that's where the confusion arises.

 
When I was very young with no money my GS1000 started slipping its clutch. It was my daily runner so I went to the shop after work  to buy new plates to swap out that evening. Unfortunately it was more than I could afford so instead I went home with a borrowed micrometer. I found to my relief that the plates were all new, but dpo hadn?t replaced the springs.
So it worked out a lot cheaper, although I had to make the gasket twice  :D
 
Strange that the clutch just let go, hadn't given signs of slipping before that. Anyone have experience of sudden clutch failures?
But maybe Paul didn't realise he had been slipper clutching it while he was backing it into those corners showing the kids how it is done.
 
Might also be worth checking the clutch plate orientation, as referred to by Piet in reply #39 in this old thread:

https://www.laverdaforum.com/forum/index.php/topic,95267.msg363305.html#msg363305
 
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