1972 SF750 stiff shifting cure

Vince said:
Quick question, is there always a bit of up and down on the lever not controlled by the spring, I am talking 5mm. Do we call that freeplay or a problem? I have a gap on the lug; it's slightly narrower than the eccentric.
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No, not normal and not good Vince. It means the hooks are not sitting in the ideal position to pick up the pin of each shift. If it were mine I'd either try a different shifter shaft/plate/whatever you call it, or grind a depression into eccentric so that the spring is fully engaged with both eccentric and lug. I did this to mine and has the added benefit of preventing the legs of the spring drifting inboard and blocking travel. (no idea why the pic came in sideways)

Selector eccentric customise.jpg
 
I got another shaft and C and all the bits inclusive except for the eccentric, and it's the same on both, approximately 3 or 4mm gap on that lug with the spring tight on the eccentric, so as I said, that translates to similar uncontrolled by the spring movement on the toe bit.. It makes for a somewhat sloppy, longer throw change than I like; it's minimal, but it's always been like that. I am getting all 5 gears. So I guess it needs either a slightly wider lug in the frame or a narrower eccentric. Have you ever done that grinding on other bikes Q. Did you lose any adjustability doing that? It's a fair bit of metal to remove on mine, close to 1/8 of an inch in the old money, that's 1/16 top and bottom. It's kind of odd that it's the same on both parts, though.
 
I was thinking maybe the inconsistency is in the bend of the spring leg, anyway, my spring is contacting the eccentric but not the other bit. Is there any variation in springs, triple compared to twins? Mine has the cranked leg on top like Piet advised.
 
It's cold in the Netherlands now. Laverdas aren't allowed to be ridden. My right big toenail is no longer blue from changing gears. A blue nail hurts, and waiting for a new season can also be painful for the bottom. I prefer a blue nail. And if you don't want that, ride a Japanese motorcycle instead of an Italian one.
 

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Vince said:
I was thinking maybe the inconsistency is in the bend of the spring leg, anyway, my spring is contacting the eccentric but not the other bit. Is there any variation in springs, triple compared to twins? Mine has the cranked leg on top like Piet advised.
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By rights the play shouldn't have any effect on total lever travel - that's determined by the lug on the eccentric at full up-down travel. But it's not a good setup IMHO. Have you got the 'high' side of the eccentric away from the pivot? ie would it have less freeplay if it was set 180 degrees away?

The diameter of the eccentric shouldn't reduce available adjustability to the point of insufficiency,. Vince. You could add material to the lug/bracket thing so it makes contact exactly when the spring does. AFAIK there's no diff b/w springs on triple or twin. The brackets are obviously different. It just seems really odd that you'd need to remove so much from the eccentric to get rid of that freeplay.
 
I was thinking about this last night. What concerned me was losing adjustability from the eccentric, but its cam effect, I think, shouldn't be affected if it's thinner; the cam effect comes from its offset mount, not its shape, I think. It's too late to muck with it now, after the Snowy Ride, I might try and thin it and see how that goes. Guess who will be wiggling gear levers of other bikes into the future to see what play they have. Just don't know why my bike is the only one affected. My econsentric is set to between 2 and 3 o'clock. Changing the position doesn't change the width of the cam, only its height, so that the clearance on the lug stays the same, notwithstanding any adjustment. I think fitting the cam in a lathe and reducing it just like your pic is what's needed, so the spring legs touch the lug and the cam.
 
Vince said:
I think fitting the cam in a lathe and reducing it just like your pic is what's needed, so the spring legs touch the lug and the cam.
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Don't machine the whole length of the cam, as this WILL change the overall throw of the lever. Try and do it as per my pic - as I mentioned the groove where the spring sits has the added benefit of locating the spring legs and preventing them from drifting inward and blocking travel. I just used a cutting disc in an angle grinder with the eccentric in the lathe chuck (drill press would work just as well, but vertical rather than horizontal).

And don't forget that the eccentric is much closer to the pivot (ie the lever shaft) so a small amount of diameter reduction There will translate into a larger reduction of freeplay at the toe end of the lever.
 
It's a good time to make that cranked 13mm openender as well. BTW, Andy Wagner's manual advised bending the spring legs out a bit to avoid the same thing. I tried it years ago, but it caused the spring to cank sideways and didnt work at all.
 
Vince said:
Quick question, is there always a bit of up and down on the lever not controlled by the spring, I am talking 5mm. Do we call that freeplay or a problem? I have a gap on the lug; it's slightly narrower than the eccentric.
Click to expand...
There's always a bit of freeplay but the spring is concerned.
Paul
 
I think having the C "spring-loaded" negates the need for freeplay, maybe a tiny bit. Maybe, always happy to learn.
 
Freeplay in neutral won't matter, but freeplay in other gears will mean a hook could potentially be 'low' (if we assume gravity is at play) and not be engaged ready for the next shift. Even if it doesn't matter, freeplay and vibration aren't a good mix.

In the meantime, I've got my old weirdo shift issue happening sporadically: 1st to 2nd - perfect. 2nd to 3rd? ...can result in finding that I'm still in 2nd. It was really bad when I first go the SFQ on the road and I wrote about it back then. I ended up curing the problem by adjusting in the opposite direction to what logic would tell you was the only sensibvle solution. So it seems it was 'overshifting' ... somehow the hook wasn't ending in position to engage the 3rd gear pin on upshift. I eventually had it cured 100% but after removing and replacing the selector cover to cure a green gasket leak :mad:, it has reappeared, but very sporadically ... on one ride I will have perfect shifting for half an hour and then I'll start getting the dodgy shift once or twice, sometimes it won't happen at all - last night on the way to and from the club meeting I reckon 1 in every 3 shifts from 2nd to 3rd it reared its ugly head again. Every other shift is faultless.

I am beginning to suspect that the SF3 internal plate/drum I fitted (with more rounded slots to smooth the shifts between gears) may be the cause. I don't know why, but in 50 years (I turn 70 today!!) I've never experienced a problem like this. And the position of my hooks relative to the pinned shift cage is visually out of whack. That doesn't bother me as long as it shifts cleanly, and the fact I've had it working beautifully in the past means I shlould be able to get it back there again. How or why it changed simply because I removed and replaced the selector cover is beyond me - and yes, I fitted the cover back with no backlash in the shift cogs engagement. It's an odd one.
 
This has frustrated me a lot over the years. A good while back, probably 25 years ago, I lost 5th for months after replacing the front sprocket and delving into this. It's surprising how it reduces cruising speed ability. Anyway, this forum has, every now and then, given me tips to sort this and other Laverda-specific oddities. One odd one was early on when up changing, I would feel the lever get blocked and staying in gear, reducing foot pressure slightly and going again would get a good change. Someone once said early bikes have corser less teeth in their dogs, apparently fixed on RGS engines. It doesn't do that any more, no idea why it's stopped. I used to constantly get false nutrals before I pissed off the left foot links, which were so sloppy from wear. So the last fix before I get too old to ride is this slightly excessive play. BTW, I am just a spring chicken at 68.
 
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