Scorch Cycles, Cape Town, South Africa

If it's a 180 you're fitting, there should be plenty of used discards around. The 250 will never wear one out, they get replaced when they've had too many heat cycles.
Remember that back in the day when TZ750's went to wider slicks, you had to trim the chain side for clearance...
 
redax5 said:
enjoyed a productive day with Mark QLD while we played with some string, amazing what one can do with some Brickies string
we do have an issue though with sprocket alignment even after machining a custom inboard cush drive unit that is going to need even more tricky shite machined up
damn it Janet  :(


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If I had your skills Red, I'd be contemplating a jack-shaft sprocket at/on the swing-arm pivot, similar to the crossover jack-shaft sprocket on page one shots of the Scorch bike.
But not crossover, just double sprocket wide enough to run forward and aft chains. I don't know if there is room on the swing-arm pivot, as it's hard to see in the pictures.

JackShaft_zpsx6hstihg.jpg


jackshaft%202_zpsatw0xqly.jpg

 
Guy here did a very similar offset sprocket setup for a roadrace sidecar. Well engineered, best chain...
Halfway through his first test run, the short chain got so hot it seized.
 
All I can add is the simplest solution will be the best, I am a fan of the setup used on ATK dirt bikes. They had a system that ran a sprocket above and below the swingarm pivot that took any effect the chain had on the rear suspension. Added to that they ran a disc brake off the front drive sprocket. The latter bit is bound to fail tech inspection and the first bit does nothing to get the sprockets aligned. Both are COMPLICATED. So I got nothin.
 
GregT said:
Guy here did a very similar offset sprocket setup for a roadrace sidecar. Well engineered, best chain...
Halfway through his first test run, the short chain got so hot it seized.
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Just thought if it was good for Busa's, and zx14's then it'd be OK for an old Laverda engined bike.
:-[ ................... but then, I'm not a mechanic, I'll take my hat and coat (bolt)
 
Red, K&J is offering offset (8mm) sprockets for the Triples in 530:

http://www.ebay.de/itm/Versatzritzel-Laverda-1000-offset-sprocket-pignon-decale-pignone-speciale-/322110732528?hash=item4aff4bb8f0:g:x3AAAOSwXSJXOeOO

If you want to run 525 or 520 even, you can machine the outer side to fit them, wich reduces clearance issues with the clutch cover or the frame/swing arm etc. if there are any.

to Chris suggestions: on one hand I like the idea, but I fear it just adds unnecessary complexity to something that can be solved way easier...
 
Puts more load on the original bearing when the sprocket is offset.
At least the transfer shaft idea is supported at both ends.
 
chrisk said:
Just thought if it was good for Busa's, and zx14's then it'd be OK for an old Laverda engined bike.
:-[ ................... but then, I'm not a mechanic, I'll take my hat and coat (bolt)
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The sidecar in question was a ZX12 - late model, injected.

I see the US setups like you've posted and wonder just how much mileage some do...That short front chain has a much higher load per link than a conventional single chain. There was much speculation - and betting of course - among the sidecar fraternity here as to how long it'd last. No one though it would only last a couple of laps though...
Being the cynical old fart I am, I remembered the 2 stage Honda camchains of the 80's and went on record as saying it wouldn't work for long.
 
GregT said:
...That short front chain has a much higher load per link than a conventional single chain.
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So, duplex front chain/sprockets and single rear  ::)
 
Grant said:
Puts more load on the original bearing when the sprocket is offset.
At least the transfer shaft idea is supported at both ends.
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We are talking about a 115 - 120HP engine with something like 115Nm I assume (if really healthy). Ignoring the mechanical friction for a moment that several bearings, chains etc. provide, I wonder how much load really is put additionally onto the mainshaft bearing.

I know though that sometimes those fail on standard bikes with roughly 30 HP/Nm less, so I agree there is for sure something on it, Grant. Nothing a regular check and/or a stronger bearing wouldn't bring to light though I feel. But then I am not a mechanic, what the hell do I know. ::)
 
The output shaft bearing was specified for an engine making around 80 bhp (on a good day).
Now feed 50% more power and a hell of a lot more torque through that bearing and shaft AND space the drive sprocket further away from the original position and this will place much larger loads on the bearing and shaft, which will be approaching 40 years old by now.
I'm not a mechanic or engineer either but I also don't go around looking for trouble with these engines.
 
Grant said:
The output shaft bearing was specified for an engine making around 80 bhp (on a good day).
Now feed 50% more power and a hell of a lot more torque through that bearing and shaft AND space the drive sprocket further away from the original position and this will place much larger loads on the bearing and shaft, which will be approaching 40 years old by now.
I'm not a mechanic or engineer either but I also don't go around looking for trouble with these engines.
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Quite correct. Plus have a look at the 'busa picture and remember that the output shaft on that - which carries the sprocket - is supported both ends - and it still will have an outrigger support bearing outside the sprocket.
The Lav box on the other hand has the sprocket mounted on an extension of the gear...not the shaft. And this sits in the output side bearing and is held in alignment by the output side shaft running inside it. We've already broken one mainshaft inside the gear on Pete's 1200...And that was deliberately built with narrow rims because I really didn't want to get into what Red's looking at now.
 
Laverdalothar said:
Red, K&J is offering offset (8mm) sprockets for the Triples in 530:

http://www.ebay.de/itm/Versatzritzel-Laverda-1000-offset-sprocket-pignon-decale-pignone-speciale-/322110732528?hash=item4aff4bb8f0:g:x3AAAOSwXSJXOeOO

If you want to run 525 or 520 even, you can machine the outer side to fit them, wich reduces clearance issues with the clutch cover or the frame/swing arm etc. if there are any.

to Chris suggestions: on one hand I like the idea, but I fear it just adds unnecessary complexity to something that can be solved way easier...
Click to expand...

Won't work... well, not for very long.

The stock method of fixing the sprocket to the shaft will not lend itself to an offset sprocket of any kind.  The splined sprocket relies on the force input being in the centre axis of the sprocket, any offset will tilt the sprocket, no matter how tight it once was, or how big the fucking hammer was that you needed to bash it onto the shaft... :D  The splines will very soon give up, another sleeve gear ruined. ::)

Even if a suitable method of rigid fixing of the sprocket is devised, the extra loads will soon give the output bearing hell. 

Problems nobody really needs.

Have to cope with exactly this problem on a customer bike.  Was fitted with wide 17 inchers and a 170 or 180 rear tyre and an offset sprocket to suit.  Now have a nicely fucked sleeve gear, chewed up needle bearings and an equally nicely fucked mainshaft... guess I'll just wander into the yard and pick one of each from the gearbox tree. :D

piet
 
Can't even fabricate an outrigger bearing, even if you dowelled the sprocket cover, as the clutch pivot arm gets in the way.
 
sfcpiet said:
guess I'll just wander into the yard and pick one of each from the gearbox tree. :D
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wish I had a gearbox tree in the backyard  :D

same opinion as Piet, actual Laverda gearbox mainshaft design does not lend itself to running offset sprockets so I have 2 choices

first choice and the easiest, just machine up custom offset sprockets for the rear wheel, sounds easy but gearing now comes into play, am stuck with a 19mm front sprocket and then when looking at 17" tyres, if we go to a 60 aspect ratio then we need to gear down to possibly 37 tooth for certain tracks and that causes dimensional issues due to the thickness of the Zane hub. Solution is to run a 17" x 70 Slick which makes a big difference to the gearing

or second choice is to make an offset front sprocket with an outboard bearing support and then modify the billet hydraulic clutch covers that we already make anyway to accept a support bearing, this would take the locking tab out of play as would be no room for it but that is no great loss, does fuck all anyway
main issue here is not the design of the modified sprocket and outrigger support, biggest issue is the lack of decent support for the cover as provided by the existing 4 x 6mm bolt holes, would not be sufficient to hold everything together I believe over a season of racing

am thinking I'll go with the rear sprocket design, have already ruined that 17" Zane rim anyway by machining it to fit our purpose, bit more machining will not matter now



 
 
Hey Red, I was thinking along the same lines as you - modify your billet cover to accept an outrigger bearing for the output shaft. Given the inherent weakness of the original sleeve gear design, it would have been nice if Laverda had done that.

I see the problem with the 4 x M6 bolts. I reckon there's enough metal around them to take them out to M8, but even then I'd have my doubts about the rigidity of the whole setup.

If you need to go any stronger than 4 x M8 bolts, you'd need to modify the crankcase. Time for a billet or carbon fibre crankcase methinks. It's only money. You can't take it with you when you kick the bucket  :D
 
need to buy some larger diameter alloy bar stock to machine the offset sprockets so decided to set up the rear brake as had all the parts required for that
worked out quite well, used the original Zane caliper hanger so did not even need to machine new hangers, makes life simple
torque arm sorted, job done

 
custom machined cush drive and rear & front sprockets, chain lines up to within 1mm which is close enough
need a slick


 
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