To lighten crank or not to lighten crank

Just thought I'd better point out that "knobs" was not meant as a derogatory insult to anyone who posted a reply. It's just a good old expression of exasperation, like,"oh fuck" wouldn't want to upset any of you delicate little flowers!!!

FFF
 
whish a Close ratio Gearbox would be available for a reasonable price... anyone has one (affordable...)? at least the main shaft??

I know Piero offers them, however, 2.000 is a bit much and I think he only produces them in batches... would suite my Motoplast engine perfectly...
 
Realy?  ;)

I have local access to all needed gears (most are standard gears from other Laverda models I was told, 5th gear is the same as on the 1000 AFAIK...), except for the main shaft, that's why I only search for that one. Was already considering getting them re-produced, but to make it economically half way affordable, I also would need to purchase 5, better 10...

are there people out there who would be interested to participate in a reproduction? Have a company not to far from me who would be able to do it... Single shaft is around 1.000? plus tax, 5 would go down to 800 or so etc., including all necessary hardening.
 
Dellortoman said:
:o

You'll be very disappointed if you try to mate a close ratio main shaft with the original the layshaft.

For optimum results, it's advisable to use gears that mesh together.
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Cam,

As mainshaft has an integral gear, this is required when building a CR box.  All other gears are individual, the actual layshaft is the same as the stocker.  Well, not quite... the CR box utilises needle bearings throughout, might be a few slight dimensional differences, but I'm sure the needles could be replaced by bushes if all else fails.  Anyway, afaIk, the CR layshaft is still available.

piet
 
  Got a CR box in my Mklll Saxon/Motodd 1200 180? - don't like it much as I've got a long and often very slippery track to my house and the high 1st gear makes it  a clutch slipping affair to keep speed down (I've got a BSA Gold Star with a RRT2 box that's even worse). I never used one for club racing as the short races meant that any chance of getting to the front depended on a lightning getaway - plus all of my motors were built for Torque and never had any noticeable power drawbacks when changing gear.
    Going back to the crank issue - I've got a very light crank in my 90? SF - but it still has gobs of low end power - guess it would have even more with heavier crank! - Regards - Phil
 
Speaking as one who has bent valves on a motor that spins up well enough without a lightened crank, you might want to get saving for a new set of valves and Pistons if you spin up any faster!!.I think Phil's wise words should be listened to on this.Spend the dosh on some Wilburs.
 
I have to comment on my learned friend Piets statement above


"Changing final drive ratios has nought to do with closer-spaced ratios in the box.  Final drive ratio dictates how fast you can go, gearbox ratios dictate how fast you get there."


This is correct Piet, in part, changing final drive ratios has nought to do with closer spaced ratios in the box, correct, inside the box nothing changes no matter what size front or rear final drive sprocket you use, but the lower that final drive ratio, the quicker you get to fifth gear, so the OVERALL ratios, from engine to rear tyre do get closer, if you gear your bike for a 100KMH top speed it will APPEAR to have very closely spaced ratios in the box, so for track, use changing sprockets can get you an advantage and a big disadvantage.

On my road bike (TOG) I have use 19/38 for a very long time, this is with a low comp, A11 cam engine, it suits me, I like it that way a lot, acceleration is a tad slower, and first gear "taller" as are all the others, but I don't use it in town, and Euro cruising is "relaxed" at around 80/90 MPH on occasions when Andrea came with me it was not exactly the best, but still OK
CLEM
 
Hi Clem,

you are right, but installing just a smaller chain-wheel f.e. (38 or even 36 with a19 Sprocket) will help to accelerate faster, yes, but with the downside of losing top speed and for standard traffic, it means that the bike revs quite high at standards speeds (50Km/h in town or 100Km on open roads f.e.). Not a big issue if your target isn't top speed AND acceleration...  ;)

What Piet meant - I think - is that if you have a close ratio gearbox, you can have a "longer" secondary transmission (for higher speed) and still get there quicker.
 
nick7 said:
Speaking as one who has bent valves on a motor that spins up well enough without a lightened crank, you might want to get saving for a new set of valves and Pistons if you spin up any faster!!.
Click to expand...

crank makes no difference to the top end no matter if it is light or heavy, if you are bending valves you have a totally different problem going on





 
I think he wanted to express a warning, that with a lightened crank, the danger of over-reving the engine is coming closer when f.e. missing a gear or so.

wonder why we all not just swap our beasts for something that has it all already...:

http://suchen.mobile.de/fahrzeuge/details.html?id=218326447&isSearchRequest=true&zipcode=&damageUnrepaired=NO_DAMAGE_UNREPAIRED&scopeId=MB&maxPrice=1000&makeModelVariant1.makeId=23600&makeModelVariant1.modelDescription=GSXR&pageNumber=1#

at least it's orange...  ::)
 
Laverdalothar said:
wonder why we all not just swap our beasts for something that has it all already...:
Click to expand...

because it is fun and extremely challenging to get these old 180 degree clunkers to produce serious power
wait until we build our Salt Lake Racer next year, will see what a 180 triple can do than
9,500 rpm for 5 klms straight on Methanol, fucking awesome, is going to be great (might need billet cases at the 3.72 klm mark :o)



 
:o

Might need new undies well before that.  :LOL:

Is the "senior" test rider going to be the pilot?
 
Davo said:
Is the "senior" test rider going to be the pilot?
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been looking at Maxene as the pilot, she has a bike licence and weighs a lot less than us old farts
just need to get her some life insurance payable to me  :D



 
Laverdalothar said:
wonder why we all not just swap our beasts for something that has it all already...:

http://suchen.mobile.de/fahrzeuge/details.html?id=218326447&isSearchRequest=true&zipcode=&damageUnrepaired=NO_DAMAGE_UNREPAIRED&scopeId=MB&maxPrice=1000&makeModelVariant1.makeId=23600&makeModelVariant1.modelDescription=GSXR&pageNumber=1#

at least it's orange...  ::)
Click to expand...

The same reason we build hot rods to drive the loop with, its pretty cool. Anybody who has the cash can buy a go-fast hang on for your life machine (organ donors). Special people (Phil, Red, Piet, Clem, Marnix, and the list goes on)) have that knack (and desire) to build a machine that has their name on it, one that makes for great conversation at the track (or the forum), and replace the need for viagra  :o :o :o. Having the money to do this is another topic since the average guy like me just doesn't have a cool million sitting in the bank to play with  :LOL: :LOL: :LOL: :LOL: :LOL:
 
Red,
Are you sure about the valve bending thing.Surely if a motor spins up so fast that ,in the case of our old engines, the heavy valves start bouncing as you hita10 k revs sooner than you thought, you will be experiencing fucked valves, bent if you are lucky, smashing their way through the Pistons to the gearbox if you are not. Have had that on a small Honda back in the day...entirely predictable, surely?if you are fitting hollow titanium valves over there with so per duper springs that can take it, let me know? :D
 
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