ND Rev Counter

Gazz

Gazz

New member
Location
Clevedon
I realise this is a big ask but does anybody have a rev counter ('79 triple) I could borrow  :o ... My counter seems very lazy above 4k, the needle moves smoothly and it doesn't flicker up to this point. but reluctant to go much further (yes I do know I have to pull back the twist grip!) I'm unsure if it's my instrument or the drive, fitting a known working tach would help me resolve this.

Assuming standard gearing what revs should be showing at 60, 70, 80 top gear..

Thanks

Gazz (UK)
 
You should be able to run it up with a reversible electric drill and an old bit of cable . Might be easier to source than a rev counter.
                        Tim
 
Yep,  Tim's right, easiest method by far.

I am happy to lend you my revo off the Jota, but I may be a long way from you (I am in Surrey).

Best way to run a speedo or revo is to get a mid size galvanised nail that has the tip cut into a square (standard building nail). File the point off and cut the head off. Mount the nail in a 3 speed DC drill and carefully centre it, fit the square end into the dial drive and off you go. Depending on the drill, you should have something like 1.5k, 4.5k and 6k on the revo, using each of the speeds (easy to calculate, as the drill should have the speeds on the electical label).

HTH

Pete
 
You need to take into account the ratio of the helical gear on the camshaft to cable drive, so that you can relate drill speed to crankshaft speed - not forgetting that the camshaft runs at half crank speed. 

I don't know what the cable drive ratio is, but someone will probably chime in. If nobody comes up with an answer shortly, I'll be home in about 6 hours and I can go and count the teeth on a spare camshaft and drive pinion.

Cam
 
I counted the teeth on the helical tacho drive gear on a spare camshaft - 10

I thought I had the matching cable drive pinion in a box of miscellaneous stuff, but couldn't find it. If someone doesn't come up with an answer soon I'll have to pull the one out of my bike and count the teeth on that just to satisfy my own curiosity.
 
Thanks for the responses guys, I've tried it on my mains drill and it revs to about 5.5k, it does this smoothly without any flicker, this is making me feel it's something to do with the drive. Unfortunately it's variable speed on the trigger and it doesn't have set speeds, it's also so old the label has worn away! I'm sure of my mates will have a newer one.

If it's the drive what could go wrong? Some form of slipping? It's a new cable. Are all Laverda cable drive pinions the same?

Thanks for the offer of the loan Pete much appreciated but I'll contact Gumbo first as he doesn't live too far away.


Gazz
 
You could have a look at the drive pinion at the wheel end of the cable. Make sure there is no wear, lots of grease and a smooth turning action.
I have seen metal filings in there from time to time, dry helical gears and seized inner cables.
Also make sure the ends of the (new) cable fit neatly into the instrument and also the drive gear at the wheel.
Grease each end of the cable and maybe some very light oil down the inner cable. Shouldn't need that if there is a nylon liner in the outer cable.
 
As well as a newly-refurbished pair of clocks (for which I'd want a large chunk of cash as a retainer if you wanted to borrow either of 'em!), I think i've got a spare complete drive pinion assembly (the part that the wheel spindle goes through) if you want to borrow that to try?
I'm in Kington Langley, not a million miles from Tony (Gumbo).
Let me know if I can help.

Alan :)
 
Grant & Alan,

Thanks for the advice guys, if I have trouble with the speedo I'll bear your tips in mind but it's the rev counter Oooops sorry, tachometer  :P that I'm having trouble with.

Gazz
 
Gazz said:
but it's the rev counter Oooops sorry, tachometer  :P that I'm having trouble with.

Gazz
Click to expand...

Oh yeah, that'll teach me to read more carefully....! :-[
Anyway, there's still a newly refurbed tacho here if you need to try it.

Alan :)
 
You must log in or register to reply here.
Back
Top