Primary Sprockets

P

PJV99

New member
Location
Worcester UK
Morning all

I'm looking for both primary sprockets to suit my '81 Jota Mk 2.

Existing set up is 2 x single chains and I would like to revert back to triplex / duplex.

Here's hoping it's not going to cost me a kidney.....

Regards

Peter
 
I've got a set of primary sprockets in very good condition. They came off a very low mileage engine that was "blown up beyond repair" about 20 years ago. I guess nowadays values have changed and blown up engines get rebuilt rather than parted out. I also have a couple of triplex chains. A very slightly used original Regina (no measurable wear) or a NOS (never used) big pin Iwis sourced from Andy Chain more than 10 years ago. It came from the last couple of metres of that Iwis triplex chain that he had in stock. He said it was likely to have been the last bit available anywhere because they stopped making it.

No idea what any of that stuff is worth though. I'm not what you'd call a motivated seller but I'd let them go for a fair price if someone needs them more than I do. Does anyone have a clue as to value?

Note: There's a NOS main shaft (clutch) primary sprocket on ebay USA for $(US)160.
Says it's for a 750, but the primary drive hardware is identical to the triples AFAIK.
www.ebay.com

LAVERDA 750 SF GT MOTOR PRIMARY CHAIN SPROCKET CLUTCH 55 T. 41 213 004 41213004 | eBay

Find many great new & used options and get the best deals for LAVERDA 750 SF GT MOTOR PRIMARY CHAIN SPROCKET CLUTCH 55 T. 41 213 004 41213004 at the best online prices at eBay! Free shipping for many products!
www.ebay.com
 
OK so just a bit of background.

The sprockets are for a nuts and bolts resto' of an 81' 180 Jota Mk2 which I originally bought in 2002.

Due to crankcase stud issues and carb' air leakage caused by corroded studs after riding the bike for a short time I decided it needed and engine strip and rebuild. When stripped I realised that the 'dpo' had made a botch job of fitting thread inserts into the upper crankcase.

Living in Worcester I was recommended to go and see a Mr Steve Winterton who would be the answer to my prayers and sort out my crankcases.

Fast forward 5 years and I finally got my upper crankcase back suitably repaired. I have to admit during this time I did loose a bit of interest in the Jota ending up finishing the resto on my 75' T150 Trident, together with other projects.

I did do some work on the Jota from time to time including frame powder coating and full painting by Dream Machine.

So now having made sufficient space I've decided I need to finish the Jota.

It wasn't until I ordered a set of chains from Jason ( new 'chain-man) I realised I didn't have a triplex chain but the later 2 single chain option fitted to the bike.

On searching the forum and taking advice I decided that I would rather convert to the older triplex / duplex option hence my note to the forum looking for a supplier of triplex sprockets.

I have decided that if I cant get some sprockets at a reasonable price I'm going to stick with the original singles option. he reason for this being that in all probability I will be selling the bike when its finished and hence I'm not sure if I can justify a high cost when there is nothing wrong with the original sprockets albeit singles are not considered a good a triplex / duplex. Also It's a simple project for any future owner to carry out if they wish.

Bottom line, I'm prepared to pay a reasonable but not extortionate cost.

Peter
 
There's a good chance you'll get away with a duplex or triplex chain on your existing sprockets if the two single chains haven't been on there for too long. Those sprockets hardly wear at all.

Lay a steel rule across the 3 rows in the valley between the teeth (where the chain rollers lie). If the outer two rows are worn more than the middle, you'll be able to rock the ruler on the middle row like a see-saw. If there's no perceptible rockability (just coined a new word), then I reckon you're good to go. If you don't have a steel ruler, a bit of shaft (bright steel round bar) will work just as well - actually, it'll probably work better because it'll self-align.

If it passes the rockability test and you're still unsure, take the sprockets to an engineering machine shop and ask them to run a dial indicator across the teeth.
 
motoddrob said:
The later model primary sprockets 2x single row had the centre row of teeth machined off
Probably the reason why he is looking for new sprockets.
Click to expand...
These were completely different sprockets, not existing triplex items with a missing row. If that were the case, a triplex could be fitted...

The 2 x simplex sprockets were spaced differently, no other option than 2 simplex chains.

Not much interchangeability between twins and triples in the primary dept., front sprockets are spaced differently and clutch sprockets different tooth count. Gearbox mainshaft is shorter on the twins. Crankshaft tab washer, clutch drum thrust washers and circlip as well as the chain itself are shared.

piet
 
For info' attached a pic' of crank sprocket.

I think that at some time a previous owner has used replaced the sprockets from a later 120, assuming the singles option was never used on the 180's?? Although an 81 bike the head has an 83 stamp and the carb inlets I believe are from a later 120
 

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get the sprockets and chains from Cam, PJV99 while you can, the twin simplex sprockets will sell to someone to soften the blow.
I would say the package from Cam, front sprocket, clutch sprocket a good used chain and an unused one would be worth about 300GBP plus shipping.
CLEM
 
the carb inlets pictured were first fitted to the Jota 120, starting 1982, but a few of the last 180's got them as well, so 1981, original, could well be.
CLEM
 
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