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In order to make quick gearing changes on the hill climb project it would be handy to have a 13T gearbox sprocket. Changing rear sprockets on Morinis is a faff with those bolt locking tabs. It has been converted to 520 chain and I'm going to also do the 375/2C now for which NLM are supplying a 14T 520 sprocket to go with the 38 6 bolt fixing '250' one Sprockets Unlimited have made up for me.

I've found an advert on Italian Ebay for Z13 sprocket for Kanguro 88-90. Is that a splined version or a 'slot' as on my 76 Strada unit?

I'm sure I can get one made, but that takes time and even delivery from Italy would be quicker.

Only the 500/501 (and 250 single) have the heavier duty gearbox shafts with splined fitting as far as I know.

Ah, if I'd looked further down the ebay.it page I would have seen a useful dimensions drawing that confirms that. It also says they don't post to the UK but might as well ask in hopes.

I have a 13 tooth gearbox sprocket of the early type - two flats.

harrymuffin wrote:I have a 13 tooth gearbox sprocket of the early type - two flats.

In 520?

You mean 5/8" x 1/4" ? If it is 5/8" x 3/8" then I can machine it narrower for you if you have the 14 as a pattern. Same goes for alloy rear sprockets as I buy the blanks from the chap in Bucknell who used to make Roger Mauphling's (?)sprockets.

harrymuffin wrote:You mean 5/8" x 1/4" ? If it is 5/8" x 3/8" then I can machine it narrower for you if you have the 14 as a pattern. Same goes for alloy rear sprockets as I buy the blanks from the chap in Bucknell who used to make Roger Mauphling's (?)sprockets.

5/8 x 1/4. Thanks for the offer. No rush for a while now What spanner twiddling I can manage needs to be concentrated on just getting both the Morinis operational again.

I have 520 14/38 on my 501 and it will not pull past 6.5k in top. Standard Excretia can. Chain is a piece of elastic so going for 530 14/40. Excretia pulled 8k / 160kph so new setup somewhere in the middle of the two.

Point is, 18'' rear wheel on 14/38 is tall geared, however old 478 had that gearing!

I used to run 13/38 on the 2C/375 for a while (when I briefly hillclimbed it) but for longer rides I now prefer it on a 14T. I don't do enough miles for chain stretch/wear to be a big issue. The tuned YZ450F dyno'd at 58BHP was quite happy on HD 520 chain so far as strength is concerned. 13/44 on the 'project' should make it lively and worth it having a 6 speed box. At present it might as well have just four, even at longer courses. The MX close ratio 5 speed box on the KTM 350SXF was perfect. Easier to use a wide range of rear sprocket size on a dirt bike though.

MickeyMoto wrote:I have 520 14/38 on my 501 and it will not pull past 6.5k in top. Standard Excretia can. Chain is a piece of elastic so going for 530 14/40. Excretia pulled 8k / 160kph so new setup somewhere in the middle of the two.

Point is, 18'' rear wheel on 14/38 is tall geared, however old 478 had that gearing!

I use 14/39 with the 501 in Rocinante and it works fine (520 chain)

Primary drive ratios.

And what are the primary drive ratios of the 507cc/501 and 476/500 engines? Could they, if they are different be owing to the starter motor being hung onto the front of the engine of the 507cc engine and the starter motor-crankshaft gear needed to be geared down and also that the two gears would actually mesh? i.e. crankshaft gear needs to be bigger than the starter motor gear so that it will turn the engine over.
I have the 507cc top end on a 5 speed bottom end and the internal gearbox ratios are different to the 6 speed gearbox but the primary gears are identical the overall crank to gear sprocket is different being much higher on the 5 speed. This bike has 14-40 sprockets and will pull 8000 or there about in top whereas the 6speed 496cc engined bike runs 14-38 sprockets and also pull 8000 in top. The only problem I have with the gearing of the 507cc 5speed is the very high first gear, bit like a Thruxton Velo or BSA Goldstar.
I am a loss as to why the need to go down to 5/8" x 1/4" chain all for the sake of going a half bhp, it would be much easier simply to take an enema and not have breakfast before competing. I admit that the 350's are over chained and the smaller chain is more than adequate and I am sure Morinis could give a viable and logical reason for the choice of chain, but purely from the point of longevity and reliability for road bikes then the heavier chain is preferable. I did consider fitting 'o' ring chains but even with a Scot oiler, sap what little power Morinis develop at the back wheel compared to some Jap crap putting out tree figure power values.

Fair comment. I had to get a custom 44T rear sprocket made to get the gearing down so I decided to go 5/8 x 1/4 while I was at it, and also got them to do a 38T. In the light of real running, rather than spreadsheet calculations, that's now probably not going to get used - unless I put it on the 2C/375, which currently needs a new front sprocket and chain. A 350 sized chain also runs a bit too close for comfort to the chain guards with a 350 in a 250 frame. Though to be fair I've done it for 35 years until now. If I was thinking of riding it on a couple of thousand miles trip any time in the future I'd have kept to the larger size.

As I told before I use 520 chains for years with a 501 motor in the frame of a `81 K model. The last one lastet longer than any chain I´ve ever tried: 30 000 km! Well, than it was realy worn of cause, with the sprockets still aceptable. But I could not believe it, when I had a look at my little book of maintanance It was an endless DID 520 VM (100 links because of a Fridegotto swing arm). And I´m realy glad that I bought three of them some years ago in a special offer

520 HD chains seemed to last reasonably well on my Gilera Nordwests (including the Frigerio 604 dyno'd at 50BHP). If I remember correctly 520 O-ring was OEM on them. The big single was inclined to develop tight spots in them though. 30000 Kms would be many years riding for me on one machine. To be fair, it would take me several to clock up using all three road legal machines.

All other bikes in the fleet run on 520. Even the ER6n, though that has a 'sealed' chain. So, *in theory*, I could buy in bulk