Narrowcase crankcase screws

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Narrowcase crankcase screws

Postby ranton_rambler » Mon May 14, 2018 9:16 pm

Just getting ready to put my cases back together so I was sorting out everything and laying out on the bench - gaskets, shims, screws etc.
There seem to be 5 screws which are 25mm long, but 2 have cross-drilled heads. I can't find any reference in the parts book, and can see no reason why they would fit in a specific place.
Any thoughts?

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Re: Narrowcase crankcase screws

Postby Eldert » Tue May 15, 2018 2:59 pm

the holes are for a wire and a lead seal .
are you sure you want to use the 50+ year old screws with rounded inside hexagons and not new ones ?


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Re: Narrowcase crankcase screws

Postby ranton_rambler » Tue May 15, 2018 8:14 pm

No locking wires when I stripped it down. The only ones I found were on the oil pump, which I still need to have a look inside. Any particular need to lock-wire the cases after re-assembly?
The heads on the M6 capscrews are good, so I was going to re-use. They're the same age as the cases. The M8 bolts might get replaced but only because they are rusty, and quite visible on the bike.

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Re: Narrowcase crankcase screws

Postby Buster » Tue May 15, 2018 10:33 pm

The lock wired bolts are next to each other under the sump and the lock wire has / had a lead seal.
Put there by the factory when the engine was built.
If the seal is there it signifies that the crankcase has never been split.

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Re: Narrowcase crankcase screws

Postby graeme » Wed May 16, 2018 1:03 am

Yes but the seals did fall off after a while so you could not say for sure if the cases had been split or not.
My old ‘80 SS had the seal for about 2 years then it fell off somewhere.

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Re: Narrowcase crankcase screws

Postby LaceyDucati » Wed May 16, 2018 10:26 pm

Mine too Graeme, my old GTS shed it's lead seal half way across Spain, funny thing is the bolts never ever came loose :-) Added to this I've never had a casing screw come loose in 30 years of riding, racing and building singles, so all a bit unnecessary.
Regards Nigel

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Re: Narrowcase crankcase screws

Postby Ventodue » Thu May 17, 2018 7:27 am

Reckon it was a factory control thing, Nigel, rather than a security measure - ?

I even HEARD the one on my SSD come off! Most bizarre - must have pinged the silencer.

I didn't stop ... :D

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Re: Narrowcase crankcase screws

Postby Jeb » Sun May 20, 2018 7:51 am

Surely this was done as a tamper indicator while under warranty. Didn't matter if they fell off after the warranty period as they were not intended to secure the screws any way.
The gas and electric companies do the same on their meters to show if they have been tampered with.

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Re: Narrowcase crankcase screws

Postby ranton_rambler » Mon May 21, 2018 9:29 pm

Crankcases are back together (temporarily) and crank shimming is about right.
I've put the gearbox shafts back in now, but the factory manual is a bit vague about endfloat. Any thoughts?
What about sealant on the gasket when I go for bolting it up for the last time?

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Re: Narrowcase crankcase screws

Postby PhilR » Tue May 22, 2018 8:18 pm

Nigel Lacey gave me this wise advice..

As the gearbox is an input/output type design, end float is not so critical and in fact only governs the amount of end float on the end gears of the shaft. On the input shaft there is no shim on the end of the shaft as standard and putting shims of less than 0.5mm is not likely to be a good idea as they will probably just get spat out.  Certainly 0.3mm float is perfectly acceptable for the input shaft and this will allow 4th gear to also move and allow lubrication of the inner spinning surface. I would say anything between 0.3mm and 0.5mm would not cause a problem. On the output shaft you may find even more than this and there is no real way of shimming the end clearance because of the roller design. There again needs to be a reasonable clearance either side of this gear to allow oil to lubricate the bronze bush and generally speaking I would leave as is.  My experience with the gear selector drum is that generally a 0.5mm shim either side of the drum usually gives reasonable clearance and any attempts to shim the drum tight will usually show up tolerancing/design problems with the gearbox and lead to burnt out selector forks. If the dogs are in good condition once they have been introduced to each other, under load that should hold the gears engaged. The selectors are not actually designed to hold the gears in mesh.

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