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Bob Davies

MH 349 cota engine casing screws

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Hi everyone, I’m hoping someone can help me here. I’m restoring a 1980 MH349 Cota and I need a set of 7mm hex drive countersink screws for the engine case. I’m struggling here been trawling the net and the best I can find is a used set in the USA for extortionate money. Thanks guys. 

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Look up your nearest industrial supplies/ fastener supplies company with a trade counter. Take one of your existing screws and they should be able to source some for you. You can probably buy a box of fifty for the retail price of a set of 8 or however many there are round your cases, but they’ll sell you a single one if you want (unless they have a minimum order). Same goes for bearings too !

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Then try a few more suppliers, the smaller guys will only supply the run of the mill general engineering fasteners as they don’t want a load of stock lying around.  These screws might be specialist but somewhere will have a load in stock, it’s finding what the special use or industry sector is that uses them regularly. Try giving a few stockist a call, eventually you might find an experienced and knowledgeable person who can point you in the right direction. Best bet is probably an old established engineers supplies - the kind where you find the staff in brown overalls. Somebody on here should be able to help. When I lived in South Yorkshire, many companies I worked at used MC Mills in Barnsley. They seemed to have, or be able to get, everything. Old school and helpful.

Good Luck.

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Just occurred to me, is it just the length that’s causing the problem ? I thought at first you meant odd size by way of M4 thread with an oversize head with 7mm hex socket, that would be odd. Found M4 x 8 long, everywhere. Just grind them to length ?

Good info on Westfieldfasteners.co.uk. Unbrako brand is a long established high quality fastener manufacturer.

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Engine casing screws are M7, various lengths. The countersunk heads are not flat on the outer slottted face but domed.

M7 is NOT a standard size. 

You will be very lucky to find anybody with that size in stock.

I considered making a set from scratch, turning from blank.

I finally bought a set from www.vallmoto.com in Valencia, Spain.

Just had a quick look, currently not shown for 349 but there are some listed for 348.

 

I know that they don't alway show what they actually have available.

Send them an e mail, but don't forget, they work 'Spanish Time'

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Ah I now see the problem. Not M4 at all. From dr nosh’s description they are probably Montesa supply only, to get the exact type. At least until someone gets a batch made. Having said that M7 is a defined metric thread, just not a preferred size (M6 or M8 are the preferred range), so there may be some M7 screws lurking somewhere but maybe not with the exact shape head you’d like. 
I just found screwsevolution.eu which stock quite a few M7 items, not quite what you want but might be worth a try as it seems old Vespa, innocenti & Citroen used them, amongst other auto industry manufacturers. Could be another search avenue. 

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When restoring my 76'  348 i managed to get some 7mm hexagon head bolts over long, cut them to the length i wanted then turned the heads in my lathe, then cut the screwdriver slot in them carefully with a junior hacksaw and cleaned them up with tiny files.  

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Plenty of places on eBay sell M7 screws. I bought hex head ones for my Cota 247, cut them to length, ground the heads to a round shape and hacksawed a slot in the head. Good as the standard screws and not expensive.

From memory I later found allen head ones on eBay which are better for the purpose, but haven't got round to fitting them yet.

Edited by cleanorbust

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These parts diagrams might be helpful when trawling the net as it gives the part numbers, dimensions and number required.

Note also that only bolt # 33 appears to be specific to the 348/349 as it starts with 51. Bolt # 32 would appear to be a carry over from the 247 as it starts with 21, bolt # 31 starting with 73 is from the Cappra I think etc,etc.

Here's bolt # 34 on cyclesavant's ebay site, $7.50 is a bit steep, but he is open to offers.

https://www.ebay.com/itm/Montesa-Cota-335-Engine-Case-Cover-Screw-p-n-6660-11201-61M-1987/303822271821?hash=item46bd37f54d:g:E-sAAOSwWzRf41ij

 

 

MH 349 parts manual page 9.jpg

MH 349 parts manual page 8.jpg

Edited by fourex
ebay site added.

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