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. 

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 !

I’ve tried that and they are M4 7mm and they informed me that they are rare and only specialist use only. 

18 minutes ago, Bob Davies said:

I’ve tried that and they are M4 7mm and they informed me that they are rare and only specialist use only. 

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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.

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.

Thanks for the info, I’ve tried them but no joy so far. 

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'

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. 

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.  

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 December 31, 20205 yr by cleanorbust

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

 

 

Edited January 1, 20215 yr by fourex
ebay site added.

No need to buy as a Montesa part. Cheaper and easier elsewhere.