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MG Midget and Sprite Technical - Fan belt size

Whats the correct fan belt size for a 1275 with a frogeye dynamo ..What are you using?
R Mcknight

Hello ? Just need the number on your belt ..I have a 900 fitted but it seems a tad long. I cant be the only person with a 1275 and a Frogeye dynamo?
R Mcknight

My car has non-standard pullies so the size won't be much help to you.

900mm is way to large for standard pullies.

I thought all dynamoes have the same pulley size so assuming you have the standard water pump pulley the dynamo 1275 belt will fit of 863mm, later engines used 838mm and 813mm belts.
Daniel Thirteen-Twelve

I bought a 863 belt and its way too short , its to replace the 900 but that is just a bit too long . I am sure i have standard pulleys . Something strange going on .
R Mcknight

try 875 888 890 or such

A good supplier will be able to provide intermediate sizes

And take a wrong sized one back if undamaged
Bill sdgpm

Can't you measure it with a bit of string?
Gary Lazarus


Take your old belt along to Halfords and compare it with the ones on the shelf. It will probably have stretched ever so slightly so you may need one a fraction shorter than the existing...(My car is a bit non-standard due to an alternator conversion, and that's what I did)

Hope that helps.
MarkH1

Yep , going to try an 890 if it exsists or an 880 , i am just curious as to why i need a strange size belt?
R Mcknight

why you need a strange sized belt?

Blame BMC for that

The fitment for A series engines doesnt allow much leeway for belt adjustment after all, I have now changed to a longer straight adjuster for that reason

Intrigued by the question I just searched my old Stock Catalogues (Lucas Spares Packs AA Patrols for the use of) This is for Lucas belts OK

Starting with Mini (cos they had dynamos and alternators during production)

Minis used two sizes during production with either dynamop or alternators KDB813 and KDB838 (1" differece in overall circumference for these)

Patience, I'm getting to A series midgets (Book ignores existence of Sprites for some reason, not Bill's fault) in a minute

I understand there were two dynamo pulley diameters depending on whether town or distance work was planned

Anyway Midget 1300 (1275 obviously)

1966-1974 (Dyn) KDB865
1966-1974 (Dyn) KDB850
both of which are going to be short for your car but do fit Dynamos and the Mini data suggests that some cars with Alternators run the same sized belt as the Dynamo cars

Looking in the Moss catalogue they offer GCB10863, GCB10838 and GCB10813 for 1275 Midgets and Sprites, these seem to be Unipart numbers. Partco sell Unipart nowadays

The part numbers of Lucas belts directly indicated the overall circumference, so if 863 is too short and 900 is too long the pulley may be odd sized for some reason

As I suggested I would try an 875 (outside the shop so you can keep popping in until they get intrigued)

Sorry this doesnt seem to help much, but even when I was an AA man we often found cars that didnt FIT the given data
Bill sdgpm

Hi Bill ..Thats given me a thought , im only saying the belt is too short as i cant get it over pulleys , so maybe the dynamo adjusting strap is wrong and not enabling me to push the dynamo close enough to the engine to fit the shorter belt ..Will look at the strap ...Thanks Roy
R Mcknight

This thread was discussed between 30/05/2009 and 02/06/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.