Hi MartinM: I

My later 91 model number 9100442 with the variation in the frame below the air filter, which I use in the Spanish Pre-77 championship, has different hubs in both wheels, and the front one is like the one in the photo you show.

So most probably the front hub in mk1 bike is original.

looking again at my hubs again the front matches the rear but the front rim does not have the lip that the rear has(rim change maybe?)mine also does not have matching frame and eng numbers is this normal?there not that far apart eng is 00312 frame is 00270

mk1

I think the wheels on your bike are original. The earlier model, like Greeves, is restoring had an equal sided hub and valanced (flange type) rim. This was then changed for the lighter conical hub with an non valanced rim......yet still retained the valanced rim on the rear, which seemed a bit odd.

The very first twinshock I decided to restore, about 15 years ago, was a Model 91 250, exactly the same as yours. It had the same wheel set up, which after a lot of checking, was definitely how it arrived from the factory.

Hope this helps.

Martin

Just checking my Bultaco books and old photos I can see photos of models 91 and 92 with different hubs in both wheels. The books talk about the changes in frame, engine, brakes, yokes, chain tensor and exhaust and says this changes where gradually introduced in the model with the exception of the yokes and engine position rearwoods in the frame.

For example some units of 91 model have the triangular final exhaust, and some the boomerang "banana" one. The same for the rest of the changes. It looks front hub was one of the very first changes, so my 910007 must be one of the very few with the "heavy" hub.

Funny to see the price of the 91 model in 1972 in Spanish shops was 34,900 Pesetas, that

Have a look here http://www.trialmadrid.com/restauracion%20sherpa.htm of the restoration made by a friend of mine of a 92 model. He is a paranoic about Bultaco.

looks like a new bike

Vinnie