Bultaco 198B Barrel and Head

[midgy]

Hi Guys,

Having now fully cleaned up my 198B barrel and cylinder head, the top of the barrel and the underside of the head are stamped 137.  It has been over-bored to 73.75 giving 256cc.

Do the Bultaco Sherpa gurus suggest my head and barrel came off an older 250 Alpina 137 from 1974/1976?

The bike was apparently supplied directly by Comerfords in early 1982 as one of about 110 bikes supplied and sold by them, and was allegedly billed as a 'Vesty Replica' 

Or perhaps just put together by Bultaco factory using what was just lying around? And presumably over-bored to the max early in its life?

Ideas appreciated. Thanks

[feetupfun]

6 hours ago, midgy said:

Hi Guys,

Having now fully cleaned up my 198B barrel and cylinder head, the top of the barrel and the underside of the head are stamped 137.  It has been over-bored to 73.75 giving 256cc.

Do the Bultaco Sherpa gurus suggest my head and barrel came off an older 250 Alpina 137 from 1974/1976?

The bike was apparently supplied directly by Comerfords in early 1982 as one of about 110 bikes supplied and sold by them, and was allegedly billed as a 'Vesty Replica' 

Or perhaps just put together by Bultaco factory using what was just lying around? And presumably over-bored to the max early in its life?

Ideas appreciated. Thanks

Bultaco cylinders are usually stamped with the model ID of the first model that came with that design.

I would have thought however that the 137 had a protruding sleeve cylinder while the Sherpa T 250s went to a soft metal head gasket/flush sleeve before the 198B. My 198 has a flush sleeve and soft metal head gasket. They did do lots of strange stuff to get bikes out the door towards the end and a 137 Alpina type cylinder and head would be fine to use on a 198B.

As for the large diameter bore, yes it's fairly common to bore a 238cc motor much bigger than standard to get more grunt rather than because the bore is worn.

 

[lorenzo]

3 hours ago, feetupfun said:

Bultaco cylinders are usually stamped with the model ID of the first model that came with that design.

 

 

feetupfun, your 198 cylinder is stamped 165, possibly ? 

[feetupfun]

46 minutes ago, lorenzo said:

feetupfun, your 198 cylinder is stamped 165, possibly ? 

Sorry, I didn't look for stampings when it was apart last, but will next time

[woody]

Comerfords made a number of Vesty replicas, most were 340 but as far as I know there were two, maybe three 250 conversions as well. They weren't full replicas of his last 340 but had a longer swingarm with pivot point moved forwards. I can't remember if the top shock mounts were moved on these bikes. If yours has the normal square section swingarm it will be a standard B model

[midgy]

Hi Woody,

Thanks for the info.  I think mine was just a cosmetic type of 'vesty replica', since as far as I can see it is standard B model apart from the engine size having been increased at some stage.  It was Pete (Bowker?) at In Motion who said:- 

"It was one bike of a batch of 110 that was converted/made into  a 'Vesty replica' 250 and was sold by Comerfords
instead of going to a dealer.  So it was a standard production model 198B with a few modifications."
 

It was also fitted with a plastic tube type chain guard on the top chain run like a Montesa 348/349 had at the time.