1956 BSA B31 Scrambler Rebuild – Part 8

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He’s nearly ready to put his bitsa Beeza back together again, but Phillip Rashleigh’s project bike has turned out to be just a little bit different to his original intentions. Gold Star scrambler, anyone?…

As a restoration proceeds, plans often change. I had planned to use the original B31 crank, however I was offered a DBD crank with the mains and big end replaced a few 1000 miles ago by a chap upgrading to a steel item.

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Why road-riding Goldie owners do this is, to be honest, a little beyond me. It’s not like they are thrashing the things to an inch of their lives and need the security a steel crank will give them! But who am I to argue? The DBD crank was at a price that I couldn’t refuse — it would have cost me just as much to get mine built up with big end and mains. The thing is, the cases require a little ‘modification’ to fit the DBD crank and although I am capable of doing the work, I do not have the facilities.

The ZB34 barrel. Not good. Thus a quick call to Roy and the cases, crank, timing idler gear and oil pump were sent on a little holiday to Bedfordshire.

With some disgrace and a touch of a red face I have to admit I also asked Roy to build the bottom end for me. It makes sense as all the components are with him, and he can take a look at shimming the crank and setting the oil pump up (something I was dreading as the drive can shear if you get it wrong). Oh, and he has an engine cleaner and bead blaster to make it nice and newish looking!

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To the barrel… well, I have been around the block with this time a few times now. I do own a ZB34 barrel, but it has to be said it is in a very poor state. Thus with a DBD bottom end and the shorter conrod (same stroke length) it comes with, Roy and I had a little chat, hatched a plan and we hope to be confusing the tyre-kickers for a few years. Keeping the DBD crank and rod set up also allows me to convert the engine to DBD spec at a later date should the parts fall my way.

If this piston really is balanced - as it seems to be - on an office wastepaper basket, it must be H-U-G-E... Random B31 stuff on eBay.co.uk

For the cylinder head, the gods of eBay looked down on me and smiled. A genuine DBD34GS Catalina head was up for auction but no one bought it — too close to Christmas. The high(ish) price put people off and no one bid. A quick email to the vendor and a deal was struck, so six days later I had the head (which is now sat on my desk). It is in very good condition, and has been used for dirt riding as there’s mud burned onto it.

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Now back to the original conundrum, and the barrel. As I’ve gone the DBD34 route I now need a big fin barrel. These are not cheap either new or used, however Phil Pearson has had a batch made and one has my name on it (or rather Roy’s). Shoot off and email to Roy and remind him to dig out a low compression piston from under his bench, for both ease of starting and sensible off road use: who needs 10:1 or more when you are on a green lane?

DBD34 cylinderhead.The rocker box was the next problem. These are cast-in on the B Series and ZB Gold Star heads, but from the late ZB / BB engines they were a separate item. Once again Phil Pearson is having a batch made. I am not going for the eccentric rocker spindles as this is a rather expensive way to go, so I am going to stick with the B Series method of rocker adjustment.

It took just a quick phone call to SRM and buy a finned tappet cover and rocker oil feed. I’d almost finished collecting the engine parts…

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So there was nothing more to do than the actual build, and to fit a magneto and dynamo. Simple really, call Sean Hawker, have a good chat and ship off the various bits I have kicking about. Once these are built and tested they’ll go to Roy for the
build.

Any Beeza owner will know how bad a six-spring clutch is. I mean, they were that desperate at BSA they bought Triumph just to get the four-spring clutch! So I have a choice, buy all new items for a six-spring clutch and fit it, or buy all the components for a four-spring clutch and fit it, or buy a belt drive system. After pricing up all three options I will be going for a Newby belt drive. It is marginally more expensive than the six or four spring chain-driven items, however as there will be no oil in chaincase it can’t leak! This wins every time for me.

Spartan are making a few brackets for me at the moment and modifying the engine plates to make them a little lighter. As Sean Hawker pointed out during one of our telephone chats, no matter what you do to a B Series bike the frame is always made from very heavy walled tube, thus the bike will always be very heavy. However if I can make an effort to keep the weight down then it all has to help, doesn’t it?

DBD34 head and barrel. Now that's more like it.

This installment shows a great deal of change in my thinking (go back to the first installment to see what the original idea was!). There’s also been a great emptying of my bank account. I know I would always want to go DBD at some point, but not knowing that the funds would ever be there I took the plunge whilst I could.

I have a cunning plan for the exhaust. I was always going to go high level and have a high level pipe here, but seeing Scrambler Goldies with a low pipe has changed my mind and so now I am going low level. The pipe will be made open and then a ‘Glass Pack’ baffle kit for a Harley Chopper will be used to keep the noise down a little — but not too much

Next time, engine together, and bike running? We’ll see


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