Monday, May 18, 2015

The Art of the Bultaco-Restored

To those of us of a certain age there is an expectation of what a Bultaco is supposed to look like. And, I think a lot of us, are of the belief that is is the prettiest motorcycle engine ever. There is the clean egg shaped cases...the upswept exhaust with the rich chrome finish... the relatively crude expansion box...and finally the very clean inlet tract with the screw-on air filter. You can easily picture the mixture entering the engine...combusting...and exiting the high mounted exhaust.

I was forced to toss the original Monobloc Amal Carburettor which came with the bike. And, by the way, that carburettor was not original to the Campera. It was originally equipped with a Zenith which was not only ugly but also prone to wear. The Monobloc and the intake manifold which came with this bike when I bought it was from a Mercurio. It was over jetted and worn out. My solution was to install a Chinese copy of a Mikuni which was originally intended for a wide range of Japanese 175 cc trail bikes and MX machines. This installation involved two different adapters bolted on to the intake manifold. An air cleaner was eventually discovered which would fit between the carburettor and the frame. It was not a pretty picture. You can see the installation on one of my earlier posts.

The Chinese Mikuni worked well but I could not bear to look at all of those mismatched pieces. It was absolutely disrupting the graceful lines of the Bultaco engine. The solution was provided by .British Bike Bits. I was able to source a Amal (Wassell) carburettor which is intended for a 175cc BSA Bantam. It is a Concentric and its concentricness means that it is somewhat longer from top to bottom than the Monobloc which it replaced which in turn means that I had to find a spacer to move it out just a bit from the mounting studs to create some clearance. If you check the picture above you will see that there is on a tiny clearance between the bottom of the carburettor and the case. The spacer, between the carburettor and the intake manifold is also clearly visible. That little spacer raised the carburettor up just enough so as to clear the cases.

I have gone out on two test rides and it works perfectly. For me if a motorcycle starts easily and idles I am about 80% perfectly happy with it. The Wassell/Amal carburettor makes the Bultaco even easier to start than the Chinese Mikuni. Just use the tickler to run some gas down the intake manifold and off you go. Never more than two kicks.


  1. I always had bother getting my Sherpa engine to idle well. I blamed it on a bit of wear in the carb body but I dont think they make an Amal 627 any more, I might opt for a different bore instead.

  2. Fantastic post - Great explainations and thinking.I'm looking forward to what you have for us next..!