Bultaco

My first job as apprentice to Chris Sidah was the '74 Alpina Bultaco. Bul what? Exactly. Motorcycle enthusiasts know this Spanish bike well, especially trials and motocross enthusiasts, but for the layman, the name will catch em off their guard.

The Bultaco is a pioneer in trials and motocross and with all the dual-sport bikes on the road these days, a good Bultaco will fit right in while maintaining the classic motorcycle look. Plus, this 250cc engine is small and simple to work on.
Armed with this knowledge, I was eager to dive in with the first assignment.

The first question every mechanic must answer when they are about to work on a bike is: Does it run?

And so we tried to turn it over. We checked for spark and then tried the kick, but that didn't work at all. The compression seemed low and the kick felt sloppy and the motor gave a pathetic weeeez for every kick. So on to the push start.

This, my friends, was a sight to behold. Let me tell you a bit about Chris. This ex-motorcycle racing/Honda expert/BMW Certified/Ducati and Moto Guzzi and anything vintage mechanic took his late 50 year old body and used it like a spry 20 year old. With a little push by me and a thrust by him we were off down the driveway and then BAM! he hops onto the seat of the bike giving the back tire traction while releasing the clutch and then back up on his feet again running and pushing and pushing and running while the bike starts to spit a sputter.

Doesn't run, but I sure wish I had all that on video, because it was a grade "A" lesson on how to jump start a Motorcycle.

On to question 2: Does it have good compression? Chris' motto "if it has spark and good compression, he can make it run" That simple.

And we check the compression with one of his many compression gauges: Also good.

Great! We can now fix this sucker.


By first dismantling the carburetor. Like with everything on a Bultaco, parts are open and easily removed. With a little disconnect of the two bolts on the slide, two nuts off the manifold and loosen the boot... voila! Off.

Now dismantle.
WARNING! Parts to this carburetor are hard to come by and so be careful when you work. Keep in mind, the needle attached to the float is made of plastic. In fact there are no metal parts attached to the float whatsoever except for the tiny rod that keeps it in place. This is very important to remember so that you don't mistakenly dunk all those parts into Carb Dip and fry your float.

After removing the gasket from the float bowl mating surface (use a small blade. These gaskets are also hard to come by and you want to keep it in tact without tearing it) low speed jet, main jet (two parts), idle stop and low speed needle, dunk all the metal pieces into Carb Dip for at least an hour. Again DO NOT dunk the float, the needle or the plastic filter!

Once the parts are removed, clean each one thoroughly. We have luxury of using an air hose, which made short work of the cleaning. All those tiny holes must be blasted clean. If there is any gasket residue, make sure it totally removed. We used a granite plate and a piece of #220 emery paper to scrub the float mating surface clean. Once all parts are shiny, reassemble and put back onto the bike.

Stay tuned for our next job: using a two part epoxy sealer on the fiberglass gas tank, fueling it up and seeing if this time it will run...