I was looking through the production year guide when I noticed the lack of any mention of the six A motor in the early 72 CMF bikes. Is this an oversite or was this a rare engine? The engine needed a lot of work so I traded it for a six B motor that I've rebuilt and raced twice. Now I'm wondering if I should have kept the A motor? Any comments on the rideabilty of the two engines A versus B. I have noticed that if you let the B motor get of the pipe it sometimes will load up on me. Not good when your trying to get through a turn with a guy on one of those Chec bikes behind you!
Gavin,
I am sure that others will chime in, I find the 'a' engine is
a bit more powerful down in the rpm range, not as pipey as the
'b', I run both and find the 'a' more forgiving in the woods, the
other definately has more power, but not as smooth a delivery.
Just my 2 cents.
-don
Gavin,
Here is what the production guide had to say on that subject:
* Early 1972 model year 100cc and 125cc Sachs engines (known as 5A) came with Bosch point type ignition and
5 speed gear box - later model year engines (known as 6B) came with Motoplat ignition and 6 speed gear box - both
came with cast aluminum alloy cylinder, sunburst head, and 27.5mm Bing carburetor
Hope this helps. I never raced the A engine so I will let the experts tell their side.
Ron Carbaugh
Gavin,
I am presently racing a 125/6a.Engine came in an early 72 CMF frame. Production date 10-71. Yes the A has a better lowend. It has saved me several times when going thru false neutrals looking for a lower gear only to use the higher gear to top a hill.As for the rarity I don't know. Presently working on a 73 125/6a. 6a with the bosch usually starts 1st kick. But I use a 28mm Mikuni.
Bob Brizzee
My favorite is the 5A, heavier gears, less of them and low end grunt when you need it! If I was road racing, I would go for the 6 speed[8D]