Early CMF questions

[Mark Annan]

Does anybody have any idea how sequential the serial numbers are on the CMF bikes?  Or what (if any) significance there is to the other digits in the serial number.  I know the first 3 are the date code (203= March of 72, 310=October of 73 etc.).  The reason I am asking is that I have what I figure must be a bike from very early in the production run.  It is a 72 Sixday MX, serial # 10650171.  That makes for a June of 71 production date.  The other digits ( 50171 ) are the serial number.  I doubt that 50171 bikes had been produced by that date!  Is it likely that this bike (actually just the frame in all likelihood) was the 171st one off the line?  If so what is the significance (if any) to the 50 preceding the 171?

The bike in question has a 5A motor with cylinder side fins cut just like on a steel tanker.  The fins on the head are cut to clear the exhaust (not cast as in later bikes).  The frame (and engine) use the smaller 8mm front mounting bolt, not the larger 10mm used on every other CMF bike I have seen.  The forks are 32mm.  The triple clamps use single pinch bolts that face the front.  Every other CMF bike I have seen uses a pair of pinch bolts that face out to the sides.  The bike had alloy fenders (have been replaced with cheap plastic) it also uses the same controls as my steel tankers.  ( Magura ISDT levers and the early small throttle )  

I figure given the Penton/KTM practice of making running changes as production progressed this bike has the 5 speed and controls from the end of the steel tank production.  Any info or opinions regarding this?

Along those same lines:  Were all 250's and 400's frame breathers?  They didn't come out until 73 (I think).  Am I correct in thinking that only the 72's  (100's, 125's and 175's)  were non high breather CMF frames?    

Thanks for any info or opinions,  Mark

 

[Paul Danik]

Mark,
   You have asked some really good questions.  I will attempt to be of some help where I can.  I do believe that all 250 and 400 machines were frame breathers. I have a yellow/gold Hare Scrambler sitting here and it is a frame breather.  This color was the earliest model production 250.  
    As you said, the "72" models of the 100-125-175 were the non-framebreather models of the CMF.
    I referred to parts manual 003, it is the first parts breakdown for the 100-125 CMF.  It only shows engine plates for the "A" engines.  It does show both the 5 and 6 speed  engine plate in both the 100 and 125.  The front engine bolt is listed as an 8MM.  The "B" engine apparently did not come about till a little later  The forks in the 003 manual are as you discribed, a single pinch bolt faces the front.
   I would assume, as you did, that your machine is the 171st machine off the line.  Maybe the 50 was used to indicate a US model, we do have 50 states!!!!!
  Thanks for posting those questions, that is part of what makes this all so much fun, getting out the old books and playing Perry Mason!!!!

 

[Mark Annan]

Paul,  

Thanks for the information.  I got this particular bike as part of a package deal.  It is in very rough shape and apparently has been ridden a lot.  I am trying to decide if it I should save it, or salvage the few usable parts from it and send the remains onto their final resting place.  I figure if it is a very early production bike it may justify saving it, but I doubt it.

Thanks again.

Mark

 

[john durrill]

Mark ,
 if its any help. we recieved our first Pentons from JP in Daytona in the spring of 72. One 100 birkie and one 125 Six-dyas . they both had Bosch mag A 5 engines in them.
For trail rideing and enduros i love the A 5 best. liked the spaceing of the gears and the extra torque of the A motor in deep sand when the going was slow. ( lots of handle bar width trees)
John