Tuesday, April 24, 2012

blown up 42 motor

Here is a 42 motor that got dropped off at the shop for the next batch of motor rebuilding.   The owner was riding the bike home and heard a strange noise,  he thought he dropped a valve and decided to try driving the remaining three miles home.   Check out the 41 to 44 fl cylinder. these things are soooo rare and hard to find.   the date code was put on the cylinder wall, and most of it was machined off when hd cut the relief for the cylinder base nut.  
This is the first time that  I have seen a motor brought in with a tie down strap holding the cylinder in place.
here is a pic of the removed front cylinder, notice the base is still on the cases.
here are the four pieces of the base

the cause of this blow up was a sleeved fl cylinder that was punched out .040.   Original fl cylinders do not sleeve well,   this one grenaded.  Luckily the cases were not harmed and the motor can be fixed.  On another note, the bike is 42f 19xx  and it has flat top lifter blocks.   The 42 el that we did last year was 42el22xx and it had countersunk lifter blocks, so I guess hd switched sometime in those three hundred bikes.  


  1. how much for a rebuild like this???

  2. A friend had his rear cylinder break similar to that on his 47 Knuck many ears ago. He started whittling a piece of wood into a wedge with his buck knife and then using a rock he pounded it in between the top of the head and the frame. It got him home.
    And it was a sleeved cylinder too.


  3. bacon-- time and materials, who knows what else might be wrong with the inside of it? congrats on the tv show, I can say i knew you back when.

    Steve, That is a great story.

  4. kidding .... was there the other day when Jesse called you . he doesn't think i charge enough hahaha see you
    at born free