October 2013
To think she was so happy just a few days ago….
I pulled the head and barrels to see what damage has been done – alas it is the front piston that seized and the rear piston has evidence of oil film loss and scraping. Interestingly these are on the sides that face each other.
I did some research online and it seems that there are four possible culprits:
- lean jetting
- low/no oil in mix
- air leak (causing localized lean/hot spots)
- timing
I can pretty much rule out air leak and I’m going to go out on a limb and rule out jetting as I believe it is stock.
A mechanic saw the photos and opined that it is most likely timing. This could be so as I haven’t touched the timing since I got the bike. I did reduce the oil to the minimum setting, as I was using modern oils and assumed I could get away with less smoke. Perhaps at open throttle it needs more.
So, clearly a bore or hone and new pistons are in order. The question is why did it seize. I would like to have some confidence in diagnosing the problem before slapping in a new set of pistons and twisting the throttle again.
Clearly this isn’t a unique experience. I found this photo on the net, clearly toasting pistons is a Puch thing. I was hoping to get away with a hone an a set of rings but, clearly, new pistons are needed. So open heart surgery has led to opening my wallet. Those pistons ain’t cheap.
It seems Elko/Konig is the only game in town for replacement pistons.
Had the identical experience, rebuilt with new pistons etc. Cause was timing, there is a spot to lock the motor by inserting a suitable pin. Then using a timing light set the point gap. If the points are set without these steps there is a good chance it is mistimed. See the instruction/repair booklet –