[SEL] Briggs & Stratton NP help needed

[Jerry Evans]

  Hi All,
         I'm rebuilding a 1946 Briggs & Stratton NP powered Pioneer 
Gen-E-Motor 12 volt genset (battery charger or whatever).

         It's running but the bore is shot, the piston is shot, the gudgeon 
pin is shot and the rings are shot !!!

         Actually the previous butcher who worked on this engine must have 
broken the oil ring - the oil ring gap was filled with "ring spacers"  and 
the other rings had gaps of about 3 to 4 millimetres !!. The generator 
still works and puts out the right voltage (15 volts I think).

         The piston is aluminium and flat topped.

         Can anyone point me in the right direction for spares. I've 
written to Briggs but their answer was unhelpful to say the least!

         My choices are:

         First prize)  Find a good (preferably new) oversized piston with 
conrod and gudgeon pin and rebore the block. (I can have rings made locally).

         Second prize) Find a new standard piston et al and resleeve the block.

         Third prize) Find a piston from another make of engine with 
similar dimensions and either rebore or resleeve to make it work.

         Fourth prize) Resleeve the block and machine the existing piston 
and have bigger rings made to fit (again, I can have rings made locally) 
but this would be a last resort as the existing piston's ring lans have 
worn unevenly on the diameter and I do not know if there is enough "meat" 
left for this kind of treatment.

         Fifth prize) Find a "piston blank" that fits the measurements and 
machine that. Hepolite used to make these but I cannot find them locally 
any more.

         I do not have the knowledge or expertise to have a new piston cast.

         The engine is a 2" Bore X 2" Stroke and the dimensions of the 
existing piston are as follows: Apologies for the metric measurements.

         Diameter: 50.6mm
         Height:  53.89mm
         Gudgeon Pin diameter : 12.4mm ( I would have thought 1/2" or 
12.7mm but thats what my Mitutoyo digital vernier says).
         Height from centre of gudgeon pin to top of piston = 32mm

         For what it's worth the engine specs are as follows:
         Model: NP
         Type No.: 306534
         Serial No.: 695366
         Manufactured August 1947

         If anyone from this great storehouse of information can help I 
will be eternally in your debt.

Keep the revs up (or down)
Jerry Evans
Near Johannesburg in Sunny South Africa.
Tel. (016) 365-5787
Intntl.: +2716 365-5787
Cell: 083 293 7191
Visit our website for old engines in South Africa.
www.oldengine.org/members/evans