Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties 1200 UL pistons origonal or copys

1200 UL pistons origonal or copys

Moderators: Curt!, Pa

Post Mon Dec 06, 2010 11:38 am

Posts: 22
Ive just recieved from Bills old bike barn some supposedly origonal pistons which i purchased from him off ebay. Item No 110376225683 They advertised them as being in their origonal boxes and covered in the old grease they used to use to protect them, I recieved them today no origonal boxes and pistons were not covered in the grease like they were described on advert. Inside the pistons is a name BOHNALITE L does this mean anything to anyone, could this be the manufacturer? Also the pistons are marked 317-384 is this the correct number, how can i tell if they are nos or copys?
I enclose a pic of the piston. Any info please as id like to get this sorted out!!!
pistons 005.JPG
pistons 005.JPG (174.35 KiB) Viewed 4462 times

Post Mon Dec 06, 2010 3:30 pm

Posts: 83
Does the bottom ring land has the same height as the top ring lands? If so they're probably NOS pistons. Bohnalite made pistons for harley.

Post Tue Dec 07, 2010 5:24 am

Posts: 1642
Location: Interlaken, NY USA

they look like the real deal, at least as I remember them.

Post Tue Dec 07, 2010 8:36 am

Posts: 634
Location: Wisconsin, USA
OEM for sure.

Post Tue Dec 07, 2010 10:53 am

Posts: 22
The 3 piston rings look the same to me, shouldnt the bottom ring be a oil control ring? They look all like compression rings. I have read somewhere that on the front cylinder they used all the same rings but on the rear they had an oil control ring, why is this?
Could i convert these pistons to take later oil control rings with the two very thin rings and the wavy ring?
regards to everyone for their help


Post Tue Dec 07, 2010 3:34 pm

Posts: 426
Location: Tucson Arizona

Reproduction piston


Post Tue Dec 07, 2010 6:00 pm

Posts: 1642
Location: Interlaken, NY USA

Cooky, be careful what you ask.....
The original configuration was indeed, 3 compression rings on the front, and 2 compression and one shallowly grooved, but not vented "oil control" ring on the rear. It usually wore smooth with use and looked like another compression ring after some use. Unless you alter the oiling system, probably the best bet is to go with the stock configuration, using 3 compression rings on the rear if you can't come up with the stock pseudo oil ring.
Otherwise, if you decide to run other than stock oiling system, (including baffles, or not, etc) I'd read all the past posts on the board on the big twin flathead oil system, and decide what suits you best. That's all I'm going to say guys, honest! :lol: :lol:

Post Tue Dec 07, 2010 6:56 pm

Posts: 83
Hey DD. Please keep talking.
I mean, sportypump sportypump sportypump
We all love sportypumps! :)

Post Wed Dec 08, 2010 7:54 am

Posts: 1642
Location: Interlaken, NY USA

:lol: :lol: :lol: :lol: :lol: Thanks Karl, for the best laugh in days!
DDD, (Demented Dr Dick)

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