Purchased a 81 flt shovel and doing restoration. Tore down engine 80 cu. In. and had the jugs miced. The guy td me the jugs were honed out 30 over but the lower part of the jugs were only 20 over. The pistons were badly scored so I want to order new ones 30 over. Don't know if they are 8.5-1 or 9.5-1.How do you tell the difference? The pistons are labeled Bohnalite # 22124-78 and show 030 on the top of the piston. Any help would be appreciated.
Ben

 

22124-78 is a Harley part number, so they are most likely stock compression. Unlikely to be 9.5:1 IMHO. Bohnalite is the manufacturer and if you google that name you can learn more about them!

Before you order any new pistons find someone who can true up your cylinders, so they are a uniform size top to bottom. If that means going to the next size up, then +.030 pistons will be a waste of money! Don't get your cylinders honed until you have new pistons in hand, so the two are married accurately to each other.

 

Maybe just common use of interchangeability of words but you do not want to have someone just hone your cylinders to fit. They need to be carefully measure and could be as bad as you describe them even rough bored to see where they are going to clean up before finial honing and crosshatch finish for proper clearance to piston. Whatever you do make sure the shop is going to bore them to make them round and true top to bottom with them bolted into torque plates.

 

Ben,
If your looking for help, we can certainly provide it.
Feel free to contact us.
Scott

 

if their scored now,your going to need to go .040 or .050 over.BTW,.020 at the bottom and .030 at the top with .030 pistons aint happening.either you misunderstood your tech,or he has NO clue on measuring cylinder /pistons clearances.if its the later,find a new shop/tech.

 

you don't "hone" to 30 over. those cylinders are prob screwed. New jugs are cheap, cheaper and safer than the amount to machine the screw up out of the originals

 

I realize that you don't hone out cylinders,but the previous owner didn't. The cylinders walls are not scored, only the piston skirts