I have read where people have put a B44 piston in a B40 cylinder before. I think they had to run a spacer and had some vibration issues. Has anyone ever run a B40 Cylinder with a B40 piston on a B40? I found a round jug B44 cylinder that needs to be sleeved and I am think about having Ed V do this and seeing if I can use a B40 piston to keep the balance factor. Jeff
I have ran a B44 piston in a B40 barrel, as the pin height is higher than the B40 you have to remove meat from the bottom of the barrel, fit C15 pushrods and cylinder studs. The vibration is increased unless you rebalance on the new piston weight for not much if any gain.
i run a B44 barrel , piston & crank in later sidepoints B40 crankcases (unstamped, N.O.S, so i couldn't resist). Having owned a B40 previously i can see the weight gain from cast iron barrel to ally. I had to change the studs as the case threads are the same but i seem to remember the B40 studs have a shoulder & are slimmer where they go in the barrel. I believe the bore is the same & the cc increase is by longer stroke so in theory a B40 piston should fit in B44 barrel ok. However the B44 barrel should be taller so you'd have to look into that. kommando states that a B44 piston has a different pin height so if you using that you may need to look at barrel height & pushrods. In my experiance all engines benefit from a dynamic crank balance even if using a piston of the same weight as original. Static balancing can seem ok but if the flywheels have a biased point on opposite sides dynanic balancing will show & rectify this.
Last edited by 441DailyRide; 03/25/1512:28 pm.
67 BSA B44 04 DUCATI ST3 71 DUCATI 350 75 CONDOR 350 (made by Ducati for Swiss Army)
I have read where people have put a B44 piston in a B40 cylinder before.
I was looking at have a alloy cylinder vs the cast iron one.
I answered the first question, ref the second question you will have to shorten the barrel to suit the piston you plan to use, more for the B44 than for the B40. The studs will need to be custom as the B44 has thicker studs through the barrel but the bottom thread is the same as DailyRider states so you could shorten some B44 ones and rethread the top. Pushrods as before, B40 for B40 piston, shorter for B44 piston (C15 may work here).
I've done this. Just shorten a B44 round barrel cylinder to the B40 length. This will save 7 pounds compared to the B40 iron cylinder. No need to use a B44 piston in this set up. Just use a 8.75:1 B40 piston. That should be plenty of compression. No need to replace cylinder studs just have some bushings made up to press into the cylinder so it better fits the B40 bolts. Then the conversation about re-balancing the crank is moot as nothing really has changed except you have just shaved 7 pounds off the weight of the bike.
I'm in the process of having some B40 9:1 forged pistons made up by JE in various over sizes for folks that want just a bit more punch out of their B40. Also it is hard to get any selection of B40 pistons when you need them. About the only company making pistons for B40's that I know of is JP in Australia and those are renown for being lousy. Thus my venture with JE. I'm also getting the B40 pistons made by then in 8:1.