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B44 Cylinder on a B40 #591760
03/25/15 9:25 am
03/25/15 9:25 am
Joined: Sep 2014
Posts: 455
Michigan, USA
J
Jeff K. Offline OP
BritBike Forum member
Jeff K.  Offline OP
BritBike Forum member
J
Joined: Sep 2014
Posts: 455
Michigan, USA
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

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Re: B44 Cylinder on a B40 [Re: Jeff K.] #591766
03/25/15 10:18 am
03/25/15 10:18 am
Joined: Dec 2004
Posts: 9,375
Scotland
kommando Online content
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kommando  Online Content
BritBike Forum member
Joined: Dec 2004
Posts: 9,375
Scotland
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.

Re: B44 Cylinder on a B40 [Re: kommando] #591770
03/25/15 10:33 am
03/25/15 10:33 am
Joined: Sep 2014
Posts: 455
Michigan, USA
J
Jeff K. Offline OP
BritBike Forum member
Jeff K.  Offline OP
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J
Joined: Sep 2014
Posts: 455
Michigan, USA
I was looking at have a alloy cylinder vs the cast iron one.
Jeff

Re: B44 Cylinder on a B40 [Re: Jeff K.] #591793
03/25/15 12:09 pm
03/25/15 12:09 pm
Joined: Nov 2010
Posts: 42
BrisVegas, Oz
441DailyRide Offline
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441DailyRide  Offline
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Joined: Nov 2010
Posts: 42
BrisVegas, Oz
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; 03/25/15 12:28 pm.

67 BSA B44
04 DUCATI ST3
71 DUCATI 350
75 CONDOR 350 (made by Ducati for Swiss Army)
Re: B44 Cylinder on a B40 [Re: Jeff K.] #591800
03/25/15 12:48 pm
03/25/15 12:48 pm
Joined: Dec 2004
Posts: 9,375
Scotland
kommando Online content
BritBike Forum member
kommando  Online Content
BritBike Forum member
Joined: Dec 2004
Posts: 9,375
Scotland
Quote:
I have read where people have put a B44 piston in a B40 cylinder before.


Quote:
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).

Re: B44 Cylinder on a B40 [Re: Jeff K.] #591847
03/25/15 5:22 pm
03/25/15 5:22 pm
Joined: Oct 2007
Posts: 1,311
Nanaimo, B.C. Canada
W
Wilfred Offline
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Wilfred  Offline
BritBike Forum member
W
Joined: Oct 2007
Posts: 1,311
Nanaimo, B.C. Canada
Don Morley, in his book on pre 65 four stroke trials irons makes mention of putting a B44 alloy barrel on the B40 to save weight on the trials bikes just by machining it to the right height. W


"It's about the ride..."
Re: B44 Cylinder on a B40 [Re: Jeff K.] #591914
03/25/15 11:36 pm
03/25/15 11:36 pm
Joined: Jun 2002
Posts: 930
Jaffrey, NH, USA
Peter Quick Offline

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Peter Quick  Offline

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Jaffrey, NH, USA
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.

Peter


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Re: B44 Cylinder on a B40 [Re: Jeff K.] #591940
03/26/15 3:52 am
03/26/15 3:52 am
Joined: Oct 2007
Posts: 1,311
Nanaimo, B.C. Canada
W
Wilfred Offline
BritBike Forum member
Wilfred  Offline
BritBike Forum member
W
Joined: Oct 2007
Posts: 1,311
Nanaimo, B.C. Canada
Brit Cycle did have a few NOS pistons for B40 and C15 but I suspect Gordo and I bought just about all they had left unless they have found more. W


"It's about the ride..."
Re: B44 Cylinder on a B40 [Re: Jeff K.] #591941
03/26/15 5:07 am
03/26/15 5:07 am
Joined: Jul 2014
Posts: 395
UK
C
craig Offline
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craig  Offline
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C
Joined: Jul 2014
Posts: 395
UK
" JP in Australia and those are renown for being lousy" I can second this comment , never again will I buy a piston off these people

Re: B44 Cylinder on a B40 [Re: Jeff K.] #591942
03/26/15 5:41 am
03/26/15 5:41 am
Joined: Dec 2004
Posts: 9,375
Scotland
kommando Online content
BritBike Forum member
kommando  Online Content
BritBike Forum member
Joined: Dec 2004
Posts: 9,375
Scotland
JP comment +1


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