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Non-matching cases question #126518
10/18/07 4:18 pm
10/18/07 4:18 pm
Joined: Jul 2007
Posts: 45
Oklahoma City OK
Jake Hartley Offline OP
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Jake Hartley  Offline OP
BritBike Forum member
Joined: Jul 2007
Posts: 45
Oklahoma City OK
Is it advisable to assemble and engine from non-matching cases from the same year and type on a 650?


"He who makes a beast of himself gets rid of the pain of being a man"
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Re: Non-matching cases question #126519
10/18/07 4:51 pm
10/18/07 4:51 pm
Joined: Oct 2003
Posts: 11,263
North Georgia, USA
RF Whatley Offline
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RF Whatley  Offline
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Joined: Oct 2003
Posts: 11,263
North Georgia, USA
Depends on the year, but usually "No".


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: Non-matching cases question #126520
10/18/07 4:59 pm
10/18/07 4:59 pm
Joined: Jul 2007
Posts: 45
Oklahoma City OK
Jake Hartley Offline OP
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Jake Hartley  Offline OP
BritBike Forum member
Joined: Jul 2007
Posts: 45
Oklahoma City OK
year would be late 71, early 72. can you elaborate? I am assuming differences in alignment of the two halves, etc....


"He who makes a beast of himself gets rid of the pain of being a man"
Re: Non-matching cases question #126521
10/18/07 5:16 pm
10/18/07 5:16 pm
Joined: Aug 2006
Posts: 103
Andover, MN
J
JGTR6R Offline
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JGTR6R  Offline
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J
Joined: Aug 2006
Posts: 103
Andover, MN
I have a very early 72 (aug 71 build) and the case halves are stamped with different wittness numbers. I assumed it was from the factory using up halves that had already been machined with new halves made for the bearing change. I am second owner (bought it when it was 2 years old) and don't think it was a reworked motor.


Mike D
72 650 Tiger 4 speed
Re: Non-matching cases question #126522
10/18/07 6:08 pm
10/18/07 6:08 pm
Joined: Dec 2004
Posts: 9,486
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,486
Scotland
I have same as JG, B44 case halves have different witness numbers but the date stamped is each is less than 7 days apart, one sump stud hole was completely undrilled with no sign of weld. Looks like the factory had 2 crankcase sets in a reject pile and made 'Good' sets by mixing.

Crank spins fine and the cylinder deck is level.

Re: Non-matching cases question #126523
10/18/07 8:55 pm
10/18/07 8:55 pm
Joined: Jul 2007
Posts: 45
Oklahoma City OK
Jake Hartley Offline OP
BritBike Forum member
Jake Hartley  Offline OP
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Joined: Jul 2007
Posts: 45
Oklahoma City OK
outside of the circumstances of the last two posters, what are the pitfalls of assemblying an engine from two "odd" halves? I assume (bad thing, I know), that some engines have replacement case "sides " put on when one side was damaged beyond repair.


"He who makes a beast of himself gets rid of the pain of being a man"
Re: Non-matching cases question #126524
10/19/07 3:44 am
10/19/07 3:44 am
Joined: Jul 2007
Posts: 45
Oklahoma City OK
Jake Hartley Offline OP
BritBike Forum member
Jake Hartley  Offline OP
BritBike Forum member
Joined: Jul 2007
Posts: 45
Oklahoma City OK
ok, y'all mentioned witness numbers: are these representative of them?

s/n side case has this series of numbers on the bottom, near the mating surface: 6 26

oil pump side has this series of numbers in the same place: 6 28

oil pump also has a number in the cam gear case 71-1081 and AM (H?)-2

any help?


"He who makes a beast of himself gets rid of the pain of being a man"
Re: Non-matching cases question #126525
10/19/07 6:25 am
10/19/07 6:25 am
Joined: Dec 2004
Posts: 9,486
Scotland
kommando Offline
BritBike Forum member
kommando  Offline
BritBike Forum member
Joined: Dec 2004
Posts: 9,486
Scotland
Witness marks are normally a set of small numbers (usally 3 for BSA) stamped out of sight on the bottom of the cases, they were stamped on the case halves at the first machining step in the factory and meant that they could be tracked if they were separated but they were always machined together. By machining them together it meant the maching accuracy could be more forgiving as each half would be wrong by the same amount, also common bores would be parallel.

The critical ares to look for on unmatched cases are the main bearing bores (hence the check for a fee spining crank) and the deck for the barrel being flat. There are other potential problems but they are not so important.

Service cases were always supplied in pairs, so if a rod damaged one crankcase half then a pair of cases was supplied for the warrenty repair.

Re: Non-matching cases question #126526
10/19/07 12:32 pm
10/19/07 12:32 pm
Joined: Jul 2007
Posts: 45
Oklahoma City OK
Jake Hartley Offline OP
BritBike Forum member
Jake Hartley  Offline OP
BritBike Forum member
Joined: Jul 2007
Posts: 45
Oklahoma City OK
these do in fact have different witness numbers. I will check the other areas you mentioned. I have now way of knowing if they were actually together in a running engine, as they were part of a bitsa I am putting together.

thanks for your help!


"He who makes a beast of himself gets rid of the pain of being a man"

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