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Discussion Starter · #1 · (Edited)
Edit: I have two Triumph unit construction motors with "homemade" serial numbers. What other details can I use to tell how old these motors are?

Clues:
- Both are unit 650s
- Both have the later style crank vent, with an elbow coming off the primary housing.
- #1 has the inspection hole on the primary housing, but not on the tranny housing.
- #2 doesn't have inspection holes on primary OR tranny.
- #2 has a tach drive on the end of the exhaust cam.
 

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JEB said:
I picked up another 650 Triumph motor yesterday, stamped TR6C DU58762. The trusty Triumph decoder website:

http://www.britishspares.com/technical/numbers/triumphnumbers.htm

says that it's a 1967 high compression motor (C= high compression).

Hey that was fun, but I have two other motors with "homemade" serial numbers. Without the SN, what other details can I use to date these motors?

Clues:
- Both are unit 650s
- Both have the later style crank vent, with an elbow coming off the primary housing.
- #1 has the inspection hole on the primary housing, but not on the tranny housing.
- #2 doesn't have inspection holes on primary OR tranny.
- #2 has a tach drive on the end of the exhaust cam.

I'm at work right now, but I'll post pictures tonight.

-JB
The tr6c, the c just meant high pipes the tr6r was low pipe model
 

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I would say that #2 is from 66-68 (maybe). Just saying that becuase mine (66) has no hole in the primary. But I could be full of shit.
Erron
 

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Maybe I don't understand your description, but you really can't date by the covers as they were interchangeable.

The crankcase vent off the back of the primary started in 1970. The oil hole in case/barrel to feed the exhaust tappet guide block started in 1966. Is there a dentent pluger under the tranny? This was omitted for '71/'72 when the leaf spring was introduced.
 

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Discussion Starter · #7 ·
VA Rebel said:
Maybe I don't understand your description, but you really can't date by the covers as they were interchangeable.

The crankcase vent off the back of the primary started in 1970. The oil hole in case/barrel to feed the exhaust tappet guide block started in 1966. Is there a dentent pluger under the tranny? This was omitted for '71/'72 when the leaf spring was introduced.
Thanks, those dates are helpful. Since both of these have the crankcase vent elbow, they must be post-70.

As far as the covers, you're right. They interchange so I don't know if they have been mixed and matched by different owners, but the bare cases have inspection holes in different spots, that's what I'm curious about.

-JB
 

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Discussion Starter · #8 ·
Do you have an oil passage on the right side of the cylinder base?

hatch said:
I'm wondering the same thing...I've got a restamped late sixties 650 that somewhere along the line was in an assembled bike. I would love to know what year it is.....no elbow crankcase vent on this one.
 

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Yes the cylinder has the oil passage, but it could be a newer cylinder on an older set of cases. I guess I'm looking for anything that sets the older unit cases apart from the newer ones, up to and including 69.....like stampings or casting changes maybe.

JEB said:
Do you have an oil passage on the right side of the cylinder base?
 
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