Triumphrat

daveforty · 02-15-2008

The 750 twins (T140 & TR7) have always had five speed gearboxes, according to the book I looked in. It is (supposedly) possible to exchange the internals four speed gearbox for a five speed gearbox, although I have no experience of doing so. It may be possible that a previous owner has swapped gearbox internals about.

tigercub · 02-15-2008

i have a 1973 parts book and it does'nt look the same, the parts book has three selector forks and this trans has two. not sure if this is an orignal engine.the gears look different too.

Emanthehorse · 02-15-2008

Triumph were notorious for using up piles of left over previous model parts before getting to ther new stuff.

If your engine number has the letter V (as in T140V), then it was originally a five speed.

It's not a straight swap.

tigercub · 02-15-2008

this was a salavge bike from ill.it doesn't have a vin # that i can go by. it appears to be a 1973 750. i got a clymer manual with it the trans seems more like a 650 but the camplate they show is on the top. mine is on the front side like a 750. i'am not an expert but i have owned a 71 bonneville and three bsa's so i know a little about these bikes.could they have put a 750 top end on a 650 bottom end or is this possably an early 750 that they used a 4 speed on like you said.

tigercub · 02-16-2008

iam starting to think i have a 750 top end and a 650 top end. is this possible?

GrandPaulZ · 02-16-2008

Yes, it's possible.

But the 650 and 750 both had the tranny camplate upright in the front of the tranny case.

Emanthehorse · 02-16-2008

Quote:

Originally Posted by tigercub

this was a salavge bike from ill.it doesn't have a vin # that i can go by. it appears to be a 1973 750. i got a clymer manual with it the trans seems more like a 650 but the camplate they show is on the top. mine is on the front side like a 750. i'am not an expert but i have owned a 71 bonneville and three bsa's so i know a little about these bikes.could they have put a 750 top end on a 650 bottom end or is this possably an early 750 that they used a 4 speed on like you said.

If there's no numbers on the primary side just below the cylinders, I have to wonder why.
Should be a raised pad with a bunch of little Triumph logos and then the engine number stamped over the top. If it's not there, some felon ground them off.
750 top end does NOT just bolt onto the 650.
What do the rocker boxes look like? 2 Long oval covers or 4 round ones? If it has the round cover, does it have the extra little round covers on the sides of the boixes? Does it have the nine or ten bolt head?
Camplate on the top was the 500 transmission.

GrandPaulZ · 02-16-2008

I said it was possible to mount a set of 750 jugs to a set of 650 cases, NOT that it is just a bolt-on modification.

Then again, re-reading the post with the question, tigercub asks "i am starting to think i have a 750 top end and a 650 top end. is this possible?"

To which the obvious answer is - OF COURSE! ...just not at the same time!

(he says 'top end' for BOTH 650 & 750)

tigercub · 02-16-2008

on the primary side below the barrel there is a 6 digit number but no letters, no raised pad. it came with a build title from ill. the state police inspect these vehicle's for stolen parts and asign a new number,they can also remove any number they want. the engine has two long oval rocker box covers and a ten bolt head. the camplate is on the side, i was looking at a 500 gearbox in the clymer manual thinking it was a 650.i was looking over the books i have and the bike and noticed that it looks like there should be a vent tube coming out of the inside primary up towards the top, but on this bike its a solid case.also in my other post i meant to say is it possable that i have a 750 top end and a 650 bottom end.

Emanthehorse · 02-16-2008

Sounds like a 750 top on a pre-70 lower.