Multiple Bent Pushrods

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NM Bonny said:
What about a link to the website for whoever’s making or selling these trannies?
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Dang! I looked at the folder I have of this gearbox and have no links to the source. Probably an internet search would produce something. I tell ya, the other photos are also amazing to look at. This thing has its own custom castings and everything. A real beaut! As I recall, this thing cost more than my Triumph when I bought it new.
 
Rudie said:
I think unfortunately you lose the kickstart ...
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THAT looks to be true . . . looking at the gearbox outer cover which has a PLUG where the kickstarter aughta be. But that makes no sense; what, a guy is sposed to push-start the bike? Still, the idea of a six speed is cool by me.
 
Rudie said:
I think unfortunately you lose the kickstart ... :(


If you are prepared to take the engine apart, last (best) version of the Triumph 5-speed gearbox are available new and used.
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Well, two things:

First, does the 5-speed tranny fit in the 4-speed case?

Second, are there different ratios available, so you can have a true overdrive 5th?
 
NM Bonny said:
Second, are there different ratios available, so you can have a true overdrive 5th?
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T140V General Data says: Gearbox (5 speed) Internal ratios 5th (top) 1.00 : 1

Not overdrive. But if yer cruizing around at 10 miles an hour in 5th gear, yer engine is turning 627 rpm . . .
 
NM Bonny said:
5-speed tranny fit in the 4-speed case?
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Yes. History is: first made by Rod Quaife during the 1960's for racers to replace the 4 speed; Triumph used it in the 650 production racers; fitted to the triples built for the 1970 Daytona 200; 71, AMA stipulated any engine part for racing, at least 200 must be made available to the general public, Triumph interpreted that as it must make 200 Tridents and 200 Rocket 3 (originally used the same 4 speed gearbox as the 650); Quaife was not then geared up for mass production so BSA bought the rights; intention had been to use triple engines for all types of US racing but they proved unsuitable for any off-road racing; factory riders reverted to 650 4 speed twins for off-road racing; mid 1971, Triumph made 200 T120RV to homologate the gearbox in twins to reduce the deficit for factory riders against other teams; 72, Triumph fitted the 5-speed to triple and 650 twin road bikes on/off while they debugged it, finally fitting it as standard from about March 1972 afaict.

NM Bonny said:
different ratios available, so you can have a true overdrive 5th?
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No. 5 speed first is lower than 4 speed first so, if you are gearing up and still have good acceleration in first, overall gearing in fifth will be quite high?
 
speedrattle said:
however, you have three bent pushrods. i cannot see how all three came loose at the same instant
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Agreed. That is strange. I might have thrown-in for a stuck valve, or two (which I have had happen before, in a Honda) but three? I am scratching my head on that one. I am still, however, betting on stuck valves because that would explain the bent rods even if the adjustments were correct, and, the engine would still run (poorly) whilst the rods are being bent until they finally become disengaged. I don't know, it's weird . . .
 
side note, on ratios think about the gearshift sprocket. stock on my 1972 T120 was 19/47, which is a buzzy ratio that doesnt allow for freeway cruising at modern speeds.

i have cut three T120 chaincases for 21-tooth gearbox sprockets, and love them. the 21 will force you to use the gearbox through the lower speeds, but first gear becomes something useable in traffic, and high gear allows you to cruise along at 75-plus.

on a five speed, first gear does nothing except move your the first twenty feet. a 21-tooth sprocket is the way to go, unless you are running on dirt or in green lanes.
 
speedrattle said:
side note, on ratios think about the gearshift sprocket. stock on my 1972 T120 was 19/47, which is a buzzy ratio that doesnt allow for freeway cruising at modern speeds.

i have cut three T120 chaincases for 21-tooth gearbox sprockets, and love them. the 21 will force you to use the gearbox through the lower speeds, but first gear becomes something useable in traffic, and high gear allows you to cruise along at 75-plus.

on a five speed, first gear does nothing except move your the first twenty feet. a 21-tooth sprocket is the way to go, unless you are running on dirt or in green lanes.
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So: more detail on this operation, please, because you’ve got me a little excited. I am running a 20-tooth up front with a standard 47-tooth at the rear. It’s better than the 19/47 stock combo, but you’ve got me going here!

First - are you talking about just opening up the hole shown in this picture a smidge to be able to slide the 21-tooth in there, or is there more to it than that? If it’s just opening up this hole, will I have to do any mods to the cover and gasket, or just seal it up as usual?

Second - what is the part number for a 21-tooth sprocket that will fit the ’71-72 T120R? The only one I can find is 57-4782, which KM Jones indicates is for the 5-speed. Will that fit my T120R 4-speed, or is there a different number?
 

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NM Bonny said:
just opening up the hole shown in this picture a smidge to be able to slide the 21-tooth in there
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NM Bonny;

Now, mind you, I have NEVER done such a thing as operating on the crankcase halves (except a little filing-off of unsightly casting protrusions) but, I have heard that you can lay the twenty-one tooth sprocket over the hole and trace onto the crankcase-half with a pencil or pen where the teeth are located and then gently remove just enough material to let it slip right on in there. Far less material removal, they say. I, personally go for the smaller rear sprocket. Yes, I am ordering a forty-three tooth soon.
 
not so hard to do, fear not. like lordmac says, leave the mainshaft in place and slip the 21-tooth sprocket on until it bumps the side of the chaincase.

then rotate the sprocket until the teeth miss all the screw holes for the trap door, and mark the tips of the teeth with a felt tipped pen.

20150906_152309_zps2cjhfcbd.jpg


then you tape the shaft and the main gearbox bearing up with paper and lots of protection, and dremel the notches out. there will be LOTS of aluminum dust, so cover everything up well, and clean it back out spotlessly when youre done. you have to have the mainshaft in place to center the sprocket.

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^^^this is not rocket science. im somewhat casual about the notches, and i use a dremel and a triangular file to work on the notches until the sprocket fits through. once its past the hole the shaft will spin freely and everything else is the same.

anyway, you will sometimes run into a problem even getting a 20 through the trap door, as there are apparently variations in the height of the teeth these days. but generally a 20 will slip in, and a 21 will always require the cut.

once you make the notches, you can stick the trap door cover on in the usual way and run whatever sprockets you like in the future.

four and five-speed sprockets are not interchangeable. look at these suppliers:

https://www.thebonnevilleshop.com/

https://www.classicbritishspares.com/

https://steadfastcycles.com/

http://www.klempfsbritishparts.com/

on the conical rear hub, you cannot go smaller than a 47, unless somehow you can find a 46-- the drum is just too big. but up front, you can run 17, 18, 19, 20, 21, and 22 if youre a glutton for a different procedure that not even me is willing to undertake.
 
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speedrattle said:
not so hard to do, fear not. like lordmac says, leave the mainshaft in place and slip the 21-tooth sprocket on until it bumps the side of the cahincase.

then rotate the sprocket until the teeth miss all the screw holes for the trap door, and mark the tips of the teeth with a felt tipped pen.

then you tape the shaft and the main gearbox bearing up with paper and lots of protection, and dremel the notches out….

sorry for the lousy pictures. ill see if i have any better ones.
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Oh, no, these photos are fine. That doesn’t look so bad.

Was I right about the part number? The only one I could find is 57-4782, which KM Jones indicates is for the 5-speed...?
 
 
if youre already running a 20, you might decide that the 21 isnt better enough. ive used 20s and 21s alng with 43 and 46-tooth rears to get specific ratios for racing, but i have NOT used a 20 on the street. just the 21.

but i put a 19 back into my 72 street bike to remember what it was like, and the 21 goes back in just as soon as i take it apart again. the only thing you need to remember about the 21 is that you have to use the gearbox, else you will lug the engine.

but as i have said, a 19/47 five-speed is mostly just a four speed with a granny gear, so the exchange is worth it, in my opinion.
 
speedrattle said:
if youre already running a 20, you might decide that the 21 isnt better enough. ive used 20s and 21s alng with 43 and 46-tooth rears to get specific ratios for racing, but i have NOT used a 20 on the street. just the 21.

but i put a 19 back into my 72 street bike to remember what it was like, and the 21 goes back in just as soon as i take it apart again. the only thing you need to remember about the 21 is that you have to use the gearbox, else you will lug the engine.

but as i have said, a 19/47 five-speed is mostly just a four speed with a granny gear, so the exchange is worth it, in my opinion.
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Thanks very much! I have ordered one—which was way cheaper than the 21-tooth I linked to BTW—just to have it in the box ‘o parts.

I just fitted a new clutch, and I do like the current roll-on acceleration. So what I may do is save it for when I step up to a Morgo 750cc kit. Either that or swap it out next time I need to replace chain-and-sprockets. But I’ll bet it would be perfect with a 750cc Bonny.
 
i use mine on an elderly morgo that hasnt had rings in over 30 years. it will still go 118 at the races with open megaphones. but mostly i just fart around on it.

and you can always change it back in a couple of hours.
 

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