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#829649 11/12/20 9:25 pm
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I got home from my last ride with only fifth gear available. Opened the box to find a broken lay shaft, clean break right between 3rd and 4th. Of course this is a '72 five speed box.
I searched for lay shaft 57-4371 at a couple of vendors. The search returned with 57-4900, as if these were interchangeable. But I've read the Vintage Bike article and I don't believe that this will work with the rest of my lay shaft gears?
It looks as if I have two options.
1. Find a good used T140 five speed to swap out everything.
2. Find a good used late T150 five speed and steal the lay shaft from my '72 T150V to fix the '72 T120V.
help


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71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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you have the early five speed with the weak first gear layshaft locking dog?

if you do, i suggest locating an entire later box, as that dog will eventually go as well. that was my situation and solution too.

eBay sometimes has 5-speed gear sets for sale. they're often early gear sets and they're missing that piece . . . because it blew and they replaced the whole internals. that's only if they were able to salvage the cases.


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DavidP #829668 11/12/20 11:34 pm
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Too bad David, I feel for you. I also expect you don't want to install 4 gear cluster?

Adam M. #829675 11/13/20 12:47 am
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Originally Posted by kevin
you have the early five speed with the weak first gear layshaft locking dog?
I assume that the gearbox is original to the bike. This is the first time I ever had it open (I've owned the bike for three years.)
After reading about the weak dog, I always free the clutch before starting and hold the clutch lever for a couple of seconds before engaging first. It engages without a clunk. I don't do wheelies or drag race, and I don't engage first while in motion.
As you say, the best option is to find someone who is parting out a T140 and get a complete later five-speed.

Originally Posted by Adam M.
Too bad David, I feel for you. I also expect you don't want to install 4 gear cluster?
That is an option. However, most of my riding is on twisty mountain roads where 3rd and 4th on the five speed are perfectly spaced. I think the only way I would be happy with a four speed is with close-ratio gears.


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71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
DavidP #829676 11/13/20 12:51 am
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i have pictures of both dogs so you can see what you have.

ill see if i can dig them out tomorrow.


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Hi DavidP, I see Bonneville Shop's $969.00 5 speed gear set is out of stock, as is the conversion kit. LF Harris made parts. Can be very hard to buy good used trans parts these days. Worn out junk can be had. Would a seller in UK have new trans in stock? Would be really bad if you used old version parts & it let go & broke the case.

I wouldn't consider converting to 4 speed. I agree 100% 3 & 4 are perfect for canyon riding. When I swap bikes with 4 speed friend I can't wait to get back on my bike with the 5 speed.
Don


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Originally Posted by kevin
i have pictures of both dogs so you can see what you have.

ill see if i can dig them out tomorrow.
Thanks. Looking at the pictures in the Vintage Bike article I'm pretty certain that I have the early dog.

Originally Posted by TR7RVMan
Hi DavidP, I see Bonneville Shop's $969.00 5 speed gear set is out of stock, as is the conversion kit. LF Harris made parts. Can be very hard to buy good used trans parts these days. Worn out junk can be had. Would a seller in UK have new trans in stock? Would be really bad if you used old version parts & it let go & broke the case.
Don
The lay shafts which come up in a search at MAP and Baxter are made by Harris. I haven't checked at Burton's yet, but the Pound keeps going up and with shipping...


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71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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Looking at the Bonneville Shop site, They do have a new gear set for T150 in stock. It's over $200 more, but by the time they get the T120/140 set back in stock the price might have gone up.
If I'm gonna spend that kind of cash I'm tempted to replace the gears in my Trident and use its lay shaft assembly in the T120.


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71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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Burton's has the T140 kit in stock. At the current exchange rate it comes to about $760 + shipping.


Knowledge speaks. Wisdom listens.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
DavidP #829800 11/14/20 12:16 pm
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https://www.ebay.co.uk/itm/5-SPEED-GEARBOX-TRIUMPH-BONNEVILLE-T140-TR7-00-0066-FREE-UK-POSTAGE/174515541139?hash=item28a1efd493:g:0VAAAOSwa~hZZzp0

If by 'Burtons' you mean Burton Bike Bits, I've had bad experiences with them and wouldn't recommend them. There are plenty of other UK Triumph spares retialers. The link above is for KBH (works out just over $750 plus postage). KBH aren;t the best price-wise, but more reliable than BBB imho.

LP Williams are likely to be more expensive but you do get excellent service. TMS are very good, as are Monty's Classics.


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Careful here guys. Gears from triples and twins have the same numbers, but the mainshafts are very different.


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Not a complete kit, but I’ve always had good service from Feked.

https://www.feked.com/triumph-complete-5-speed-gearbox-cluster-650-750cc-twins.html


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I got several orders from Feked lately....5 day delivery to NY USA....shipping charges were very reasonable...


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When the 5 speed box was improved, Triumph didn't change the layshaft. They did revise and improve the M/S 1st & 2nd gear, the L/S 3rd, L/S 2nd, L/S 1st, L/S drive dog and the L/S fork. I'm reading this from Triumph's service bulletin # 1/73 These all have to be changed complete, but the layshaft itself isn't.

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Yes, from what I've read the original CP-1000 upgrade kit was just the lay shaft gears and dog, the two main shaft gears and a first gear shift fork.
I understand that the Trident main shaft is different. AFAIK that's the only difference between the two gearboxes. Except they never were dumb enough to use a leaf spring for indexing the Trident box.
Thanks for the links, I'll have a look. I've dealt with Burton once. The seat on my Trident came from them, good quality and service on that.


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92 BMW K100rs "Gustav"
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I believe the layshaft gained a circlip groove for high gear at some point.

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My parts book shows the leaf spring as well. My '72 T150V has the plunger. According the Stuart it was built in October of '72, perhaps they switched back by then.
Originally Posted by Mike Baker
I believe the layshaft gained a circlip groove for high gear at some point.
And it appears that mine has that circlip. For all I know this gearbox has already been upgraded?


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Originally Posted by DavidP
Originally Posted by Mike Baker
I believe the layshaft gained a circlip groove for high gear at some point.
And it appears that mine has that circlip. For all I know this gearbox has already been upgraded?

[Linked Image from i.postimg.cc]

https://www.britishmotorcycleparts.co.nz/57-4900-layshaft-assy-inc-4th-5th-gears-5-speed

Last edited by L.A.B.; 11/15/20 5:54 pm.
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From looking at Kevin's post from 2018 about upgrading, it appears that I already have the later 1st gear dog.
The lay shaft broke flush with the fourth gear. If I can get dimensions for the gears I could be certain.
Sure would be easier to just replace the lay shaft with those two gears pressed on.

Dog1.jpg Dog2.jpg
Last edited by DavidP; 11/15/20 6:28 pm.

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92 BMW K100rs "Gustav"
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Thats the new layshaft dog. The other gears should be stamped with different numbers if your box has been upgraded. m/s 1st & 2nd 57-4653, l/s 3rd 57-4647, l/s 2nd 57-4657, l/s 1st 57-4654, l/s fork 57-4660. As I wrote before, these parts are supposed to be installed all at the same time. If your box wasn't upgraded and you have the new l/s dog, could that be why your l/s broke?

DavidP #829926 11/15/20 11:07 pm
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Triumph layshafts aren’t known to break, this is the first one I’ve heard of.
Of course there can always be a faulty one, but I think it more likely that a fragment chipped off during a gear change and unfortunately found its way between between 2 gears, levering them apart such that the shaft could not cope.
That’s only a guess, who could know for sure?

DavidP #829933 11/16/20 12:06 am
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Okay, I have a partial upgrade.
LS 1st, 2nd, and 3rd are later parts, but 4th is the old number.
MS 1st/2nd is later, 3rd is early. I think the upgrade kit only changed 1st/2nd on the main shaft?
I can't see a number on the selector fork.
Maybe some bozo just put the newer gears on the old lay shaft?


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71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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DOPE
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new job, no time until now.

here are pictures of two of the early 5-speed locking dogs:

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]


notice the recess in the back side that isn't poresent in the new ones.

also, it's only 0.393-inches thick:

[Linked Image from i.imgur.com]

my machine was an april 1972, T120RV DG . . . . it had the leaf spring.


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DavidP Offline OP
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Thanks,
I noticed the recess in the back of your broken one from your earlier post. That was the clue that mine might be the later version.
Mine is an EG model, just a month later. Still has the leaf spring. I only get a false neutral shifting down from 3rd. Perhaps that will improve with a new lay shaft.
It now looks as if I can get by with a new lay shaft, complete with the new 4th and 5th gears, and new needle bearings and thrust bearings. Probably buy a new selector fork just to be certain I have the correct one.


Knowledge speaks. Wisdom listens.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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