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Hello Stuart,
I was going from the Roy Bacon dating, which is a little confusing! Of course if 90282 is October '68, it's a '69 model year, (starting 85904?). Funnily enough, I'd spotted this once before, and thought no more about it. I was just prompted there to check the numbers on my own '69 Bonneville, something I'd never checked, and that really makes no sense, they are matching and are T120 11439, no DU, no month and year code! I have the original green log book with date of first sale and those numbers, and rough as it was when I got it some 40 odd years ago, the spec is '69 with all it's lovely mix of fasteners etc.
I think it's time for a drink.
Cheers,
Mick.
Hi Mick, the numbers on my 68 are t120r10940. turns out i have the leaf spring and oddball cam plate. Can you give me any info? Having a hard time indexing the tranny. Thanks. John

Hello Stuart,
I was going from the Roy Bacon dating, which is a little confusing! Of course if 90282 is October '68, it's a '69 model year, (starting 85904?). Funnily enough, I'd spotted this once before, and thought no more about it. I was just prompted there to check the numbers on my own '69 Bonneville, something I'd never checked, and that really makes no sense, they are matching and are T120 11439, no DU, no month and year code! I have the original green log book with date of first sale and those numbers, and rough as it was when I got it some 40 odd years ago, the spec is '69 with all it's lovely mix of fasteners etc.
I think it's time for a drink.
Cheers,
Mick.
 

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Discussion Starter #23
Leaf spring were not used on the T120 and T120R until late in the model year 1970. They were then used through the 71 and 72 models. In 1973, with the 750, the factory went back to the spring and plunger. The leaf spring was notoriously for bad shifting. But, if indexing is your problem, you need to figure out why you have a leaf spring in a 1968 model. You may have some parts that aren't going to work well together. Posting pictures is probably the best way to get forum members to help you identify what you have. For re-assembly of the transmission and indexing, hermit.cc has the best description of the easiest indexing method. Index to Hermit's Gearbox Articles I believe that his fastest, easiest method that hermit leads with is what Hughie Hancox recommended in his videos.
 

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Discussion Starter #24
Hi Mick, the numbers on my 68 are t120r10940. turns out i have the leaf spring and oddball cam plate. Can you give me any info? Having a hard time indexing the tranny. Thanks. John
Leaf spring were not used on the T120 and T120R until late in the model year 1970. They were then used through the 71 and 72 models. In 1973, with the 750, the factory went back to the spring and plunger. The leaf spring was notoriously for bad shifting. But, if indexing is your problem, you need to figure out why you have a leaf spring in a 1968 model. You may have some parts that aren't going to work well together. Posting pictures is probably the best way to get forum members to help you identify what you have. For re-assembly of the transmission and indexing, hermit.cc has the best description of the easiest indexing method. Index to Hermit's Gearbox Articles I believe that his fastest, easiest method that hermit leads with is what Hughie Hancox recommended in his videos. If it's a 5-speed transmission, then scroll down on hermit's page and you will see some links to John Healy discussions of indexing a 5-speed with the leaf spring.
 

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Hello John,
I'd agree with all of the above, but like my bike, there is something odd about your numbers. There should be a DU ahead of the number, or if '69 onwards a month and year code in letters. Are you sure that you have the leaf spring detent? If you have either of the plunger bodies shown in the attachment below the lower front of the gearbox, you will have the plunger detent (the 2nd image s the '69 one). I'd love someone to chime in about the numbers!
HTH
Mick.
 

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Hello John,
I'd agree with all of the above, but like my bike, there is something odd about your numbers. There should be a DU ahead of the number, or if '69 onwards a month and year code in letters. Are you sure that you have the leaf spring detent? If you have either of the plunger bodies shown in the attachment below the lower front of the gearbox, you will have the plunger detent (the 2nd image s the '69 one). I'd love someone to chime in about the numbers!
HTH
Mick.
Hi Mick, I wish i did have the plunger style. Way better in my mind. Definatly leaf spring. No DU. Just T120R BE10940. Any advise is helpful. Wondering about the cam plate as well. I have not taken the gears out as yet, so i,m not certain it is different. Thanx. john
 

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Discussion Starter #27
Hi Mick, I wish i did have the plunger style. Way better in my mind. Definatly leaf spring. No DU. Just T120R BE10940. Any advise is helpful. Wondering about the cam plate as well. I have not taken the gears out as yet, so i,m not certain it is different. Thanx. john
The "E" in the numbers indicates your motor is a 1971 model and therefore would have the leaf spring. The "B" indicates it was build in February. The Healy links on hermit.cc's gearbox pages should help with the indexing. Index to Hermit's Gearbox Articles Scroll down towards the bottom for the Healy links. I have a late-1970 T120 and it came with a leaf spring. I had the case machined to accept the plunger and am very happy with the result.
Mike
 

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Hello John,
From the above, your machine will be oil in frame, definitely not pre-oil in frame '68! Go with the info above for indexing. It transpires that the camplate is the same for late plunger and leaf spring set-ups, so you you could convert to plunger down the line, I'd see how it goes out on the road first. Don't get hung up on not being able to select all of the gears with the engine not running and at a standstill, it has been mentioned elsewhere that the engaging dogs will not line up on all of the gears when things are not rotating, no problem when you are rolling!
Mick
 

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Hello John,
From the above, your machine will be oil in frame, definitely not pre-oil in frame '68! Go with the info above for indexing. It transpires that the camplate is the same for late plunger and leaf spring set-ups, so you you could convert to plunger down the line, I'd see how it goes out on the road first. Don't get hung up on not being able to select all of the gears with the engine not running and at a standstill, it has been mentioned elsewhere that the engaging dogs will not line up on all of the gears when things are not rotating, no problem when you are rolling!
Mick
Hi Mick, thank you for the info. So, my bike has had the motor changed. I guess it doesn,t mater what the ownership says on it. Comes down to what fits. Yes, was wondering about gear engagement at a stadstill. I feel that should at least replace the leaf spring? It shows some wear. Here is a question, inner cover, gasget or no gasget? thanks again. john
 

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The "E" in the numbers indicates your motor is a 1971 model and therefore would have the leaf spring. The "B" indicates it was build in February. The Healy links on hermit.cc's gearbox pages should help with the indexing. Index to Hermit's Gearbox Articles Scroll down towards the bottom for the Healy links. I have a late-1970 T120 and it came with a leaf spring. I had the case machined to accept the plunger and am very happy with the result.
Mike
Hi Mike, just want to say thanks. yes, next time the motor is out of the frame, i will change to the plunger style. john
 

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Hi Mick, thank you for the info. So, my bike has had the motor changed. I guess it doesn,t mater what the ownership says on it. Comes down to what fits. Yes, was wondering about gear engagement at a stadstill. I feel that should at least replace the leaf spring? It shows some wear. Here is a question, inner cover, gasget or no gasget? thanks again. john
Hello John, There was never a gasket fitted as standard, and fitting one means that you have more end float on the layshaft. It may not matter, but either way a good sealant (I use Loctite 518) is fine, as there is no pressure in a gearbox. If your leaf spring is smooth, even if a little worn, I personally would leave it alone for now, it would take some time to "run in" a new one.
Mick.
 

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Discussion Starter #32
Hi Mike, just want to say thanks. yes, next time the motor is out of the frame, i will change to the plunger style. john
Hi, John--
When I looked at my leaf spring, it looked quite worn as well. My bike had 11000 miles on it. Seems like it could be a good idea to replace yours. Depending upon the true miles on this motor and gearbox, there are some other parts that wear in there and make shifting less positive. You might inspect the gear change quadrant and plungers and the springs that regulate the movement of that quadrant. I'll be interested to see what Mick says about the gasket. I've gone back and forth on this question.
 

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Hi Mick, thank you for the info. So, my bike has had the motor changed. I guess it doesn,t mater what the ownership says on it. Comes down to what fits. Yes, was wondering about gear engagement at a stadstill. I feel that should at least replace the leaf spring? It shows some wear. Here is a question, inner cover, gasget or no gasget? thanks again. john
Hi,
Gaskets are available and are sometimes touted as remedies for shifting problems (end-float adjustment?), but none of the parts books covering 1965 through 1971 include them and they are not necessary for sealing - a good sealer like Hylomar is all that's necessary for that. So, in my opinion:

A-Tisket, A-Tasket, but no red or gray gasket!
 

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I use a gasket on my 1971 but i have also fitted all new bearings and end float is correct. The leaf spring has always been good on my bike. Easy to index using the details in the haynes manual which i studied in 1979 in the absence of any other manual. the method uses a straight edge across 2 parts then push the cover into place. Its been easy since the first few attempts back in 1979. Now, it is never any bother.
 

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I use a gasket on my 1971 but i have also fitted all new bearings and end float is correct. The leaf spring has always been good on my bike. Easy to index using the details in the haynes manual which i studied in 1979 in the absence of any other manual. the method uses a straight edge across 2 parts then push the cover into place. Its been easy since the first few attempts back in 1979. Now, it is never any bother.
Rambo - in what way does the gasket relate to new bearings and end float? Or did you use the gasket just to be sure there was no leak?
 

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When replacing the mainshaft, i also replaced all the bearings including the roller bearings. New thrust washers and checked the fitting depth of the closed end roller bearing and glued it in place. Using a thin gasket and it all works perfectly and been assembled for 7 years now. I also replaced two gears as i had some brand new ones in my bits box. i still have a few brand new gears and a layshaft coated with brown preservative. Bought at a jumble with a new renolds chain for £40. Good find of brand new gearbox parts.
I used a gasket as one was included in the gasket set. I was also fitting a new crankshaft at the same time. Since that build, i have replaced the piston rings when pushrod tubes began to leak and now have a totally oiltight engine. Great to be able to park and not leave a mess on the ground. My garage is carpeted so try not to spill oil on it.

What i did find with this gearbox is, when i used a synthetic gear oil, i was missing gear changes and it would jump out on acceleration on second gear. I changed back to a mineral 75/85 gear oil and it came back to the way it was. This box has almost no clonk engaging first gear. I have never had any bad experience with the leaf spring. 20 years ago, the helper leaf spring snapped off and dropped into the bottom of the case but it still worked and not noticed the spring had snapped.

i use Hylomar on joints to good effect. Easy to clean and parts separate easily later.
 

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Rambo,
Thanks for the details. Very interesting observation about the synthetic gear oil! That has to be the easiest gearbox 'fix' ever!

Hylomar is great stuff! The only leak I've ever had from the gearbox was when I neglected to seal the drilling for the shifting fork shaft. But it was ok as long as I didn't leave the bike on the side stand for extended periods.

My bike is currently leak-free but I think it's more an indication that I was lucky enough to land one with good cases and covers than skill on my part.

I'm amazed how guys can put carpets down in their shops and keep them clean. The fellow I bought my bike from has Persian rugs all over his shop and they are spotless. I recently tried putting a runner beneath my bike. No drips from the bike, but I got greasy hand prints all over it from getting up off the floor after playing around with the chain. Oh, well, back to concrete!
 

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Hello John, There was never a gasket fitted as standard, and fitting one means that you have more end float on the layshaft. It may not matter, but either way a good sealant (I use Loctite 518) is fine, as there is no pressure in a gearbox. If your leaf spring is smooth, even if a little worn, I personally would leave it alone for now, it would take some time to "run in" a new one.
Mick.
Hi Mick, so, have a look at this pic, tried to get it as clear as i could. it,s the bottom of the cam plate. no indent for the plunger.
Hello John, There was never a gasket fitted as standard, and fitting one means that you have more end float on the layshaft. It may not matter, but either way a good sealant (I use Loctite 518) is fine, as there is no pressure in a gearbox. If your leaf spring is smooth, even if a little worn, I personally would leave it alone for now, it would take some time to "run in" a new one.
Mick.
729507

Rambo,
Thanks for the details. Very interesting observation about the synthetic gear oil! That has to be the easiest gearbox 'fix' ever!

Hylomar is great stuff! The only leak I've ever had from the gearbox was when I neglected to seal the drilling for the shifting fork shaft. But it was ok as long as I didn't leave the bike on the side stand for extended periods.

My bike is currently leak-free but I think it's more an indication that I was lucky enough to land one with good cases and covers than skill on my part.

I'm amazed how guys can put carpets down in their shops and keep them clean. The fellow I bought my bike from has Persian rugs all over his shop and they are spotless. I recently tried putting a runner beneath my bike. No drips from the bike, but I got greasy hand prints all over it from getting up off the floor after playing around with the chain. Oh, well, back to concrete!
Hello John, There was never a gasket fitted as standard, and fitting one means that you have more end float on the layshaft. It may not matter, but either way a good sealant (I use Loctite 518) is fine, as there is no pressure in a gearbox. If your leaf spring is smooth, even if a little worn, I personally would leave it alone for now, it would take some time to "run in" a new one.
Mick.
Hi Mick. so, here is a pic of the cam plate in my bike. it has no indent for the plunger.
 

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Hi Mick, so, have a look at this pic, tried to get it as clear as i could. it,s the bottom of the cam plate. no indent for the plunger.

View attachment 729507


Hi Mick. so, here is a pic of the cam plate in my bike. it has no indent for the plunger.
The dips in the edge of the camplate are the indents, the leaf spring just engages with these in the same way that a plunger does, just a different mechanism. The camplate T(57-)4055 was used on the 1970 (plunger type) and 1972 (leaf type setups.
Cheers,
Mick.
 
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