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/6 gearbox options

Andey
Posts: 117
Joined: Wed Sep 02, 2020 12:45 am

/6 gearbox options

Post by Andey »

Basic question, (and probably answered somewhere and a while back) can I install a R80 gearbox onto a ‘76 /6?

Or even just the shift mechanism/shift cam?

Limited to rebuilding the existing gearbox and noticed the spare shift mechanism I have is a pre 75 (neutral switch is different)

Thanks!

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srankin
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Re: /6 gearbox options

Post by srankin »

I can't answer the first question as to direct fit of an R80 gear box to your /6. It might be possible but may require changing the flywheel and clutch assembly as well as other bits to make the newer version gear box work.

As for the second question I do not believe internal parts are interchangeable from the one era gear box to the other. St.
Owner of a 84, R80RT and 78, R100RS

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schrader7032
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Re: /6 gearbox options

Post by schrader7032 »

As ST mentions, we need to know the year of the R80 transmission. Sounds like it may be a post 1980 box.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

Andey
Posts: 117
Joined: Wed Sep 02, 2020 12:45 am

Re: /6 gearbox options

Post by Andey »

Thanks for the reply guys!

So I have a 75 /6 gearbox… I replaced the bearings etc. and realised a while ago that the shift mechanism is the old style and I was planning on replacing it with a post 75 style shift mech.

But realised it’s actually hard finding those!!

But what I see more of are the r80 style shift mech, and was wondering if I could put it into the /6 gearbox.

Also I was imagining the r80 gearbox would probably be better in design and have seen some /6 bikes with the r80 gearbox, so was wondering if it was a straight swap? Or as ST mentions I could do it with a flywheel clutch swap?

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schrader7032
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Re: /6 gearbox options

Post by schrader7032 »

If the R80 is 1981-on, you will need to get rid of the older flywheel and clutch pack. Lots of effort and cost.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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srankin
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Re: /6 gearbox options

Post by srankin »

As I mentioned, I really don't think the internals of the two transmissions are the same so a newer style shift pack won't fit into the older trans.

My friend at his shop grafted a 77 engine into a 85 bike for a fellow. Sort of the same thing you are thinking about. I won't be at the shop until next week but I will ask him if he had to install the 85 flywheel and clutch pack onto the 77 engine to make the 85 trans work. I think he did, but as I tell people I have a teflon memory and I can't be sure. All I remember is the fellow who wanted the bike built that way spent a lot of money to do something he could have done cheaper. That is another story.

So if no one else answers I will let you know next week Monday or Tuesday. St.
Owner of a 84, R80RT and 78, R100RS

Andey
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Re: /6 gearbox options

Post by Andey »

srankin wrote:
Sun Jun 19, 2022 7:47 am
As I mentioned, I really don't think the internals of the two transmissions are the same so a newer style shift pack won't fit into the older trans.

My friend at his shop grafted a 77 engine into a 85 bike for a fellow. Sort of the same thing you are thinking about. I won't be at the shop until next week but I will ask him if he had to install the 85 flywheel and clutch pack onto the 77 engine to make the 85 trans work. I think he did, but as I tell people I have a teflon memory and I can't be sure. All I remember is the fellow who wanted the bike built that way spent a lot of money to do something he could have done cheaper. That is another story.

So if no one else answers I will let you know next week Monday or Tuesday. St.
Do let me know.

I’m not after anything fancy, but would be good to keep some options on the table…

Thanks!

Andey
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Re: /6 gearbox options

Post by Andey »

schrader7032 wrote:
Sun Jun 19, 2022 6:50 am
If the R80 is 1981-on, you will need to get rid of the older flywheel and clutch pack. Lots of effort and cost.
I’m a little lost on the R80 timeline.

The /7 doesn’t count right? It’s a just “newer” /6?

The real R80 is the finned gearbox version?
Technically, at least as seen on the bike, the /7 was only 1977 and 1978. They dropped that designation in 1979 and 1980. It might say /7 in the fiche but there were enough changes that I consider them different. So, the term "R80" by itself might be used from say 1979 to 1984 and longer.

I don't know about finned gearboxes and when that came into being. Bottom line, it comes down to model year. Thru 1980, the standard large flywheel and clutch pack were used. Then in 1981, they wanted to reduce the mass of the flywheel/clutch and created what was called the "clutch carrier". With that change, the input shaft to the transmission was changed. So there was a big configuration change from 1980 to 1981. That is why I'm wondering what year R80 you are referring to.

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srankin
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Re: /6 gearbox options

Post by srankin »

I am talking about /7 era bikes, it might be possible to fit a R80/7 transmission onto your bike. Definitely I think the 81 and newer bike's transmission might need major work.

Same goes with the internals of the /6 transmission versus /7. I don't believe there was any great change in shifter packs in the two series bikes. 81 again introduced an improved shift pack and that along with the lighter flywheel and clutch pack makes for much smoother shifting versus the older transmissions.

So I may be mistaken but installing a /7 trans for years 80 and older won't buy you any improvement in shifting over what you have now on the /6. Anything 81 and up may fit or may not fit without changing the flywheel and clutch pack. I can't be 100% certain. I don't believe you can change the internal shift pack from the /6 or /7 unit with a 81 newer unit.

As I wrote, my friend had a person who has a 85 R100RS and wanted to build it up to 78 R100RS specifications. Doing so, he used a 77 engine and had to make the 85 transmission work in the mix. I forgot the extent he had to mix and match parts to get the whole thing to work. St
Owner of a 84, R80RT and 78, R100RS

Andey
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Re: /6 gearbox options

Post by Andey »

Andey wrote:
Sun Jun 19, 2022 12:36 pm
[quote=schrader7032 post_id=81819 time=<a href="tel:1655635800">1655635800</a> user_id=2299]
If the R80 is 1981-on, you will need to get rid of the older flywheel and clutch pack. Lots of effort and cost.
I’m a little lost on the R80 timeline.

The /7 doesn’t count right? It’s a just “newer” /6?

The real R80 is the finned gearbox version?
Technically, at least as seen on the bike, the /7 was only 1977 and 1978. They dropped that designation in 1979 and 1980. It might say /7 in the fiche but there were enough changes that I consider them different. So, the term "R80" by itself might be used from say 1979 to 1984 and longer.

I don't know about finned gearboxes and when that came into being. Bottom line, it comes down to model year. Thru 1980, the standard large flywheel and clutch pack were used. Then in 1981, they wanted to reduce the mass of the flywheel/clutch and created what was called the "clutch carrier". With that change, the input shaft to the transmission was changed. So there was a big configuration change from 1980 to 1981. That is why I'm wondering what year R80 you are referring to.
[/quote]


Wow, that’s freaky.

I didn’t write the timeline comment above, but I’ll take it! Someone using my account name?

All good.

I think I’m understanding more about the transition of /6 to post 81 R80

Still wondering about the shifter pack if it’s possible to reverse engineer a /6 gearbox. So difficult to find the newer shift paw

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