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Author Topic: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?  (Read 103 times)

Offline Callumjack

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1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« on: December 26, 2021, 10:33:48 AM »
Hi

Im looking for an R65.. but they are few and far between.. and i wondered about an R80/7 as they seem more plentiful.

That being said I prefer the smaller, less bulbous tank from the R65/R80G/S model... than the usual R80/7 tank

I was told that if anyone knew if this could be done.. it would be you guys..is it possible ??

Many thanks and Happy New Year to you all !

Offline Tony Smith

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #1 on: December 27, 2021, 01:56:42 AM »
 Yes - but.

Clearance for n the RHS side of the frame tube will be OK as the 1981 R65 has all its relays, regulators and ICU there

The LHS should be OK but you may need to relocate some cables.

The big thing will be adapting the rear mounting, the /7 uses a plate with 2 rubber mounted threads whereas the R65 has rubber pads on the tank and frame rails and is retained by a wire bail over the main spine tube.

All doable but you will need to fabricate and adapt.
1978 R100RS| 1981 R100RS (JPS) | 1984 R65 | 1992 KLE500 | 2002 R1150GSA |

Offline Callumjack

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #2 on: December 28, 2021, 09:51:28 AM »
Ah Many thanks--has anyone any photos of what this may look like ?

Have scoured the internet and not found one....perhaps Im the first..unlikley !

Offline georgesgiralt

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #3 on: December 28, 2021, 11:39:11 AM »
As the frames are identical, IMHO it is only a matter of finding the proper rubber pads and ensuring the plate where the OEM tank is affixed does not interfere with the bail lock...

Offline Callumjack

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #4 on: December 28, 2021, 02:57:30 PM »
Ah George..i should have worded my question better.

What I wondered was what an R80/7 with an R65 tank looked like in the flesh...i assume the original seat will work with it ?

Thanks again all

Offline georgesgiralt

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #5 on: December 28, 2021, 05:09:04 PM »
That's not sure either. As the subframe of the R65 is different from the R80, and bottom of passengers are quite similar, the seat can be a different size/shape on both bikes to accommodate those.
Why don't you try it on and report back ? It could be interesting to know.

Offline Tony Smith

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #6 on: December 29, 2021, 02:50:43 AM »
The subframe doesn't enter into the equation at all as the tank does not project past the rearmost edge of the main frame loops

We used to have member from the same town as me who had a /7 tank on his R65. Aside from moving relays and fabricating a rear mount he had no trouble.
1978 R100RS| 1981 R100RS (JPS) | 1984 R65 | 1992 KLE500 | 2002 R1150GSA |

Offline Callumjack

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #7 on: December 29, 2021, 06:38:38 AM »
Ah ok--its starting to make sense now

So simplistically... the only difference between an R65 frame and an R80/7 frame. is the seat subframe and the swingarm...ie the front engine loop frame element is the same on both bikes

i know the R65 is shorter wheelbase.. so had always assumed there was a bigger difference between the two frames.

Many thanks

Offline georgesgiralt

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #8 on: December 29, 2021, 06:44:16 AM »
The subframe doesn't enter into the equation at all as the tank does not project past the rearmost edge of the main frame loops

We used to have member from the same town as me who had a /7 tank on his R65. Aside from moving relays and fabricating a rear mount he had no trouble.
Yes Tony but the seat could be different in it's length. And let a gap or interfere with the tank. This could be something to fear ....

Offline Tony Smith

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #9 on: December 29, 2021, 06:13:44 PM »
The subframe does not make the slightest difference to the tank mount.

When I converted to long wheelbase I had a gap between the tank and the R65 seat. Fitting my spare R100 seat cured that.

Again, no modern BMW airhead fuel tank projects beyond the sub- frame joint and the subframe is therefore irrelevant to the topic of tank fitment.

If there is a difference in tank length it is trivial and is likewise irrelevant.

Of I had a spare /7 tank I would fit it to show you, but the only tank I have on hand is the K100 tank I plan to fit along with fairing, seat and ducktail, whilst that job requires a number of mounts to be fabricated that tank also does not project past the sub-frame joint which means that mounting the tank and seat can be considered separately.

All I can suggest is that if you ever get the opportunity to view an R65 sub-frame alongside a /7 one you will see where the length has been inserted.
 


1978 R100RS| 1981 R100RS (JPS) | 1984 R65 | 1992 KLE500 | 2002 R1150GSA |

Offline Callumjack

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Re: 1981 ish R45/65/R80G/S tank... on an R80/7..can it be done ?
« Reply #10 on: December 30, 2021, 05:10:07 AM »
Many thanks

Regards and HNY to all of you !