My new Project: R65

Crapaud

Crapaud

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Thanks to all the help I received from numerous Airheaders on here, I now need a new project for the long winter months.

Tomorrow I will be collecting a R65 in need of some TLC. I know little about R65s but very willing to learn. I intend to completely strip it down and begin a full ground up rebuild. The initial intention is to build an ultra light weight off-roader in the style of the early BM off-roaders ie a pea-nut tank with the minimum of extra crap to be the simplest that it can be to still be basically road legal but suitable for off-road use.

By first thoughts are to fit a KTM front end so that I can share bits with my KTM 300. Might want to extend the drive shaft and fit longer travel rear suspension etc.

The target is to build something that can be used at next years Dawn to Dusk in the Big Twins class. I can't race this year as my wrist is still knackered so this gives me a year to get ready.

How easy is it to up the power output on a R65 whilst keeping it nice and light?

Also the frame? I want to completely strip the frame and have it braced up and strengthened before I rebuild it.

All advice and piss-taking gratefully received.:D:D:D

Sid
 
I can't offer advice but wouldn't mind giving you a hand as and when as I'd be interested in doing the same thing myself at some point.
 
Canuck said:
I can't offer advice but wouldn't mind giving you a hand as and when as I'd be interested in doing the same thing myself at some point.
Click to expand...

Cheers mate:thumb2

All offers of help very gratefully accepted.:)

I'm away on holiday from this weekend (driving down to Budapest in the Bentley for F1 race) so not starting stripping the R65 until I return. You are welcome up here anytime to help.:thumb2

Sid
 
When are you off Sid? If I can, I'll pick up "Ol' Blue" before you disappear, as I now have some space in the garage again.
Pete
 
Sid, iirc the pre 1981 R65's are only 24bhp. After 81 they up'ed them to 50bhp. So you might not need to worry about a power increase.

However if you have bought one of the lower horse bikes it might well be easier to find an 80/100 engine to replace it.


Val.
 
Its Feb 82 twin shock so I assume 50bhp. Owner said it acccelerated up to 70mph easily enough. Got a brand new Odesey battery.:
And nice set of panniers. Spares include a new exhaust spanner and another brand new Haynes manual (my old one is a bit oily:) ). Twin disc on front so could be an airhead that stops?

Also got Koni Dial-a-ride shocks.

Now safely tucked up in my workshop:)
 
Update.:)

Completely stripped it down to the very last nut and bolt. I've learnt many lessons from the previous strip-downs and this one was done in a much more organised manner with everything carefully boxed up so I'll know where everything is come rebuild time.

I was amazed at how light the little engine was compared to the heavy flywheel R80/7s I had previously worked on. I could easily lift this motor on to the workbench.:)

It obviously needs the push-rod seals doing but apart from that everything else looks sound. Oil came out like new from motor and gearbox as previous owner had said it had recently had a full service but I thought it best to be sure.

I want to build a super lightweight off-roader to use in next seasons Big Bike challenge. Anything not absolutely essential to make the bike go and stop will be removed. Lightness is the absolute priority.

I've just acquired a complete front end from a Honda Africa Twin XRV 750 in perfect condition. It will be interesting grafting that on to the front end of the bike.:)

Will need to extend the twin-shock swinging arm. Who/where does that please?

Also want to brace up and strengthen the frame. I searched for more details on here about this but it only went to a dead link. Did someone have a pattern of plates to be welded into the frame for this?

I must take lots of pictures and do a stage by stage build up process.:)
 
From memory (when I bought mine - 1982:D) the new lighter flywheel R65 and R80G/S shared the same bottom end.
If this is the case, it might be possible to fit 80 barrels/heads?

I obviously stand to be corrected by those that know, and don't have to rely on hazy memories :pullface
 
Spout said:
From memory (when I bought mine - 1982:D) the new lighter flywheel R65 and R80G/S shared the same bottom end.
If this is the case, it might be possible to fit 80 barrels/heads?

I obviously stand to be corrected by those that know, and don't have to rely on hazy memories :pullface
Click to expand...


I think 80 barrel's can be made to fit a 65 bottom end and crankcase but they require some machining work around the base of the barrel
 
Guy tells me in belgium, shortened 1000cc barrells and normal 1000cc pistons will give you a short stroked engine and about 850cc of pure fast revin:cool: stonk, worth thinkin about:eek:

steve


Crapaud said:
Thanks to all the help I received from numerous Airheaders on here, I now need a new project for the long winter months.

Tomorrow I will be collecting a R65 in need of some TLC. I know little about R65s but very willing to learn. I intend to completely strip it down and begin a full ground up rebuild. The initial intention is to build an ultra light weight off-roader in the style of the early BM off-roaders ie a pea-nut tank with the minimum of extra crap to be the simplest that it can be to still be basically road legal but suitable for off-road use.

By first thoughts are to fit a KTM front end so that I can share bits with my KTM 300. Might want to extend the drive shaft and fit longer travel rear suspension etc.

The target is to build something that can be used at next years Dawn to Dusk in the Big Twins class. I can't race this year as my wrist is still knackered so this gives me a year to get ready.

How easy is it to up the power output on a R65 whilst keeping it nice and light?

Also the frame? I want to completely strip the frame and have it braced up and strengthened before I rebuild it.

All advice and piss-taking gratefully received.:D:D:D

Sid
Click to expand...
 
VAL. H. said:
Sid, iirc the pre 1981 R65's are only 24bhp. After 81 they up'ed them to 50bhp. So you might not need to worry about a power increase.

However if you have bought one of the lower horse bikes it might well be easier to find an 80/100 engine to replace it.


Val.
Click to expand...

Wrong - I bought an R65 new in 1980 - and i still have it. They are 45 BHP. The post 81 models were 50BHP, but the fuel consumption compared to the 45BHP model was shite. I easily get 65-70 mpg out of my 1980 R65, i had two mates who both had the post 81 models and they struggled to get 50mpg and with no great noticable difference with 5 bhp power increase .

Spout said:
From memory (when I bought mine - 1982:D) the new lighter flywheel R65 and R80G/S shared the same bottom end.
If this is the case, it might be possible to fit 80 barrels/heads?

I obviously stand to be corrected by those that know, and don't have to rely on hazy memories :pullface
Click to expand...

Not without a large amount of machining on lots of parts - for a very short time near the end of the R65's life, BMW made it with the R80/R100 bottom end and very very short barrels, these engines are very rare, i've only ever seen two - i had one, but sold it :blast.

jaber said:
Guy tells me in belgium, shortened 1000cc barrells and normal 1000cc pistons will give you a short stroked engine and about 850cc of pure fast revin:cool: stonk, worth thinkin about:eek:

steve
Click to expand...

The bmw dakar factory bikes in the early eighties run an R65 bottom end with shortened 1000cc barrels = high revving 900cc twins.

Requires lots of work including machining the crank web if you want to copy it.
 
Made a good start on this project today.

Built an engine stand so I can safely work on the motor.
P8140349.jpg


P8140350.jpg


Thanks for all the advice above but I think I'll stick with the 650cc for now. If I find it too slow I'll always have the option to tune it at a later date.

Chassis wise the Africa Twin 750 front end arrived.:) I offered it up to the spare frame just to see how it will look:
P8140351.jpg


P8140352.jpg


P8140353.jpg


Also decided to use the original R65 tank as Ithink this is the same as the G/S tank?
P8140354.jpg



Still to find out who can extend my swinging arm. Any ideas?
 
Started on the engine today. The pushrod tubes were corroded and leaking at the seals so I'll get some nice shiny stainless ones from Sherlocks.

So easy to work on engine now that it is safely in the stand.

P8150355.jpg


P8150356.jpg


Followed the step by step instructions in the Haynes manual and carefully labelled each item and put it in separate containers.

P8150357.jpg
 
Looking good sid! I use egg cartons with small bits of paper that I write on to describe where the bolts/nut/s springs etc are from. I also number things 1.2.3.4 etc so that I know in what order I took things off... saves me from getting things mixed up as my memory is shite!
 
I used to make notes and label things but digital cameras are a much better option these days (plus you can later use the photos to bore poor sods with a rebuild thread :D).

Looking good Sid. I'm looking forward to seeing this as it progresses. :thumb2
 
Looks good :thumb2

Shame you don't know an expert in airhead engineering locally that could oversee your work and advise on matters technical :D
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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