R80G/S suspension raise?

  • Thread starter Thread starter Bradd
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Bradd

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Must replace the suspension on a 1981 R80G/S & am toyying with the idea of raising it. This would involve fitting 2nd hand motocross forks to the front & extending the driveshft by 100mm.
I could send it to HPN to do but this (expensive) but was wondering if anyone had any experience trying this themselves, would an engineering company be able to extend the shaft drive?
 
Both Tarka and Tim have modified front ends on their bikes so they would be a good source of info. At the back why not fit an 1100 swinging arm, bevel box and shock? One of the Belgian guys has done this and it looks great.
 
Rob Farmer said:
Both Tarka and Tim have modified front ends on their bikes so they would be a good source of info. At the back why not fit an 1100 swinging arm, bevel box and shock? One of the Belgian guys has done this and it looks great.

I think Touratech do a kit to fit an oilhead rear end in to an airhead. It will involve fabricating a top shock mount on the subframe though, may have to get a smaller battery or relocate it?
 
Here`s a couple of pics of mine...
 

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And again...

Note to the pishtakers...I haven`t finished coating the fence and then I`m going over the posts with masonry paint,also I`ve yet to weed the path...ok ? :D
 

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The bike has 41mm forks off a Yamaha DTR125 ( Honestly !! ), fitted with Africa Twin Progressive fork springs and 25mm spacers.

I machined 2mm off the bottom of the steering stem,and then used a stock 800G/S top taper roller bearing,with an 'off the shelf' taper roller from a bearing supplier on the bottom.

The front hub is DTR,laced to an Akront alloy rim with stainless spokes.

The rear subframe is the 800G/S seat loop with the diagonal lower tubes cut off and replaced with longer,thick wall, tubing (actually steam pipe from work,bent on a hydraulic former) and gusseted at the joints....all TIG welded...you don`t need HPN or anyone like that to build a subframe mate,this has had nine years of use with no problems.
By keeping the original seat loop,the seat still fits and locks on.

I made up some tube adaptors and welded them to the rack frame,so an off the shelf Ventura bag loop can be fitted for some luggage capacity.

Pillion pegs are clamp-on custom bike ones.

The silencer is a modded 4" alloy CCM motocross one,changed from right side to left side mounting by removal of the lugs and welding new ones on,and also I made the outlet spout,to stop the exhaust from discolouring the rear mudguard.
The inlet fitted straight onto the BMW collector (actually it`s a Keihin stainless one ).

The rear wheel has a 2.5" rim laced to a stock hub with stainless spokes....I can fit a 130/80 tyre,although some tyres rub the shock.

In the photos,the bike has a standard rear shock,but it normally has a Spax fully adjustable rose jointed unit.

The fairing is a GPZ style twin headlamp unit,with Cibie 60/55 w lamps,so along with the 55 w spots,it has 230 watts of light on main beam !!!

The fairing houses twin Fiamm airhorns too.

The tank is an Acerbis 45 litre polyethelene one.
 
I bought a ready made bolt on drive shaft extension and some ready to fit Marzochis from Arcueil Moto years ago, they were the people who prepped the bikes for Rahier and Loiseaux. Try an email to them http://arcueil-motor.fr/, maybe they still have some bits.
 
This is the one I was thinking of with the 1100 rear end, can't remember whose bike it is though...Sorry.
 

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Thanks, this looks like an interesting way to go, so will start looking to see what parts I can find.
Tarka great looking bike I'm hoping to do some of the things youve done. You didnt mention extendeding the driveshaft, isnt the geometry & shaft affected.
Have emailed Arcueil, waiting for response.
 
Bradd said:

Tarka great looking bike I'm hoping to do some of the things youve done. You didnt mention extendeding the driveshaft, isnt the geometry & shaft affected.
Have emailed Arcueil, waiting for response.


Thanks for that mate !

Sorry,one of the few unmodified things is the final drive...:D

Even though the Spax is longer than stock,and the forks are considerably longer than standard forks,the handling is spot on,so the geometry must be fine. The bike needed no 'getting used to'.
My understanding of the reason for the extended shaft/swingarm on the early Dakar twins ( Andrew Sexton mod in particular ) was to add stability at high speed...and those bikes mostly had R90 frames (due to them being more rigid) which may have had a different rake from the GS.
 
Rob Farmer said:
This is the one I was thinking of with the 1100 rear end, can't remember whose bike it is though...Sorry.
That's another Belgian nutter Rob. He calls himself CrazyIvan and he has rebuilt several airheads already. I know because he has built me a new rearframe :D

The 1100 swing arm is NOT a straight bolt on operation on an airhead, but it obviously can be done.

Cheers,
Michel
 
I know because he has built me a new rearframe

What are you up to Michel? Can we look forward to seeing something a bit Special Soon? :cool:

I measured up my 80 and 1150 swinging arms and they are exactly the same width so it should just be a case of matching the bearings to swap them over.
 
Rob Farmer said:
What are you up to Michel? Can we look forward to seeing something a bit Special Soon? :cool:
A bit special yeah, but nothing too spectacular.

I have had the tank repainted, a new rear frame and pannier rack made, seat revamped, R100 fork fitted and a K1100 brake caliper. That's about it, I'm pretty much done for now. I'll take some pics one of these days :)

Cheers,
Michel
 


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