Frames and monolever

[ChasF]

I had this plan to buy a secondhand frame and monolever to modify and perhaps even build up a complete rolling chassis before taking my R80 apart to supply the engine and gearbox. The only difference I can see between my 100GS and 80G/S frames is the top suspension mount is more substantial on the 100. I notice that the mono frame is about a third of the price of a GS (paralever) frame from Motorworks - there must be a good reason for this.

Also, can anyone confirm if the monlever arm are all the same or is the G/S one different

 

[ians]

I had this plan to buy a secondhand frame and monolever to modify and perhaps even build up a complete rolling chassis before taking my R80 apart to supply the engine and gearbox. The only difference I can see between my 100GS and 80G/S frames is the top suspension mount is more substantial on the 100. I notice that the mono frame is about a third of the price of a GS (paralever) frame from Motorworks - there must be a good reason for this.

Also, can anyone confirm if the monlever arm are all the same or is the G/S one different

The G/S swinging arm has the shock absorber mounting on it, the others don't it is on the bevel box.
The top shock mounting point is lower on the paralever frame. This means your seat height will be higher and then the front end looks funny with this set up. I know this from experience so I welded a shock mount onto a normal monolever swinging arm and positioned it to give a satisfacory seat height for my short legs, then used a shorter shock (Ohlins)
The price difference is down to rarity and collectability of monolever G/S frames.
Good luck with your project, mine was quite easy but I would not do it again as it can get expensive to find things like spoked wheels etc.

 

[ChasF]

Thanks ians. The idea is to put longer forks and extended swinging arm onto an R80G/S but I would like to keep it on the road whilst I do some of the chassis work. Can I use any mono frame - I'm fairly sure the geometry is the same but are there other important differences. I can reposition the top shock mount and strengthen it if that is different.

From what you say, I could use a swingarm from a road going mono but there may not be space for the shock absorber. This may not be an issue as I notice the HPN modified driveshaft doesn't have a shock absorber

 

[ians]

If you going that route I would say yes use any road going mono swinging arm and modify it to your requirements. They are cheap and plentiful but the G/S one is much harder to find.
As for frames the road models have back brake and foot peg mounts completely different and other minor points to look out for, so it would be much easier to start with a GS paralever or G/S mono frame.