800 to 1000

[MikeO]

Siebenrock kit is plug and play
It's a couple of hours work tops no other mods and it works and is as reliable as stock
It is designed to work with stock heads
Like i said mine has covered over 30k...It's still fine and has done a fair amount of off road
Spain

What a great pic...

 

[ChasF]

Thanks Garry, looking around I see it's possible to get the appropriate kit at a reasonable price and budget is always an issue. The advantages of going the Siebenrock route is that I can retain the 800 barrels and pistons which will allow me to put it back to original. I could also get some secondhand heads modified and fit Moorespeed pistons at a later date if I feel the need for more power. I'm changing the suspension, brakes and gearing at the same time and whilst I have a lot of the parts now there's still a fair bit to be spent.

Great photos BTW - I'm planning a trip to the Balkans in May on this bike if it's ready in time

 

[richie moore]

The one thing that I think is worth knowing is my pistons are the same size as BMW, the siebenrock are not, so you cant fit BMW pistons in Siebenrock cylinders unless you find some well worn ones . Also the reason Garrys 800-1000 kit feels good is the bevel drive ratio is normally lower on the 800, when you put them on the dyno they just do not make the numbers, but what do I know.

 

[chrisshrops]

hi Richie,hows your work load,as I need some of you valves in my r100 heads and a piston kitt.

 

[ChasF]

Thanks for the information Richie, seems strange that Siebenrock would go to all the trouble to use a different sized bore, and frankly, a bit of a disappointment. I'll be in touch next week re cost of exchange barrels and the head work.

 

[richie moore]

Chris I have valves and pistons in stock, email me about what you want I am sure I can help. Chas its no problem for siebenrock to make the pistons and cylinders whatever size they want, it just keeps you on there system.

 

[Garry H]

The one thing that I think is worth knowing is my pistons are the same size as BMW, the siebenrock are not, so you cant fit BMW pistons in Siebenrock cylinders unless you find some well worn ones . Also the reason Garrys 800-1000 kit feels good is the bevel drive ratio is normally lower on the 800, when you put them on the dyno they just do not make the numbers, but what do I know.

The Siebenrock kit does use standard BMW piston rings though
I would expect the bores and pistons to last up to 100k + if looked after correctly

My Basic gearing is 3.2
A monolever G/S is 3.36
A R100GS is 3.09
It does make it feel more lively especally in the monlever ( this has quicker acceleration than a stock R100GS for sure but feels too much for the primative suspension )
The Basic is spot on for this type of bike in my opinion it will still cruse at 80 no probs
And without the protection of a decent screen and fairing that pleanty fast enough
You dont want it geared too tall if you want to use it off road
I don't understand why people over gear bikes
My moded air head is running a R850GS bevel box and it's far better off road and still quick enough on the road

 

[Ras Thurlo]

great bike btw



I agree with Garry that the 3.2 (32/10) gearing is a great all round gearing for an airhead GS.

Having experience with the 3.09, 3.2 and the 3.36 (37/11) - I think 32/10 is the best for general dual sport use. I have tried taking my 3.09 geared bike offroad and it really sucked. The 37/11 is a bunch better for the dirt but not right for the road.

A related topic in gearing - a lot of people go for +5% 1st and 5th when modding their GS. I did this too for my dirtbike, because I was going along with the received wisdom. For me a taller 5th is a no brainer, but I dont like the lower first.

Yes its great to have a low geared first for a heavy bike like an airhead off road, I just think its better done through the FD ratio. The lower 1st may make some sense if (as Gary pointed out) a lot of people seem to want to have too high a final drive ratio and one final drive.

I found that the lowered first leaves too much of a gap between 1st and 2nd and often you are forced to hold first for far longer in order not to be caught out in low revs second. So I will be putting my 1st back to OEM and will be keeping 37/11 and 32/10 final drives according to what riding I am doing (enduro vs dual sport). These two ratios have a 5% differential, which in effect means lowered 1st on a 32/10 is identical to OEM 1st on a 37/11.