Siebenrock camshaft 1978 r100s

[Steven1901]

Hello all, I am a newbie to the forum so hope this post is in the correct place, and thanks for having me.
I have just bought a r100s 1978, I am wanting to fit a Siebenrock asymmetric camshaft, my engine has the long nose cam with points and, if I'm not mistaken, Siebenrock only make the cam for the later canister ignition type cam. My idea is to fit this cam as I like the extra torque. I am aware that the oil pump will need changing, new timing gears, chain and tensioner, timing cover replacement and I will fit aftermarket electronic ignition. Is there any reason this can't be done, is the crankshaft the same on both engines? are the valve sizes the same? everything is standard including valves which I plan to have replaced with unleaded friendly ones any views and ideas would be much appreciated, thanks in advance, steve

 

[mikeyboy]

I’ve done the same conversion on a few engines,
You will also need to replace the front main bearing housing as the timing chain tensioner fittings are different on the single row chain.
Essentially you are into a complete motor strip .
One thing I would say though,
I normally fit a moorespeed 328 cam as I was informed by Richard that the asymmetric cam is a bit much on a road motor and the idle is poor.(it may well be ok with a heavy flywheel motor)
His 328 cam is very good ,with reasonable low down torque and a good mid range,the top end power seems to go on forever .
I’m not sure what your question relates to regarding the valves.
Either way the rs heads will be fine as they are.

 

[mikeyboy]

I’d also add,
If you’re going to all that trouble,it would be worth considering fitting some of his omega forged pistons to up the compression.
Even better if you can fit some later nicasil barrels.
Feel free to pm me with some contact details if you’d like to talk it through in more detail

 

[mikeyboy]

This motor is pretty much exactly the same spec as just mentioned,but it’s a light flywheel motor,with 40mm port RS heads
Mated to a smooth case gearbox with late internals

 

[Steven1901]

I’ve done the same conversion on a few engines,
You will also need to replace the front main bearing housing as the timing chain tensioner fittings are different on the single row chain.
Essentially you are into a complete motor strip .
One thing I would say though,
I normally fit a moorespeed 328 cam as I was informed by Richard that the asymmetric cam is a bit much on a road motor and the idle is poor.(it may well be ok with a heavy flywheel motor)
His 328 cam is very good ,with reasonable low down torque and a good mid range,the top end power seems to go on forever .
I’m not sure what your question relates to regarding the valves.
Either way the rs heads will be fine as they are.

Thanks Mikey, great info, that was going to be my next question if the cam is as good as Siebenrock say. I think I'll go with your recommendation on the moorespeed cam as it is for road use and I don't want it to be too aggressive. The reference to the valve sizes was just to make sure both engines use the same heads basically so I am not upgrading the cam but then only to restrict its performance with smaller valves. Do the carbs need re jetting with the moorespeed cam. Thanks

 

[timeandtide]

You couldn’t have had advice from a better man.
Veritably the horse’s mouth!

 

[barny]

Good advice from Mikey and maybe worth talking to Richie Moore nice bloke and he knows his stuff.

Moorespeed BMW products

Specialising in the BMW aircooled R100 series of twin cylinder motorcycles – especially the GS series and the Yamaha XT600 Ténéré 34L, 55W, 1VJ and 3AJ models.

www.moorespeed.co.uk

 

[Vulpine2]

And IIRC Richie does unleaded friendly valves that are cheaper and better than original BMW ones...