BMW K100RS - unleaded fuel

I have a 1985 K100RS (registered in Dec 85) and the handbook, which appears
to be for the right bike, say it needs Leaded Fuel. I have seen references
to frame numbers by model in the Haynes Manual which imply my K100RS was OK
for unleaded fuel. I e-mailed BMW who replied that I should use every
third tankful as LRP, or use a lead substitute additive, but they seemed to
assume I had an R100RS not a "K" - repeated requests back to them have
solicited no response!
Does anyone know the definitive answer to this, perhaps based on an engine
number (mine contains 0285 which I believe to refer to the week and year of
the engine manufacture) which would seem to make more sense than a frame
number ( on this basis mine appears to have a production date of December
1984)?
Or has anyone just ignored any need for leaded in early Ks and used unleaded
anyway - if so - any ill efffects ?

Sorry for rambling on ....

TIA
Mike

 

In

http://www.bmbikes.co.uk/specpages/K100.htm



--
Steve Parry

http://www.gwynfryn.co.uk

K100RS SE
F650
(not forgetting the SK90PY)

 

In

Soz thats the unfaired one ..

http://www.bmbikes.co.uk/specpages/K100RS2valve.htm

for the RS

--
Steve Parry

http://www.gwynfryn.co.uk

K100RS SE
F650
(not forgetting the SK90PY)

 

Thus spake Wellsie unto the assembled multitudes:

A mate of mine has a K100 and says the following (quoted from email by
permission):

"I did look into the leaded/unleaded problem. My manual states that I can
use either, so I use unleaded (95 RON) and haven't noticed any problems.
By problems I would think that the following would happen, but doesn't:

- pinking (or pinging if you're talking to an American!)
- detiorating exhaust valve seats - I don't think this is happening because
I have NEVER had to adjust the valve clearances. They always remain exactly
the same
- overheating - never been a problem for me.

"One thing, though; I haven't done any really long journeys on it. They say
that this is when your engine might suffer if the unleaded thing is an
issue, rather than the little journeys I do round here where maybe the
engine doesn't get hot enough to cause any problems. So maybe that's it,
rather than my bike being quite happy with unleaded. But then that's what
the manual says ...

"However ... I do know that in about 1986 there were some significant
modifications done to the K. I don't remember what, exactly, but I wouldn't
be surprised if they changed the valve seats or something, because it was
about that time that people were beginning to get a bit hyped up about
global warming and other such c**p (IMHO - another story ;-), and BMW have
always been quite good about keeping up with things like this (not because
of any altruistic feelings - simply for marketing purposes).

"You might like to check your manual again and see if there is anything
about unleaded in it at all. I seem to remember that the wording can be a
bit obscure, having probably been translated by a German.

"I think your best bet is to contact someone in a BMW shop who has been
around for a long time. SPC Motorcycles in Hampshire are good, I think; I
would also contact James Sherlock, Moto-Bins and Motorworks (all easily
found on the web); these are independent BMW specialists who sell mail
order parts but also recondition engines, gearboxes and so on and seem to
know what they are talking about; furthermore they have no axe to grind.
Motorworks actually state that they are happy for people to ring them up
just for advice."

HTH

 

According to the Motorworks cattledog, pre-Oct 85 engines weren't designed
for unleaded, and the simplest and cheapest conversion is a 2nd-hand
unleaded head at 170 of your Earth pounds.

 

I have a pet theory that I apply to my bikes, if it has an aluminium head
it can run on unleaded, cast iron then its 4 star (or whatever).

Simply, an alloy head must have some form of valve seat inserts so it'll
be fine. The proof of this particular pudding is the Guzzi. I've run it
on 95 U/L since the demise of full strength 4 star. It hasn't gone bang
yet.

An old A35 I tested on unleaded lunched its head in fairly short order
(3000 miles).

 

Thank you all for your advice, I think I will just use unleaded with the
occasional tank of LRP. As suggested I also asked at James Sherlock's
whilst ordering some parts, and they said they know of BMWs made for 4-Star
that have run up to 100k without problems on just unleaded.

Mike