Petrol...Valve seats etc...

[jonnie comet]

Just sat sitting thinking.......Question re 70's airheads......Will they run on standard pump petrol, or do they need additives/hardened valve seats etc?.........Carrying on on this theme, how far back do you have to go (series 5/ series 6/ whatever) do you have to go, before you need to worry about this sort of thing?

Going to look at a 'bike, and don't want to make a complete twat of myself by asking the vendor this question, so I thought I would simply make a complete twat of myself here.....

 

[cookie]

i think hardened seats came in sometime mid eighties.

best wait for someone who knows for sure though.

 

[Ogmios]

recieved wisdom
(a phrase that to me means; i keep hearing it from 'experts' / but have no proof ) is that at that age, there's so much lead embedded in the valve seats that you wont need to worry about it.
This based on a mileage of 40thou+ by that age.
Oh - i think unleaded valve gear came in 1986 with the mono rear models.

i've had an '81 R65 and an '80 R80/7 - both with them miles or more on them and it never worried me nor caused a problem.
BUT,
as i say - this is unverified "recieved wisdom"
Good Luck.

 

[Kenny]

As a general rule of thumb...if it is the older twin shock airhead then it will need petrol additive but the heads will also be well hardened by now from usage

I believe very early monoshock ( first couple of years ) also needed additive...but I can't confirm this...can't see BWM building a new model only to change it to hardened seats a couple of years later

 

[John Roberts]

Mine is an '82 RS, I use the Castrol additive mainly because it's so easy to use, the dispenser is calibrated in litres so you use one mark per litre of petrol you put in. Or twenty marks for twenty Litres.

 

[Ogmios]

forgot to say

also had an '86 R65 Mono which definitely ran on unleaded.
i checked that specific point when i got it.

 

[cookie]

the whole sorry story here

 

[jonnie comet]

Many thanks for the replies gents.....Interesting stuff.....Appreciated....

Staying with this, has anyone had experience with these things?

http://www.motorworks.co.uk/bmw/products/product.php?f=b&bke=bmw&q=broquet&x=17&y=6

Seems like a 'fit and forget' unleaded replacment jobby.....

 

[bustupbiker]

Snake oil me thinks..

 

[John Roberts]

I had a look at the valves and seats of my '82 R100RS this evening. NO sign of valve seat pocketing (but it's only done 65,000mls)

There was just a little pitting, on the inlets, actually, I'd have expected more on the exhaust valves and seats so I ground them and they came up quite quickly to the correct dull even finish.

What worries me now is whether I have knackered the hardened surfaces as Ogmios says in post 3?

PS Just thought you'd like to know that I broke an oil ring trying to put the piston back. Bugger. You know, a trouble shared is a ... bollox, no it isn't.