Hi I want to know if it's ok to use unleaded in a k100 1984 ,I've phoned a few bike shops they say yes,but I've been on a few forums and according to the frame numbers it's leaded only,I've bought one of those catalyst thingies youdrpp into the fuel tank from ebay has anyone else used one of these?cheers

I think you will find you will be asked for the VIN just to be sure but I suspect being 1984 it will be designed for leaded fuel. In my case I run 98 Octane with a lead replacement additive.

Very early K100 really need LEADED fuels. If you do NOT use leaded fuels in these bikes, then do keep an eye on the valve clearances more often than usually done.
BMW modified the bikes so they are OK on UNleaded fuels. The modifications occurred at:
K100: at serial number 0007291
K100RT: at serial number 0024999
K100RS: at serial number 081107

Thanks I may use the fuel catalyst just in case ,just drop it in the tank and leave it,it's supposed to last 250,000 miles ,it cost £27 from good old eBay its two metal pellets enclosed in a nylon mesh sleeve,if my valve seats burn out I will know it doesn't work lol .

Hi Reddragon52. In my '84 KRS built in nov 83 i've always used unleaded, even if "one" says it's impossible... here in France its type is 95 unleaded and i ve never had any trouble with it with more than 60000 km done. So as Bert says, you just have to check your bike regularly. The kind of sorcery you're talking about seems to be strange... in fact, you could put a piece of lead in your tank, will work????

Well, they sell lead pellets for putting in your tank.......

I think the product referred to is Broquet or something similar, quite expensive and as with most things praised to the skies by some and roundly condemned by others - me I don't have a clue never having needed it.
Regards,
K-BIKE