Fuel consumption, worn jets
 

Now I know this has been mentioned in a recent thread, but I can't find it even though I've done a search.

What should need renewing on a 55,000ml. airhead with Bings, please? I've always been getting around the low 30's, well- 30 to 35mpg over the last 23 years. It did pi** me off rather when I saw in the workshop manual that it should be over 45mpg. What do other people get? While I'm about it, 3,000mls from the back tyre & 6,000mls plus from the front, is that normal?

try

this search

for lots of good tips.

Basically needle jets, jet needles, float needles, diaphragms, and all o-rings. On high mileage or old bikes the floats too - they get heavy and float a little low, but still look good.

45 mpg would be cruising at 70 or so mph, no more. Mileage drops fast as speed goes up - as does tire mileage...

Your tire mileage sounds like you're running VERY sticky rubber. OR riding VERY fast.

I've burned a rear on an R100S in 3500 miles of 100mph riding, but never worse than that with a touring tire. Sports rubber of course goes from 5 laps up...

Also pay attention to tire pressure - go by the tire manufacturer, not BMW - BMW's numbers are for 30 year old design tires, modern rubber is quite different. The manufacturers all have specs for their rubber on various bikes.

[This message has been edited by Grant Johnson (edited 26 February 2005).]

Hi, Grant
That was very useful search you quoted, it turned up trumps. So I ordered a pair of needles and jets and was then stumped as to how to take out the old needles. So back to the search once more and got the answer to that (you twist the needle 90 degrees and pull it out, you can do it by hand rather than using pliers) Neither the BMW nor the Haynes manual tells you how, so info once again much appreciated. Actually I'm disappointed that there's no visible wear on either part, but I'll go ahead and change them anyway.

I hope you and Susan and the others enjoyed your pint(s) down in the Smoke, I did use the idea of coming down as motivation to get my bike back together, but, alas, too much work involved. Bugger. See you at the UK meet later in the year.

Hi John, yep we had a great time - 19 altogether showed up, we had a few pints and a terrific Chinese meal.

Re the needles - the wear is microscopic - a few thousandths of an inch wear is worn out, and it's very difficult to see as the wear is a smooth taper.

The wear on the needle jets is impossible to spot, it's inside, but we'll assume that brass wears more than the steel, especially when the wear on the brass needle jet is on a very concentrated area, and the needle is worn over a long length.

See you in June!