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I need a new main jet. The old one is 140, but the dealer (and Max BMW parts fiche) only show a 135 or 145. Which way to go? I assume 145 is larger, uses more fuel and whichever one I get, I should get two so the two sides match, correct?

The main jets should match, what is wrong with the old ones? I'm sure Bing can sell you a 140, do you know what was fitted originally, some differeance between a 135 and a 145?

My Bing manual shows 135 and 140 for the R75/5 and 145 for the R75/6.

davidaid wrote:I need a new main jet. The old one is 140, but the dealer (and Max BMW parts fiche) only show a 135 or 145. Which way to go? I assume 145 is larger, uses more fuel and whichever one I get, I should get two so the two sides match, correct?

According to the Haynes manual all R75/5 and R75/6 bikes take the 135 main jet. The R75/7 takes a 145. There is no mention of a 140 main jet.

So it appears that some previous owner has swapped main jets at some point for some unknown reason. My own approach would be to rejet both sides back to stock, which in your case is a 135. And yes, whatever you do both sides need to be jetted the same.

But it doesn't stop there. Since you don't know what the previous owner was up to he might have made some other changes. In an effort to accomplish his objectives he might well have put in different needle jets, needles, or raised or lowered the needles. While you have the carb (carbs?) apart I would want to find out what the needle jets, needles, and needle positions are. I used the plural form because it might not be a good assumption that the previous owner made identical changes to both carbs.

What part of Idaho are you in davidaid? During the summers I am sometimes around the Boise area.


Ken

chasbmw wrote:The main jets should match, what is wrong with the old ones?

I broke one.

I just ordered the 135 after consulting here and with the dealer and I needed a new o-ring.

Ken - I am in the Boise area, too. I seem to recall some posts last spring mentioning you were moving here?

Thanks for the information about the needles. The dealer cleaned them all up a couple of years ago - new floats, diaphragms, etc. but maybe they didn't replace those if they "looked" okay. In any event, everything ran fine when they were done up until now. That's what I get for letting it sit!

davidaid wrote: Ken - I am in the Boise area, too. I seem to recall some posts last spring mentioning you were moving here?

Yes, I've closed on a house here, near the airport. My master plan is to spend late spring, summer, early fall and the Christmas holidays here in Boise. The rest of the time I'll be in Big Cedar Oklahoma, the timing arranged to keep on keeping on with the rallies at my place.


Ken

Ken likes the wood nymphs too much to abandon AR.

Duane Ausherman wrote:Ken likes the wood nymphs too much to abandon AR.

So true, except for the AR part. I sometimes get confused myself, but I'm pretty sure I live in OK.

I've been looking around to see if I could spot any sign of the local covens of wood nymphs. But of course I know very well that if they're around they'll spot me first and decide if I'm anybody they might want to show themselves to.

Now, down around the Boise river, where I was looking, I did spot some delightful ladies washing clothes in the river. But I also spotted right away that they were Sireens, not wood nymphs. The big clue is that they were wearing clothes, whereas the wood nymphs prefer to be moon clad.


Ken, feeling an urge to get back to the Kiamichi wood nymphs back home in Oklahoma.

Ken in Oklahoma wrote:
Yes, I've closed on a house here, near the airport.


Ken

Well, at least you'll be close to Big Twin. Pretty sure there are no wood nymphs there and the only Sirens are on the cop bikes. Let me know if you want to help work on my bike - you know, if you get bored. I've got a laundry list of minor things it needs that I will at least be posting here for the superb help.

I also meant to mention in my last post that Fred from Big Twin is going to check tonight to see if he has a 140 jet in his collection. I thought that was cool of him to do. They're good folk.

Ken, you should host one of the rallies in Boise. That way some of us PNWerners and some of the left coasties could make it.

Of course you must find some Idahoian Wood Nymphs first.