FIRST - carefully measure the length of your needles from the slide body to the tip.  You will need to install the new ones to the same position.  The needles will install in 4 positions (4 lengths) which affect the mid-range fuel/air mix.

The needles have tricky notches that are engaged by that retaining clip. To disengage the needle from the clip, you rotate the needle 1/4 turn while gently pulling simultaneously. It will move only to the next tricky notch and stop. Rotate again 1/4 turn while gently pulling, etc.  After the last notch, it will come out. The needles can be slippery, so your dish washing rubber gloves can be handy.  New one goes in the same way, in reverse.

PS:  I found this handy chart, which provides the needle length for each notch. Most bikes use notch 2 or 3.  I know this chart works for my 40mm Bings. Are 32’s the same, anyone?

Not clear to me which you want.....

► David described how to remove and adjust the Needle.

► The Needle Jet is above the jet block. Remove the float bowl. Use a 10mm box wrench to unscrew the jet block. This will remove both the jet block, complete with Main Jet. The Needle Jet is held in place by the block. If it doesn't drop out with the block, you can rap the top of the carb with a plastic screw driver handle and it should drop right out. The jet is simply a loose slip-fit into the body.

Thank you for seeing this in the wrong category, I've asked for it to be moved to the technical section under "My Airhead needs help".

I know the two parts are confusing needle jet and jet needle.  If i mixed them up my dyslexia shines again.  I am working on the jet needles, they are notched (worn) where exposed below the slide body and should be replaced. 

Dave, the table is very helpful, needle is 47 mm  

was able to remove jet with your info.

see attached photo

If the Needle is worn because of 40 years of banging around, then may I suggest that the Needle Jet is equally "banged up" ?

After all, the Needle only touches the Needle Jet. 

Good point, i have them on order too, 2.66.

thanks

An 1981 RT is well into the EPA and DOT mandated carb leaning era that started in the mid-70's. Pollution and fuel efficiency were mandated over performance or engine life. 

May I suggest that this is a good time to look at the European jetting charts for earlier RT models (found in such places as the Haynes BMW Twins manual). You will see that US models are significantly leaner than the exact same European model. By returning to a ever so slightly richer mixture I think you'll find that the engine actually performs much better. 

Just some food for thought.

For my ‘78 R100RS engine, I have settled on 2.68 needle jets w/needles in position #2. Gets great mileage, with no issues like pinging or running hot. Seems very happy. Plugs look good. Idle jet is stock #45, and main jet 165.

Currently my carbs have: needle jets;2.66 , idle jet;#45, main jet; #160, jet needle; set on #2 notch (47mm). 

Will going to the higher needle jet and main jet help achieve the better performance? 

thanks,

@red-horse Higher number, larger jet. 

According to the Bing chart, your jetting is “stock”, as supplied with carb numbers 113/114. I don’t feel qualified to recommend any changes. I’ve only heard/read that the US models were jetted pretty lean for emissions compliance. 

The main jet will only affect the last 1/4 of the throttle. Don’t spend much time there. The needle jet is where we ride. For me, it’s a stretch to imagine that you would perceive any performance improvement going to 2.68 needle jets (but who knows?). If anything, I would think maybe a little happier, cooler engine. A note; according to Snowbum, moving the needles one notch is equivalent to moving three needle jet sizes (like going from 2.66 to 2.72). So, I’d keep your needles at position #2. Changing needle jets makes a very small incremental difference = fine tuning. 

Anyone with experience in this area?

Dave and Wobbly,

thank you both for following this subject.  I believe that the next step up in jets will make the bike run cooler, as you both said.

I'm in the process of replacing the push rod tube seals and have the carbs off for a through cleaning.  I'll replace the jets et al  when everything is put back together.  

Happy New Year

Mr. Wobbly, maybe this thread would better serve the membership if it could be moved to the "wrenching" or "my airhead need help" section?

thanks again,

redhorse

81 R100RT 

Posted by: @red-horse

Mr. Wobbly, maybe this thread would better serve the membership if it could be moved to the "wrenching" or "my airhead need help" section?

thanks again,

• No thanks needed, I'm simply here to help.

• I was able to secure larger jets by fishing around in the Max BMW parts fiche within other models. Believe I ended up with 2.67 needle and 5 points larger on the Main without moving the needle position on a '79 RT. The low end performance increase was noticeable and it added color to the BP7ES plugs.

• Good idea. Although flagged as a Moderator, I do not have "Move" permission. But a request was made to Scot to do that.

Have a happy new year.

All these folks with fuel injection these days, they miss out on all this fun!  I said I’m not qualified to make jetting recommendations, and that’s true, but I can say if it were my ‘81 RT, I’d give it a go with 2.68 needle jets. And 165, or even 170 main jets wouldn’t hurt anything.  Might help when you pull out for a fast pass.