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Needle and needle jet
Posted: Wed Nov 07, 2012 7:33 am
by SteveD
My needles and needle jets haven't been changed for what must be getting up to 80K kms.
I have the bits so I thought I'd change them out tomorrow.
I'm planning to remove the carbs from the bike and drop the jets in from the bottom? The needle is straightforward.
Any potential problems that I should avoid?
Re: Needle and needle jet
Posted: Wed Nov 07, 2012 7:50 am
by Kurt in S.A.
When you reinstall the assembly from the bottom with the needle already in place, be sure the jet engages the needle down the center and also be sure that the atomizer (the part on the left) fits up into the small hole in the throat of the carb. If not, then you could bend or shear things when you begin to tighten the assembly into the carb. And put a small amount of silicone grease on the o-ring.
Kurt in S.A.
Re: Needle and needle jet
Posted: Wed Nov 07, 2012 9:41 am
by montmil
What Kurt said. Plus...
Be cautious in removing the needle jet assembly. Some heavy-handed types have rounded off the soft brass "hex" and created more problems for themselves.
Re: Needle and needle jet
Posted: Wed Nov 07, 2012 1:13 pm
by barryh
No absolute need to remove the carbs unless you have to for other reasons. I just had my needle jet assemblies out for a clean up and did it with the carbs in position. No problem provided Kurt's caution is observed. My tip would echo Monte's. If the assembly has not been removed in a long time the gunk from the crankcase breather can cause some corrosion that makes them tight and if really siezed there is a risk of shearing the boss out of the carb. First time I did mine I had to spend days with penetrating oil and heat cool cycles to get one of them out safely. They cleaned up Ok and are in fact the very same parts you see in the picture above. I now take them out annually for a clean andI use a light touch when screwing them back up. Just tight enough not to fall out and no more.
Re: Needle and needle jet
Posted: Wed Nov 07, 2012 5:59 pm
by georgesgiralt
Hello !
If the needle jet and main jet holder is stuck, DO NOT force it.
Take the carb out of the bike, remove the head and piston and slightly seize it in a wise.
Then hot around the stuck part with a hot gun, slowly and gently. And try to undo it using a 6 face socket.
If you exercise patience and subtlety, using a very soft hammer give light but brisk taps on the socket's handle with the handle in tension. it should come without problem. If not remember that this brass piece is cheap and the carb body is not. So try to preserve the carb body at all cost......
When I had to remove them on my R65, one came easily the other was a pita and I had to spend a lot of time heating the carb to get this sucker out. Even with the 6 face socket, it came out damaged so I bought a new one in order to be sure I can remove it next time...
Re: Needle and needle jet
Posted: Wed Nov 07, 2012 9:01 pm
by ME 109
Excellent precautions and remedies.
Re: Needle and needle jet
Posted: Wed Nov 07, 2012 10:10 pm
by SteveD
Thanks.
So if I leave the carbs on, reinstall the stack from the bottom first, then install the needle/slide/diaphragm from the top ensuring the needle is well centered, I'll be right!
Re: Needle and needle jet
Posted: Thu Nov 08, 2012 6:13 am
by SteveD
Boy have I found some gunge in there. Thick dark sludge and some small bits of rubbish likely from the tank. The left MJ was partially blocked too.
Jeff, what number carbs have you got? I have 94/40/111 &112. MJ 160, needle jet 2.66, needle on 2nd notch.
I have a spare pair of carbs 94/40/103 & 104. They're very clean and the floats are new. They have the same numbers on the small parts. I might swap 'em over and give the others a good clean.
The spare carbs appear to have steel needles and they don't measure much different to the new brass looking ones I have, though just a tad longer by about 1mm. Should I bother swapping them out for the brass ones d'ya think? Keep the good ones for the set for cleaning?
In my little box of carb bits accumulated over the years, I have MJ's 160,165,170. I also have needle jets 2.66, 2.68 & 2.70. If I leave the needle on the second spot, what's gonna help the midrange? Some say more is best, others say just before too lean is best.
Staintune touring mufflers, stock airfilter (though the K&N is ready if needed 
)
Oh, one more 
In the absence of any carb cleaner, what might make a reasonable substitute? I can get carb cleaner tomorrow. My small cheap ultrasonic cleaner from Aldi has cleaned up the brass bits very nicely.
Re: Needle and needle jet
Posted: Thu Nov 08, 2012 8:46 am
by ME 109
Not sure of the numbers Steve, won't get a chance to look until tomorrow.
I have 160 MJ
2.68 NJ
2nd notch for me too. I believe that to be the correct notch for our carbs.
I think carby cleaner is best.
Re: Needle and needle jet
Posted: Thu Nov 08, 2012 8:49 am
by SteveD
Thanks Jeff. I might go from the 2.66 to the 2.68 NJ's and go get some carb cleaner today sometime.