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What are all these?

Jethro

Jethro

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I'm getting some parts from Bike Bandit and while browsing the Mikuni Jets noticed this page:

http://www.bikebandit.com/partsbandit/product~pf_id~2471820~dept_id~811775.asp

Now of course I know what these are, but if you go to order them, it appears there are many different sizes of them. I didn't know these changed size- does anyone know the rhyme or reason of this? Does a bigger main jet or needle require a larger needle jet housing or what?
 
I have never heard of changing them as a jetting issue, but one of teh carb tuning websites (can't remember which one) mentions that the needle sleeves can wear from round to oblong, which changes the fuel metering while on the needle.

D.
 
Gee-s-is Posted: Mon Feb 28, 2005 12:19 pm Post subject: jets

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If your main jets excceds what the needle jet can pass in fuel then of course you have to increase the size of the needle jet or change the size and tapper of the needle it self, and yes they do wear out, if you have ever done a set of VM carbs the needle its self is forced into an offset towards the back of the slide, this is done with a needle plate with a dimple on it that does this, so the needle doesn't vibrate around in the needle jet causing surgeing, so if you pull a set of carbs apart then make sure the dimple on the plate faces down
Click to expand...

Yeah but this isn't the needle, it's the brass needle housing. Or maybe Bike Bandit just has thier pictures messed up? Maybe they actually mean the needle itself, not the needle sleeve? The link shows a picture of the needle sleeve and shows about 12 different sizes of it labled A,B,C etc.
 
I beleive the proper term is emulsion tube, but I'm not sure, may also be the needle jet, vs the jet needle. I always mix those up. Anyway, the tube can wear from the needle moving back and forth, causing the round whole to go oblong. When that happens you need to replace them in order to get accurate jetting. Some carbs seem to be worse at this then others, and I personally have never had to replace one. You can pop them out of your carbs by taking out the main jet and using a small dowel to press it thru the carb body.
 
I beleive the proper term is emulsion tube, but I'm not sure, may also be the needle jet, vs the jet needle. I always mix those up. Anyway, the tube can wear from the needle moving back and forth, causing the round whole to go oblong. When that happens you need to replace them in order to get accurate jetting. Some carbs seem to be worse at this then others, and I personally have never had to replace one. You can pop them out of your carbs by taking out the main jet and using a small dowel to press it thru the carb body.
Click to expand...

Right, but does anyone know why there are 12-15 different sizes of emulsion tubes? Q-4 to O-8?

No one knows?
 
Finally I know what you're talking about Geoff. :lol:

You can change the needle jet to change your jetting just like you can change your jet needle. There is a slight difference in what one will do over the other, and normally changing the needle is easier, and effective. I don't remember the exact situation where you would choose the tube vs the needle.
 
lhanscom said:
Finally I know what you're talking about Geoff. :lol:

You can change the needle jet to change your jetting just like you can change your jet needle. There is a slight difference in what one will do over the other, and normally changing the needle is easier, and effective. I don't remember the exact situation where you would choose the tube vs the needle.
Click to expand...
I agree.
I've called them emulsion tubes, bleed pipes, needle jet.
Like all jets, they come in different sizes. Regular people like us generally never need to experiment beyond jet needle changes. We rarely try throttle valve cut-away changes either, but you can.
The needle jet atomizes the fuel before it enters the carb throat.
 
Do K&N jet kits come with replacment emulsion tubes? I thought they only had replacement jet needles to use the stock emulsion tubes. Maybe I'm going too far into this, but I thought I knew everything about my carbs and the parts available for them. I've only had them apart maybe 20 times.

Joe Nardy Posted: Mon Feb 28, 2005 6:04 pm Post subject:

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For different carburetors?
Click to expand...

The page listed is for all VM30-34 carbs- basically the same carb.
 
The jet kits I've seen just come with needles, no emulsion tube.
 
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