Mikuni Keihin Hitachi home
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Hitachi emulsion tubes / needle jets

Factory Pro manufactures stock replacement, nickel plated, emulsion tubes for the 750 and 1000 XV Virago's and maybe the 920.

Yamaha

XV750

Hitachi		 Factory Pro nickel plated replacements in stock CRZ-EMU-XV750

for Hitachi carbed bikes

$60 / 2pcs

 


International buyers will be billed an additional $16 for shipping
Yamaha

XV1000
XV1100

Hitachi

 Factory Pro nickel plated replacements in stock CRZ-EMU-XV10/11

for Hitachi carbed bikes
$60 / 2pcs


International buyers will be billed an additional $16 for shipping

 

Hitachi  "Emulsion" Tubes Worn needle jet orifice
emuwr3.jpg (9351 bytes)

 

 

This is enough wear to cause problems.
Top Left side - This is a picture of the needle jet area of an emulsion tube from a stock 38mm CV Mikuni carb as installed on Ducati,  Yamaha TDM/TRX 850, YZF750, FZR1000, etc..
It has approximately ~5000 miles or  8000k usage on a Ducati or TDM 850 - WITH A STOCK Aluminum NEEDLE.
Notice that the center hole is noticeably worn at the "V", the 12 o'clock position, which would be towards the engine, as installed in the carburetor.
This causes 2 conditions. First, it allows more fuel to enter the carburetor, as in using a needle with a small base diameter AND the fuel that enters the carb - it enters in larger droplets, resulting in poor combustion.
We carefully check needle jet condition on the vehicles when we create and install carb recalibration kits.
If you install a kit and it is much too rich at low rpm, and lowering the fuel level 1mm doesn't fix it, check the needle jets for any wear - it's not uncommon.

Additional:  Eventually, in the 36mm horizontal mount and 38mm downdraft Mik's, the carb body plastic insert, where it holds and guides the slide from rattling back and forth, will wear out - allowing the slide to rattle and bang the needle fore and aft in the needle jet orifice - causing accelerated NJ wear. This wear is biased towards the lowered slide position - as in idle and low rpm areas - as in "in-town", "stop and go" driving.
The gist of that is that you may only get 5,000 miles out of your needle jets in your VL / VS bike that you use for cruising 4th Street and hanging out at McDonalds - but your long distance , highway cruising buddy might get 25,000 miles before mileage deteriorates to 25mpg or worse.
I haven't heard of anybody who has got the "60,000 miles" that some Tech Bulletin claims is normal with a stock needle...... I WILL change this if I ever find that person who made it to 60,000 miles on his/her VS / VL and has the original needle jets/emulsion tubes. In fact - I'll GIVE any carb needle jet rebuild to any VL 1500 owner who makes it to 60,000 miles on the original needle jets!  Marc

Slide Guide Wear:
Example: The original needle jet lasted 5,000 miles in your usage. After replacing the worn emulsion tube / needle jet, they only lasted 3,000 miles or less. That's because the slide guide slot in the carb body is worn - not because of the emulsion tube or needle is bad.
Even Suzuki knows that - even though their highly optimistic estimate of 60,000 mile life with a stock needle is based on perhaps a VL1500 or VS1400 run at high speed on a highway.

A "step" inside of the needle seat in the carb slide?
It's there in virtually every Mikuni CV carb. It's supposed to be there.
It's to try to keep the needle bearing onto only one side of the needle jet - otherwise, the needle bangs back and forth onto both sides of the needle jet at idle and low rpm, instead on only one side.
Of course, if one "notches" the plastic needle shim, they are lowering the needle about 2 clip positions and that will lean out the mixture, but that doesn't really permanently fix anything.

Be famous! (for something besides "that"!)
Have an emulsion tube that's worn? Send it in (in a padded envelope) with make, model, mileage, usual use (in-town, commute or sport), your name and the difference between running before and after replacement. We'll put some of them at the bottom of this page.

US=USA
CA=California
CN=Canada
Aus=Australia
SW=Switzerland
FR=France
UK=United Kingdom
Euro=all European countries
 
 

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