Yamaha FZR400, 3EN / 3EN2

Finger and screwdriver Adjustable "Long Boy" extended Yamaha fuel screws

Long Boy Fuel Screw Kit  $89.95
pn: 3020m1

 with 4 new extended screws, springs, washers and o-rings.

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"Long Boy"
Finger and screwdriver adjustable extended Fuel Screw

Frustrated with trying to find an "almost 90 degree"  screwdriver to fine adjust your fuel screws for best idle and cruise?
Use Factory Pro's new "finger adjustable" fuel screws to adjust fuel screws for best throttle response. Traveling to high altitude? It's easy to lean out the lowend temporarily.

Make your life easier!

Remove old short stock fuel screws, old o-rings, old washers and old spring. The o-ring might be stuck in the carb, so, take a light and make sure it's really out if it didn't come out with the screw (or you can't find it after you took out the screw)
Use a small bent wire to pull it out if it doesn't drop out. Keep the old parts for "spares".

Each screw assembly comes with:
4 Long Boy fuel screws 
 4 new o-rings
4 new washers
4 new springs


Item Description

Sample pic of some fzr400 stacks from the R&D sessions - The production stacks are all the same length on the 400.

pn: VEL-Y01S64-1515


The 3EN uses the 1WG airbox, so the stack adapter rubbers will fit the airbox, but we need the carb bellmouth OD to verify that the rubbers will fit the carbs.


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American Flags

A sample picture of Dave Norgard's race winning 1WG fzr400 carb set with his" formally secret" Factory Pro Superflare stacks.

Boost power and response with the improved resonant qualities of hard aluminum stacks vs. resonance absorbing soft rubber stock stacks.
The Factory Pro Superflares feature an improved taper inner diameter profile for air straightening and an optimized inlet radius that promotes enhanced pressure wave pressure wave propagation and recovery rates.

SPECIAL NOTES for professional tuners concerning modified engine fzr400's:
Since a high percentage of fzr400's are racebikes or trackday bikes, with different pistons, porting and cams, the desired stack length may be different from what the stock engined 400 wants.
For modified bikes, please send a dyno chart, preferably under full load, and I'll try to custom fit stack lengths for you.
Also, please send the length of the stacks you are using, measured from the inside airbox base to the top of the stacks.
And maybe a digital picture of the stock stacks, in the airbox, too.
Factory Pro's patented "quickchange" stacks are potentially available in lengths as short as about 10mm to 80mm, in 5 and 10mm steps
Thanks - Marc


stock part numbers:

1WG airbox and snorkel
3EN intake manifolds
3EN stock stacks and
3EN emulsion tubes / needle jets

 Emulsion Tubes, nickel plated, Factory Pro

Factory Pro replacement  emulsion tube / needle jet for Yamaha 

CRZ-EMU-100160k x 4 pieces   $132

replaces original
Yamaha pn: 3EN-14141-90 and 3EN-14141-92
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American Flags

Factory Pro nickel plated emulsion tubes - longer life than original - better fuel atomization than worn originals. Cures lowend richness caused by needle jet wear.

RTR-YAM-1    $99.95

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Ignition Advance Kit

This Factory Pro kit advances the timing 5 degrees. With stock engines with stock compression ratios, there is more power everywhere. Part throttle power is better - helping corner exit speeds. Improved in-town drivability.

(sample pic)

SHFT-PRO-YAM-1  $139.95

(add $20 for ceramic bearing)


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Trans Detent Arm Kit

Make shifting MUCH quicker and virtually eliminate missed shifts. This is exactly the same kit that Yamaha Racing has used. Huge shift action improvement.

Pretty much every fzr400 and 600 aficionado has one. 

The kit requires the removal of a 27mm clutch nut - so, you'll need a:
Deep 27mm socket and an Air or electric impact wrench
If you insist on not having an impact wrench, you'll need / appreciate.......
A friend to hold the rear brake on while you loosen the 27mm nut while the bike is in 3rd (ish) gear.....

Every time I say - "I'm going to discontinue that kit." You guys, start calling and buying them again! OK- OK!! One more year!  2015!!!

:-)  Marc
User's comments



TL-float height gauge $59.95
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The only way to accurately measure float heights. Works on nearly every carburetor.

Low Inertia EC997 Eddy Current Dyno in operation in Switzerland at Pichard Racing

For Factory Pro Tuning Center locations - click here!

Tuning Hints

True Rear Wheel Horsepower
Factory EC997 Eddy Current Dynamometer


Absolutely NO carb parts sold in California.

New and improved Suzuki Teka SFI  2

with new TPS display and "MMT" Memory Module Tuner

Finally - Quick, easy, cost effective Suzuki tuning with no expensive "add-on boxes"
Suzuki cruisers and sportbikes

Please click here for more info

Contact Factory Pro
M-F, 9am - 5pm, Pacific time, -7 or -8 GMT

800 869-0497
 USA and Canada

415 883-5620

parts information

EC997 dynamometer information

Product Support /Tech SECTION
click here


Mailing / Shipping address:

Factory Pro
101c Roblar Drive
Novato, CA

And most importantly
Restart back at the HOME page and click on the red box in the top left to find the bike that you want parts for...
restart at HOME page


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EFI and Carb Tuning - Most all FI and carb tuning

by Wheelsmith Racing

Flight Training - train with AMA race winner Todd Harrington.

The Harringtons own American Flyers, one of the most established flight training facilities in the USA.

 8 locations

The Rich Oliver Mystery School will help you discover your hidden inner strength. 
It will challenge you. It will teach you a new way of thinking, and a new way of riding. You can take your riding to an exciting new level!  

We use a variety of proven drills and training techniques. 
Practicing these techniques with our Yamaha dirt track trainers will enhance your abilities both on the track or the street.  

It doesn't matter what you ride or race, the Rich Oliver Mystery School improves everyone's skill level and mindset!

WW2 vintage flying Special

Book a sightseeing flight over the Wine Country or a Kamikaze aerobatic flight or a biplane flight over famous Sonoma Raceway, the Golden Gate Bridge and the San Francisco Bay for one or two during the spring and get a free souvenir t shirt!
(NEW!  Ask about the P-40 flights!)

707 938 2444

Just tell them that you saw this on the Factory Pro website!
Northern California's most unforgettable flying experience.  No experience required.  Open weekends!

The extension of the laboratory for engines of the Swiss Federal Institute of Technology was completed in about 1935. Its architect was Rudolf Otto Salvisberg (1882-1940). He had a successful career in Berlin but returned to Switzerland after the advent of the Nazis. His architectural style was somewhat similar to that of Erich Mendelsohn. The staircase of the laboratory is in normal use but well preserved.
Edited to the tunes of Chemical Residue by Herbie Hancock.