Honda GB500


John Barret's GB on the EC997 dyno

Carburetor Tuning Kit

CRB-H54-1.0   $89.95

1. Choose your shipping method


Standard drop-in carb kit

This Factory Pro Carb Recal Kit, when properly tuned, adds more low-end / midrange and if the proper main jet is selected, more top-end power. Works with stock and aftermarket exhaust systems as there is a selection of main jets supplied, along with suggested settings for initial installation.
Easy to install and tune - no slide drilling.

Pilots jets - 26 series original   21 series - a bit longer
The longer 21 Series pilots can be used in the GB500 carb.



Pro Shift Kit - Transmission Shift Improvement kit

gb500  89-90
xr500r  83-84
xr600r  83-00
nx650  88-89
xr650l  93-13

replaces oem 24430-MG3-000 arm and 24435-MG3-010 spring

SHFT-PRO-H74-KT   $139.95

F-Pro Microbearing Detent arm and F-Pro z95-h74 shift spring
(does not include clutch cover gasket)

1. Choose your shipping method


(415) 883-5620

Virtually eliminate Missed Shifts

Imagine being able to find neutral easier

Make that downshift on that nasty uphill instead of finding a false neutral.

Help prevent damage to shift forks and  gear engagement dogs caused by
the mechanical shock of missed shifts.

Make this big Honda single shift loads better with an hour's worth of labor.

The F-Pro Microbearing Shift Detent Arm and F-Pro Shift Spring will improve shifting and virtually eliminate missed shifts for less than $100.

The problem with the transmission is that there is too much friction involved in the rotation of the shift drum. The shift mechanism is just too slow - causing missed shifts, especially 1st to 2nd and false neutrals.

The F-Pro microbearing arm decreases the friction, makes the shift drum rotate quicker and into the full shift gear position in less time - helping prevent missed shifts.
Each missed shift stresses the gear engagement dogs and slots, bends shift forks and otherwise causes extreme shock loading to the entire drivetrain. In other words, "breaking things".

This kit will not fix a broken transmission. This kit will help prevent damage to a good transmission caused by missed shifts - helping a good transmission stay "good".
If the shift forks are already bent and the gear engagement dogs are already rounded, it's too late - and just split the cases and replace the forks and gears. 

This is a Factory Pro "Pro Shift Kit" and includes the "Proven by" well, I can't tell you because they asked me to not tell, Factory Pro Microbearing Detent Arm and F-Pro spring.

Does not include the clutch cover gasket
(usually required unless you are extremely lucky - but it usually breaks by the lower, left case studs

Takes .5 to 1 hour of actual work and attention to install.

 No case splitting required.
Does not even require clutch basket removal.

To install the arm and spring, it requires removal of the right footpeg, oil line, oil filter and clutch cover, etc. - then the detent arm and spring are accessible, just below the clutch basket. Clutch basket does not have to be removed.
There are important washers, important dowel pins and such that need to be kept track of, so,
make sure you have a Honda Service manual before removing the clutch cover.
We don't supply installation instructions, and the Honda Service manual is your best friend.

Call 415 491 5920 or 415 472 4962 for install help.

Virtually eliminate missed shifts - Make shifting smoother and better than some new bikes.

We specially make a Microbearing Pro Shift Kit for the models listed to the left.

F-Pro Microbearing Detent Arm
F-Pro Detent Spring
DOES NOT include shift cover gasket

1-2 hours to install - it's under the clutch cover.

MG3 replacement arm and spring


pic supplied by Chuck Wallace.




True Rear Wheel Horsepower® Factory EC997a Eddy Current Dynamometer

Send us a picture of your bike/
Include your name, city, bike year and any other information that you would like to supply for background information.
Click here

.John Barrett's GB500 at Wheelsmith Racing
San Rafael, CA     June 10, 2010



On the EC997 dyno - Tuned in realtime and using a 5 gas EGA.



On the EC997 dyno

Installing the carb kit and view of the slipon muffler


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.