Factory Pro's Shift STAR kit - help prevent missed shifts and damage caused by missed shifts.


Feed back to

"How's it working? Aug 2012

Yes, works great! It's a must have item.  5th gear used to only last me about a month due to missed shifts, now I'm going on 3 months since my last rebuild.

Jason Moser
Sault Sainte Marie, MI




Microbearing shift detent arm and F-Pro shift spring

yz250f  / yz450f   14-15 only
replaces 1SL arm and 90508-26080 stock spring
1. Choose your shipping method


F-Pro Shift Kit

The arm and spring kit.

The Pro Shift kit Microbearing Detent Arm and F-Pro Shift Spring will upgrade your bike.

Perfect for when you are tired of paying attention to shifting and just want it to shift right. MX. SM, Desert,  trail -

Virtually eliminate missed shifts  - Shifts 3ms to 5ms quicker

Make shifting quicker and help eliminate missed shifts. Helps address missed shifts caused by weak spring.

Helps prevent shift fork and gear engagement dog damage caused by missed shifts.

Installation: Slightly more complicated than replacing the clutch basket.

No case splitting required.

Installation Instructions - click here


Yamaha Shift Star kit worked awesome!  Not one missed shift all weekend.  Easier to find neutral, too - Which is good because I have to put it in neutral to start it for some reason. Doesn't like to start with the clutch in. With the close ratio tranny, I did a lot of shifting.

Leigh Thomas - Mojave area



Tech Tips

 Factory Pro's
patented HDJ  MAJ installation for crf / wr / yzf
 Keihin FCR carbs

Where's my main air jet and what do I do with that drill bit and tap that came in my Factory Pro HDJ kit for my Keihin FCR carb?

First step is to eliminate the fixed main air jet restriction.
It's about 40mm down the MAJ hole (left picture).

Set your 3mm drill so that it has 45mm to 46mm of drill bit exposed from your drill chuck.
(see right picture)

Remove the stock emulsion tube (that's what the main jet screws into) so that you can clean out the carb well. By only having 45mm to 46mm of the drill bit exposed, it prevents you from drilling too far.

Then, use the supplied tap from our HDJ carb kit, thread the Main Air Jet (aka "MAJ") hole.
You only need to go far enough to be able to thread in the new replaceable jet that we supply.

Clean the hole, of course.

After it's clean, complete the MAJ Modification by installing the supplied Main Air Jet and installing the new Factory Pro HDJ Emulsion Tube.

If you aren't confident in your ability or in your understanding of what you are trying to accomplish - no worry - Call us up or talk to someone locally who has more experience in these matters.
If you are still not sure, see if there's a Factory Pro Tuning Center locally or visit your favorite local dealership or shop and get some help there -

We all have to learn, and usually having an experienced person around makes everything "easy".

This modification is something similar to what we've done in many different carb types over the years, though it might be new to some who haven't used our "1.7-RK" carb kits before.


Available from:




Yamahas yz250f and yzf450f Shift STAR Installation

Remove the clutch cover. Remove the clutch assembly
(use your shop manual)
Remove the little top hat collar and don't lose it.  
Pinch the pawls together and gently remove the pawl holder. Hold around the outside so the pawls, springs and plungers stay together.  
Turn the star till it reaches the stop (it's either 6th or 1st gear). Turn the clutch shaft to get it to go into the "next" gear.

Unscrew the center stud - it takes a deep 12mm socket.


Use a 10mm socket and remove the 6mm pivot bolt for the stock detent arm.


This is what comes out.

You will replace the detent arm and the spring with new Factory Pro parts.

Put in the new Factory Pro Microbearing Detent Arm and new heavier duty spring.

A good hint is to Loctite the pivot bolt with Blue  Loctite. Not absolutely required, but a nice touch.

Lever the arm out and slip in......  
the new Factory Pro Detent STAR. Install the center stud.  
There's the new detent arm and the new preproduction detent STAR.  
Here's how the shift pawl holder is assembled.

These are the spring loaded plungers.

Next, install the pawls.
Squeeze the pawls in and slip into the ID of the Detent STAR.  



Absolutely NO carb parts sold in California.

New and improved
Suzuki Teka SFI 2
with new TPS display and "MMT" Memory Module Tuner feature

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

no fax

Factory Pro
101c Roblar Drive
Novato, CA

If it's
4pm at Factory Pro it's 9am in eastern Australia.

parts information

EC997 dynamometer information

Product Support /Tech SECTION
click here

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...

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