Tuning -

Carburetion and Ignition Tuning

std and kit carbs

Ignitech Tuning

Vince and Kim Rolleri, Huntington Beach - Feb 2012

For many years, Factory Pro and the EC997 dyno were fixtures at the AMA races - tuning most all the non-dynojet sponsored Supersport teams  -  and, under cover of darkness and early in the am, more than a few sponsored teams that would show up in street clothes and "naked" bikes  using the EC997 dyno and it's high speed 4 and 5 gas Exhaust Gas Analyzer.

The results were superior enough that at VIR, the dj guys started threatening teams with loss of free power commanders if they caught them track comparing dj vs EC9977 produced maps. - because the pit scuttlebutt was that the EC997 maps were better and smoother for the rider.

Wheelsmith Racing in northern California is one of the few dyno facilities experienced in sorting out tz and rs 250's - having tuned, even for Rich Oliver and Vince Rolleri. Wheelsmith is one of the few tz250 dyno facilities with a load dyno and a 5 gas analyzer.

So - you want to dial in that part throttle jetting for silky smooth part throttle.
Get the right pilot jet size.
Find the right main jet stagger.
Get those powerjets finally sorted.
Figure out what ignition timing you really should have.


Historical 2 stroke 250gp horsepower chart by Factory Pro



Hey Marc, 

Just wanted to drop you a line after having a chance to go and roll around on my scooter.

Some good news and bad news.  Actually, one follows the other.

The good news:  the bike is WAY faster.  It felt faster (wheeling out of corners) and felt really good with the throttle response.  And, my subjective opinion is validated by my datalogger.  See attached, x-axis is track position <m>; y-axis is speed <kph> .  The PURPLE curve is my fastest-ever lap and the BLUE curve was the third lap in my first session out after our tuning.  You can clearly see how much harder the bike is accelerating…and check out the difference in top speed just after the start/finish straight (first peak in the curve…a full 10kph!). 

So, the bad news:  the bike is WAY faster.  J   and, I don’t think I realized just how much faster I was going into each corner, so I overcooked it a bit into one of the faster corners on lap six, lost the front and crashed, thus ending my first weekend a bit earlier than expected.  But, I wont hold you accountable for that one!! J

So, i need to regroup a bit, get everything back in shape and take advantage of my newfound speed more effectively.  Still have a few things I’d like to test. 


Vince Rolleri
Western Region Manager

19072 Tonga Lane
Huntington Beach, CA 92646
Office: (714) 963-3542
Fax: (508) 836-3223
Mobile: (508) 951-9643

Email:  vince.rolleri@dovermotion.com


Website: www.dovermotion.com

Improve shifting - upshift and downshift

Hybrid Ceramic Microbearing 
detent arm
(fits 92 and up)


replaces yam #3XV-18140-00    

1. Choose your shipping method


Steel Microbearing
detent arm
(fits 92 and up)


replaces yam #3XV-18140-00    

Factory Pro TZ250 Transmission Detent Arm

Decreases shift duration by 5 to 10 ms.
(Don't forget to lower quickshifter kill duration!)

Dramatically improves downshifting.
Virtually eliminates missed shifts.
Lessens foot pressure required to up and down shift.


So, there you are.  - with a real racebike and all.........

How could a company like Factory Pro could POSSIBLY ever improve on a genuine Yamaha RACE part! Heck! Factory Pro is in northern California - NOT even in Japan! How could Factory Pro even think that they could make a better part than the other "factory" guys????


The goal was to make the TZ/TZR shift as well as an RS 250 Honda. Yeah - now it's better than the RS.

Compared to the "notchy" stock Yamaha shift action, there is no comparison.

Hmm. A couple of questions to a few well known Yamaha tz mechanic type guys. "Yep. The Yamaha's shift action is notchy. Yep. Sure is. Yep. Always been like that. Rider complains a lot on some tracks. Yep. We don't know how to make it much better."

With the Factory Pro MicroBearing detent arm, instead of having to anticipate downshifts into low speed corners, you can downshift easily, without additional thought being directed to shifting, leaving more mental energy to devote to race strategy.

MUCH easier and quicker downshifting and improved upshifts.

The Factory Pro Microbearing Detent Arm reduces the rotational friction so that the shift drum rotates quicker -  the gears engage more  reliably under super quick downshift conditions.
 By decreasing the number of missed shifts, shift forks and engagement dogs last longer. Same feature as our exclusive "streetbike" kits.

The Factory Pro Microbearing Detent Arm removes friction for the quickest shifting short of an air shifter.

This is a limited production part number and includes: Factory Pro Microbearinged Detent Arm, decreasing the effort required to shift and decreasing the number of missed shifts. This kit DOES NOT include cartridge gasket or a stronger detent spring.

I guess 250 guys want a box now that will control servo motors and power jets based on engine rpm and throttle position. I'll work on that....... Hmm... I guess you REALLY want 3d mappable ignition timing...... as that's the major limiting factor to power production on the high compression, leaded fuel, USA spec, TZ250's  Note: IGNITECH does all that and is cost effective to buy and not difficult to tune, but takes a while to sort out for each bike.

I guess it's a not a secret that we sorted out a whole passel of 250's in the 2002 - 2003 AMA seasons on our High Speed EC997 Low Inertia Dynamometer at tracks all across the USA, too.

Try to find even consistent  USA top 10 2003 250 person who didn't benefit from the  EC997 dyno's use.
There IS ONE guy, but, you'll have to find him.
First one to find him gets a 50% Detent Arm discount!
(April 2012 - nobody has found him, yet)

If you are doing any 250 dyno tuning at all and were considering using a "dealership level" dyno - it's pretty misleading - as final settings best dyno power settings in a Sweep Test inertia dyno (i.e.  dj dynos) are 10% to 20% off of the correct settings as per the real world results and a High Speed EC997 dyno optimal settings -


BTW: EC997 Dyno was used and tested on by AMA / Stargel Racing's Chuck Sorrensen, Rich Oliver, Jason DiSalvo, PM's Roland Sands, Bruce Lind, Jeff Malone, Ed Sorbo, Simon Turner, Greg Esser, Corey West, Sandy Noce, Sean Wray, Kent Gormat, Glenn Christianson and many more....



Stock Detent STAR pics below are for reference only.
Information only

Detent "star" profile
TZ250 92(ish) to 2006

detent_star_tz250_92_01_3XV_inside.jpg (11395 bytes) detent_star_tz250_92_01_outside.jpg (10677 bytes)

hold down bolt: 8.0mmx1.25mm

dist across small pawl indents: 32.0mm
dist across peaks:41.0mm
mount hole (backside) 16.97mm
overall height: 21.3mm


Rich Oliver #1


EC997 Dyne System tuned

John France


EC997 Dyne System tuned

Chuck Sorensen #1

Stargel Aprilia

EC997 Dyne System tuned

Greg Esser


EC997 Dyne System tuned

Simon Turner #3


EC997 Dyne System tuned

Bruce Lind


EC997 Dyne System tuned

no pic Jason Di Salvo

Cruise America rs250

EC997 Dyne System tuned

 Factory Pro proved that  dynos CAN WORK in tuning these high strung GP machines.
The EC997 dyno is the only dyne system that was primarily designed to tune to the "Nth" degree and that's what riders, racers and tuners want.

Common "dealership level" dynos just don't do the job.

In other words, if we could consistently make all of these top ranked 250 Grand Prix riders happy - the EC997 dyno and it's own integrated Hi Speed 4 gas EGA should be the the Number 1 choice of any aspiring tuner.

Kit 250 email

2004 Congratulations!!

#1 Rich Oliver

2004  250 Grand Prix Series AMA National Champion!

Unlike heavy, 900lb behemoth dynos, the Factory Pro Low Inertia Eddy Current Dynamometer develops performance on 2 cycle engines!

2003 Congratulations!!

#1 Chuck Sorenson
Stargel Aprilia / Factory Pro Aprilia

2003  250 Grand Prix Series AMA National Champion!

Unlike heavy, 900lb behemoth dynos, the Factory Pro Low Inertia Eddy Current Dynamometer develops performance on 2 cycle engines!



Subject:  Thanks from Bruce Lind
Date:  Wed, 20 Jun 2001 23:55:57 EDT
From:  Tzrider2@aol.com
To:  Marc@factorypro.com

but I am concerned about the ignition cutting out or misfiring under load.

I make a decision to revise a long standing personal position and run my bike on the Factory dyno. If it does not misfire under that load, then it won't on the track. This will also give me a chance to see what the exhaust gas analyzer shows for the fuel curve with the jetting I have installed and give me a relative indication of horsepower.> >

Off I go.

Marc and Paul are both there. Just finishing up another TZ250.>

I start the engine and roll it up on the dyno. Paul secures the bike and we start the process. He types a bunch of information into the computer. Then we start running the engine at various throttle and rpm settings. When we are all done, the engine has performed
flawlessly. Not only that, the numbers indicate that my set up is very close to optimum. A little fat in the middle and just a smidgen lean on top. One Power jet smaller and and one main jet richer will probably be perfect.

Will I be able to tell the difference in the seat of the pants test? Probably not...

By the way, the (corrected) top number at 12,200 rpm was 75.8 True bhp.

I have been informed that you normally add 15 % to the Factory dyno True HP number to equate to a Dynojet Dyno. So for braggin rights lets say 87 bhp at the rear wheel.

Paul tells me it is the second highest number he has seen on a 250 and very, very close to the highest.> >

Both Marc and Paul have a good laugh when they tell me "Well, it's pretty obvious now why you are not winning races"

 I could have told them that. It's not the bike that is holding me back.

Hasn't been for about two decades!>

Bruce Lind

Message: 1
Date: Tue, 19 Jun 2001 19:10:53 -0400
From: "Tony Iannarelli" <tony@samnet.net>
Subject: FACTORY Pro Tuning

I just wanted to publicly thank Paul from FACTORY for all of his input at the recent Loudon National.

I wish I could remember half of the stuff he said about 250 motors!


Tony Iannarelli
SAMnet Racing