Dialing in your PMS

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Written by Steve Graham   
Saturday, 26 June 2004

There are several methods of approaching the process of dialing in the PMS on the stock carb.  This article outlines one method that can used, and which is designed to balance out the other circuits in the carb for best driveability.

The Pilot circuit (which the PMS screw controls) is responsible for primary fuel delivery at idle and throttle positions below about 1/4 turn (see Bulldog's article for more complete explanation).

All circuits in the stock carb are functional at all RPMs (except the accelerator pump) and will need to be balanced for best performance.  Primary responsibility for fuel delivery will change with RPM, but they all provide fuel at all settings.  For example the PMS circuit never turns off and is always delivering the maximum that it can contribute at any RPM.  The main and needle circuits are essentially off at idle RPM levels, but will always leak a little fuel regardless of RPM.  This procedure outlined in this article will not make up for being too rich, too lean, wrong main sizes or wrong needle clip positions, but will provide best drivability that can be achieved with these other circuits.

It can be a long process, and some folks have chosen to do it over time, making adjustments between rides.  Others have packed their bags with whatever tools they needed, and gone for an extended tuning ride to do it all at once.

On initital setup of your carburetor, set your PMS to a safe and slightly rich setting based on the recomendations that have come with your jet kit or the recommendations of someone who may be helping you to set it up.

Then proceed as follows.  Adjustments should be made one at a time, then ride tested to evaluate whether another adjustment should be made.  Each time you ride to evaluate, be sure the bike gets completely warmed up before deciding on a next step:

  • If you are getting backfire on decelleration (test this with hard decels - not braking but complete release from fairly open throttle positions), turn the PMS out 1/2 turn at a time until it stops. 
  • Next, turn the PMS in in 1/4 to 1/3 turn increments until you are able to induce backfire on decel.  At this point we have a good reference point for where the circuit is too lean and can adjust to balance out the circuits.
  • Balance out the circuit by turning the PMS back out in 1/8 turn increments until the backfire on decel quits.  This will be the point at which the circuits acheive best balance for the operating temperature and elevation where you did your testing.
  • If you have slight hesitation at initial throttle, turn the PMS out one more 1/8th turn.
  • If you are unable to completely eliminate the backfire on decel, you may need to move up to the next size pilot jet.  You may also need to consider the settings in the other circuits of your carb, ie: main jet size and needle clip position.  If you are already using a larger pilot jet, you may be set too lean on either of these two other circuits.
  • Having acheived this best balance, take the time to turn the PMS in all the way and record the number of turns as a reference (I like to use 1/8 turn increments, ie: 2 1/8 turns).  Then turn it back out that number of turns to where your best setting is. 

You now have a reference for where your PMS will need to be set to achieve best balance with the other circuits in the carb.  If you know you are going into a hotter environment than you normally ride in, you can adjust it slightly to compensate.  Just keep track of the turn increments and turn back when you return.  If you get lost in the process, turn it all the way back in and then back out to the position that you got your best performance from.

MaxMix users should halve the turn increments that I am suggesting in this article.  The MaxMix PMS screw is much smaller at the tip, and will be considerable more sensitive to these adjustments.

Anytime you make a change to your bike that could potentially change the jetting requirements, you need to dial in the PMS again.  For example changing the air kit, pipes (even removing baffles), or porting the manifold.  Naturally any change to the main jet or needle clip position will require this to be done as well.

Good luck, and please leave feedback (link below) if you have any tips or commentary that others would benefit from.

GRAM



Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page.

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DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only.  Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure.  You assume all risks associated with the use of this information.  NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION.  Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.


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  Comments (5)
Written by redhotrider, on 01-31-2011 16:25
My buddy Just gave me his new style Maxxair PMS adjustable screws. They were for a 2003 1100 V-star. Question is are they the same threads and profile as mt 2006 1700 RoadStar? Yea I know I only need one,LOL
rejet
Written by cathycoons@sbcglobal.net, on 05-19-2010 08:31
Thanks , will give it try 
Vernon
Written by ROSSETAW, on 08-29-2009 19:33
question 2005 roadstar when i roll the throttle on everything runs good if i hit it hard i notice ( when the aircleaner was of K&N THAT A MIST OF GAS HIT MY LEG ??? BARONS 4TH CLIP 172.5 JET COBRA SHOTGUNS W/ BAFFLES WITH BARONS PMS SET AT 2 AND A QUARTER TURNS OUT ?????
nightmare on 2001 roadstar 1600
Written by dod2500, on 07-01-2008 21:54
Help I installed a patrick racing ported intake and air filter kit it said to remove the original jet & install the 195 
set pms to 3.5 turns needle on 3rd groove ran good for 30 miles now it back fires out carb & shoots flame backfire out exhaust on accellaration whats next ?thanks dod2500
Mom, ya ever get that not so fresh feeli
Written by vwtech0, on 05-25-2008 09:16
I got a PMS question. How many turns out is the PMS stock? I hit mine with the drill bit for a micro second so I'm not sure where mine was, or if it even moved. I found it 1/4 turn out. Everywhere I look, they're instructing to turn out 2-3.5 turns. I have a 1700 roadie, not a 1600. If you look at the online installation instructions for the dynojet jetkits, the 1700 instructions say 3 turns, but the 1600 instructions say 3.5 turns. Kuryakyn Hyperchargers give these instructions: Setting Up The Mixture Screw - While the carburetor is removed for re-jetting, remove the pressed-in plug covering the pilot mixture screw and as a starting point, set the PMS two turns out from lightly bottomed. 
Once the bike is completely reassembled, start it and allow the engine to reach normal operating 
temperature.  
The engine should idle on its own without the enrichener.  
Search for the highest idle speed by slowly turning the PMS inward and outward; there will be a small range where idle 
speed is maximized. 
Once the highest idle speed has been located, turn the PMS inward 
ever so slowly until the idle begins to drop then back it out just enough to make the idle 
speed pick back up. 
You have now located the ideal PMS setting.

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