A few questions from a medium-skilled self-taught loves-to-tinker mechanic.

Are the PMS screw, the Pilot Jet Adjusting screw, the Fuel Mixture screw, and the Mixture screw all the same thing? If so, why are you techies creating confusion with us civilians?

Also, I have no backfire on decel ('05 RS, Cobra Loboys staggered, jet kit), but I am running rich. Do I turn the whatever-its-name-is screw in until I DO get backfire to start your method?

What if I don't ever get backfire, will that mean I'm way too rich on other circuits which are overwhelming the pilot circuit?

I notice that jet kits come with a drill and screw to remove a plug that covers the Mixture screw. Why does Yamaha cover the screw with a plug? Is it so we can't mess with their setting which has been set perfectly at the factory and never changes and is correct for all riders, all locations, all weathers? If so, HMMMM.

Shep

The screw is covered with a brass plug from the factory Shep.

The EPA mandates it to discourage folks messing with anything that could effect emmissions (like pipes air kit etc.)

If you leave it as is, then add anything that changes your airflow, you will be lean (I don't think you could reduce airflow from factory - increasing it will make the PMS circuit lean).

Those are all essentially the same (the different names you used). Nearly everyone I know in Road Star circles uses the PMS acronym.

You can try taking yours down until it backfires, then follow the instructions in the article to get your best balance between the PMS circuit and the needle circuit.

If it never backfires, even when screwed all the way in, you are too rich on the needle or main and are getting too much fuel through those circuits. They always bleed a little fuel even at idle. If they are set wrong or the main is to large, they bleed too much and DO overcome the pilot screws ability to adjust.

GRAM

Thanks, Gram, that explains everything.

Now, can you explain women to me?

Shep

"Now, can you explain women to me?"

There was this biker, he was a very generous and good person. He was kind to people and helped people whenever he could. So one day he is riding down the California coast and God appears and tells him because he is such a good person he will give him anything he wants.

The biker thinks for a few seconds and says “I want a bridge so I can ride to Hawaii whenever I want.”

God responded, ”That is a very monumental task! Think of the natural resources it will deplete, the steel, the concrete, the complexity, that is a very difficult, if not impossible, task. Are you sure there is nothing else that you would like instead that may be a bit more reasonable?”

The biker thought for a moment and said, “Okay, I want to understand my wife. Why she cries, what she wants, how to make her happy.”

The was a short pause before God responded, “Was that a 2 lane or 4 lane bridge you wanted?”

If God can't do it .... I amnot so sure Gram can either.

If I could explain Women, I'd be fat, happy , retired, selling books by the millions, and living somewhere in the carribean

I'm sure they feel the same way about guys...

GRAM

Hey Doc

Guy Here

Took the bike out to Carleton Place last Sunday. Adjusted the PMS screw a dozen or som times until I had not lag on throttle start and no backfire. Martin and I went for a ride to the market today and the bike started acting up as soon as we got downtown. It actually stalled at one point and woun'dn"t start, lots of backfiring etc. Sure could use some help on this one. Short of taking it into Dream Cyle to get Paul to look at it.

Guy,

Responded to your e-mail.

Doc

Gram,

About adjusting the PMS on the road:

I'm getting around 40 mpg on my '05 RS on country roads. I'm still running rich by the color of the inside of the pipes (black and sooty).

I'm going on a long trip soon, and I would like to adjust the PMS each day, a quarter turn in at a time, and see how I go. ("In" is leaner, right?)

I would check the color of the plugs each day, and keep track of gas mileage, it should go up as the mixture leans out.

My questions:

Does the above sound reasonable? I won't wreck anything, will I?

Is adjusting the PMS a five-minute job with the bike's tool kit (plus the special jeweller's screwdriver for the actual screw), or an hour-long job with special tools?

I have to remove the air cleaner, correct?

Should I notice a difference with just PMS adjustment, and not the other carb circuits? (I ride like a little old lady, not from Pasadena.)


Shep<br><br>Post edited by: Shep, at: 2005/04/12 09:03

I have never seen a Road Star (at least not one with aftermarket accessories) that did not have a black tailpipe Shep.

Your mileage is in an acceptable range, leading me to think you most likely are close to dead on with regard to your jetting.

Remember that adjusting the PMS has little effect after you open the throttle at all. It only has a major effect on mix at idle. The PMS circuit has four exit pinholes that allow fuel to flow into the carb, and three are closed when the throttle is closed. The PMS screw only adjusts flow through one of the four exit holes.

Adjusting the PMS is real easy, once you have done it the first time. Might want to go through the process of removing your air cleaner housing, and using a small mirror to locate the PMS tower on the back of the carb at home. Once you get a feel for where it is, you should be able to make adjustments fairly quickly on the road (just a few minutes).

You are correct that turning the PMS in leans the circuit. I don't think you need to check you plugs each day, but won't hurt if you want to do it.

There is no &quot;perfect&quot; jetting for a Road Star. It operates over too wide a range of temps to ever be perfect. You are looking for your best balance in your normal operating temperature once the bike gets warmed up. If we had radiators this would be less of a problem. Thats why everyone's tailpipes get sooty. In every ride there will be times when you are real rich due to operating temps on the bike. As the bike heats up, it tends to heat the incoming air too, and that leads to running richer. On rides through hot ambient temps, you are going to run richer than through cooler temps.

Radiators (and their temp control valves) keep operating temperature range to a minimum and fairly constant. Without them we are at the mercy of ambient air temps and have to acomodate a wider range.

Pay attention to your bike's decel performance. If you can induce backfire on a hard decel you are too lean. It will be most noticible when you are running at a relatively high RPM and close the throttle completely off. At that point you are putting the carb through a high vacuum cycle and the main and needle circuits are largely shut off. The bike will be using the PMS circuit as its primary fuel supply.

Good Luck!

GRAM

I have a stock (for now) 04 RS. I had the PMS set at 3 turns and it seemed to run fine. I have since taken off the AIS garbage and now have a backfire when shifting (at each gear change). I tried to turn the PMS out and it seems that the problem is getting worse.

I'm at 4 turns now. I was going to start going back in with it to see what would happen. Since this is also a PITA do at 1/4 turns can anyone offer a suggestion that may eliminate the 3 hour adjusting ride?

Thanks
Tom Maule