Any experience with the Maxmix PMS screw vrs. a #40 pilot?

The #40 pilot is too rich for me and was told the Maxmix was a more agressive screw. What exactly does "agressive" mean? more fuel? a #40 might be just as good but I purchased the $10. screw anywho. It has a different taper at the tip. Thank you for your imput.

1999 R* stock carb, 4th clip, 55.6 starter main, 170 main, Dyna 36A @ 5000rpm, Road House 2into1 exhaust and K&N V98 air filter.

The MaxMix is awesome for two things:

Easy to adjust.


Provides more fuel per turn (so screw doesn't have to be as far out with smaller pilot jets)

It is touchier to adjust. In particular with larger Pilot jets. If your Pilot jet is oversized, you will have a considerably reduced control range (less turns of adjustment between closed and wide open).

If the #40 is the right size for you, it should work well. The MaxMix will need just about 1/2 the turns the stock needle would. If the Pilot is oversized, and you are already using the stock screw barely turned out, it will be difficult to adjust.

Its pretty handy for making on the spot adjustments while you are out riding.

GRAM

I may be confused reading this, but you need a pilot jet whether or not you use a MAXMIX PMS screw. I use the #40 and MAXMIX screw and it works fine. I am a little rich at idle, but in midrange where I ride I am looking pretty sweet based on plug checks. ANy other adjustments tend to make my bike backfire or idle a little rough, so I live with the tad bit rich at idle with no complaints. I am running a 185 main and I have not really done a proper check on it, but what I have seen looks decent (but I just do not ride WFO anymore, if I did I would have bought a Hayabusa). These settings are using a MAXFLO and Hard Krome 3" dual side burners.

The MAXMIX screw is more agresive so you do not have to use as many turns on it. Figure half of what the stock screw is. With a stock PMS screw I would be running almost 4 turns out (and the screw would probably rattle out at that setting) where I run 1 3/4 turns with the MAXMIX. Plus the MAXMIX is easier to adjust - I use a short piece of fuel hose on on mine to make it even easier to reach.

Grey long time no hear on the R* forum!

I'm oversized right now with the #40 I'm putting the #35 back in and swaping out the stock mix screw for the Maxmix, so I should be fine then. Just a few more question please.

The pilot air jets: one under the diaphram that can be exchanged for smaller than stock and one in the mouth of the carb that cannot be exchanged. How do they work with the Mixture screw?

I have already filled and drilled the pilot air jet in the mouth of the carb and works better filled solid ever since I changed from stock to modified exhaust headers.

The float bowl measurement/adjustment that critical before adjusting the carb? can be off just a tad? is there a way to measure the float without purchasing a special measuring tool from Yami? doesn't seem to be off but should be checked?

pre-thanks

Do you have the Maxflo jet kit in your ride? Different from others?

Apologies Draco,

Your post was addressed to "Grey" so I assumed you were talking to someone else.

I switched to "threaded view" and saw that you were posting to me. Again, sorry to miss it.

The air inlet in the front of the carb is used to emulsify (atomize or turn to air enriched form) the mix coming through the pilot. It does not do a great job fwiw.

The one in the top of the carb is not part of the pilot circuit (if I remember correctly). The one in the top of the carb is an air bleed for the slide. Changing it out adjusts how quickly the slide rises in response to throttle input.

Checking the float bowl level is real easy, and best done with the carb on the bike. I use RC model clear gas tubing (mine is actually see through yellow) to check it.

On the bottom of your carb there is a tube that drops straight down, then turns 90 degrees toward the gap between the jugs on the engine. There is a small (5 mm I think) hex head screw (head faces toward the gap) that adjusts or closes flow through that tube. It is a float float bowl drain.

Attach the RC model gas tubing to the drain tube, then while holding it above the float bowl open the drain screw. The gas will flow in to the tube and rise to the height of the floats. I hold the clear gas tubing up against the carb throat.

This is best done with someone holding the bike up vertical. But I tend to do it on the sidestand and it works well enough. The level in the clear gas tube should not rise above the seam between the float bowl and the bottom of the carb body.

When done, close the float bowl drain screw. It does not need much more than a slight tightening. If you ovetighten it, it will strip.

I would take the time to check it, but it is most likely ok.

GRAM

So the pilot air jet (mouth of carb) isn't directly connected to the mixture screw PMS, it comes into play and mixes air with the #35 pilot jet. I think I'm reading correctly. Ok I got it.

The pilot air jet under the diaphram (where the sized jet can be changed smaller) I thought had something to do with the plunger too? (not sure how that works). I had made an experiment and drilled out that stock air jet oversized. That it would "richen" by forcing the needle/diaphram to rise quicker?

Do what would make conditions right to reduce the size of that pilot air jet under the diaphram? needle taper?

by the way thanks for the education.

We are close. The pilot Air coming from the front of the carb mixes with the fuel coming from the pilot jet, then is metered (at idle only) by the PMS screw. The PMS screw merely closes the hole that allows the mix to get into the carb throat. The hole it goes through is right behind the butterfly. There are three other holes in the carb throat that the pilot circuit can use to send fuel into the carb throat, that are effectively closed when the butterfly closes (it covers two of them, and the third will have no vacuum since it is in front of the butterfly). Once you open the butterfly at all, the pilot circuit is fully open and the PMS screw has little to no effect as it can only close one of the four holes.

You are right about air bleeds in the top of the carb. They meter vacuum for the slide and allow a metered amount of the vacuum to engage the "Coasting Enricher". The vacuum for the slide (you called it the plunger) comes from a very large hole in the carb throat which is just behind the butterfly valve. As the butterfly closes it induces vaccuum which increases vaccuum to the slide (pulls it down). Pulling the slide down increases air velocity in the throat and helps to maintain mix state at lower RPMS where velocity would not be sufficient if the slide where left higher.

Sorry to make this so damm long,

There are two airbleeds in the top of the carb. The one located right next to what looks like a brass ball bearing near the back adjusts the amount of vacuum coming into the slide chamber. If this is the one you opened up, it will cause your slide to come down more quickly. This will mean carb throat velocities are higher for a momentary second as you close the throttle, and mix should be slightly leaner (same essential amount of fuel coming from the idle/pilot circuit - but more air from the carb throat as the velocity or pressure is increased more quickly).

The other air bleed is located on the left side of the carb just behind the slide. It allows vacuum to activate the coasting enricher. It has no effect on the slide as it is a sealed vaccum chamber that activates the enricher. Opening this one up will cause the coasting enricher to engage at lower vacuums, thus enriching the circuit sooner in very high vacuum situations. The Coasting enricher really only comes into play in situations where RPMs are high and you close the throttle completely off.

Anyway, not sure this is answering your questions very well, but might help understand what the airbleeds are doing in the top of the carb.



GRAM<br><br>Post edited by: GRAM, at: 2005/02/15 12:45

The other air bleed is located on the left side of the carb just behind the slide. It allows vacuum to activate the coasting enricher. It has no effect on the slide as it is a sealed vaccum chamber that activates the enricher. Opening this one up will cause the coasting enricher to engage at lower vacuums, thus enriching the circuit sooner in very high vacuum situations. The Coasting enricher really only comes into play in situations where RPMs are high and you close the throttle completely off.
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Yes your correct. I meant to call the (plunger) the &quot;coaster enricher&quot; and was trying to do what you explained in the above post. After drilling the Pilot Air jet under the diaphram I also almost clipped the $20 spring on the coaster en-richer too. Another tip told me to chang out the &quot;starter main jet&quot; to a 77.5 trying to &quot;richen&quot; that circut and get the same effect on hard decel. So I tried a few things that didn't work and was fun. The problem I was having was trying to get rid of carb cough after changing exhaust headers. Never had a problem with slip-on mufflers and BAK but do with new headers and same BAK. A phenomina

I have read everything written I could find about the carberator and found little about the pilot air jets they were never really explained to the extent you did here for me. THANK YOU...

Glad to help Draco.

You might want to check into adjusting your accelerator pump too.

If you want to get totally bored, you could read the article here on the clinic that outlines the pilot circuit too.

GRAM