PMS Adjustment with MAXAir too far out - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 15 (permalink) Old 08-27-2018, 09:57 PM Thread Starter
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PMS Adjustment with MAXAir too far out

So I have a 2008 V-Star 1100 Classic that my son rode for a few years. Just before I got it, he drilled out the exhaust baffles to lower the sound. When I got the bike, it was backfiring on decel fairly bad, so I decided to get into the carbs and see what I could do. Since then, I've had the carbs out twice, maybe 3 times, and tried a set of Baron's needles to no avail. I ended up putting the original needles back in, but while the carbs were out I drilled out the PMS plugs and installed a set of MaxAir PMS screws so that I Could make adjustments easier. I couldn't find a photo of the MaxAir PMS screws on line anymore, but I found something very similar made by Baron and will try to post a photo here. I set the new PMS screws to 3 turns out as a starting point, but the bike would barely idle and just touching the throttle would casuse it to bog-down and stall it out. So I started to adjust the PMS screws out and eventually got the bike to idle, then tweaked the PMS screws out some more at idle to improve the idle. It was a couple more turns out and the idle really picked up and smoothed out. So these PMS screws are now sitting 4.5 and 5.0 turns out. I took the bike out for a good long afternoon ride, it ran well - for a while - then started having trouble maintaining an idle. When I got back I found that one of the PMS screws had vibrated loose and fell out - I am thinking that at 5 turns out, there just isn't enough spring force on the PMS screw to hold in place and it vibrates out. I found it just sitting in the V. I put it back in and decided to retest the PMS settings, again tweaking them out to get to the smoothest idle and again was back to 4.5 / 5.0 turns. So, I am thinking i have to make another change, either with another set of PMS screws that won't need so many turns out to get to a good idle fuel mixture or with the main needles. Anyone else have experience with these MaxAir PMS ? Everywhere I read says 3.0 - 3.5 turns should be close to the sweet spot. 4.5/5.0 turns is way out there. Should I try another brand of PMS? Should I make an adjustment to the stock jets to allow more fuel at zero throttle (idle)?

First photo is the stock needle set up that is in the carbs now.
2nd Photo is of the Baron PMS screws that are very similar to the MaxAir screws

Thanks for reading...
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post #2 of 15 (permalink) Old 08-28-2018, 05:55 AM
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I know little about this bit Im going to guess anyway and then see what the experts say.

Larger jets sounds like its in your future.

Read the wiki thoroughly. It may help.

https://sites.google.com/site/vstar1100kb/home/tuning

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Previous Bikes:
2005 Yamaha YZF-R6T
1990 Kawasaki EX-500
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post #3 of 15 (permalink) Old 08-28-2018, 06:32 AM
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Remember that the Max PMS screws tune differently:

For Carb Tuning - One Stock PMS Turn EQUALS 1/2 OLD Style MaxMix or Metric Magic Turn (2 to 1 ratio)

At 4 or more turns you are waaaaayyyy rich. Start out with the MAX PMS screws at about 1/2 turn out and adjust from there, 1/8th of a turn at a time. Most have found with the MAX screws it will run best with them barely open. Good luck and keep us informed.
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Les B.
2001 Vstar 1100 Classic (sold), Cobra Slash Cut full exhaust, Dropped 1 inch with lowering links, ORK, 4.5 inch handlebar risers, Ultimate passenger seat, Passenger pegs moved forward 4 inches, Handlebar clock, KN air filter, Viking saddlebags, Additional rear lighting
Loose nut "me" behind the bars
2006 Harley Electra Glide Ultra Classic

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post #4 of 15 (permalink) Old 08-28-2018, 06:55 AM
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I'm usually very hesitant to use any parts in a carburetor that aren't a factory part or at least identical to one. The Baron PMS may have a different taper than stock so that may be why you had to set them that far out... I'd go with factory screws no matter how inconvenient. The backfiring/popping on decel is most likely a result of the AIS which was designed to function properly with the OEM exhaust. Any modifications to the exhaust system may cause the AIS valve to function improperly.

Also, be wary of the info on that VStar 1100 site... there's some good info there but there's also BS being perpetuated. For instance they refer to a diagram entitled "Working Range For Each Carburetor Part" which was created by some random dude with a gmail account and goes against what is outlined in both Mikuni and Keihin carburetor factory tuning guides I have been using since the 80s. The PMS does nothing to the overall air/fuel mixture past 1/4 throttle opening... on some model carbs that circuit is only effective up to 1/8 throttle opening so don't rely on the PMS and the main jet to solve your tuning issues, those are at the extreme ends of the ranges. Most of your riding will be somewhere in the middle throttle range which means you need to concentrate your efforts on the jet needle and needle jet.

As for your exhaust, if the mufflers were completely gutted then essentially you have drag pipes and they are notorious for introducing what is known as "drag pipe sag", a dramatic drop in power due to an overly rich mixture usually at the lower-mid throttle position ranges caused by harmonic reversion. To correct this, pipes need either baffles or at the very least something like lollipops to break up that harmonic reversion.


Quote:
Originally Posted by lesblank View Post
... At 4 or more turns you are waaaaayyyy rich. Start out with the MAX PMS screws at about 1/2 turn out and adjust from there, 1/8th of a turn at a time. Most have found with the MAX screws it will run best with them barely open. Good luck and keep us informed.
Agreed. My bro's 1100 was tuned correctly with the PMS at 1/2 turn out.
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Last edited by Diogenes415; 08-28-2018 at 07:02 AM.
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post #5 of 15 (permalink) Old 08-28-2018, 07:20 AM
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Diogenes, I agree that all the info on WIKI is not always 100% correct. But I've found it to be a very good starting point when trying something new. No two bikes are the same and if modifying a system it will always need fine tuning to get the best results.
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Les B.
2001 Vstar 1100 Classic (sold), Cobra Slash Cut full exhaust, Dropped 1 inch with lowering links, ORK, 4.5 inch handlebar risers, Ultimate passenger seat, Passenger pegs moved forward 4 inches, Handlebar clock, KN air filter, Viking saddlebags, Additional rear lighting
Loose nut "me" behind the bars
2006 Harley Electra Glide Ultra Classic

https://sites.google.com/site/vstar1100kb/home
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post #6 of 15 (permalink) Old 08-28-2018, 08:46 AM
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Tweak the screws a bit and ride the bike 5 miles. Make any adjustments based on the last mile.

If you try to do any adjustments when the engine is not hot, you will go in circles
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post #7 of 15 (permalink) Old 08-28-2018, 03:52 PM
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i have the max air screws and they have the same taper as stock. stock setting for screws with no change in air intake is 2 turns out... when you gut the exhaust you will hear popping. That's caused by a lean condition. the carbs are set lean from the factory to meet emission laws, popping is caused by fuel that is to lean to burn in the combustion chamber collecting in the exhaust then getting ignited. a stock bike pops but you can't hear it because the exhaust muffles the sound. if you want to get rid of popping open the pms screws a quarter turn or until it quiets down. if your at 4 turns out something else is wrong.
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post #8 of 15 (permalink) Old 08-28-2018, 04:52 PM
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Quote:
Originally Posted by nick57 View Post
i have the max air screws and they have the same taper as stock.
Yes and no. Max Air has an old and new version of PMS screws. The old style with steeper taper, but they could be the new style which have the same taper as OEM. The OP needs to compare his stock with the Max Air to see if taper match or are different, if not he will be adjusting to wrong setting with poor results. Here's info about Max Air PMS screws:

"The difference between the Stock PMS screw and the Old Style MaxMix screws are how fast they taper to a point. The old style MaxMix does it much faster, so if a stock PMS screws is 3 turns out the MaxMix is 1.5 turns out. New MaxMix screws have the same taper as stock, and should be adjusted that way."

Les B.
2001 Vstar 1100 Classic (sold), Cobra Slash Cut full exhaust, Dropped 1 inch with lowering links, ORK, 4.5 inch handlebar risers, Ultimate passenger seat, Passenger pegs moved forward 4 inches, Handlebar clock, KN air filter, Viking saddlebags, Additional rear lighting
Loose nut "me" behind the bars
2006 Harley Electra Glide Ultra Classic

https://sites.google.com/site/vstar1100kb/home

Last edited by lesblank; 08-28-2018 at 05:11 PM.
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post #9 of 15 (permalink) Old 08-28-2018, 08:16 PM Thread Starter
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So to address some of the questions so far, the MaxAir PMS are the same taper as the stock. If I remember right, the bike just won't idle at a 1/2 turn out. And even at the same taper of the stock screws 4 turns out seems like something is really off. I am a starting to think maybe I have the needles set up wrong or the choke is bound open. I will check on the choke first. I attached a Pic of the stock needle set up and think that is right but if you see anything wrong there let me know. At this point I am less concerned with popping on decel as much as I am about just having confidence that the PMS settings are good and they won't fall out! I will work on some more over the weekend and see what I can find.
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post #10 of 15 (permalink) Old 08-28-2018, 08:37 PM
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4 turns out your trying to correct a lean problem, may be vacumn leak.one of the rubber caps could be toast.your needles look like stock. could be clogged jet or passage. the pilot jets are notorius for dirt they have small holes on the sides make sure u can see a lot of daylight thru them and blow out the passages.i skip around a bit i hope to improve
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