To Shim or not to Shim

It appears that you have a California ABS 2. This is a full blown emission bike, with evaporative emissions and the lazy emission camshafts. You are limited with what you can do with the jetting.
You should already have .020" shims under the needles as it is from the factory (I'm almost certain of this). However, there have been several occasions that I've found that the needle shim thickness are inconsistent. Measurement's can vary from .015" to .020". I have a bag of .020" shims from PJ Motorsports for more consistent and equal settings when I do a bank of carbs.

There was only one set of ST carbs that I've seen, that did not have the shims under the needles. I put the .020's in and the owner was pleased with the results. Slightly less MPG and stronger midrange and top end. But I made other changes too...

Adding additional shims to the needles would really fatten up the the midrange/top end and across the board. My opinion is that it's too much. This includes going up to the 128 main jet on an unmodified ABS bike. If you're looking for more low end grunt and a stronger midrange, switch the slow speed/pilot jet to the #40 and start off at around 1 3/4 turns out on the mixture screws. this will get you close to were you need to be.
 
afrymoyer said:
It appears that you have a California ABS 2. This is a full blown emission bike, with evaporative emissions and the lazy emission camshafts. You are limited with what you can do with the jetting.
You should already have .020" shims under the needles as it is from the factory (I'm almost certain of this). However, there have been several occasions that I've found that the needle shim thickness are inconsistent. Measurement's can vary from .015" to .020". I have a bag of .020" shims from PJ Motorsports for more consistent and equal settings when I do a bank of carbs.

There was only one set of ST carbs that I've seen, that did not have the shims under the needles. I put the .020's in and the owner was pleased with the results. Slightly less MPG and stronger midrange and top end. But I made other changes too...

Adding additional shims to the needles would really fatten up the the midrange/top end and across the board. My opinion is that it's too much. This includes going up to the 128 main jet on an unmodified ABS bike. If you're looking for more low end grunt and a stronger midrange, switch the slow speed/pilot jet to the #40 and start off at around 1 3/4 turns out on the mixture screws. this will get you close to were you need to be.
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Thank you, This Bike is ABSII but came from Virginia, It does have the PAIR installed. Maybe I should check VIN for exactly what it is for reference.
Pretty sure idle jets are stock and I'm sure the idle screws are at 1 3/4, when I go to 2 turns out I get a lot of Back fire, and by that I mean like gunshots.
That got me thinking about the shims
It has Staintune Exhaust installed which is a factor.
 
Slydynbye said:
Thank you, This Bike is ABSII but came from Virginia, It does have the PAIR installed. Maybe I should check VIN for exactly what it is for reference.
Pretty sure idle jets are stock and I'm sure the idle screws are at 1 3/4, when I go to 2 turns out I get a lot of Back fire, and by that I mean like gunshots.
That got me thinking about the shims
It has Staintune Exhaust installed which is a factor.
Click to expand...
IIRC, all ABSII ST1100s were 'California' models.
You might reach out to the Romax folks that just rebuilt a set of ST1100 carbs for me.
They might have some insight on it.
 
Slydynbye said:
Thank you, This Bike is ABSII but came from Virginia, It does have the PAIR installed. Maybe I should check VIN for exactly what it is for reference.
Pretty sure idle jets are stock and I'm sure the idle screws are at 1 3/4, when I go to 2 turns out I get a lot of Back fire, and by that I mean like gunshots.
That got me thinking about the shims
It has Staintune Exhaust installed which is a factor.
Click to expand...
Weather it's from Virginia or anywhere else, It's still an ABS 2 which has California emissions. The factory service manual will have all the specifications your looking for.
You've kinda answered your own question. Installing needle shims will add more fuel and fatten up the mixture. Because your PAIR system is working, again you will get MORE after burn in the exhaust system, same as running out the mixture screws two turns. As you've found, having the Staintunes on the bike, significantly reduces exhaust back pressure and allows the PAIR system to work even more efficiently. More fuel, more air (PAIR), more bang in the exhaust. You also know that the carb air cut's are working too when you roll off the throttle(even more fuel in the exhaust).
 
Popping or Backfiring on Deceleration: The primary sign of a failing or leaking air cut-off valve is a sharp popping, snapping, or backfiring noise from the exhaust when you suddenly close the throttle. The valve is supposed to temporarily enrich the idle mixture during deceleration; if it leaks or fails to seal, the mixture goes lean, causing unburned fuel to ignite in the hot exhaust pipe. [1, 2, 3, 4]
 
afrymoyer said:
Weather it's from Virginia or anywhere else, It's still an ABS 2 which has California emissions. The factory service manual will have all the specifications your looking for.
You've kinda answered your own question. Installing needle shims will add more fuel and fatten up the mixture. Because your PAIR system is working, again you will get MORE after burn in the exhaust system, same as running out the mixture screws two turns. As you've found, having the Staintunes on the bike, significantly reduces exhaust back pressure and allows the PAIR system to work even more efficiently. More fuel, more air (PAIR), more bang in the exhaust. You also know that the carb air cut's are working too when you roll off the throttle(even more fuel in the exhaust).
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So are you saying that without Pair I would get less popping? On my 98 ABSII I had done that and increased jetting on Idle and Main, That Bike ran REALLY well. Also had removed PAIR.
 
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Slydynbye said:
So are you saying that without Pair I would get les popping?
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I have 2 ST1100s with Pair and one without (removed by PO).
Over 100,000s of miles I have noticed no real world difference in the amount of 'popping' between any of the 3 ST1100s. ;)
 
Al st1100 said:
Popping or Backfiring on Deceleration: The primary sign of a failing or leaking air cut-off valve is a sharp popping, snapping, or backfiring noise from the exhaust when you suddenly close the throttle. The valve is supposed to temporarily enrich the idle mixture during deceleration; if it leaks or fails to seal, the mixture goes lean, causing unburned fuel to ignite in the hot exhaust pipe. [1, 2, 3, 4]
Click to expand...
Interesting article on link 3 he advocates disabling the cutoff. I suspect they are shot but, hesitate to separate carbs as that is a major headache to reassemble.
Increasing idle jets adds to popping which seems to go counter to the logic of the cutoff valve enriching the mixture and reducing pop
 
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Slydynbye said:
Stock exhaust or aftermarket? Have you ever de-gunked the Pair system?
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Exhaust headers are now Delkevic but the sillencers are still the stock ones.
Never touched the Pair system but I have removed the fuel cutoff from all of my ST1100s.
 
Uncle Phil said:
Exhaust headers are now Delkevic but the sillencers are still the stock ones.
Never touched the Pair system but I have removed the fuel cutoff from all of my ST1100s.
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I guess I meant Stock muffler/Silencer. Totally agree with fuel cut off. Had to remove one of mine while going across Death Valley at 106 degrees, not pleasant, never again.
 
Slydynbye said:
I guess I meant Stock muffler/Silencer. Totally agree with fuel cut off. Had to remove one of mine while going across Death Valley at 106 degrees, not pleasant, never again.
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I was pleasantly surprised at the price and the fit of the Delkevic 'headers'.
They fit perfectly with no hassle, came with proper gaskets, and the stock silencers went right in with no hassle.
And everything - including the clamps were stainless steel.
I had to replace all the exhaust systems on all 3 of my ST1100 runners where they rusted out on the right side joint (looks sort of like an upturned palm of the hand and collects water).
And I changed out the bolts that hold the heat shields in place with stainless steel socket head screws.
 
Slydynbye said:
So are you saying that without Pair I would get less popping?
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[edit, I misread the quote] No, it’s purpose is to reduce popping. You can read about it in chapter 1 in the Honda Service Manual. I’m not going to dig it up to post here again as I have many times before. It’s dead simple to check that the PAIR (air suction) valves are functioning properly (a short hose and your mouth, engine off).

Edit: the manual’s troubleshooting for decel afterburn does mention the air cut valves which seem to seldom come up in PAIR discussions, most posters just looking for justification for removing the PAIR system. Check them, if they’re OK leave them be. They are passive, rock-solid, don’t fail and reduce emissions.

John
 
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John OoSTerhuis said:
Yes, that’s it’s purpose. You can read about it in chapter 1 in the Honda Service Manual. I’m not going to dig it up to post here again as I have many times before. It’s dead simple to check that the PAIR (air suction) valves are functioning properly (a short hose and your mouth, engine off).

Edit: the manual’s troubleshooting for decel afterburn does mention the air cut valves which seem to seldom come up in PAIR discussions, most posters just looking for justification for removing the PAIR system. Check them, if they’re OK leave them be. They are passive, rock-solid, don’t fail and reduce emissions.

John
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Is there a place that mentions servicing the Pair system? I suspect at 107K it might be time :giggle:
 
Not sure what you guys mean by “servicing” the PAIR. You check them to verify that they are functioning properly. The system is described on p.1-32. The official check if you don’t use my quick-n-dirty shortcut is p.5-17 in the Service Manual and p.7-8 in the Honda Common Service Manual. If it fails (unlikely) you can take the valves out and apart, Inspect the vacuum lines from the intake manifolds and their connections for leaks FIRST. Inspect the valves’ rubber diaphragms for holes/leaks and the reed valves for damage. I took mine apart for grins years ago @~145K and they were fine, just cleaned a bit of oily gunk off the rubber valve parts. FWIW

John
 
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