PAIR Removal without Carb Removal

[Arkterra]

Hypothetically, if one started having issues with the PAIR system could one simply plug the fresh air pipe in the carb manifold going to the PAIR valves, plug the vacuum lines on the left side of the bike, and leave the rest of the system in place?

I ask because I am contemplating not removing my PAIR system but disabling it in a way that prevents me from having to remove the carbs and reduces possible vacuum leaks. At a future time when Carb removal was warranted I'd fully remove the system.

 

[Smudgemo]

If that happened, I think I'd pull the carbs and replace all the insulators, the coolant lines and vacuum hoses and know for fact all that old stuff is good for another 20 years. It's not terribly difficult and enough of us have done it that we can walk you through it.

 

[CYYJ]

I agree with @Smudgemo - the moto is over 20 years old, and all that stuff under the carburetors is also over 20 years old. If you are not having problems at the moment, no sense going in there and stirring things up (I think that's how you are thinking at the moment), but, if you think problems are developing, it's probably best to remove the carbs and fully remediate all the hoses, etc. under the carbs.

FWIW, I removed the throttle bodies from my 2012 ST 1300 a year ago and overhauled and serviced everything under there... it wasn't that difficult to get the throttle bodies off. I have not yet taken the carbs off my 2001 ST 1100 yet, but only because it is stored on a different continent and I don't have the facilities there to do the overhaul.

Michael

 

[Arkterra]

Thanks. I've already pulled the carbs once and replaced all the coolant lines and the notorious leaking elbows. They had started to weep coolant so I'm glad I did. Thanks for the input. I don't have a developing problem that I know of with the PAIR system just trying to pre-game some solutions incase I do and am out on the road.

 

[Uncle Phil]

If it is any comfort, I still have the PAIR system on 3 of my 4 ST1100s, two of which have over 100,000+ miles and have had no issues.

 

[John OoSTerhuis]

In 24 years on the ST forums, I know of no documented failures of the ST1100 PAIRs system. I’ve heard of two reputable reports of a failure but without a picture… IOW, the system is bulletproof and the odds of a failure are basically zero. It’s a passive system that simply reduces pollution and has no effect on performance. IMHO, forget about it and GO RIDE!*

The test to rule out the PAIRs from a suspected after burn or other drivability issue is dead simple (p.5-17). Can be done roadside with your mouth and an 8” length of vac hose, engine off. Check to see that all four intake manifold vacuum port hoses are still attached first.

But to answer the original question — yes, the steps mentioned would remove the exhaust emission control system (secondary air supply system, AKA: PAIR), with the caveat to plug both the port on the front of the carb body and the hose to the air suction valves that connects to it. This could be done roadside, but I’d finish isolating the system from the ST by installing the block off plates at the exhaust ports when I got home.

JMNSHO, John
*Official STOC Motto

 

[Andrew Shadow]

Many ST1100 owners seemed to be concerned with removing/disabling the PAIR system. Why?

 

[John OoSTerhuis]

Many ST1100 owners seemed to be concerned with removing/disabling the PAIR system. Why?

Good question. Let the rationalizations begin…

John (yeah, this is a pet peeve of mine as many long-timers know)

 

[Andrew Shadow]

(yeah, this is a pet peeve of mine as many long-timers know)

I tend to agree with you. I have had two ST1100's. I never saw any reason to remove the PAIR system. I have never seen any convincing argument for removing a passive system that does not have a history of causing problems. Nor have I ever read of any susbstantive gain from doing so, thus my curiosity.

 

[ST11Nut]

I removed the PAIR system on my '91 to reduce the burbling exhaust during deceleration. While it didn't completely eliminate the burbling, it reduced it greatly. YMMV

 

[John OoSTerhuis]

I removed the PAIR system on my '91 to reduce the burbling exhaust during deceleration. While it didn't completely eliminate the burbling, it reduced it greatly. YMMV

Hi Dan,

FirST off, all ST1100s “decel burble“ to some degree, even those that are produced for other markets without PAIRs. Yours still does it even after removing the PAIRs. If they were causing it, why didn’t removing the system eliminate it? The reduction you report after their removal is subjective I’ll assume, or do you have an empirical measure to support your contention?

Sorry, if you didn’t do the dead simple test of the system described in the service manual to confirm your claim, it’s unsupported. If you don’t have a picture of the failed PAIR system part, it didn’t happen. If a PAIR failed you wouldn’t have “burble” during high rpm throttle roll-off (high intake port vacuum), you’d have loud banging noises — “after burn” (most often erroneously called “backfire” which occurs on the intake side), not burbling. If you still have after burn and the PAIRs pass their test (or even after they’re removed) you may have an air leak in the exhaust system (reported) or malfunctioning air-cut valve(s) (see the manual’s troubleshooting procedures).

If someone wants to remove their ST1100’s PAIRs, just go ahead and do it, don’t rationalize it.

Again, JMNSHO

John

 

[newtonhubcap]

Hi all. Still rather fresh with the ST1100. Last season I developed the coolant odor when motor is warm. Looking to do a rather extensive ride this year so I decided to replace all coolant hoses, vacuum hose, o-rings as well as all the hoses for the pairs. I do work in a Honda dealership and was going through the parts fische and noted that all the pre-formed pair hoses are discontinued. So, I am debating on whether I will delete the pairs system's unless some one knows of a source for the pair hoses or alternate option of replacement hoses. At this point in time I have not done nationwide dealer search for these hose but I honestly doubt there are any. I personally would prefer to retain the pair system.

Next upcoming project will to upgrade to the 40amp alternator but that will be a project for next winter.

Appreciate any and all info.

 

[John OoSTerhuis]

The PAIRs’ hoses are bulletproof. Don’t worry about it. Caveat: the elephant trunk hose on the front of the carb case may be frozen/welded to the nipple on the case and be destroyed during removal. BTDT

Edit: if those are your pictures, the elephant hose end looks OK.
PS have a techSTOC when you do the alt upgrade (borrow my tool kit) and you should have lots of help.

John

 

[Uncle Phil]

If you remove the PAIR system, you will need a 'way' to plug the big nipple at the base of the carbs. I recently did an engine 'swap' (long story) where the PAIR system had already been removed from the 'donor' engine. You also need block off plates for where the metal lines go into the engine. It's not a big deal but it does not make any difference in the way the ST1100 runs. I've got two with it and two without it.

 

[John OoSTerhuis]

it does not make any difference in the way the ST1100 runs.

Well… minor point but it does make a difference: the non-PAIR ST100s are polluting more than those with.

 

[ST1100Y]

FWIW, "Hayabusa PAIR blocking plates"are avail at eBay, designated to seal the ports at the engine heads...
By eliminating post-oxidation of exhaust gasses in the down-pipes the engine might run slightly cooler...
Sealing the air side is essential, you don't want the system to run lean due false-air...

I'd removed it on the '94 (pump diaphragm leaked), struggled a little getting the carbs settings & sync right again...
PAIR still in place in the '00 ST though...

 

[Uncle Phil]

Well… minor point but it does make a difference: the non-PAIR ST100s are polluting more than those with.

Pollute more yes, run different - not much according to my 'butt' dynamo ...