Disable air pumps - 1996 Honda VFR750F

I followed a web article tonight (I will try to post a link later) and while poking around under the gas tank for a good once over on my new-to-me 4G VFR (purchased June 2009), I disabled the PAIR system air pumps per the instructions in the article. As I understand the PAIR system, it is an emission control system that pumps air from the airbox via two air pumps, and routes the cool air from the airbox into the exhaust (at the exhaust valves, pre-catalytic). From what I understand, the system is unnecessary except as an emission control, and by robbing cool air from the airbox, it actually steals power, perhaps as much as 5-8 HP. I don't know about y'all but I wanted those ponies back.

I removed the airbox cover, spotted the two air outlets inside the front of the box, and followed the 3/4" air hoses from the front of the airbox (two 90degree spigots exit the front, one right one left) down and to each side until I located the air pumps. The left side pump is much lower on the engine than the right side pump. As described in the web article, the air pumps also each had a 1/4" vacuum line running to it. The process for disabling the system was simple, per the article. I removed the 3/4" air hoses, taped off (using electrical tape) the air outlet spigots coming out of the airbox where they connect to the 3/4" hoses, and replaced the hoses on the now-blocked spigots. I then removed the vacuum hose from each air pump, crimped it back on itself with a zip tie, secured the vacuum hoses out of the way with another zip tie, and I was done. these were the instructions provided in the article I read by (Richard?) Wilson.

Results? I did not dyno before, nor did I dyno after the change, so I don't have laboratory numbers, but on a 30 mile ride mixed superhighway, as well as local roads the bike was noticeably quicker in every gear and throughout the rev range, so much so it made me say "wow!" The bike has never wanted to wheelie before, but the difference in roll on power seemed to me significant. This makes sense, in that as the engine revs increase, the PAIR system is stealing more and more air, and if not starving the motor, it's reducing the available air for combustion. My bike's carbs may be jetted, the prior owner mumbled something about it, but I have a stock exhaust system with a D&D polished aluminum slip-on can. I think there may be some mild jetting, because with the stock exhaust can in place, you can smell the motor running rich

I checked this forum for how-to and results threads/posts, and found nothing specific here - so . . . . y'all already know about this tuning trick, and I'm preaching to the choir, or y'all have no idea what I'm talking about, but you might want to explore this option for an easy and noticeable performance improvement.

Other things I fixed while under the hood may have helped the bike wake up, in that I had (unbeknownst to me, when I was checking the bike over in advance of a trip to Norfolk from Winston-Salem NC tomorrow) 2 pinholes leaks in the fuel line from the petcock to the fuel filter (replaced the fuel line, easy, less than $20), and replaced the fuel filter, which looked shot to me - it hadn't been replaced since I've owned the bike, so may be original. I also vacuumed the top of the air cleaner (filthy), and re-oiled it. That may account for a little more power, but I wouldn't think it would be enough to notice extra horses.

Peace -

the Pimpdaddy

 

The pair valves are designed to function only when letting off the throttle, so that any unburned fuel vapours get burned off in the exhaust system. The carbs will reduce air flow when the throttle is backed off. This is why they were deemed neccessary. Soley to appease the tree huggers.

Cleaning the air filter, on the other hand, is very important in regards to maintaining a a healthy, happy engine. As are the the fuel filter and supply lines. If you haven't changed the spark plugs in a while, you may be ready to say wow again.

 

As the PAIR pump takes its vacuum directly from the intake tract, it may only SLOW DOWN when you let off the throttle. By its plumbing, it seems to work all the time. There is no electrical (or any other) connection to the motor that would react to throttle position.


There is a diaphram inside the valve that is operated by air pressure. It is designed to only open when pressure decreases, when the engine is slowing down. The extra weight loss is the only benefit, but only if you remove all the gear, not just pinching off the lines.

I'm just trying to help bust the myth of people thinking that there is going to be any HP gain from doing this mod.



:crazy:

 

I did this on my bike, too, and di not notice any sort of "power" benefit. The biggest benefit for me is that the RH PAIR unit is no longer in the way of the carb adjusting screws, and I have an excellent place for my HID ballasts in front of the airbox tray.

To the OP - I would be concerned about the longevity of the electrical tape you used to block off the air outlets on the front of the airbox. I actually epoxied a piece of plastic over my holes on the inside of the airbox.

 

To clarify, I taped electrical tape on the tips of the 90 degree outlet tubes that exit the front of the airbox, I was concerned about the carbs sucking in any foreign object from the inside of the airbox. the electrical tape is secured because I slipped the air pump hoses back over the stems, and spring-clamped them back in place. Thanks for the words, fellas, the bike ran great all the way to Virginia Beach, VA and back to Winston-Salem this weekend - wow, was it hot for today's return trip!

So any power improvement I noticed was due to the air cleaner being, well, cleaner? I'll try to post the link tonight, the guy who wrote it (I think) dyno tested the mod, and there was some improvement in the numbers, as I recall . . . more to come

 

Good to know, I wasnt aware thre was another diaphragm other than the pumper.

 

All the cool kids know you have to add Slick 50 with the PAIR mod to get the 5-8HP gain!

BZ

 

No tests are described in the manual I have. Just a description of the function, in the general info section relating to emissions. (bottom 1/3 of page 1-42)
The pump (valve?) does look to be dis-assemble able, so look for diaphragms with holes, and ensure parts move freely. Likely to be a spring or two in there.

 

There is a test listed in the common service manual, pages 7-8/9. It seems a little over the top for me, but if you have time to kill and nothing better to do, go for it.

I haven't done it on this bike yet, but I did check and clean the diaphrams on the ST1100. I was already there, changing the coolant hoses, another five minutes wouldn't kill me. They were a little dirty, which would be expected, as they are connected to the exhaust ports.

The reeds are probably the more important valves, as they prevent the gases from entering the air filter. If I see a build up in the filter housing, I will check them. Otherwise I will leave them alone, as they are easily damaged.

:crazy:

 

I had the right hand plastic component that's part of the system what ever its called break on me now when I open the throttle the engine dies
I have a spare engine and swpped the carbs out and this was from a UK whereas my bike is a Californian modal
So my question is
A: a link where I can buy the plast valve thing
Or B: what have I done and how do I fix it

So if someone has the plastic component I will buy it right hand side plastic component from the pair system