* Pair Valve, leave it or lose it C800 / C50 / M800 / M50 / VZ800 *

First of all before we start, the question we must ask is do we need a pair valve? Well the answer to that in the UK at least is no! The pair valve is there for emissions only and injects air so that any un burned fuel can be ignited in the exhaust.
I have read a lot over the years about disabling the pair valve on bikes & this seems to be an extremely common practice on our bikes. Some do the complete removal of the pair valve & others modify it by blocking the tube with a golf tee. Now I can kind of understand it for the guys that are doing the Nekkid Jugs mod because the pair valve housing although not as big as the air box is still slightly blocking the view of the jugs and although chromed is not all that esthetically pleasing.
I was considering doing this mod simply because I was thinking like a lemming in sheep clothing but whilst out riding today suddenly thought no! I actually like the burble that the exhaust gives because the pair valve is in operation. When the bike was totally stock there was no burble in the exhaust on deceleration that I noticed at the time but as I went through each air flow mod I noticed it slightly more & more. From drilling the exhaust ends to debaffling to K&N's to the V&H Cruzer install.
I think some people get confused with the difference between a deceleration burble and a full on backfire, mine has never done what I would describe as a proper backfire, even after all the mod's that I have done. I like the burble that we get with the pair valve in operation & mine is staying where Mr Suzuki put it

Interesting write up Mr I

Reviving an old thread here, I don't think it got the deserved attention the first time round.

With the Short cut exhausts on, I love the sound my bike makes when decelerating, BUT it does backfire occasionally. The sound doesn't bother me, but I would be concerned if this was damaging my engine.

Does backfiring damage the engine? And does the pair valve cause (or prevent) this? It's not a mod I would do for cosmetic reasons, only if my bike was being harmed in some way.

Bunso Steel wrote:

Reviving an old thread here, I don't think it got the deserved attention the first time round.

Thanks, Kind words always go down well & encourage the next little write up

Bunso Steel wrote:

With the Short cut exhausts on, I love the sound my bike makes when decelerating, BUT it does backfire occasionally. The sound doesn't bother me, but I would be concerned if this was damaging my engine. Does backfiring damage the engine? And does the pair valve cause (or prevent) this? It's not a mod I would do for cosmetic reasons, only if my bike was being harmed in some way.

Hmmmm You don't make things easy for us do you. Several questions all interlinked and probably deserving long answers. Please remember I am only giving my opinion in this thread.

Is back fire bad? Hell no! Is back fire bad? Hell yeah! You could probably get a thousand variations of each answer depending on who is giving the answer. Some people will use the kill switch to give an almost explosive backfire sound just for the fun of it and swear they have done it a thousand times before and never had an issue. Whether the poor sod who bought the bike after him ended up replacing a knackered engine or not would have to be seen. There are so many variables that make the difference between acceptable and not acceptable and why they are or are not, its very hard for one person to say or give a definitive answer.

A few basic questions need to be asked before we start sweating over whether we have a problem or not.
Does it happen only on a closed throttle?
Does it happen on closed throttle and deceleration?
Does it happen on closed throttle, deceleration and fixed throttle position?
Does it happen on closed throttle, deceleration, fixed throttle position and open throttle (acceleration)?
Is the bike bog standard or have any adjustments been made to the fuel and or air intake / output?
Does the bike have the baffles removed or are they still fitted or has the exhaust been modified in any way?
Does the bike do it on any combination of the above would possibly lead to different answers but all are fixable or acceptable.

Some possible answers to the above would be,,,,,,,
Its only exhaust burble, don't worry its normal, you have added either an exhaust which no longer muffles the sound. There is a leak in the exhaust, either at a joint or through deterioration often around original weld points. The seal at the head is leaking (was new seals put in place when an exhaust was either put back on or replaced? The bike is running lean. The bike is running rich. The timing is out. The valves are burnt. The valves are tight.
There is no one answer to cover all of these questions but they start easy and get harder to fix to a degree the more you tick yes to the above. We should always start at the easy end and go through a process of elimination.

What we need to know is how your bike is setup - Exhaust (baffled or un-baffled) Air filter (standard or aftermarket) Fuel injection (standard or FI-module added)? The chances are you have nothing more than deceleration burble (backfire) caused by the pair-valve. This is easy to test by use of either a golf tea or bolt in the right hole.
However on a side note, I for one would not dream of running your exhausts without the baffles in, unless it was being run alongside a FI-Module.

Mr Intruder wrote:

I like the burble that we get with the pair valve in operation & mine is staying where Mr Suzuki put it

Interesting. I really hated the burble. I remember referring to it as a "muted gurgly pop pop"

I have left the pair valve alone on other bikes I have had as I like it but to be honest I would bodge it up if I attempted bypassing it. Different folks, different strokes tho

CycleBiker wrote:

Mr Intruder wrote:

I like the burble that we get with the pair valve in operation & mine is staying where Mr Suzuki put it

Interesting. I really hated the burble. I remember referring to it as a "muted gurgly pop pop"

I expect we would also probably feel the same about each others taste in music so thats fine.

Mr Intruder wrote:

However on a side note, I for one would not dream of running your exhausts without the baffles in, unless it was being run alongside a FI-Module.

WHY

captain crash wrote:

Mr Intruder wrote:

However on a side note, I for one would not dream of running your exhausts without the baffles in, unless it was being run alongside a FI-Module.

WHY

Very simply Mr Crash Sir, because the bike would be running leaner than a vegetarian crack whore
.
.
.
I think I have answered that here 3/4 the way down.

Mr Intruder wrote:

Hmmmm You don't make things easy for us do you. Several questions all interlinked and probably deserving long answers. Please remember I am only giving my opinion in this thread.

I think I speak for many members when I say your opinion is well respected round here, and I for one pay close attention to advice that you give! It might seem like a nooby question, but I don't ask just for myself, but for anybody else who has the same questions but for whatever reason hasn't asked yet. It's good to have information in one place.

My bike is completely stock except the shortcut exhausts, and I always have the baffles in. We couldn't see any gaskets when removing the old system, (I know you are supposed to replace rather than re-use anyway, but I needed to put the bike back together and get it out of my mates garden.) so a leak at the header could be possible, although I cant feel any red hot gas when I stick my hand down around there. (which is a stupid thing to do yes)

Thanks Joe

From what you have just said I would be very surprised if what you are hearing is any more than the affects of the Pulsed Air Induction Reed valve.
I very much doubt that you have an issue with the header seal but if there is, it would possibly have the same effect as the pair valve or possibly exaggerate it . One way to settle your mind on the subject would be to block off the pair valve and see if it makes a difference. I would bet a pound to a pinch of shite that the backfire (deceleration burble) all but disappears.
Bluesman has the same set up as you so maybe he could enlighten us a little on how his is reacting in comparison to yours?

vegetarian crack whore

Mr Intruder wrote:

Thanks Joe

From what you have just said I would be very surprised if what you are hearing is any more than the affects of the Pulsed Air Induction Reed valve.
I very much doubt that you have an issue with the header seal but if there is, it would possibly have the same effect as the pair valve or possibly exaggerate it . One way to settle your mind on the subject would be to block off the pair valve and see if it makes a difference. I would bet a pound to a pinch of shite that the backfire (deceleration burble) all but disappears.
Bluesman has the same set up as you so maybe he could enlighten us a little on how his is reacting in comparison to yours?

Disabled mine by blocking off both hoses, in all honesty it has made no difference at all....

I think a TRE will make a much bigger difference to coughing and farting on decelaration, especially in stop start traffic.

Never ever read or heared about anyone blocking the pair valve and still getting the deceleration burble, as it is caused by injection of air to burn unused fuel in the exhaust. If the pair valve has been blocked the you need to work out where the air that causes the burble is getting in.
Out of curiosity, what pipes do you have on your bike & did you fit them yourself?

How very strange?

Mine never had a big issue to start with, there is almost nothing on gearing down or slowing at speed. Mine has always been at slow stop start traffic speeds. I'll hook it back up at the weekend and see.

General consensus for the Oz Boulevard guys is that it is caused by the timing retard in the lower gears at slow speeds.

As for leaks, I have spent hours looking for them as my pipes have a bit of a chirp, the old VW Beetle whistle, no soot, no leaks anywhere to be found.

ozrider wrote:

Mine never had a big issue to start with, there is almost nothing on gearing down or slowing at speed. Mine has always been at slow stop start traffic speeds. I'll hook it back up at the weekend and see.

General consensus for the Oz Boulevard guys is that it is caused by the timing retard in the lower gears at slow speeds.

I find it strange that your main experience of this is at slow to stop, mine never did that at low revs!

Has anyone else experienced what ozrider is experiencing?

captain crash wrote:

mine never did that at low revs!

Has anyone else experienced what ozrider is experiencing?

Deceleration burble yes but not at low revs either.

my bike backfires some times when im not going that fast and slowing down but this is manly when going from one speed bump to the next and not being botherd to put my bike in third gear so although only in second gear and not going that fast i am exhellerateing then letting throttle of as i brake before next speed bump if i go slower in second then let throttle of the bike dont do it there go my 2 pence worth

fat intruder wrote:

my bike backfires some times when im not going that fast and slowing down but this is manly when going from one speed bump to the next and not being botherd to put my bike in third gear so although only in second gear and not going that fast i am exhellerateing then letting throttle of as i brake before next speed bump if i go slower in second then let throttle of the bike dont do it there go my 2 pence worth

Sounds about the same, slow stop start type riding such as peak hour commuting.

Don't forget Fat intruder is riding a carbed bike and he is slightly flooding his engine between speed bumps, which is then pushed out in to the exhaust to be burnt off. So if your symtems are the same then it is simply down to lugging the engine which is never a good thing to do from any angle.

changed my mind mine does wat i said but not half as much as i thought iv been trying to cruse (go slower) resently and found that if in a high gear and going slow then it backfires sometimes yep maybe some fiddleing with my carbs comeing up might check my spark plugs to see how rich its running and clean them

captain crash wrote:

Don't forget Fat intruder is riding a carbed bike .

Is that why he is Fat Intruder, too many carbs?

fat intruder wrote:

changed my mind mine does wat i said but not half as much as i thought iv been trying to cruse (go slower) resently and found that if in a high gear and going slow then it backfires sometimes yep maybe some fiddleing with my carbs comeing up might check my spark plugs to see how rich its running and clean them

I would have thought from what you have said, that Crash was right in his earlier post. I wouldn't be fiddling with the carbs for the sake of it mate. This is mostly down to lugging the engine with to much throttle in to higher gear. The extra fuel is then pissed out into the exhaust and explodes.
If I were you I would adjust the lazy riding style before the carb.

Maybe he just likes to fiddle, I got caught fiddling once by my Mrs & she went mental

Reconnected the pair valve today and went for a ride. Stiil no difference until I remembered someone saying it only works on the 'closed' throttle.

Turns out I rarely ever totally close the throttle when gearing down......who knew. When I fully closed the throttle it backfires and farts, I'll try again with the pair valve removed..

im not sure now but when rideing today something made me think that maybe my exhaust is blowing a little were the back bit joins to the down pipes just a feeling i got but if it is it cant be a lot and i cant be bothered to have a look will check it soon but i should state what ever it is that makes it do it im not that fussed im sure ill get round to sorting it sometime . and crash your a silly sod never let your missis find you fiddleing over her sister

Did you ever get your result Brian?

hi guys, I made ​​a small change to the pair valve.
First let me say that the pair valve modification does not affect the performance of our intruder, but is only there for emissions and injects air So That any one burned fuel can be ignited in the exhaust, as mentioned by Mr Intruder, but only changes the sound of exhaust in release.
The changes I have made, since the pair valve like aesthetically, they are very hidden, as I have physically removed the pair valve, but I only did so to isolate it electrically (without the FI indicator on) and mechanical functions (revenue and closed out).
Start with the electrical modifications:
2 x 2ohm resistor 5w (serial) or 1x ohm 5w 5 located in the cover of the pair valve and connected to the same place in the connector.
The mechanical part:
Closed the input from the air filter housing by means of a rubber stopper inserted into the filter box and adding plugs created with simple metal sheet placed between the cylinders and the two tubes that are screwed on. With little money I removed the pair valve!

ceretz wrote:

hi guys, I made ​​a small change to the pair valve.
First let me say that the pair valve modification does not affect the performance of our intruder, but is only there for emissions and injects air So That any one burned fuel can be ignited in the exhaust, as mentioned by Mr Intruder, but only changes the sound of exhaust in release.
The changes I have made, since the pair valve like aesthetically, they are very hidden, as I have physically removed the pair valve, but I only did so to isolate it electrically (without the FI indicator on) and mechanical functions (revenue and closed out).
Start with the electrical modifications:
2 x 2ohm resistor 5w (serial) or 1x ohm 5w 5 located in the cover of the pair valve and connected to the same place in the connector.
The mechanical part:
Closed the input from the air filter housing by means of a rubber stopper inserted into the filter box and adding plugs created with simple metal sheet placed between the cylinders and the two tubes that are screwed on. With little money I removed the pair valve!

Small correction on what I wrote above.
The resistors must be either a pair of 20 ohm, or a single 50 ohm, exscuse for error hello

I'm disabling the pair valve because with my unbaffled straight pipes it pops and cracks extremely loudly when letting off the throttle. So I'm thinking about deleting the pair valve box. What do you guys think?

If it is bothering you either completely remove it, possibly using Moccasin Mikes Pair Valve removal kit LINK or block the breather tube with a bolt or golf tee.

You have a K&N and rejet don't you? I have similar straight thru pipes to you, mine are just shorter, and when it was unbaffled they would pop and crack on almost every deacceleration. However I don't have fuel processor or hi flow air filter. Since I put the baffles in its much better, but does give the occasional big bang when I let of the throttle (rarely) but I actually quite like that, keeps the pedestrians on their toes.
Getting rid of the airbox would look great on your bike. I'm not a fan of the shape of it and I think its one too many big blobs of chrome on the marauder.
Would you complete the nekkid jugs mod and do the other side?

I don't have the K&N filters or the re-jet, *yet*. I'm doing a stage 3 re-jet with K&N filters soon. I wanted to put forward controls on it first.

I'm leaning towards removing the pair valve box. The other side doesn't have a box or anything to clean up, just the exhaust pipe coming out. I'm powder coating the exhaust, wheels and the chrome rear fender supports gloss black and painting the front fork guards and the plastic chrome covers under the seats gloss black as well.

Bunso Steel wrote:

You have a K&N and rejet don't you? I have similar straight thru pipes to you, mine are just shorter, and when it was unbaffled they would pop and crack on almost every deacceleration. However I don't have fuel processor or hi flow air filter. Since I put the baffles in its much better, but does give the occasional big bang when I let of the throttle (rarely) but I actually quite like that, keeps the pedestrians on their toes.
Getting rid of the airbox would look great on your bike. I'm not a fan of the shape of it and I think its one too many big blobs of chrome on the marauder.
Would you complete the nekkid jugs mod and do the other side?

Sounds good, will be looking forward to seeing that.

Me too!

I'm painting the front fender gloss black then the tank and the rear fender gun metal grey with a gloss black racing stripe down the top middle of both. The stripe will be the same width as the front fender. Should make for a nice contrast.

So many plans, so little money. The life of a full time student.

Mr Intruder wrote:

Sounds good, will be looking forward to seeing that.

I like it when when the bike sounds like shit but runs like cake. If you know what i mean. Angry but tame. Dangerous but safe

Ain't got a fookin clue what you mean but you make it sound very appealing and I would like some of that as well please.

Reviving this, But which line(s) do I block to eradicate the popping on deceleration?
http://www.moccsplace.com/images/pair/vol/vacuum.jpg

Think worked it out. It stopped the flames but not the backfire. I really need to get these pipes on tighter I'm guessing

It's the two black ones at the back from what I've read (the two with mesh on them), the removal of the rubber ones are for pair valve removal.

I just blocked one tube, but I think it was the wrong one lol. In this diagram which two is it? I blocked the "pair valve vacuum"

http://www.moccsplace.com/images/pair/drawing.jpg

The two that connect to the pair pipe in the drawing.

Heres a great guide for dumb people like me http://www.moccsplace.com/images/pair/pairvol.htm

That's good  I didn't know you had to block the air filter one as well? no need to remove the pipes. just join them with a drill bit inside or 2 golf tee's.

does anyone have a picture of which pipe i block off to stop the pair valve from working ?

ive been reading about this for hours and just cant understand exactly what to do with which pipes to stop the valve from working. every reply ive ever read has been very vague or they have been guessing.
can anyone explain properly how to block off this pair valve ?

Read this link to your other post - it should answer your question.  Try not to post the same question in two sections - people may miss them.  It's better to open it up as a new thread as you have done.

Good luck with it