Jetting almost there...Yes or no??
01-23-2011, 12:35 PM
#1
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Squid
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Location: Mooresville, NC
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Jetting almost there...Yes or no??
Hey guys- I have a 2004 VTR with 4500 miles. Dyno jet kit with largest mains and I am not sure where the needle sits...fuel screw is 2.5 turns out. I have a K & N filter and Yosh slip ons.
After installing the slip-ons I had terrible popping. I knew I was lean on the pilot but uncomfortable doing the work myself. Took the bike to the Honda dealer and he found a broken pilot jet (must have been the Dyno Jet installer before me). He was convinced this was my lean issue. He cleaned the carbs, replaced the jet and sent it home.
Today here in Charlotte NC it's 45 degrees (ice has melted). I took the VTR out to test her. This bike runs so well with no hesitation BUT I still have a slight pop coming off of throttle.
Question- could the cold 45 degree temps still be part of the problem? Should I wait until it warms up a little to test again? Since the bike runs so well should I deal with the slight pop? Will the slight pop (if it doesn't go away when warmer) hurt anything? Should I leave well enough alone (did I say the bike sounds and runs well) and deal with it OR will a fuel screw adjustment help or maybe even a larger pilot? It runs sooooo good but I am a perfectionist and that little pop bothers me. This is not a Harley with drag pipes
After installing the slip-ons I had terrible popping. I knew I was lean on the pilot but uncomfortable doing the work myself. Took the bike to the Honda dealer and he found a broken pilot jet (must have been the Dyno Jet installer before me). He was convinced this was my lean issue. He cleaned the carbs, replaced the jet and sent it home.
Today here in Charlotte NC it's 45 degrees (ice has melted). I took the VTR out to test her. This bike runs so well with no hesitation BUT I still have a slight pop coming off of throttle.
Question- could the cold 45 degree temps still be part of the problem? Should I wait until it warms up a little to test again? Since the bike runs so well should I deal with the slight pop? Will the slight pop (if it doesn't go away when warmer) hurt anything? Should I leave well enough alone (did I say the bike sounds and runs well) and deal with it OR will a fuel screw adjustment help or maybe even a larger pilot? It runs sooooo good but I am a perfectionist and that little pop bothers me. This is not a Harley with drag pipes
01-23-2011, 01:16 PM
#3
Out of my mind, back in 5
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Well, getting a carbed bike to run right in all temps is nigh on impossible... Getting it right at 45F means getting it wrong in summer temps... So doing anything based on how it runs in 45F is just plain wrong... And that really should be obvious...
Other than that, you have chosen the complete list of components that I generally dislike, so as for the rest of the setup, you are on your own...
I have no real experience with those parts beyond knowing I couldn't get the result I wanted out of it all...
Other than that, you have chosen the complete list of components that I generally dislike, so as for the rest of the setup, you are on your own...
I have no real experience with those parts beyond knowing I couldn't get the result I wanted out of it all...
01-23-2011, 02:46 PM
#4
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If you do a search, you'll find that jetting opinions are like...you know what I mean, ...everybody has one.
With stock air filter and Yosh slip-ons, I chose the option suggested by 8541Hawk and went with 48 pilots and a needle shim (I'd done the shim with the stock cans). Main jets are stock. Mine runs great at all rpm with the street baffles in or out, but I'm not running a K&N. Many on here recommend against it.
As for the popping (decel backfire), disabling the PAIR might help slightly, although the PAIR valve is supposed to shut off airflow to the exhaust ports during deceleration. The backfire comes from unburned gas (caused by rich mixture during deceleration) going through the straight slip-ons and hitting air containing oxygen. The stock cans have baffles, so the exhaust cools more before exiting.
If you took the muffler off a carbureted car and ran short, straight pipes, it would pop on decel as well.
With stock air filter and Yosh slip-ons, I chose the option suggested by 8541Hawk and went with 48 pilots and a needle shim (I'd done the shim with the stock cans). Main jets are stock. Mine runs great at all rpm with the street baffles in or out, but I'm not running a K&N. Many on here recommend against it.
As for the popping (decel backfire), disabling the PAIR might help slightly, although the PAIR valve is supposed to shut off airflow to the exhaust ports during deceleration. The backfire comes from unburned gas (caused by rich mixture during deceleration) going through the straight slip-ons and hitting air containing oxygen. The stock cans have baffles, so the exhaust cools more before exiting.
If you took the muffler off a carbureted car and ran short, straight pipes, it would pop on decel as well.
01-23-2011, 02:59 PM
#5
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I managed to come up with a winning set up with MIG pipes, K&N filter, and a Dynojet kit.
5th grove on the needles,
Mains; 185 front, 190 rear
Air screws out 2.5 turns
Slow jets are 45's and would like 48's, but it works well.
Dont mess with the airbox, use the plugs that come with the K&N
Carb synch is a must.
Mine popped on deceleration for a year till I finally removed the PAIR system. Now it's just loud. It runs sweet here (750 ft) to the mountains nearby (3-4000 ft)
5th grove on the needles,
Mains; 185 front, 190 rear
Air screws out 2.5 turns
Slow jets are 45's and would like 48's, but it works well.
Dont mess with the airbox, use the plugs that come with the K&N
Carb synch is a must.
Mine popped on deceleration for a year till I finally removed the PAIR system. Now it's just loud. It runs sweet here (750 ft) to the mountains nearby (3-4000 ft)
01-23-2011, 05:16 PM
#6
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01-24-2011, 09:34 PM
#9
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.... PAIR system, search forum.... down load the manual..... there is a thread for removing it with pictures.. air injection system for smog control, there are two injection points(each head) running through the head into the exhaust at the valve... there is a hose off each one running a valve under the airbox that then runs to the airbox to retreave fresh air to inject into the exhaust. there is a vacuum that runs to the front carb... carb vacuum increases opens the valve and the vacuum of the exhaust draws air from the airbox into the exhaust stream mix and burns the excess fuel in the exhaust. it is not good for performance modification and it causes backfiring
It has absolutely no effect on performance since the air is injected (or in the case of PAIR, induced by syphon created by exhaust flow) into the exhaust port outside of the combustion chamber.
The PAIR valves purpose is to prevent backfire when vacuum is 22" Hg or higher. That high of a vacuum only occurs on deceleration. The PAIR valve then shuts off the air flow to the exhaust port. On cars the "anti-backfire valve" was called the gulp valve, bypass valve or diverter valve, depending on its method of operation. Late model computer controlled AIR systems on cars used an electronic "smog pump" which was shut off by the ECM during decel or an ECM controlled diverter valve if the pump was belt driven.
Since the PAIR valve is a diaphragm unit, I'm guessing that on older bikes the diaphragm may have failed, causing the backfire on decel. But with straight through open exhaust of relatively short length (as on a motorcycle) a decel backfire might be expected and is not a big problem.
However removal of the PAIR valve and plumbing does make getting to the carbs much easier.
01-25-2011, 11:31 AM
#10
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not sure which part of what i wrote is wrong,
your definition is more informative but the same as mine. as far as performance goes, it does hinder it,, not in a stock application per say but in a performance tuned car or bike it does, it changes the exhaust back pressure/pulse & temperature,, and in turns effects the flow pressure between the intake and exhaust. it is and was designed for emissions(smog control) which is generally not a performance enhancing or maintaining tool. all of my bike runs better with out it, and the PAIR was operational. if it didn't hinder performance than race teams would use it. they do not and it is not a total result of weight.
maybe everyone should leave it on, the?. removing it cleared up the ridiculously loud popping/backfireing with stock carbs and jetting.
your definition is more informative but the same as mine. as far as performance goes, it does hinder it,, not in a stock application per say but in a performance tuned car or bike it does, it changes the exhaust back pressure/pulse & temperature,, and in turns effects the flow pressure between the intake and exhaust. it is and was designed for emissions(smog control) which is generally not a performance enhancing or maintaining tool. all of my bike runs better with out it, and the PAIR was operational. if it didn't hinder performance than race teams would use it. they do not and it is not a total result of weight.
maybe everyone should leave it on, the?. removing it cleared up the ridiculously loud popping/backfireing with stock carbs and jetting.
In the emission control section of my class, my lecture on AIR/PAIR grew over the years to fill an entire 4 hour class. Most car manufacturers have not used AIR/PAIR for almost 20 years. The reason for this is computer controlled fuel injection and improved engine controls. I'm not sure, but I would guess that fuel injected motorcycles don't require PAIR anymore either. It all depends on whether the car/motorcycle passes the Federal emission standards.
AIR and PAIR were always "add-on" smog devices, not required on any car or motorcycle if said vehicle could pass the emission standards without it. Some cars in the late '60s and '70s with identical engines would require AIR (smog pump) if the car had a 4 speed, but not if the car had an automatic. It all has to do with passing the Federal emissions test on the dyno.
As far as racing goes, no race vehicles have ever been required to meet emission standards of any type. As a matter of fact, where your computer controlled fuel injected car runs a 14.7:1 air/fuel ratio, a Top Fuel Dragster runs at almost 1:1 air/fuel ratio, burning 8 to 10 gallons of nitro methane fuel in a single run.
To me the best reason for removing the PAIR is in the last sentence of my previous post.
And if you think you have more power with your PAIR removed, I might suggest that you install a set of Split Fire spark plugs as well, for another 10hp.
Last edited by VTRsurfer; 01-25-2011 at 11:34 AM.
01-25-2011, 11:40 AM
#11
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I'm gonna agree a little with both of you...
I agree with VTRsurfer completely, PAIR will never ever as far as I can see have any direct effect on performance...
But, indirectly it will... Anyone that have tried tuning a bike or car with PAIR enabled can tell you that... First of, it screws up any readings you might take with just about any tool available... Second, it will mask a lot of the small signs that could get you measurable performance increases...
So, while VTRsurfer is right, it doesn't affect performance, the reason why you disable it before you do any tuning is simple... With it still operational, you are just guessing...
But, if you like, once the bike is tuned up, enabling PAIR again, will make no difference to power output or fuel efficiency... That is, if you really want to comply with some stupid rule...
I agree with VTRsurfer completely, PAIR will never ever as far as I can see have any direct effect on performance...
But, indirectly it will... Anyone that have tried tuning a bike or car with PAIR enabled can tell you that... First of, it screws up any readings you might take with just about any tool available... Second, it will mask a lot of the small signs that could get you measurable performance increases...
So, while VTRsurfer is right, it doesn't affect performance, the reason why you disable it before you do any tuning is simple... With it still operational, you are just guessing...
But, if you like, once the bike is tuned up, enabling PAIR again, will make no difference to power output or fuel efficiency... That is, if you really want to comply with some stupid rule...
01-25-2011, 12:04 PM
#12
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Very true Tweety. If you wanted to take air/fuel ratio readings from the exhaust, you would need to disable the PAIR by pinching off the hoses or disconnecting and plugging the PAIR inlet to the head...or just rip it all off and throw it in a corner, like most of us have done.
01-25-2011, 02:34 PM
#13
Out of my mind, back in 5
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I still threw every last PAIR system I came across in the bin though... But that's just based on my criteria that if it doesn't improve performance it's considered dead weight...
Last edited by Tweety; 01-25-2011 at 02:37 PM.
01-25-2011, 04:12 PM
#14
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As I said, neither the dyno or me could feel, hear or otherwise detect or measure any difference...
My guess is that the reason you noticed a difference is that the bike was not in best tune at the time, regardless of PAIR or not...
My guess is that the reason you noticed a difference is that the bike was not in best tune at the time, regardless of PAIR or not...
01-27-2011, 08:55 AM
#17
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Wow!! I guess you got your explanation and then some. I'm no smog/emissions expert or anything, but I figured since removal of the PAIR system was a common mod I'd give it a shot. After I did, the popping on decel disappeared. Absolutly no performance gains, but it sounded smoother. From what it sounds like in your post, my bike did the same thing. Jetted it, it ran Great, but with a little noise on decel. If you do a search on it you should find some detailed instructions for removal, it's really not that bad. Give it a shot! If the bike is running great I would DEFINITELY try this before touching the carbs again. You really got nothing to lose, other than the pop. Once again, I'm no expert, just a backyard mechanic with a smooth sounding Hawk!!
01-27-2011, 02:17 PM
#19
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01-29-2011, 05:53 AM
#20
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Squid
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I read the PAIR system removal instruction on the site and it does look very easy. For those of you that have made this change, how difficult is it to remove the front cylinder reed housing? In the photos the rear looks easy to get to but I can't see the front cylinder?
01-29-2011, 06:30 AM
#21
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Not a problem at all. It was about 2 years back I did mine so I don't recall the exact details, but was not difficult. I didn't flip the reeds, I used block off plates. Pulled the PAIR valve out and pluged the hoses and attachment points on the airbox.
For me this was about learning more about working on my bike and clearing up some space around the carbs. For you I'd say it is a logical next step to stop the pop
For me this was about learning more about working on my bike and clearing up some space around the carbs. For you I'd say it is a logical next step to stop the pop
01-29-2011, 07:50 AM
#22
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Just be careful when you remove the bolts on the front cylinder PAIR housing or the rear for that matter. When I removed the bolts on mine, the first one came out fine but the second was partly seized. Undeterred, I used more force and snapped it. Then the usual agony of trying to get the sucker out followed. I expect this type of problem to become more common as our bikes age. Good luck!
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