Author Topic: Why do you need a restrictor ring for the SU-5589 drop-in air filter?  (Read 219 times)

Offline BikerBoy

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I've seen multiple people say that you need a restrictor ring if you use the K&N drop-in air filter, the SU-5589. I bought mine on ebay and it didnt come with a restrictor ring. so why do I need one? Seems like my bike runs ok without one.

Thats what it looks like

Offline The Buddha

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #1 on: September 30, 2019, 01:34:02 PM »
Restrictor just guarantees you don't run lean. You can make one with cardboard or something, maybe a stiff plastic sheet.
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Offline BikerBoy

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #2 on: October 03, 2019, 10:29:06 PM »
Restrictor just guarantees you don't run lean. You can make one with cardboard or something, maybe a stiff plastic sheet.
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Ok, thanks, I bought the K&N filter off ebay but it didnt come with the ring...Ive upgraded the jets to 142.5 and added a delkevic ss70 exhaust, so since its not stock is the restricter still neccessary? Thanks

Offline Bluesmudge

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #3 on: October 03, 2019, 10:58:10 PM »
How does your bike ride? When my GS was "asking" for the restrictor ring it had a weird dead spot around 4500 rpm. I have +1 jets and a Vance and Hines full exhaust that has an added decibel killer and spark arrestor. The bike runs much better with the restrictor in place.
The restrictor is supposed to bring the filter back to approxinaty the stock airflow.

Offline BikerBoy

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #4 on: October 09, 2019, 12:54:34 AM »
How does your bike ride? When my GS was "asking" for the restrictor ring it had a weird dead spot around 4500 rpm. I have +1 jets and a Vance and Hines full exhaust that has an added decibel killer and spark arrestor. The bike runs much better with the restrictor in place.
The restrictor is supposed to bring the filter back to approxinaty the stock airflow.
I took it for a ride and its kinda weird, has kind of a dead spot around that area of 4-5000 rpm. Also it likes to die at idle, even when warmed up with the choke off, but when I adjust the idle screw to around 1200 rpm it fixes the dying problem, but then I have a hanging idle issue (which Ive read is caused by a lean condition). So I think maybe I need the restrictor to limit the airflow, thus enrichening the mixture. Sucks that it looks like I need to buy another filter just for the re stricter though, as Im not too handy with fabricating items like that.

Offline herennow

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #5 on: October 09, 2019, 05:49:39 AM »
what year is your bike, if mid 2000's the standard main is 130 so you are +6 jets up THATS HUGE.......

What do you have for the other jets.

The flatspot around 5K RPM at WOT is well known for being a rich spot and is often seen with +1 jets.

Is your flat spot at WOT under load, or all the time.?

Offline BikerBoy

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #6 on: October 09, 2019, 06:29:18 AM »
what year is your bike, if mid 2000's the standard main is 130 so you are +6 jets up THATS HUGE.......

What do you have for the other jets.

The flatspot around 5K RPM at WOT is well known for being a rich spot and is often seen with +1 jets.

Is your flat spot at WOT under load, or all the time.?
its a 2008 gs500f converted to naked.

I followed the jetting matrix from here: http://beergarage.com/GSJet.aspx  I have 20, 60 or 62.5 (I can check my parts in the garage and deduce which one it is later), 142.5

Ive been playing with the air fuel screws (I got extended ones from ebay so its really easy to change this setting) and the idle screw to hopefully change it so it starts and runs well. Ill take it for a ride tomorrow and tell you how it behaves, thanks  :thumb:

Offline herennow

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #7 on: October 09, 2019, 03:47:31 PM »
There are a few posts that go into more detail but the main only kicks in above 3/4 throttle.
The mid jet does nothing except when choke is on. It's purely a choke jet. I'd leave it as is.
From 1/4 to 3/4 of throttle (mark it) fuelling is totally controlled by needle and needle jet. Normally one would shim needles etc. But this is a CV carb and reacts mostly correctly to change in vacuum.

Offline BikerBoy

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #8 on: October 09, 2019, 06:50:32 PM »
I see, thanks. Im wondering if the lack of a restriction ring is making my mixture too lean, like I said I put on a (very open flowing) delkevic ss70 exhaust, and so I thought that I would want the air filter to be open flowing too. People have said the restriction ring mimics the stock air filters airflow, so Im just wondering if thats even desirable to use the restriction ring since the jets and exhaust are upgraded.

I guess I could buy another air filter new and use the restriction ring from it, then sell it without the restriction ring and only lose 20 bucks or so. But Id rather not go down this path if it doesnt have a chance to fix my problem. Im just not knowledgeable enough to know if its the restriction ring or something else.

Offline herennow

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #9 on: October 09, 2019, 07:17:09 PM »
Forget about the restrictor ring, if you want to test the effect put a but of duct tape securely over the mouth of the filter to close off 10%  then 20% of the area. Ride it and see if that improves or makes worse.

if you think it's running lean, open your choke and go for a ride and see if it gets better.

Remember, Unless you are at WOT or very close to it,  you are not testing anything to do with the main jet.

Good luck

Offline The Buddha

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #10 on: October 11, 2019, 10:07:45 PM »
The 5589 and slip on are 2 sizes up from stock with or without restrictor. If anything, restrictor may mean 1 up from stock, same as stock paper filter.
On an 89-00 That would be a 127.5 main, and on the 01+ that would be 135 mains.

We do +1 on pilots and 1 washer and 3 turns on mix screw on all years even if 100% stock, and that's a starting point, air screw adjustment form there to suit, and set the float heights to stock - At the top of bowl.

I dunno how its even running with 142.5, have you tweaked something elsewhere to compensate ? I had a miserable time getting +1 past the perfect which for 2970 K&N and pipe was 150 mains, 152.5 it was discernibly worse in comparison, and with 155 it was utterly miserable.

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Offline BikerBoy

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #11 on: October 12, 2019, 07:29:46 AM »
The 5589 and slip on are 2 sizes up from stock with or without restrictor. If anything, restrictor may mean 1 up from stock, same as stock paper filter.
On an 89-00 That would be a 127.5 main, and on the 01+ that would be 135 mains.

We do +1 on pilots and 1 washer and 3 turns on mix screw on all years even if 100% stock, and that's a starting point, air screw adjustment form there to suit, and set the float heights to stock - At the top of bowl.

I dunno how its even running with 142.5, have you tweaked something elsewhere to compensate ? I had a miserable time getting +1 past the perfect which for 2970 K&N and pipe was 150 mains, 152.5 it was discernibly worse in comparison, and with 155 it was utterly miserable.

Cool.
Buddha.
So you think I should only go +2? so maybe 20/62.5/135 or so? I dont understand, can you explain this in more detail? Why dont you understand why its running with 142.5, do you think thats too big, or too small? I just followed the jetting matrix on the internet. Thanks

Offline herennow

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #12 on: October 12, 2019, 08:54:59 AM »
it's too much, the standard way when jetting is to get the next three size up jets and go step by step and test , never to make a big jump. I might also go back to the 60 mid. Going  up on the choke jet only messes with your cold running when the choke is open. dos nothing to normal running without the choke.

Remember the MAIN jet ONLY WORKS WHEN YOU ARE AT WOT. so bike can run fine UNTIL you get to to 3/4 throttle. IN fact you can remove the main jet and the bike will run exactly the same until you throttle above 3/4 and the main jet comes into play

THis is a CV carb, it adjusts largely to increased airflow (vacuum) by providing more gas automatically through the diaphragm. BUT is does this only in the range from small openings up to just over 3/4 throttle opening.

If you want to check main jet size you need to find a long gentle hill and pull in a highish gear from 3k rpm to over 7 k AT WOT. Throttle has to be fully open. Anything else and you are testing the needle/needle jet / diaphragm which is self adjusting.

Carbs are really hard. most folks give too much gas in the mixture in the false belief that more gas = more power.

You have to go step by step and take notes and only change one thing at a time.  Trust me.

I've previously posted where you can get a dozen jets for 10 bucks from china. you should be able to find it. Quality seems good.

I looked at that jetting sheet - Im sure many of those high jetted bikes are " projets" that never run right.....

Offline BikerBoy

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #13 on: October 14, 2019, 11:48:03 PM »
Ok thanks Im going down to 60 and 137.5 to see how that works.

Does anyone know if this carb needle already has washers on it? I bought it used and am not sure where the #3 washer would go. I see a big washer on the bottom of the needle (on the left of the picture I took). Im just not sure if that counts as a washer. It has a big washer at the bottom and a small washer at the very top too. Does this look like its in the right order? Heres a picture, click on it to zoom in. Thanks

« Last Edit: October 15, 2019, 12:02:16 AM by BikerBoy »

Offline The Buddha

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #14 on: October 14, 2019, 11:56:34 PM »
60 is fine for the mids with 5589 and slip on. IMHO 137.5 is too rich, 135 better, but your call.
The stock configuration of that washer on the needle is on top of the e clip, and the rejetted (1 washer under needle) setup is where we put the needle under the e-clip. Usually we don't put a washer on top of the e-clip as well, but this person seems to have done that. Its OK. You can leave it, or take it off. Leave the washer under the e-clip.
So you have 20 pilots 60 mids, 1 washer and 137.5. Set the floats to the top of the bowl and run it and see. That may just leave you a hair richer than ideal. In a cold, humid area you may be perfect, if you're in a hot and arid area, you may be much richer than ideal.

Sorry for the late response, 142.5 was very rich. I'm wondering what else was tweaked to correct for that, like setting the floats very very low for example. Will cause a lot of other problems, no idea what exactly, I never did more than 1 size up, and didn't change floats to fix for that.

Cool.
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Offline BikerBoy

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Re: Why do you need a restrictor ring for the SU-5589 drop-in air filter?
« Reply #15 on: October 15, 2019, 12:17:10 AM »
60 is fine for the mids with 5589 and slip on. IMHO 137.5 is too rich, 135 better, but your call.
The stock configuration of that washer on the needle is on top of the e clip, and the rejetted (1 washer under needle) setup is where we put the needle under the e-clip. Usually we don't put a washer on top of the e-clip as well, but this person seems to have done that. Its OK. You can leave it, or take it off. Leave the washer under the e-clip.
So you have 20 pilots 60 mids, 1 washer and 137.5. Set the floats to the top of the bowl and run it and see. That may just leave you a hair richer than ideal. In a cold, humid area you may be perfect, if you're in a hot and arid area, you may be much richer than ideal.

Sorry for the late response, 142.5 was very rich. I'm wondering what else was tweaked to correct for that, like setting the floats very very low for example. Will cause a lot of other problems, no idea what exactly, I never did more than 1 size up, and didn't change floats to fix for that.

Cool.
Buddha.
Thanks for the reply, so I can leave my needles how they are, thats good. I have a spare carb and its needles had an extra washer on the bottom too, I could those off and put them on the other one for 2 washer each, but Im not going to do that now, Ill see how it runs with the new jets, and Ill order some 135s too.  :thumb: