CV air screw setting, 82 Katana

[Escobarclan]

1982 GS1000S Katana

My Kat is stumbling on each gear only at low rpms, she also has a hunting idle problem. She came with an open header exhaust and new pods to boot. I realize that whoever did this should have put a stage 3 jet kit in, and might have done as much, but I do need to make sure the carbs are sync'd before i address the jets, which might actually be stage 3's.

I'm going to sync my carbs (cv type) tomorrow, but I'm kinda worried about the air screws on top of the carbs. I've read they are not to be tampered with because of big brother's emission laws, and I really couldn't care less. I can see someone has messed with them before me, so how do I know they are set right? #'s 3 and 4 exhaust pipes are a little blue and might be running too lean, can the air screws be responsible for this?

Do I have to sync the carbs first or set the sir screws first? I've gathered that they should be set at 2 1/2 turns from closed? Is this right? Am I driving anyone nuts yet?

[TheCafeKid]

The adjustment screws are to be set to highest idle. The suggested 2 1/2 turns is probably a STOCK baseline, in which case you can throw that out the window for now, as your intake and exhaust are no longer stock. Ive never truely tuned CVs, but i would think that you synch, then set your adjustment screws after, as unless they are all synched together, your adjustment might be faulty once they are. As they are CVs, im pretty sure you can synch, and then mess around with your jetting, or at least check your jet sizes to assure that a kit was put in or not without having to re-synch, tho i may be wrong. My 77 750 uses the old mechanical slide VM type carbs, where to adjust needle position, you have to remove the slide arm, which means you have to resynch every time. JOY hehe

[Escobarclan]

When you said to set he air screws for the highest idle, do you mean that after the sync, to turn them all at the same time/turn to get the highest idle rpms off the engine, then adjust the main idle back down?

How can I tell if I backed them off too much? ( I HAVE to get this right, sorry.)

[psyguy]

sync / adjust mixture - technically you can do in any sequence you like

it seems though that if you have the sync done first then it's a bit easier to adjust the mixture (highest rpm method) - as you can more easily hear the effects of turning the mixture screws if the bad sync isnt anymore contributing to the poor idle

if youre using colortune for getting the mixture right the sync can be done later on

[psyguy]

Carbs adjustment

take off the tank
set the pilot mixture screws at 2 turns out from lightly seated
warm up the engine and let it run
adjust the idle at aprox 800-900rpm
SLOWLY turn the screw at carb #1 INWARDS - at some point the rpms are going to start dropping and the engine wont run as smoothly
start turning the screw back out while you get the highest rpm read and a smoother sound from the engine
at some point further turning out the screw wont make any difference (and even further out may again take away the smoothness and the rpms)
you want your screw as much IN as possible without affecting the rpms/smoothness
re-adjust the idle to 800-900rpm
stop the engine to let it cool down a bit or place a big fan in front of the engine and do this while the outside air is cooler (morning/winter)

proceed with carb #2
etc.

adjust the idle rpm to your service manual's specs

[Escobarclan]

Ok, thank you. Is there any input you have on the #'s 3 and 4 pipes turning blue? Such as running lean? Is this one of the effects of the air screw, sync, or both?

[psyguy]

Ok, thank you. Is there any input you have on the #'s 3 and 4 pipes turning blue? Such as running lean? Is this one of the effects of the air screw, sync, or both?

most likely too lean (but other than due to the poor pilot mixture this can as well be caused by the wrong jet size (too small) - they may not have been changed from stock when the air/exhaust was changed
or, there's air leaks after the carbs (at carb boots)

poorly adjusted valves contribute as well

[Escobarclan]

Boots are new, I sprayed em' and they aren't leaking (wish they were), valves are just right. Even if she does need stage 3's, will she still run right at idle with a good sync and air screw set?

How can I tell if she already has stage 3's as opposed to 1's?

[psyguy]

Boots are new, I sprayed em' and they aren't leaking (wish they were), valves are just right. Even if she does need stage 3's, will she still run right at idle with a good sync and air screw set?

yes, she should (if the carbs are clean) and the spark is good

How can I tell if she already has stage 3's as opposed to 1's?

i think (but not 100% sure) only by taking the main jet out to see its size

...........................

[Escobarclan]

Yeesh, I don't even know what stock jets look like. The jet screw in the bowl looks real shiny, as if new, alot newer looking than it should, but it's just not definative.

[katalica]

Hi,
Pull one of your main jets,and the size will be engraved on it, you might need magnifying glass but it's on there.Should be around mid 130's I use 138 's with header and k'n's on my 82 1000 Kat,also a stage 3 will have adjustable needles which you will probably have to remove from the diaphragm to check for adjust-ability. The main jet will be the one you can look up through and see the needle inside of the jet.Hope this helps a little. Good luck

[Escobarclan]

thanks, how can a jet be adjustable? by turns or washers?

[Steve]

The jet needles he was talking about are adjusted by adjusting the position of a clip into one of several grooves at the top of the needle.

The only other 'adjustments' on a CV-type carb consist of replacement of the jet with one of a different size and the idle mixture, which is adjusted by turning a screw.

.

[Escobarclan]

Hey thanks guys, I'm gonna pull the bowls when I get home and see what I got.

Going to:

1) Sync

2) Adjust Air screw

3) Make sure sync is still good

4) Check jets and see what I have

Thanks again, I'd be lost without ya'll, or out of a few more hundred from a shop, if I could even find one.

[Colin Green]

The jet needles he was talking about are adjusted by adjusting the position of a clip into one of several grooves at the top of the needle.

The only other 'adjustments' on a CV-type carb consist of replacement of the jet with one of a different size and the idle mixture, which is adjusted by turning a screw.

.

Hi Steve,

I have got my beast running not too bad now by trying the highest rev method. I found the "highest rev" to be rather difficult to determine but persevered until I found what I thought to be the smoothest idle (and highest?). Combined with several road tests I now have it running a lot better. She still stumbles a little when loading at very low revs, doesn't seem to pull as hard and idle drops a little as she gets hotter.

What effect does adjusting the height of the needle have? ( I never went there when rebuilding my carbs (for my GS1100G)