K&N Filter and Carb Adjustments

[vur]

I think I may have a lean running condition within my '84 GS750EF. The previous owner installed a K&N filter and I think the increased air flow (over the stock filter) may be causing me some lean running problems.

My Symptoms:

• Requires choke slightly on for at least 5 miles before it is warmed up enough to run without the choke.
• Engine has slight "surging" sensation at pretty much any speed below 7000 rpm
• Plug appearance indicates lean operating conditions (all four plugs are similiar)

Questions:

• Is my choke operation during warmup "normal"?
• Has anyone else have carb tuning issues after installing a "higher flow" air filter?
• Any other thoughts?

Current Path Forward:

• Before I dive into changing idle air jets I was going to try restricting the air intake (duct tape likely) to see if my drive ability issues correct them selves.

Other Notes:

• Valve clearances are OK
• Compression currently not know. During valve clearance checks the compression seem think it may be low (compared to other motors I have turned over with a wrench). Still need to confirm

Thanks

 

[tkent02]

Does sound lean, for whatever reason. Could be from the filters, but most likely it's air leaks or something not working right, floats set wrong, whatever.

If it's just a K&N filter in the stock airbox it shouldn't be very far off, if it's pods it will be a big change.

Turn your pilot screws out, might need to raise the jet needle, and go up one size on the main jets.

 

[rapidray]

If it hasn't been done before you need to drill the plugs that cover the mixture screws with a 1/8 inch drill bit & remove the plugs with a sheet metal screw. Be VERY careful when drilling the plugs so you don't damage the screw heads! After that, re-install the carbs &, with the bike idling, turn the screws in or out until the bike idles the fastest it will idle. Do them one at a time & then move on to the next. If the bike starts idiling too fast, after you do one, turn the idle down & move on to the next one. It is easy & when done correctly you should see a BIG improvement in the ease of starting & drivability of the bike. Good luck, Ray.

 

[catbed]

i installed KN drop in filter and i raised the needles and it made a big difference. next is to upgrade to a bigger main. do as rapid ray says first though.

 

[vur]

High Idle Speed with Choke On

High Idle Speed with Choke On

Another Symptom I have:

• Idle speed increases to ~ 4000 rpm with choke fully on

Another indication of lean idle conditions being corrected by adding more fuel with choke I believe

Just to confirm, does everyone one else experience a DECREASE in idle speed when they fully apply the choke (i.e. fuel mixture becomes richer)?

Thanks

 

[rustybronco]

Another Symptom I have:
Just to confirm, does everyone one else experience a DECREASE in idle speed when they fully apply the choke (i.e. fuel mixture becomes richer)?

Thanks

82 gs850g...
70 degree temps today, full choke 3500 rpm fast idle, back it off a little 5000+ rpms fast idle.
after the initial start up and then taking it off choke 400-500 rpms.
warm idle speed 1050rpm
but who uses full choke in these temps?

bone stock, k&n air filter.
ran fast enough to beat a harley wannabe this a.m. (guess he didn't like me wearing a h.d. leather when I heard those screemin turkeys)

 

[vur]

Thanks for the reply.

Also just looked at my Suzuki manual and all is clear now on the "choke" operation. It is not really a "choking" operation per say, more of an idle speed control circuit...

The manual calls it the "Starter System" which essentially introduces air and fuel - now I understand why I get a fast idle....

Manual Description:

"Turning the choke knob all the way left, slides starting plunger to draw fuel into the starter circuit from the float chamber through starter jet.
Starter jet meters fuel, which than flows into starter pipe and mixes with the air coming from the float chamber. The mixture, rich in fuel content, reaches starting plunger and mixes again with the air coming through a passage extended from behind the diaphragm.
The two successive mixings of fuel with air are such that the proper air/fuel mixture for starting is produced when the mixture is sprayed out through starter outlet into the main bore"

 

[catbed]

the choke on these mikunis is really an enrichener system. it doesnt actually choke air, just adds more fuel.

 

[Skateguy50]

If it hasn't been done before you need to drill the plugs that cover the mixture screws with a 1/8 inch drill bit & remove the plugs with a sheet metal screw. Be VERY careful when drilling the plugs so you don't damage the screw heads! After that, re-install the carbs &, with the bike idling, turn the screws in or out until the bike idles the fastest it will idle. Do them one at a time & then move on to the next. If the bike starts idiling too fast, after you do one, turn the idle down & move on to the next one. It is easy & when done correctly you should see a BIG improvement in the ease of starting & drivability of the bike. Good luck, Ray.

I know im supposed to adjust them but no one really explained that well how to adjust them, thanks for sharing. I just turned them all 1 1/2 turns back from when i felt pressure and it "sounded" ok so left it.

 

[Steve]

If you set them all about 2 turns out, instead of 1.5, your cold-bloodedness might be helped a bit. Some guys prefer to start adjustments at 3 turns, but anywhere between 2 and 3 is a good place to start.

Besides enhancing normal operation, running the idle mixture a bit richer GREATLY enhances cold operation, enabling you to get off the 'choke' MUCH sooner. With my wife's '82 850L, I don't remember how many turns out the screws are, but we start the bike, put on helmets, leave. By the time we are into third gear, the 'choke' is OFF.

.