What fuel/air screw turns out/in should I start with using cheap emgo pods 78' gs750

[Guest]

Hopefully this post title helps others, because I searched more specifically throughout the form for the 78' gs750 which has smaller stock main jets than other bikes of similar engine size and era, which may produce different results. Also has VS carbs (or VM, whatever they're called that aren't CV ). Has cheap emgo pods which I will replace at some point with UNI's.

Long story short, after tearing the bike apart to diagnose no fire cylinder 2 & 3, I got cylinder 2 to fire after fiddling with air and fuel screws, but now no fire on 1,3,4 (1 and 4 were firing before going through testing things...). Compression good coils good condensers good it's all good, just a ratio thing.

What I'm looking for now is a starting point / direction for the air and fuel screws. The idle screw is all the way out (not pushing against idle throttle body at all). I know when I reassembled something isn't exactly perfect and that's why 1 and 4 aren't firing anymore, and that's ok. Just want to get it dialed in.

Thanks!
-MD

 

[Big T]

Fuel - 7/8
Air - 1 1/2
Also, bench sync them before reinstalling

 

[Rob S.]

Just a reminder - APE pods look and perform every bit as good as K&N's for half the price.

 

[Guest]

Fuel - 7/8
Air - 1 1/2
Also, bench sync them before reinstalling

Thank you, I will try these settings! Funny I literally just came across a semi-related thread with many paragraphs of text that had the same suggestion with a semi-similar bike using the VM carbs.

 

[Guest]

Just a reminder - APE pods look and perform every bit as good as K&N's for half the price.

good to know, thanks!

 

[zed1015]

Get rid of those horrible cheap Emgo pods.
They are well known for being restrictive and will strangle the motor.
Start with good quality free flowing pods such as APE,K&N, Uni filter etc .
Leave all other carb settings stock apart for going up a couple of sizes on the mains and fit air corrector jets to cure the off idle hesitation/rough running..
Air corrector jet kit. Suzuki GS1000,GS850,GS750.MIKUNI.LEDAR.PODS,K&N,FILTERS. | eBay

 

[Guest]

Update: Got all 4 cylinders to fire with 7/8 fuel screw out and 1.5 air! It idled ok and had response on the throttle, which was awesome. After it warmed up a bit and I missed with choke and idle screw it died. I'll continue to tweak and tune, it still feels lean to me...

Also, took a temp reading and 2 outside cylinders reading 280 degrees and 2 inside reading 250...seems a bit warm after only idling for a minute or two, thinking still lean, thoughts? Fuel screw out another 1/4 turn or air screw in another 1/4-1/2 turn?

 

[Big T]

The screws only affect the idle mixture

You tune that with high idle, or a Colortune

 

[Guest]

The screws only affect the idle mixture

You tune that with high idle, or a Colortune

So, I tried to go at them with colortune today...with no success. Cylinder 1 intially showed me a blueish/whiteish light, and then it faded away. The cylinder stayed warm but definitely wasn't firing like it should be....so....not sure what to do about that. Messing with air screw while colortune in didn't have any affect. Cylinder 4 same result. This is with idle at around 1100rpm, are you saying that I need to jack that way up in order to get a reading?

 

[earlfor]

Thank you, I will try these settings! Funny I literally just came across a semi-related thread with many paragraphs of text that had the same suggestion with a semi-similar bike using the VM carbs.

****** QUOTE ******

Originally Posted by Big T
Fuel - 7/8
Air - 1 1/2
Also, bench sync them before reinstalling. ****** UNQUOTE ******

The most important thing said above was, "bench synch them before reinstalling.

You will get no where without doing that. If you don't know exactly what that is and how to do it say so now.

 

[Big T]

So, I tried to go at them with colortune today...with no success. Cylinder 1 intially showed me a blueish/whiteish light, and then it faded away. The cylinder stayed warm but definitely wasn't firing like it should be....so....not sure what to do about that. Messing with air screw while colortune in didn't have any affect. Cylinder 4 same result. This is with idle at around 1100rpm, are you saying that I need to jack that way up in order to get a reading?

The 1100 rpm idle is spot on
High idle method involves tweaking each air screw to its highest idle
Something's wrong if your mixture readings are fluctuating

 

[allojohn]

Your pilot is way too rich at 20, back it off to 15 stock you'll be fine.

 

[Guest]

****** QUOTE ******

Originally Posted by Big T
Fuel - 7/8
Air - 1 1/2
Also, bench sync them before reinstalling. ****** UNQUOTE ******

The most important thing said above was, "bench synch them before reinstalling.

You will get no where without doing that. If you don't know exactly what that is and how to do it say so now.

yep bench sync'd would like to vaccuum sync but don't have tool just yet

 

[Guest]

Your pilot is way too rich at 20, back it off to 15 stock you'll be fine.

any chance that is putting some excess fuel in my exhaust

 

[allojohn]

any chance that is putting some excess fuel in my exhaust

Maybe.... you also need to lower the e-clip on the needle two spaces. There are a few of on here running '78 750's (pods) with these settings.

 

[Forden]

Can someone enlighten me about bench syncing? I'm in the middle of a carb rebuild and I see it mentioned several places, did a search, but no one seems to say what it IS. Getting the slides lined up after reinstalling?

thanks much

 

[zed1015]

Can someone enlighten me about bench syncing? I'm in the middle of a carb rebuild and I see it mentioned several places, did a search, but no one seems to say what it IS. Getting the slides lined up after reinstalling?

thanks much

Yes! It's just levelling the slides making sure their adjusters are close to mid position so you are somewhere close when it comes to vacuum balancing.
In an ideal world the cylinders will be doing equal work with all the slides opening equally but in reality once vacuum balanced they will be slightly different due to piston ring seal and other variances.