1981 Suzuki GS 850 carb tuning

[Jeris]

I recently inherited an ‘81 GS 850. The bike is bogging while throttle is wide open and has a hard time cold starting. The previous owner put pod filters on. He said he thinks the stock main jet may be the culprit. Carbs have been cleaned and synced. Does anyone have any starting point suggestions on how to fix this issue?

[Nessism]

Member Zed sells "air correction jets" for people running pods. Also, make sure your pods are K&N, Uni, APE, or some similar quality pods. Most people buy the cheap low quality china junk pods.

[KiwiAlfa156]

Might sound silly, but make sure the pod filters are clean and correctly oiled. Engines pump air, jets just add fuel at the correct ratio for the mass of air being passed through the engine at various speeds and loads. Dirty filters adversely affect air flow and pods (especially gauze/oil cotton) seem to get dirty quickly. If you are tuning, you want to do so with a reliable, repeatable base-line.

[Big T]

Did you get the air box with the bike?

What maintenance have you done?

[gustovh]

Is the bike an L or a G? Have you checked the valve clearance, the place to start, then full carb tear down and soak, good time to check jet sizes. then you will have an idea of what you need. What the PO says makes no difference in what I check when dealing with a new to me bike. Start at the beginning and check things over by the #s. JMO

V

[KiwiAlfa156]

Also, re:cold starting. The choke is an enrichener and only works properly when the throttle is closed and full engine vacuum is applied to the circuit. So cold start with choke and no throttle, only blip the throttle once the choke is closed or almost closed.

CV Choke.jpg

[rphillips]

Most folks around our local shop installed a size bigger pilots, on our GS's, to help with the cold starting... Also don't remember anybody going to pods' and not having to go a few sizes bigger on the main jets. Pretty good info already.... Oh yeah, let me give you your first "WELCOME", and let you know we love pictures

[Who Dat?]

A larger pilot is almost never needed, if everything else is set correctly. Tight valves REALLY affect cold starting, so start there.

Once the valves are set, try the proper starting technique. Set "choke" to full. Turn key ON. Pull clutch lever. Push starter button. Do NOT move throttle. If/when engine starts, modulate engine speed by adjusting "choke". As it warms up a bit, it will accept a throttle blip. It is then about ready to ride.

Assuming the pods are correctly oiled (note that some of them are paper, therefore run DRY), larger main jets are likely needed. How many sizes larger will depend on the quality of the pods and slightly by the exhaust system.

[Nessism]

A larger pilot is almost never needed, if everything else is set correctly. Tight valves REALLY affect cold starting, so start there.

Once the valves are set, try the proper starting technique. Set "choke" to full. Turn key ON. Pull clutch lever. Push starter button. Do NOT move throttle. If/when engine starts, modulate engine speed by adjusting "choke". As it warms up a bit, it will accept a throttle blip. It is then about ready to ride.

Assuming the pods are correctly oiled (note that some of them are paper, therefore run DRY), larger main jets are likely needed. How many sizes larger will depend on the quality of the pods and slightly by the exhaust system.

What you say is true, but when it comes to jetting for pods, it's not as simple as just bumping the mains a few sizes. Dynojet sells a jet kit, which comes with mains, and different needles. They also provide a drill bit to increase the vacuum port size in the slide. Dynojet kits are expensive; in the range of $130. Zed's air correction jets are much cheaper. I haven't had much experience with the CV kits he sells, but the VM kits are like magic; guys slam those in, bump the main one size, and the bike runs well after.