Jetting recommendations for Skunk with 4-into-1

[Guest]

Just what it says.
I am removing the stock exhaust on my Skunk and installing an old header with muffler on it.
As the baffle is not there, I am having a 1.5" tube installed/welded to the end cap, adding a washer to the tube and perforating it to surround with heavy fiberglass packing.
The bike will still have the stock airbox with K & N filter. No other changes.
Those of you with '78-'79 1000's and a pipe please offer what you are using in the carbs for main jets and which clip for the needle.

Thanks for all replies.

[tkent02]

Just a guess, probably somewhere around 102.5 - 110 for the main jet. Maybe need to raise the needle, maybe not. It will of course take fine tuning. Every engine and every pipe i different. Replacing the airbox with pods makes a bigger difference than just the pipe will. Without doing that not so much jetting change.

[GSScoobie]

Aren't there at least a few dozen members of this forum that are running a stock '78-79 1000 with a header on this forum?
I have seen plenty of pictures of them here.
Could those owners please list what they did to the stock carbs?

[tkent02]

You are using a custom baffle. You will need customized jets.

[Agemax]

Aren't there at least a few dozen members of this forum that are running a stock '78-79 1000 with a header on this forum?
I have seen plenty of pictures of them here.
Could those owners please list what they did to the stock carbs?

as TK says, you have a custom exhaust which nobody else has, so no one can give you any specific info on where to start.
buy some 110's and see how it runs, then go up or down accordingly

[80GS1000]

A good baseline tune with an aftermarket 4-1 on a GS1000 comes from the Dynojet kit. With your mods, stage 1 is a good place to start.

http://www.dynojet.com/jetkits/motorcycle/suzuki.aspx#1000

Your custom config will require custom tuning.

[GSScoobie]

Well it appears that I am not the only one around here with old timer's disease.
Not one person that has done this has replied yet.
Perhaps no one writes these things down or remembers what they did?
I ordered 102.5 and 105 main jets from Z1 and will see what works myself I guess.

[hampshirehog]

Your bike will be different to everybody else's when you customise that pipe so your carb tuning will be different as well. As you're just messing with the pipe you won't need too much of a change and somewhere between 95 (standard) and 105 will more than likely work.

I've got 2 1ks - both with 4-1s (one Marving, one Micron) and standard airbox. One likes 95 mains, the other 102.5s.

[Agemax]

Well it appears that I am not the only one around here with old timer's disease.
Not one person that has done this has replied yet.
Perhaps no one writes these things down or remembers what they did?
I ordered 102.5 and 105 main jets from Z1 and will see what works myself I guess.

a vast majority of us old timers Have done this, except mostly we use recognized systems and not home made one off silencers.
if 105's works fine in one GS it dosent mean to say it will work straight away in your GS, every engine is different, mileage,state of carbs, ignition system, engine condition and service status (shims done recently, compression checked,plug condition etc etc)
the best option is to fit a dynojet kit and work from that. buying jets until you get it right is a drawn out process but it is the only way, but then you dont get the DJ needles which helps enormously .

we are not mind readers and we cant wave magic wands to make your bike run right, you have to do the leg work using any advice that is given to you

[Gregory]

Hi Scoobie,
I have a 78 gs1000 with 4 in 1 vance & hines, stock airbox. I just started working on mine a few weeks ago and was told to get 105 mains, and that is what i put in. I cant tell you whether they worked yet because right now I am at the stage of tuning in the carbs.

I will keep you posted.

[GSScoobie]

I got the parts made yesterday. I had a muffler shop add a piece of 1.5" pipe to the nub that was the only thing on the cap of the muffler.
I took a washer that I had drilled some holes in to have welded on the end to assist in the gas going through the packing to silence it a bit more than just straight through.
Then I just started cutting some grooves in the tube with an L model sawz-all.
Hopefully I can jam enough of the packing around it so that it is relatively quiet.







If I had the right tools I probably would have just drilled a bunch of small holes and wrapped it with stainless steel screen to keep the packing from blowing out.
I hope that this works.