78 gs1000 Needle Shimming

[Guest]

Lets keep it simple. Whats the best technique on shimming the needles?
My Bike: K&N Pods, 4-1 Kerker, Chem Dipped jets cleaned out with guitar string, bench sync'd my carbs.
Syptoms: Idle-1/4 throttle is fantastic, 1/4-3/4 throttle starvs for fuel and sputters, 3/4-Full throttle the power comes back on but could be better.

Ive never done this before or messed with shims or washers. Tips on shimming the needle?

I know im working backwards so Ill make sure to look up how to do a Valve adjustment before shimming.

Can you, or do you need to, adjust timing with electronic ignition upgrade?

[Big T]

You don't shim the needles on VM carbs, they have a number of positions available

The clip on your needle should be set on the second groove from the tip of the needle

What are your jet sizes and screw positions?

[Caferob]

You don't shim the needles on VM carbs, they have a number of positions available

The clip on your needle should be set on the second groove from the tip of the needle

What are your jet sizes and screw positions?

Needle clips, like the dirt bikes yes. ok. I couldn't read the numbers on the jets. I saw a "." barely. I wanna say 20 something on the smaller one and the main was triple digits.

[OldVet66]

You can shim VM needles with a washer half a clip width but until you get your jetting and settings into the ball park you would be chasing your tail. I would recommend starting with a Dynojet jet kit (https://www.z1enterprises.com/dynoje...0-1978-79.html) The taper of the needle is superior to stock needles for what you are doing. Then stop working backward, do your valve adjustments and make sure there are no vacuum leaks, put in the jet kit, find reasonable settings, sync the carburetors and start tweaking until they are dialed in. I'm running the 142 jets (somewhere in the 130's for stock jets). The jet kit also has shimming washers. All motors are different so start with a known ball park setting and work your way out from there. You also want to pull the two outer vent hoses off the carburetors. Electronic ignition will work from the factory (I would recommend Dyna-S) but I would also recommend using a timing light and slip the 2-3 module to the timing mark after setting 1-4. When I first installed mine I marked the Dyna plate as near as I could from the points plate and it was good enough to start the bike right off before timing it.

[Caferob]

You can shim VM needles with a washer half a clip width but until you get your jetting and settings into the ball park you would be chasing your tail. I would recommend starting with a Dynojet jet kit (https://www.z1enterprises.com/dynoje...0-1978-79.html) The taper of the needle is superior to stock needles for what you are doing. Then stop working backward, do your valve adjustments and make sure there are no vacuum leaks, put in the jet kit, find reasonable settings, sync the carburetors and start tweaking until they are dialed in. I'm running the 142 jets (somewhere in the 130's for stock jets). The jet kit also has shimming washers. All motors are different so start with a known ball park setting and work your way out from there. You also want to pull the two outer vent hoses off the carburetors. Electronic ignition will work from the factory (I would recommend Dyna-S) but I would also recommend using a timing light and slip the 2-3 module to the timing mark after setting 1-4. When I first installed mine I marked the Dyna plate as near as I could from the points plate and it was good enough to start the bike right off before timing it.

Im about to pull the carbs off once again and will try my hardest to check the jet numbers. Ive already got the electronic ignition installed and the bike was running fine last year. This year its been slowly running like crap. I am talking with a member to teach myself how to do the valve adjustment because ive never messed with a shim-type valve adjustment.

"I would also recommend using a timing light and slip the 2-3 module to the timing mark after setting 1-4"

What did you mean by this?

[rustybronco]

Ive already got the electronic ignition installed and the bike was running fine last year. This year its been slowly running like crap.
"I would also recommend using a timing light and slip the 2-3 module to the timing mark after setting 1-4"

What did you mean by this?

Set 1-4 with a timing light. Move the inductive clamp to the # 2 or three 3 plug wire. Check 2-3 timing mark while it's running and if necessary shut the engine off and loosen the screws holding holding the 2-3 module to the plate and move it slightly one direction re-tightening the screws and re-check. Rinse, wash and repeat.

[OldVet66]

The Dynojet jets are 138 and 142. That would be a Mikuni 130 and 132.5. I would think your main jet should be at least a 130. I'm not sure How the stock needle affects that, but I am sure you will have better luck with the Dynojet jet kit. The stock pilot jets are #15 and don't need to be messed with at all for what you are doing. 20's are too large. A lot of people riding a GS1000 have no idea how they should run. Dialed in, they will definitely put a grin on your face.

[Caferob]

Set 1-4 with a timing light. Move the inductive clamp to the # 2 or three 3 plug wire. Check 2-3 timing mark while it's running and if necessary shut the engine off and loosen the screws holding holding the 2-3 module to the plate and move it slightly one direction re-tightening the screws and re-check. Rinse, wash and repeat.

Is this instructions for an electronic ignition? When i pulled the cap off, it was one big piece, not like points and condensors.

As for the dynojet kit, I just dont have 120 bucks right now to spend on that. I need to save some bucks because I also need an upgraded RR. the bike is running at 17volts

[OldVet66]

What brand ignition is it and does it work with your mechanical advance?

[850 Combat]

Hopefully, Robert, the 17 volts won't be too hard on the electronic ignition.

Todd, the VM carbs came with steps for needles? I somehow thought that by 1978, they had no adjustment, and you needed a kit to get that.

[Big T]

850, nope, all of the VM carbs have 4-5 adjustment slots on the needles.
It's the BS carbs that have the fixed needles

[Steve]

... I just dont have 120 bucks right now to spend on that. I need to save some bucks because I also need an upgraded RR.

An "upgraded" R/R can be purchased for $45 or less. Get the Dynojet kit.

.

[Caferob]

So I added some small washers to the needle and the bike responds a bit better but still need bigger mains I believe. Hesitation 1/4-3/4 throttle.

Instead of buying the $120 kit, why not 4 of these guys: https://www.z1enterprises.com/mikuni...ets-130-2.html
I read that the Dynojet 138 size is equivelant to the Mikuni 130's. Ideas?

[OldVet66]

A lot of research went into the taper of the main needles so it transitions properly from the idle circuits to the main jets with the changes you have made from manufactures specifications in air flow. It will get you in the ballpark and from there, there is a lot of adjustment to get it dialed in for your specific motor. It's worth the cost in your time because depending on your motor you may never get satisfactory results the way you are doing it.

[Caferob]

I pulled the carbs and it has 102 main jets. im thinking of buying the mikuni 130's from z1. less than 2 bucks each. i think its worth a try. needles seem fine as of now so i figure ill mess around.

btw - i have shims available to anyone who needs the, and whatever jets i dont use i can donate to whomever needs them.