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Fuel metering screw-gs1000

  • Thread starter Thread starter Anonymous
  • Start date Start date
Carbs

Carbs

I know this might be of little help, but I have CV carbs on my GS1000.
I put a Harris on and changed the air filter out to a K&N.
My fuel screws (on top at front) are set on 3 turns out. runs perfect.
I also have 117.5 main jets in it. Standard is 115.
 
fuel metering screws-gs1000

fuel metering screws-gs1000

Hi Phil, :D
So you've made the transition from gs4 then? Good man!! Check out www.oldskoolsuzuki.info
That's for gs/gsx and is pretty cool. 8)
Thanx for the info, I'll be getting around to some K&N's at some point, but not sure when. Everything is money at home at the mo, so they've gotta go on the backburner for a while! :cry:

gsdude 8)
 
Hello

Hello

Hello to umbrella land! Im so glad I left that rainy country years ago!
Well, I hope that information helped a little.
I'm sooooooooooooooooooo pissed off with my bike, I completely restored it, spend a lot of dosh and come to find out today that when I rebuilt it, I had the barrels honed out and STUPID me didn't put new rings in!
Hence i go a 100 miles to 2 quarts of oil! Bummer!
So guess next week I will be busy again........
Tell Mr.Blair that he needs to join GS Resourses! Phil.
 
Ole Tony needs more than gs resources mate!!
But, when you look at the opposition, they make him look so good!
And I reckon that you might wanna buy some shares in Texaco! LOL!

gsdude 8)
 
Just something i found when trying to find the best setting for the pilot fuel screws on the VM carbs on my GS750.

Initially, i set the fuel screws and air screws as advised on this site. This was 1-1/2 turns out for the fuel screws, with the air screws at 1-3/4 turns out. The carbs were synched spot on equal, and i know all other carb factors were OK.

The engine was slow to come down to tick over at these settings, and the pipes started to blue slightly, as if the idle mixture was weak.

What i found after some experimentation with the fuel screws (i left the air screws at 1-3/4), was that how the engine starts when hot, is a good indicator of the correct fuel screw setting.

At the initial 1-1/2 turns out, i had the symptoms i described above, and poor hot starting. I had to open the throttle to get it to start. I tried turning the fuel screws out a bit and it started better.

I found that you need to adjust the fuel screws so the engine starts and idles OK when hot, with no additional throttle opening (just press the starter button). Don't screw these out any further than necessary to achive this. Then you can make your fine mixture adjustments on the air screws.

My fuel scews ended up 2-1/4 turns out, with the air screws 1-1/2 to 1-3/4 turns out. The bike runs spot on at these settings.

Footy.
 
fuel metering screws-gs1000

fuel metering screws-gs1000

Cheers for that Footy,
When I do get some time, I'll try that idea, sounds well cool!
gsdude 8)
 
Footy. said:
Just something i found when trying to find the best setting for the pilot fuel screws on the VM carbs on my GS750.

Initially, i set the fuel screws and air screws as advised on this site. This was 1-1/2 turns out for the fuel screws, with the air screws at 1-3/4 turns out. The carbs were synched spot on equal, and i know all other carb factors were OK.

The engine was slow to come down to tick over at these settings, and the pipes started to blue slightly, as if the idle mixture was weak.

What i found after some experimentation with the fuel screws (i left the air screws at 1-3/4), was that how the engine starts when hot, is a good indicator of the correct fuel screw setting.

At the initial 1-1/2 turns out, i had the symptoms i described above, and poor hot starting. I had to open the throttle to get it to start. I tried turning the fuel screws out a bit and it started better.

I found that you need to adjust the fuel screws so the engine starts and idles OK when hot, with no additional throttle opening (just press the starter button). Don't screw these out any further than necessary to achive this. Then you can make your fine mixture adjustments on the air screws.

My fuel scews ended up 2-1/4 turns out, with the air screws 1-1/2 to 1-3/4 turns out. The bike runs spot on at these settings.

Footy.
Click to expand...
I don't know if your bike is stock or not, but 2 1/4 turns is a lot. If it works for you, that's great. I have to wonder if you're compensating for some other problem by adjusting the pilot fuel screws out so far.
My '79 1000 has 1085 pistons, K&N pods, and V&H pipe and I only had to turn my pilot fuel screws out to about 1 5/8-1 3/4 to get good performance and good plug color. That's with the stock #15 pilot jet. 2 1/4 would blacken my plugs.
 
Footy.[/quote]
I don't know if your bike is stock or not, but 2 1/4 turns is a lot. If it works for you, that's great. I have to wonder if you're compensating for some other problem by adjusting the pilot fuel screws out so far.
My '79 1000 has 1085 pistons, K&N pods, and V&H pipe and I only had to turn my pilot fuel screws out to about 1 5/8-1 3/4 to get good performance and good plug color. That's with the stock #15 pilot jet. 2 1/4 would blacken my plugs.[/quote]

Hi Keith.

The bike is a GS750E, the English version. It has the standard airbox and filter. The exhaust is a Jama original 4 into 2, but differs from the original Suzuki by having a balance pipe connecting the two sides under the gearbox.

I thought at first that the fuel screw setting coudn't be right at 2-1/4 from what is quoted here. So i stripped the carbs again just to be sure there was nothing wrong, and everything checked out.

I am wondering if the English version has a different size idle circuit air jet? My Haynes manual does list differences in the carb settings for the UK and Canada bikes, compared to the US version. Presumably this was for the different emission laws in the late 70's?

My pilot jet is as yours at #15. My manual lists the English set up as pilot air jet 1.2 and the air screw setting as 1-1/4 turns out.

The US spec doesn't refer to the air jet size, and both the air screw and pilot screws are listed just as `pre-set'.

It's a pity the manual isn't more specific about these differences. It seems Suzuki did some experimentation with the VM carb idle set up on the GS750. Depending on engine number, the pilot jets listed for the VM26SS carb, can be #22.5, #27.5, or #15. These go with recomended air screw settings of 1-1/4, 1-3/4 then back to 1-1/4!!

So i think they must have altered the fixed air jet size in the carb body?

Here's my thoughts on these `fuel screws', i don't know what others think?

Looking at the idle circuit, i would consider these to be better described as `volume' adjustment screws. I think the pilot jet size and the pilot air screws dictate the correct air/fuel mixture. The pilot `fuel screws' we are talking about, controls the amount of this mixture that feeds the engine when the throttle is closed.

At idle the throttles are not completely shut, so some air is entering here as well. So if the `volume' screws are not screwed out enough the mixture will `weaken'. I think the more these are screwed out, the less the actual mixture strength is altered by them. I think the air screw setting then becomes `the' factor in getting the correct mixture at idle.

So what would be the effect of these screws being out too far? Surely if you have too much air/ fuel mix bypassing the throttle, you wouldn't be able to get a low enough tick over using the normal throttle adjuster would you??

I think you would also get the effect of the engine being slow to come down off the revs, because of too much air/fuel bypassing the throttle? This also happens when the screws are not out enough, so we have to find the `sweet spot' in between i think.

Just my thoughts on these bloody screws 8O

I do think that if we start with these screws at a low setting. then turn them out untill the engine starts OK hot with no throttle `assist', we will be close to the right setting for any particular set up. (Air box or not, exhaust type etc). Then fine tune the idle mixture with the air screws.

Footy.
 
The pilot fuel screw regulates a second fuel passage to the carb throat.
It's for fine tuning the pilot circuit to each cylinder.
Maybe your carbs are jetted a little differently. Even with my mod's, 2 1/4 would blacken my plugs. Glad it works for you though.
 
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