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Fuel metering screw-gs1000

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

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Due to fuel starvation at low speeds, I think that my metering screws are set wrongly- there's more to it, but that's the diagnosis! 8O
I've got them set at 1 & 3/4 turns and she's not happy, can anybody advise me as to the correct settings please?
cheers,
gsdude 8)
 
Depends on the jetting, air intake and exhaust, but the general concensous is 2-3 turns out.
 
Most deffinately slide carbs, not cv's.
A standard airbox with a Harris performance pipe is the other bits, should they amke any difference!
gsdude 8)
 
Did you just get and install the Harris pipe, or was the pipe always on it, the bike normally ran well and is now developing problems. If you did change the pipe, what jets did you have in the carbs and what jets did you change to.
Adjustment can vary over a wide range depending on modifications.

Earl

gs-dude said:
Most deffinately slide carbs, not cv's.
A standard airbox with a Harris performance pipe is the other bits, should they amke any difference!
gsdude 8)
Click to expand...
 
Fuel Metering Screws-gs1000

Fuel Metering Screws-gs1000

Hi Earl, =D>
The Harris was added by me and I've kept the standard jets which I was told would be OK by the shop that I bought the pipe from.
I had no problem at all with it untill some new rings were fitted. My bro cleaned out the carbs and when I wasn't around, he'd taken the metering screws out for a clean! I said to him about factory settings and he juss said to refit them and back them off by 1 & 1/2 turns coz that's what he's always done!!!! #-o
So, since then I've had a spot "o" bother! :-({|=

gsdude 8)
 
Re: Fuel Metering Screws-gs1000

Re: Fuel Metering Screws-gs1000

Normal/average setting for the VM slide carbs is pilot fuel screw between 3/4 and 1 3/4 turns out. I always had mine set to between 1 and 1 1/4.
The pilot fuel screw is the one underneath the carb at the forward end of the float bowl. Turning out richens mixture.

The Pilot airscrew (on the side of the carb) averages about 1 1/2 to 2 turns out. Mine were usually set to 1 1/2 out. Turning in richens mixture

Can we assume he did not install the pilot airscrew with it left all the way out? :-)

If the idle passageways are clear, I would expect it to idle OK with settings in the range I gave. If it does not, I'm inclined to wonder if the carbs were cleaned with a spray can of carb cleaner and possibly an "O" ring or two has been destroyed, gumming and blocking a passageway.

I am assuming the seller of the exhaust has enough experience to know if the exhaust requires rejetting or not. Usually. the keyword is performance. You cant have your cake and eat it too. If they sell it as a "
performance" exhaust, you can bet rejetting is required to get that performance.

Earl





gs-dude said:
Hi Earl, =D>
The Harris was added by me and I've kept the standard jets which I was told would be OK by the shop that I bought the pipe from.
I had no problem at all with it untill some new rings were fitted. My bro cleaned out the carbs and when I wasn't around, he'd taken the metering screws out for a clean! I said to him about factory settings and he juss said to refit them and back them off by 1 & 1/2 turns coz that's what he's always done!!!! #-o
So, since then I've had a spot "o" bother! :-({|=

gsdude 8)
Click to expand...
 
fuel metering screws-gs1000

fuel metering screws-gs1000

Hi earl,
thanx for getting back to me!
Since it's almost midnite here, I'll have to try out your advice on the morrow in the pm"
Cheers my friend :D
gsdude 8)
 
Re: Fuel metering screw-gs1000

gs-dude said:
Due to fuel starvation at low speeds, I think that my metering screws are set wrongly- there's more to it, but that's the diagnosis! 8O
I've got them set at 1 & 3/4 turns and she's not happy, can anybody advise me as to the correct settings please?
cheers,
gsdude 8)
Click to expand...
The pilot fuel screws (underneath) are set differently on each bike. With your stock filter, I would start at 1 turn out and test. If you have low speed fuel starvation, I hope your help didn't seat the sharp-tipped pilot screws too firmly because the tip can break off in the carb body. Any chance the clip on the jet needle was moved? If stock, the clip should be in the 3rd position from the top.
After setting the pilots to 1 turn out, you need to set the side air screws using the highest rpm's method. Know how to do that? Then you need to vacuum synch the carbs. The VM carbs won't run well if not closely synched. After this, you can accurately fine tune the pilot screws. With out of synch carbs, you can't accurately tune the pilot screws.
 
Fuel Metering Screws-gs!000

Fuel Metering Screws-gs!000

There seem to be a few ideas that have been suggested here, many thanx guys, so this is what I've done at the mo.
I've set the pilot fuel screws to 1 & 1/4 turns and the pilot air screws to 1 & 1/2 turns.
I've taken her for a thrash down the A31 and she pulls like a train WITHOUT fuel starvation!! :D
There's a slight misfire, but with some new plugs and the vacuum guages on the carbs, I'm hoping that will sort things out and she'll be smoother!
I don't know how to set the side air screws to the highest rpm's Keith, so if you get five minutes, I'd appreciate the info! :)
Cheers,
gsdude 8)
 
fuel metering screws-gs1000

fuel metering screws-gs1000

Right, I'm quite happy with top end and mid range now, but she seems to be lacking at the bottom end a bit!
I assume that I've got to tweak the fuel screws a tad. Would this be a quarter in or out? Does winding them in add more fuel or the reverse?
Do please excuse my ignorance or what could be seen as "he can't be bothered!" This is due to having to do a job or two for "'er indoors :twisted: " while the sun is out!
gsdude 8)
 
The pilot fuel screws (underneath) are turned out to richen. The side air screws are turned out to lean the mixture.
Your original complaint of fuel starvation would not be cured by turning the pilot fuel screws in. You said they were at 1 3/4 with the fuel starvation problem and are now at 1 1/4 with no fuel starvation problem. So somethings not right about your diagnosis, because turning the pilot fuel screws in a 1/2 turn more would have worsened a genuine fuel starvation problem.
A vacuum synch may help your low end power complaint. I set the vacuum levels at about 3,000 rpm's. Get them so the difference is 1/2 " or less between the highest and lowest level to avoid mixture peoblems. After initial level observation, always adjust the higher vacuum levels down to the lower ones, it's easier that way. Don't over-tighten the throttle slide adjusting screws and holder nuts, 3.5 ft/lb is correct. Place two strong fans on the motor. Don't over-heat if synching is new to you. You could need to clean the carbs too. I suggest replacing the o-rings in the rubber manifolds too. Apply some hi-temp' bearing grease to them and torque to 6 ft/lb.
Before a synch, adjust the side air screws for highest rpm's. Place the bike on the centerstand and warm up first. The screws should be at about 1 1/2 to begin, as you already have them. They won't require much turning from this point. Start with any carb you like. Turn a screw and listen for the highest rpm you can achieve. you should only have to turn the screw about 1/4 turn to maybe 1/2 in either direction to achieve highest rpm. Once you've achieved highest rpm, then lower the rpm to about 1,100 rpm's by using the idle adjuster knob underneath. Go to the next carb and repeat. When done, the screws are generally between 1 1/2 to 2 turns out. Now you can synch. A good carb synch requires correct ignition timing and correct valve clearances too.
By the way, your stock air box still has the lid, correct? A missing lid will significantly lean the mixture.
 
fuel metering screws-gs1000

fuel metering screws-gs1000

Hi keith,
Yeah, mebbe ur right about my original idea, but after my last thoughts, I've taken her out again, and she's good with the top end and middle, it's juss the bottom end that's not happy.
I thought that winding the screws out a bit further would let more fuel in, therefore sorting that little hickup out!
Wot u fink?
Thanx for the advice on the vacuum gauges, I'll try that at some point towards the end of the week coz I'm starting a week of nights!
I'll keep you posted,
gsdude 8)
 
Adjusting the pilot fuel screws out a little more may help. Keep in mind that trying to adjust these accurately, is not possible if the vacuum levels are not uniform. Plug reads at lower speeds will not be accurate either. I would synch the carbs FIRST and then fine tune the pilot screws. I realize you said the bike ran fine before the screws were played with and you didn't notice any carb synch problems.
Besides "seat of the pants" performance, I get plug reads for the pilot circuit by riding the bike at a steady 30/35 mph in 4th gear for a couple of miles and chop the bike off and read. Use new plugs or clean the plugs before testing. If you have no mixture problems at 1/3 throttle, you can just go for a couple of miles at this throttle position to clean the plugs of any possible pilot circuit mixture problems.
You do still have the stock airbox LID on, correct? Without the lid, you'll run lean in all 3 jetting circuits. This requires needle and main adjustments too.
 
fuel metering screws-gs1000

fuel metering screws-gs1000

Yeah, I've got the standard box with the correct lid in place. I probrabely could do with a new filter thinking about it, but everything is complete.
My brother is going to "colour tune her next w/end and then an amigo of mine will vacuum them, hopefully the same day.
And I'll print off this little lot and take it with me coz it's gonna be well helpful cheers mate! :D
gsdude 8)
 
fuel metering screws-gs1000

fuel metering screws-gs1000

Hi Chaps,
Juss to let you know what's happnin'
The colour tune test told us that there was a spark on 3, but no explosion in the combustion chamber on tick over!!! ](*,)
Ripped that carb apart in situ, lotsa cleaner sprayed up and thru every orrifice going and then back together.
Hazzah!! Brrm!!! \:D/
Today, fun and games with setting the vacuum guages coz there's three that are good and one that's out, but she runs so well compaired to this time last week. :D
The fuel metering screws were backed off by an 1/8th of a turn in the end.
Many thanx for your time and input, s'been mighty helpful :D
If you're ever in Dorset, look me up and we'll have a jar or two!! :wink:

Cheers,
gsdude 8)
 
gs-dude, are you saying the pilot fuel screws are only 1/8 turn out from seated?
 
I would go with what Keith says. Get the pilot system consistent, synch the carbs than try adjustments. If the carbs are a bit out it will run like a dog down low. No amount of fiddling with the screws will fix that. You will be amazed at what a carb synch does if you are used to them being out!
 
fuel metering screws-gs1000

fuel metering screws-gs1000

No Keith,
I've got them turned out to 1 & 1/8th turns instead of 1 & 1/4.
With the vacuum gauges that I've got, balancing carbs seems like a weird sort of magic trick, but I guess it's easy once you're fully sorted!
But still, I'm quite happy at the mo coz tis the best that she's run in Christ nows how long!!!!!!!!!!!!!
gsdude 8)
 
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