GS1000G - Carb Jetting

[kent]

Dan, If you would like, I still have the factory needles and am pulling the 115 jets and putting the 120 jets back in my carbs this weekend, your more than welcome to have these if you would like to go back to stock, then make adjustments from a baseline. Also at the same time I would replace the carb boot o rings

 

[KEITH KRAUSE]

This may seem like a dumb question, but is it possible to get one or two cylinders reading two rich while the others are fine; when all your jets, needle positions and mixture screws are set exactley the same? And if this is the case is it o.k. to run different needle positions or mixture screw turns for individual clyliders to remedy this? I would think that all your plug reads should be the same if all the adjustments are the same...but Im getting different reads for different plugs.

I'll answer your question but it's best to start your own thread about your problems.

There can be several reasons why you would see uneven plug colors, some reasons are worse (more expensive/more work) than others.
Poor compression, worn parts, weak ignition/spark, etc, can cause it.
You can still get uneven plug reads even if there's nothing "serious" wrong.
Most common reason is a poor vacuum synch. If the carbs aren't synched well, different levels of vacuum will draw different amounts of mixture. I always tell others here that the carb synch is a basic part of jetting and you can't get accurate reads or trust the reads if the carbs aren't synched well.
Many owners adjust the various mixture screws/pilot fuel screws/air screws incorrectly too.
Float levels may be a little different.
Worn jetting parts or damaged o-rings will factor in here.
I personally would never set jet needles at different positions or install different jets across to repair a problem. That's what I call compensation jetting and it doesn't really work. Other problems will come up sooner or later. I suppose if you have no choice (money or enough knowledge) and it's a matter of the bike simply running or not, then it's your bike. I've seen it all when it comes to temp fixes to make up for the real problem.
Adjusting the various mixture screws at slightly different points is nothing unusual though. These screws are meant to be the pilot circuit's fine tuning that's needed because there can be small differences in each cylinder. The screws can come straight from the factory set a little different from each other. I doubt they are set beyond 1/2 turn difference though and usually are closer, within 1/4 turn of each other or better.

 

[J_C]

Dan, I rode home with the bike today. My girlfriend followed with my truck full of tools. I have my mercury sticks in the truck, and I assume my colortune is in one of the other boxes, Let me know if you want to do some tuning with them!

 

[salty_monk]

Thanks all, I'll try to do some tests 1/3rd throttle tests asap & feedback results. Not quite so easy round here.

Kent - Yes please, I think that might be my best option at the moment. Where did you get your inbox K&N? I might just switch out the uni for one of those. They state no re-jetting necessary. I'm going to get a full set of O rings "just in case". Looking carefully I guess mine are probably shot as I can see some kind of sealant has been used. It's squeezing out around the edges. I probably need to get the rack off.

I took a look at the Uni. It actually seems pretty clean. Do I need a special filter oil to oil it if I clean it out & go that route?

How do you guys get in to adjust the mixture screws? Number 2 especially seems hard to get to behind the petcock vacuum pipe especially without 2nd degree burns

Is it worth me trying to ride it again with no filter & doing some chop tests like that? Just wondering if a switch to K&N pods could save me some messing about & gain some HP at the same time. I know it seems like a "work-around" but if it really is that rich at all throttle positions then it might be all I need. Is a pilot jet change part of the dynojet kit?

Cheers,

Dan

 

[KEITH KRAUSE]

Not knowing what brand or stage jet kit jet needles you have, it obviously could be more difficult to re-jet for the pods and any adjustments may not work well enough. Working with unknowns can create problems. As always, it's up to you.
Since you're taking the carbs apart, I'm interested in any other changes, such as pilot jets, etc.
If you want to try pods and hope to "make them match" the present jetting, it's not that simple. Sure, you can put on the pods (and I'd suggest a pipe too while you're at it) and test at 1/3 throttle and maybe the plugs/performance is good with the needles where they are now. If not, you can make adjustments and keep testing. But the 122.5 mains aren't nearly big enough for the pods, even with stock exhaust. If the stock pilot jets are still in there, they have to be changed also. Then there's the issue of the air jets. Older kits supply different air jets. Some kits supply those restictors that I still can't figure out if I agree with or not. Doesn't matter.
So, you may be able to make the needles work, but all the rest will still have to be figured out. Jetting for pods and stock exhaust can take a little more time. That's a poor flow match. Personally, I see no good reason to run that set up. Either go pods (I suggest K&N) and quality pipe with a VERIFIED stage 3 kit, or go stock.

 

[salty_monk]

Ok, understood. I remembered last night that when I got the bike it was running BPR7ES plugs so hotter than standard. I guess they could have been giving the mechanic some false reads hence the changes he made. (Being kind to him...)

Anyway, I am going to try to make the mixture screw adjustments tonight if I get time, not sure if I'll have time to do the throttle chops tonight but maybe tomorrow I can do them at lunchtime on the freeway. I guess if a cop stops I'll tell him I fouled a plug

The bulk of my riding is local at way less than half throttle so that in itself should make a difference.

I may also whip the bowls off & pop the 115 mains in that Kent has offered me too whilst they are still on the bike.

I may have to wait till the missus goes away on vacation with the girls to have the carbs off completely so I have the car to use & I need to pick up the O ring kit etc yet.

I also have the offer of a better stock pipe that I'm going to try to pick up.

Dan

 

[salty_monk]

DAMN BIKES... :lol:

Tonight I pulled the tank & attacked the mixture screws, first off number 2 (next to the vacuum hose) is seized, I couldn't turn it either way.

I wrestled with it a while & then as I'd already wound the others into 1.5 turns out I thought I'd give it a go & see what happened.

It wouldn't idle at all except on choke, if I screwed in the idle stop it would race & then as I screwed it out it would slow down & eventually die.

I then tried 2.5 turns (again only 1, 3 & 4). Same thing, slightly less pronounced & would pop in the exhaust after letting the throttle go.

I put it back to 3 turns & set the idle. Nice & stable again.

Prior to this I cleaned the plugs. The base of the thread etc was quite black but the tip of the plug electrode etc was more tan in colour. (This was after my usual ride home today).

Very strange, I don't understand it. I guess I need to pull the carbs or pick up another set on Ebay to work on so I can "flip" them...

It doesn't appear to have an air leak but that is what these settings seem to be saying to me.... strange!

Dan

 

[KEITH KRAUSE]

Just have a second as I'm off to work.
3 turns out on the mixture screws is too much on a stock bike, so if it only idles with excessive mixture screw adjustment, that suggests the pilot circuit is lean or possibly clogged or something vacuum related. Hard to get accurate reads if the bike won't co-operate as planned. But it is the jet needles I'm trying to figure out. The pilot circuit can come later if need be.
You should get rid of the plugs and install the correct 8's.
I wish there was a safer way to get accurate plug reads but without a Dyno there's no other way really.

 

[kent]

Hey, Dan. I'm shipping the cluster, and the carb parts off today. I don't know where the K&N came from, it was already installed in the bike when I got it.

 

[salty_monk]

Just have a second as I'm off to work.
3 turns out on the mixture screws is too much on a stock bike, so if it only idles with excessive mixture screw adjustment, that suggests the pilot circuit is lean or possibly clogged or something vacuum related. Hard to get accurate reads if the bike won't co-operate as planned. But it is the jet needles I'm trying to figure out. The pilot circuit can come later if need be.
You should get rid of the plugs and install the correct 8's.
I wish there was a safer way to get accurate plug reads but without a Dyno there's no other way really.

It was only 3 of the 4 as I couldn't adjust number 2 however as all the plugs look the same I assume it's seized at 3 turns out.

Would adjusting only 3 of 4 cause the idle problems or is it definitely something in the idle circuit?

So I can do the 1/3rd throttle chop tests with the mixture screws in the current 3 out position?

By the way, it has standard 8 plugs in there now, I swapped those out when I changed to dyna green coils & added new wires. The old wires had gone brittle.

Kent - thanks mate. Chef sent me a link on Ebay & no doubt Z1 could order me one if I phone Jeff.

I think getting another rack off Ebay might be my best option, at least I can then get those up to scratch & then swap them all over in one hit. Think I need a "reserve" bike :lol:

Dan

 

[KEITH KRAUSE]

It was only 3 of the 4 as I couldn't adjust number 2 however as all the plugs look the same I assume it's seized at 3 turns out.

Would adjusting only 3 of 4 cause the idle problems or is it definitely something in the idle circuit?

So I can do the 1/3rd throttle chop tests with the mixture screws in the current 3 out position?

I think getting another rack off Ebay might be my best option, at least I can then get those up to scratch & then swap them all over in one hit. Think I need a "reserve" bike :lol:

Dan

Hard to say where the stuck screw is set.
Just one carb having a pilot circuit problem can cause a rough idle or stall condition.
The mixture screw assists the pilot jet. It's the fine tuning for each cylinders exact needs. Turning it outward (richer) allows more mixture. Factory settings range from about 1/2 turn to maybe 1 1/2 turns out. If it only idles with the screws 3 turns out and the bike has a totally stock intake, then it obviously needs the fuel because it's not getting enough through closer to factory settings. That could mean the pilot circuit is partially blocked or the pilot jet is too small or the wrong length (wrong jet), or a poor carb synch, valve clearances are off, float levels set incorrectly...anything that could cause a lean condition/lack of correct mixture. The screws being so far out is to compensate for something else wrong.
The mixture screws are primarily for the pilot circuit. There can be some small overlap but if you test at a solid 1/3 throttle, then you're on the jet needle with little effect from the pilot circuit. However, it would be optimum to have the pilot circuit mixing correctly (as I planned in my earlier post) and get the most accurate reads you can by road/chop testing. This mixture screw issue creates two problems. One, getting the most accurate jet needle reads, is fairly easy to eliminate. Simply test with the throttle a bit more open to further minimize any pilot circuit overlap. No need to go beyond solid 1/2 throttle, just mark the throttle housing and grip (without allowing for any slack) and you can trust the reads are related to the jet needles. Just don't go beyond because you may start getting some small main jet effect, which you don't want.
The second problem with the mixture screws apparently can't be eliminated though. I previously saw no problem with getting the pilot circuit mixing correctly just by returning the screws to something very close to stock/factory settings. Now it appears one carb could be off and that can cause a poor idle and other performance problems at smaller throttle openings. Things like this can really make jetting difficult. Cleaning/adjusting may help 3 of the carbs, but there's that unknown. I can't say how it would perform overall at throttle openings up to 1/4. Obviously, you want all 4 carbs adjusted correctly, not just 3.
How does the stuck screw look? How does it compare to the other 3? If the head is in good condition, (not shaved off/damaged) does it appear to be recessed nearly the same as the others? The other 3 should appear close to each other.
A word of caution about buying used carbs. I'm sure you can imagine.
I've seen used carbs with different jets, mechanical damage, water corrosion, different floats and parts from other carbs. You really have to ask questions and hope to get straight answers. Even then, the present owner might not be aware of changes made. I used to rebuild/refurbish carbs for side money and you can get screwed even if you think you did your homework. If you get another set, I hope you get an unmolested set and don't open up a can of worms. If you really decide that's best, and there's no other reason you haven't told me, I'd at least try to free the stuck screw by various methods we've talked about at this site.
This is getting deep! We go from simply installing stock mains and returning the mixture screws to normal and tuning your adjustable jet needles, to swapping carbs and talk of pods and other scary stuff!:lol:
What did I get myself into?

 

[salty_monk]

Thanks Keith, well it's been this way for nearly a year (with me) & does not appear to be hurting anything except gas mileage (which isn't that bad), it also seems to run very well down here at sea level unless I open it right up (no roads for that near here!). Very strange.

I'll try to pick up a set of carbs off Ebay & make sure I ask plenty of questions first then fingers crossed & hope....

I have my eyes on another bike too which might make things easier, if that happens I'll take these off the bike & see what's going on before going the Ebay route as I'll have the time to play with it. I can't afford to have it not running for any length of time just yet.


Dan

 

[KEITH KRAUSE]

OK. Whenever you need help just ask.
By the way, a rich mixture as it appears you have, causes a lot of carbon build up on many parts and that causes problems too. It's not just poor gas mileage.

 

[J_C]

Be awfully careful if you try to get that screw out. I suggest not using an easy out unless you feel like trying to track down new carb bodies, as I had to. have you tried soaking it with some wd40 or liquid wrench etc?

 

[kent]

I have never tried this, but a buddy of mine that used to work in a bike shop says he would boil the carbs in water, the expansion rate is different between the different metals, and the heat would cause the aluminum to release the screws and jets. just a thought.

 

[salty_monk]

Just thought to mention that my carbs have no pipes on the vent T's. Just the vent T's pointing up. I take it this will not really have any large effect unless they are blocked?

Dan

 

[Guest]

Someone put a jet kit in there.

 

[salty_monk]

?? Would they remove the pipes when doing that then?

Dan

 

[Guest]

I know the answer but Keith does such a better job in explaining it.

 

[KEITH KRAUSE]

Just thought to mention that my carbs have no pipes on the vent T's. Just the vent T's pointing up. I take it this will not really have any large effect unless they are blocked?

Dan

Off to work so no time for explanations.
The rule is...if you run pods, or modify the air box with significantly large extra holes, remove the float bowl vent lines to avoid various degrees of fuel starvation (fuel starvation from inadequate venting varies a little from bike to bike apparently).
If you have a totally stock air box, leave the vent lines on. I really don't know if removing the lines on a bike with stock intake has any negative effects. If any doubt, get some lines (about 18") on there and route them under the seat as the factory does.
I don't see how no lines on a stock bike could have anything to do with your richness problem, if that's what you're thinking.