GS1000G - Carb Jetting

[KEITH KRAUSE]

Salty, I took too long with the first reply so I have to be a little brief. I'll try to help more after work tomorrow evening.
It seems like your bike is ready for the re-jet so I'll just assume that. However, Chef said your filter was dirty and that needs to be cleaned and oiled correctly first.
What we need to know is if you're going to run the 4-1 pipe or keep the stock exhaust. You even mentioned pods but you're probably staying with the stock air box? Gotta know what you're going to run first.
I agree 1 and 4 are rich and I would assume 2 and 3 are also. Hopefully, the carbs were vacuum synched well so you get uniform plug reads when needed.
I can't say how good the mechanic is but I question how ANYONE can just make changes that drastic (the jet needle position change) and why he would decide to install 7.5 richer mains on a stock bike? Did he Dyno the bike? Did he actually road test at 1/3 and full throttle, etc?? The 3 turns out on the mixture screws is excessive too. No reason for that.
As for a jet kit, it must be in there based on your info. What I wonder is if the kit is stage 1 or 3? A stage 3 jet needle wouldn't be designed for a stock bike and would make jetting more difficult, if possible at all, even if you set it a leaner positions to compensate. The installed main jet may be a hint though that it's a stage 1 kit because a stage 1 main jet would be right about 122.5 in this case. The drilling of the vacuum ports to the diaghragm chambers was risky though since it's generally only done when running pods or making significant air box changes. It's meant to improve throttle response. I can't really say from actual test experience what drilling the ports would do to a stock intake bike. Never had a reason to try it. Seems like it could be too sensitive to throttle openings but hopefully there's no real problems here. Without more positive ID info, we'll just have to test and hope the needles and port mods work out.
I hope the carbs haven't had any other changes that would throw us a curve. If not, it should be fairly simple to get your bike running well again.
What pipe will you run and what intake?

[salty_monk]

Keith,

At the moment I'm running stock airbox & pipe. I don't have any immediate plans to change that as I can't afford to have it off the road for any length of time but I will if necessary.

I am going to try running it locally with no filter asap to see what happens & will also try to do some chop tests like that if possible. If it runs ok like that then I will likely simply switch to pods as it would be an easy mod. I think that this could be too lucky though!!

I will also try to open up the carbs & take some pics so we can actually see what's in there.

Dan

[salty_monk]

Dan, you can borrow my carb sticks. Let me know. I'll be picking them up from Burbank next weekend probably


Oh, I also have that colored spark plug thing. That might help a bit

Yes please.... We can have a play one day! We still have to sort out your fork seals.

Dan

[KEITH KRAUSE]

OK, stock bike. Sounds like you'll be happy with that.
What's obviously wrong is the larger main jet and the excessive mixture screw adjustment. What could be wrong is the size of the jet needles but we can just test and hopefully the needles can be adjusted and everything's fine. It also sounds like the jet needles are positioned too rich.
Here's what I'd do if the bike were here. I'm trying to minimize the work so...
I'd first pull the plugs and clean them off decently and be sure to check gap. Then, pre-adjust those mixture screws to something closer to factory, about 1 1/4 turns out. If the air filter needs cleaning, clean and oil it correctly. Don't over-oil, especially since we'll be checking plug reads. Now warm up the bike completely. Set idle to factory recommended idle, about 1,000/1,100 rpm's. Adjust the mixture screws for highest rpm/best idle. With the bike on the centerstand, start at any carb. Slowly turn a screw in either direction until you hear the rpm's max. Fine tune it. Now re-set the idle to base idle by using the idle adjuster knob. Repeat to the other carbs. If there seems to be no response from adjusting the screws, tell me. That suggests the pilot jet is the wrong one or other pilot circuit problem. If it goes as it should, your mixture screws are now set correctly.
Now you need to take some solid 1/3 throttle position chop tests to see how rich those jet needles are. The larger 122.5 mains still in there will not effect the jet needle reads as long as you keep it at this throttle position. Mark your throttle housing and grip if needed. Don't measure any throttle cable slack. Be careful. I'm lucky to have a great place to high speed test without police or lots of traffic. Take a plug wrench and rag and a piece of snug fitting tubing to help you remove and install the hot plugs those last few threads. Be careful of cross-threading.
As I said above, I can just get into top gear and settle at 1/3 throttle and chop off. You can test at 4th gear and keep the speeds down some without it feeling like you're revving hell out of it if that helps you. After full warm up, on level or uphill road, run it approx' 1/2 mile at 1/3 throttle. This helps to burn off any pilot circuit effect on the plugs while getting to the test site. If it's still safe, continue to run another 1/2 mile to 1 mile. Chop off by shutting off the throttle and quickly pulling in the clutch lever and turning off the ignition. Coast to a safe test spot with the clutch lever in. Read the plugs. Depending on those reads, we can make the necessary adjustments. If as rich as we suspect, you'll have to lower the needles by raising the e-clip position. Let us know the colors and any performance issues you felt while testing.
Since I believe the needles will need to be moved and the carbs taken off the bike, I've saved changing the mains for that time. I see no reason why the stock 115 mains shouldn't be used. Your full throttle problems are obvious so I see no reason to even attempt a full throttle chop test just to see how those larger mains effect the plugs. I'd install the 115 mains.
Just to be complete, there are some that would suggest changing back to the 115 mains BEFORE making the jet needle tests. That's fine and I have no problem with that. As designed, your carbs don't allow any main jet effect at solid 1/3 throttle position. But if you want, change the mains first. I just want to make less work. You can use a short tool and access the bowl fasteners with the carbs still installed on the bike if you don't mind working "upside down". I do all the time. Up to you. Just be careful of tightening things too much or leaving something loose or bumping the float assembly too hard, etc.
With the stock mains in and the mixture screws set, the only thing it appears we need to get right is the jet needles.

[Suzukfan78]

Fine tuning?

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.

[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...

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

Dan