GS1000G - Carb Jetting

[salty_monk]

So far I know it was way Rich at Bruce's (you could smell it) & I couldn't use more than half throttle (it wouldn't go any faster at wider throttle opening & when you backed off it would surge forward). It did run well at up to half throttle though.

It has a stock 4 - 2 exhaust & a "Uni" foam filter.

It ran well at Bruce's (5000 feet & hot) without the filter or side covers on the box but seemed to have a flat spot on lesser throttle positions although I didn't run it for long.

On the way back it seemed to come to life in Sacramento when we got under 2,000 feet & cooler temps.

Here at sea level it runs much better but is still surgy at WOT & gas mileage is not that good (max 40mpg on a run, generally 30-35mpg)

The carbs were cleaned just before I bought it & here's what it says on the receipt:

Replace main jet to 122.5
Drill slide to close faster
Mixture screws 3 turns out
Needle move up 2 steps (from this I guess it has a Dynojet kit fitted otherwise there shouldn't be any steps.....)

Last time I pulled the plugs they seemed ok to me, possibly a little rich but I'd just been running around town & parked it, I did nothing special beforehand.

I haven't done any chop tests yet.

I haven't opened up the carbs yet to see what is actually in there.

I'll try it with no filter here up & down the street sometime soon & open the carbs up for a look at what's there. (Never opened these before but I've messed with some webbers)

It seems to me that if I go back to stock mains & move the needle back down it will probably be somewhere close.

I guess I'll need to buy or borrow a set of synch gauges too.

My other option is to get a K&N in box or pods & 4-1 pipe to lean it out that way. The pipe is on it's way out anyway but I do have the option of buying another stock set (but maybe I'll sell those & go 4-1 anyway.....)

Dan

[Joe Nardy]

Further info:

I rode Dan's bike for a short while around Bruce's house (keep in mind that this is at about 5500 feet. Dan lives at sea level). It runs and pulls strong from idle to about 1/2 throttle. At that point it begins to surge. At full throttle it bogs and loses power. Backing off from full throttle increases pull. The idle and pilot circuits seem okay. We suspected rich main jets and possible rich needles too.

We removed the air filter and left the sides off of the airbox. Dan took it for a ride and said it ran much better at higher throttle positions. BUT, it ran poorly at lower throttle settings. This makes some sense as the low end jetting was pretty good. Removing the air filter made it run too lean. The mid-to-top end jetting was previously too rich and leaning it out made it run better at these ranges. This seems to verify our suspicion of rich main jets and possible rich needles.

Keith is without a doubt the man to talk to about this. He'll have your bike running like a top if you do as he says.

Thanks,
Joe

[Tom MLC]

Dan, you know at altitude my bike ran like a tired dog too. She did well around Yosemite, and also the Tahoe & Virginia City run. But anywhere above 8,000 feet and she just had no power.

Unless you're planning another trip to higher regions, you probably will want to set your carbs to the local conditions. I'm curious to see what advice you get here. I need to learn more about CV carbs so I can work on my GS1100.

BTW, those stock pipes might fetch a handsome bounty on ebay. They look like they might clean up pretty well. Wait until the winter then put 'em up on ebay. A couple hundred bucks is not unreasonable.

I had an excellent weekend riding with you & others. Thanks for the chance to meet you & make new friends. If you're ever up in San Jose, please let me know.

Cheers,

Tom

[salty_monk]

Further info:

Keith is without a doubt the man to talk to about this. He'll have your bike running like a top if you do as he says.

Thanks,
Joe

He's local too I think.... I'm all ears

[Billy Ricks]

Here are the specs for stock jetting.
Specs in mm.
Carb Type- Mikuni BS34SS
Bore Size-34 mm
ID# - 49160
Idle r/min - 1050 +/- 100 r/min
Fuel Level - 5.0 +/- 0.5
Float Height - 22.4 +/- 1.0
Main Jet - #115
Main Air Jet - 1.7
Jet Needle - 5D57-3rd
Needle Jet - X-8
Pilot Jet - #40
Bypass - 0.9, 0.8, 0.8
Pilot Outlet - 0.7
Valve Seat - 2.0
Starter Jet - #45
Pilot Screw -Pre-Set
Pilot air jet - #160
Throttle Cable Play - 0.5-1.0
Choke Cable Play - 0.5-1.0

[chef1366]

I'd throw a 117.5 main jet and ride it. You can also clean that Uni filter and oil it. It looked a little dirty.

[salty_monk]

Might just switch it out for an in-box K&N if I can find one. Z1 doesn't list them.
That will lean it out slightly right across the range & then switch the mains to get the WOT back in range. That's the plan anyhow!

Pods might be overkill but I'm going to try it here with no filter in first & check the plugs. If they read ok & it rides ok I'll just switch straight to pods.

Kent told me he has a 115 stock jet in his with 4:1 & in box K&N. Seems Pods make the biggest difference.

I also want to here Keith's thoughts on it first too.

Dan

[salty_monk]

Some plug reads of #1 & #4 after my 4 mile toodle home at around 1/4 throttle, through lights, stop signs etc

#4 with flash


#4 no flash


#1 no flash


#1 with flash

[J_C]

You went at a 1/4 throttle through stop lights and stop signs??? Youre hard core for these plug chops man!


Let's take a field trip to Keith's house \\/

[KEITH KRAUSE]

Hey guys, just read this thread. On my way out 'til later this evening.
Jeez! Those plug reads with/without flash are SO different I can't figure them out. No help really. One looks rich and the other looks lean. Don't know why but plugs don't photogragh well sometimes.
I'll have to read all the comments first and try to help with any jetting changes. It does sound on the rich side, both main and jet needle position at least. I have to wonder why the mechanic decided to raise the needles two positions? Also, on a stock bike, ???, why the apparent jet kit? If stock, why a 122.5 main if 115 is really the stock size?
Salty, one necessary question, is the bike ready to be re-jetted? Other than jetting, is it tuned well? Valves, good blue spark, ignition timing, clean carbs, synched carbs, etc?

[salty_monk]

Hi Keith,

Thanks for joining in! The no flash pictures are probably more true to how they are in real life especially #4 no flash. The #1 no flash is a little dark.

As far as the jet kit etc, I honestly don't know. Doesn't make sense to me either! TPO gave it to this guy for a carb clean & synch because he had had an operation & left it sitting for a while.
He was about 70 & owned the bike from new so I don't see it ever having run pods or 4:1 or anything different. Maybe he was trying to rejet it for the Uni filter or maybe he just left it to the mechanic who thought it would run better that way!

I got it about 50 miles after the work was done.

The valves were recently adjusted by me. They are all approx 0.06 now so all well within tolerance.

It has new DYNA green coils, new wires & plugs also fitted by me so spark is good. I don't know about ignition timing, I assume so as it runs well. I don't think you can change it anyway as it's CDI not points??

The mechanic was meant to clean the carbs & there seems to be no problems with them getting fuel so I think they are clean. They also seem to be synched quite well, I don't have the tool to check them but there is no excess vibration etc that would make me think they are off by any huge amount.

Idle is stable at 1,050 (although I did have to tweak it back down as it started to rise after a 1,000 miles or so but after I tweaked the stop it's been stable ever since).

It starts well on choke & doesn't hunt or do anything else horrible.

Hope that helps.

Cheers,

Dan

[J_C]

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

[chef1366]

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

You have a color tune? I wan't to borrow that.:-D

[J_C]

Yep! I sure do. You can certainly borrow it

[KEITH KRAUSE]

OK. Read the thread a little better.
Something I noticed was a general question about higher elevation jetting for the CV's. I don't have as much experience with that as some of you may, but if you understand how the throttle position relates to each jetting circuit, you can easily test and come up with the right jetting. Of course, as I always say, the bike must be tuned and ready for any re-jet.
I've seen some jetting charts that suggest what to do/use depending on the elevation. I admit I haven't looked at one in quite awhile and I'm going by memory and some limited past experience with this type of jetting.
A 5,000 foot gain would generally require 1 full size (5) smaller main jet. A step (2.5) smaller would certainly help but I think 5 is right. Just remember, it won't really matter unless you open the throttle to 3/4 and beyond. The main won't have any significant effect, if any at all, below 3/4 throttle posion.
As for the jet needle, that's more of a problem at least for US bikes because the stock jet needle is non-adjustable. If you really want the mixture to be closer to correct and don't mind the work involved, then you can place a jetting spacer meant for "1/2" position changes, directly on top the e-clip. If the only change is the 5,000 foot elevation, a 1/2 position change may be a tad too much but it should run well enough and a tad rich is better than a tad lean on a longer trip. Personally, I think lowering the jet needle about .015" is even closer to correct but it can be hard to find such a specific spacer so that generally puts you back to using a typical jetting spacer that's approx' .022". If you do have adjustable needles, then just do the same thing.
As for the pilot circuit and any throttle position up to approx' 1/4 throttle, simple leaner mixture screw adjustments should be all that's needed. Using the highest rpm method, the screws can be set once you're at that higher elevation. If you can't reach the screws because of the tank or don't want to play with them on the ride, then you have to make a guess as to how to set them before the ride. Any factory caps have to be off of course.
About 1/4 to 1/2 turn in leaner would work for most bikes.
Setting them correctly without being at that elevation will take some possible trial and error as you can imagine. The CV mixture screws can vary from 1/2 turn to approx' 1 1/2 turns straight from the factory. A 1/2 turn on bikes with their screws at the "leaner" factory setting will stall if you seat them that 1/2 turn in. If your bike has them set further out you obviously have something better to work with. If pre-setting them, best you can do is keep a record of how the bike ran and make any needed adjustments for the next ride. You'll find the sweet spot and be able to set them before any high elevation ride. You can of course modify your air box by adding air flow that can be reliably re-sealed when no longer needed but that's up to you. CV's can be finicky about modifying the air box flow too much.