Jetting a 1980 1000G for JUST a Pipe...

[Gimpdiggity]

So everyone, I need some new mufflers for my bike. I had been looking at replacing them with just some stock replacements, but I really like the idea of going with the 4-1.

I had been hesitant to go with the 4-1 because I have pipe/pods on another bike and I am constantly messing with the jetting to get it right. But today it was mentioned to me by Brian that with only the pipe it probably wouldn't require as much tuning to get it running right. It hadn't really dawned on me that the pods were probably the main culprit in my jetting issues on my other bike, but it makes quite a bit of sense.

So my question is this. If I were to go with a Vance and Hines 4-1 pipe on the 1000g, but leave the stock airbox and stock filter in place, how much of an increase in fuel should I expect to use?? Would I be looking at going up only about one jet size and maybe raising the needles just a little?? Or would a pipe require a bigger increase than just that??

Any advice on WHERE to start with this would be great. I've had good luck with jet kits in the past, but if I'm only going to do the pipe I'm going to TRY to get away with only ordering the parts that I need...instead of the whole kit.

Thanks!
Jeff

[chef1366]

I'd start with a 125 main jet.
Raise the needle 1 notch by replacing the needle plastic spacer with washers and then removing 2 of them
Richen the idle mixture screws.
Sync
You should be good to go.

[Gimpdiggity]

I'd start with a 125 main jet.
Raise the needle 1 notch by replacing the needle plastic spacer with washers and then removing 2 of them
Richen the idle mixture screws.
Sync
You should be good to go.

Just out of curiousity, because I haven't ripped the carbs apart yet...

But do you happen to know what the stock jet size is on the bike?? I was just looking at Dynojet's site, and the kit for the 1000g comes with some really wonky sized jets. I'm guessing it's because the kit is actually designed for both the 1000 AND the 1100...but they list the jet sizes as 114, 118, 165, and 170...

...oh wait though...I just remembered this...doesn't Dynojet use wonky numbering systems for their jet kits?? Some numbers don't match up to what the "stock" sizes would be...right??

[chef1366]

Dynojet's numbers and Mikuni's numbers are different.
The stock main for your carbs is 115 Pilot 40

[Gimpdiggity]

Awesome.

Thanks Chef. Looks like I'm going to start looking for some good prices on a 4-1 exhaust. The two stock mufflers both have small holes in them...oddly enough right where the end of the hard bags hung over them. I think water must've dripped right down from the bags onto the spot, but who knows.

One last question...do these bikes generally like a bit richer jetting regardless of mods?? I know on the other bikes I've done carb work on, they benefited from richer fuel jetting even without any mods. I have read before that many times the bikes were jetted lean to get them past some EPA regulations, and that jetting them can help them run a bit smoother even without any mods.

[bwringer]

Richer jetting is safer than lean, but correct jetting (tan plugs) gives best power, fuel economy, etc.

With the factory setup, all these bikes really need is a bit richer on the idle mixture screw and possibly a slightly lower float height. I've never raised the needles on the GS850s I've cared for, but I understand it's a good idea with their bigger brothers.

Curiously, the stock mains in the 1980+ GS850G/GL, GS1000G/GL and GS1100G/GL/GK are all 115.

Going to 125 mains is sort of a big jump, but it will be a safe setting. From there, you might need to do some plug chops with your new pipe to determine if you might want to go to a 122.5 or 120. It also depends on the new pipe, of course.

[Gimpdiggity]

Richer jetting is safer than lean, but correct jetting (tan plugs) gives best power, fuel economy, etc.

With the factory setup, all these bikes really need is a bit richer on the idle mixture screw and possibly a slightly lower float height. I've never raised the needles on the GS850s I've cared for, but I understand it's a good idea with their bigger brothers.

Curiously, the stock mains in the 1980+ GS850G/GL, GS1000G/GL and GS1100G/GL/GK are all 115.

Going to 125 mains is sort of a big jump, but it will be a safe setting. From there, you might need to do some plug chops with your new pipe to determine if you might want to go to a 122.5 or 120. It also depends on the new pipe, of course.

Maybe I'll start with some 122.5s and go from there. They would probably still be rich enough to be considered safe.

Before I do any of this, however, I need to find an exhuast.

[salty_monk]

I have used 122.5 with some success & that was using a K&N inbox filter. I am at sea level. No needle change required, a tweak on the pilot screws (I ran about 2.5 turns out I think). I think it also ran equally ok at 117.5 & 120 too.

Kent has an 1100g 8 valve with a V&H, K&N inbox & Dynojet kit fitted. He ended up sticking with the stock 115 mains after trying 120's.

I have a bunch of Mikuni & DJ jets to fit that bike from my own messing around... I would be willing to ship them to you to mess around with if you left me a decent deposit & refund most of it when you shipped me back what you didn't use if that would help you out.... Deposit would depend on how many sets I could russle up. Most of them have only been used to test on my 1000G so barely used.

Dan