GS1000G 1980 BS34 CV Carbs - Lean Running?

[gs7.11]

Just throwing this out there, but with a 4 into 1 and bore kit, its going to need more fuel? I would bump up 1 on the pilot and shim the needle, which is what we used to do to bikes when installing slip on mufflers. Cleaning jets with lemon oil/juice? Sorry, but I wouldnt be chasing jetting issues after cleaning jets with it. Just my 2 cents worth

I said lemon juice, who mentioned lemon oil?

Have you ever tried it? Obviously not. Perhaps you should confine your comments to things you actually know about? Lemon juice is quite an effective acid, and easily eats away at fuel deposits, whilst leaving the brass of the jets unharmed, It works very well. Furthermore, you need to read more thoroughly:
"I've cleaned them thoroughly with a combination of carb cleaner, lemon juice and compressed air...."
I've found lemon juice to be more effective on stubborn jets than the carb cleaners we can get in the UK, which in any case are mostly degreasers.

As regards, the 4:1 and big bore kit, again you are making too many assumptions. I have found, empirically, that the 4:1 I have had on my bike since 2000 doesn't affect fuelling much, if at all, at low throttle settings. This is now the 3rd set of different carbs I've had on in that time. Both of the other 2 sets ran fine, and only needed to go up one size on the mains, and that only discovered on a dyno. There are good sound engineering reasons why this is the case, and as a former aircraft engine technician I understand them.

I also understand that an increase in capacity draws more fuel mixture through the carbs, not just air, so it's not automatic that you need to upjet for a big bore. Especially at low throttle settings. I've not found it necessary now on several GS1000s, if that is all that is changed. I am unusual in some cases in that I like stock airboxes and don't automatically reach for a set of K&Ns.

I anticipate that I will need to go up on the mains, but at the moment for road use where I'm not on WFO very often, the top end is fine. I think I mentioned that. My problem is not with carb cleaning or anything else other than what I mentioned: probable leanness at cruise, and I was asking for direct experience of that.

Thanks anyway.

[Steve]

What head is on your engine? If it is a '79 or earlier, it will have smaller intake ports for the VM carbs.
With your BS34s, there will be a drastic step from the carbs to the smaller ports, which would really upset airflow.

If you have an '80/'81 head, we can stick with addressing carb settings.

.

[gs7.11]

What head is on your engine? If it is a '79 or earlier, it will have smaller intake ports for the VM carbs.
With your BS34s, there will be a drastic step from the carbs to the smaller ports, which would really upset airflow.

If you have an '80/'81 head, we can stick with addressing carb settings.

.

Ya don't say!

15-Fourth-Wall-List-trading-places.jpg

Yes, it's an 80/81 head.

Sometimes, it's not what you say, it's how you say it.

[gs7.11]

So allow me to rephrase this as I'd still like some information:

Is there anyone who has a stock '80-on GS1000G and has experience of lean running on the stock carbs, stock airbox?

[Nessism]

There are many people with 1000G's here and running lean with them is not typically a problem. I've owned two different 1000S's which use the same head/pistons/carbs as the G, with just minor airbox differences between them, and neither of them was lean running.

Did you lift the needles yet? Realize of course that using a big bore kit may have some effect on the jetting. And if you are running a non stock air filter that could too.

[thebrandonbeezy]

I ran a a 4 to 1 and k&n drop in filter. (80 1000g) Had a lean spot from 4500 on up.
I removed the the spacer completely, pulled hard all the way about 7500ish then i stepped up to a 125 main, then a 128 which then would pull hard to about 11000.
I had the screw at i think 3.5 turns. Some where in there.
To finish it off i should have gone back and added small shims to the needle to lean it out to a proper amount. But i didnt mind it a little extra rich. Also added some timing. Don't remember how much though

[thebrandonbeezy]

Yes i know 11000 is a little too high

[gs7.11]

There are many people with 1000G's here and running lean with them is not typically a problem. I've owned two different 1000S's which use the same head/pistons/carbs as the G, with just minor airbox differences between them, and neither of them was lean running.

Did you lift the needles yet? Realize of course that using a big bore kit may have some effect on the jetting. And if you are running a non stock air filter that could too.

Thank you for the help.

So lean running is not a commonplace thing then. Which confirms I have an issue.

I haven't lifted the needles yet as I haven't had time, and don't want to sand down the spacers without being sure why I was doing it. I've also bought another set of carbs, which I can clean up and compare with the originals. I've also bought an Ultrasonic cleaner so will be trying that out too.
The air filter is stock.
I'm reluctant to think that the big bore is causing issues at low throttle/rpm as I've fitted quite a few and never had to make any changes before for other than WFO operation. I might be wrong, as I'm not arrogant, but inclined to look elsewhere first.
Thanks.

[gs7.11]

I ran a a 4 to 1 and k&n drop in filter. (80 1000g) Had a lean spot from 4500 on up.
I removed the the spacer completely, pulled hard all the way about 7500ish then i stepped up to a 125 main, then a 128 which then would pull hard to about 11000.
I had the screw at i think 3.5 turns. Some where in there.
To finish it off i should have gone back and added small shims to the needle to lean it out to a proper amount. But i didnt mind it a little extra rich. Also added some timing. Don't remember how much though

Thanks.
My prob is lower rpm than that. Points to a pilot jet rather than needle?
The bike runs fine (enough, may need a dyno run to be 100% sure) at anything above half way, so I think the stock 115 main jet is good enough for now and shouldn't be interfering with mixture at below 4000.

[Big T]

I agree that your main jet is OK, but the lack of taper on the needle may be the issue.
The pilot/cutaway/needle jet/needle all overlap in that range

[duaneage]

I have a stock 1000g and a V&H 12500 model pipe. I have 42.5 pilots and actually went a little lean on mine to 114 mains. That's what a lot of testing revealed to give best plug color at speed and overall perfect driveability. I have a tiny flat spot right at 2800 but it's not worth tuning over. I never touched the needles though it is probably worth trying aftermarket.
I went the big jet route for a few months until I got serious about testing. Wasted a lot of gas and dirtied oil. Learned to respect the test results, not theories of others.

Every bike is different.

[gs7.11]

I agree that your main jet is OK, but the lack of taper on the needle may be the issue.
The pilot/cutaway/needle jet/needle all overlap in that range

Thanks

I have a stock 1000g and a V&H 12500 model pipe. I have 42.5 pilots and actually went a little lean on mine to 114 mains. That's what a lot of testing revealed to give best plug color at speed and overall perfect driveability. I have a tiny flat spot right at 2800 but it's not worth tuning over. I never touched the needles though it is probably worth trying aftermarket.
I went the big jet route for a few months until I got serious about testing. Wasted a lot of gas and dirtied oil. Learned to respect the test results, not theories of others.

Every bike is different.

Thanks. Useful feedback.

[gs7.11]

Well, if anyone is intetested, I found the problem:
Emulsion tubes.
In the end having tried absolutely everything, including Dynojet needles, removing vent pipes etc etc., I have ended up back at box stock jetting, unsurprising really with stock carbs and Airbox.

The emulsion tubes appeared ok, with no ovalling or other visible wear, but one I'd fitted new ones, it was immediately obvious I'd fixed it.
Hopefully this might be useful if anyone else has similar issues.

[londonboards]

Well done.

Im really interested to know what it was about the old tubes that made the carbs not work.

Do they have the same number stamped on them? Do they look the same?

If it was me, I would be tempted just to put the old ones back in to see if the problem comes back. I know that sounds crazy but I would want to eliminate the idea that taking them apart and putting them back together wasn’t what fixed it. If indeed they are the same tubes (by number and manufacture) what went wrong with them?