1977 GS750 (now 850 ) VM26SS Carbs / replacement jet question.

[Guest]

Hi! I Have a 77 GS 750, that i've put 850 Jugs and Pistons into when I blew the rings of the 750 a few years back. Everything is running great once its going but the carbs / jets are now lacking.

What is happening is that it feels starved for fuel. I have to have the choke all the way on and it still needs a bit of convincing to get it started. Once running everything sounds good and tight about 1,300, but when I let go of the throttle the bike just dies around 1,000 RPM. I've been playing with the air mixture / fuel screws and nothing seems to help, so i'm thinking I need bigger pilot jets? Cue the problem.

I can't seem to find larger jets for the VM26SS carbs! I was thinking that because it's basically an 850 now (with pods and a 4-1 exhaust) I should be going larger than stock 850 specs... so I was thinking 120 mains & #40 Pilots. Anyway, I'm hoping for a website lead where I can order these jets.

Also, any other tips would be appreciated!

Thanks y'all!

 

[zed1015]

Fit these for the bottom end off idle leanness with the pods .
Air corrector jet kit. Suzuki GS1000,GS850,GS750.MIKUNI.LEDAR.PODS,K&N,FILTERS. | eBay
Leave all other settings stock and go up a couple of sizes on the main from stock 850 jetting and you shouldn't be far off.
The main jets you need are common and are the large head Mikuni ones.

 

[Guest]

Thanks! I'll pick these up.

 

[Guest]

Fit these for the bottom end off idle leanness with the pods .
Air corrector jet kit. Suzuki GS1000,GS850,GS750.MIKUNI.LEDAR.PODS,K&N,FILTERS. | eBay
Leave all other settings stock and go up a couple of sizes on the main from stock 850 jetting and you shouldn't be far off.
The main jets you need are common and are the large head Mikuni ones.

So to clarify, I don't need to increase the Pilot jets with this mod?

 

[zed1015]

So to clarify, I don't need to increase the Pilot jets with this mod?

No! You keep ALL other carb settings stock for the 850 apart from increasing the main jet.

 

[hannibal]

I had never seen these air corrector jets before Zed posted them a while ago. Since then, Zed seems to mention them any time someone says pod filter. Just realized Zed is the seller of the jets in the Ebay listing he links to.

I would love to have some independent reviews on how well these air corrector jets work.

 

[zed1015]

I had never seen these air corrector jets before Zed posted them a while ago. Since then, Zed seems to mention them any time someone says pod filter. Just realized Zed is the seller of the jets in the Ebay listing he links to.

I would love to have some independent reviews on how well these air corrector jets work.

I have to say that the advice i offer regarding pods or any other issue is genuine and correct and aimed only at solving the problem .
I don't only comment on pod threads although obviously if the threads call for the use of the air jets then i will offer that recommendation.
The air jets though are a proven common cure to the off idle hesitation which is caused by the resultant higher atmospheric pressure over the needle jet when removing the air box which results in a lean condition in that specific fuelling window.
It's a very simple solution that works and you will see that Mikuni themselves use the exact same approach to solve the same issue with an adjustable main air jet (BS30/97) on their performance carbs which are designed to run open.
If you look at the seller feedback on the listings you will see a multitude of independent reviews although i'm sure there will be some satisfied GS forum members along with their own favourable comments.
Regards, Rob.

 

[Rijko]

Can't comment on these correctors or how well they work, but i know for the GT750 they were offered by Suzuki to eliminate 'bogging'.
Sounds like the same thing - use an air restrictor to solve too much air inlet.

 

[Guest]

Does anyone have a link to where I can get pilot jets for these carbs? looking for #40. Found the 5mm mains on ebay.

 

[Guest]

#40 pilot jets for VM26SS carbs? Those sound enormous...but partzilla should have them. Search by bike/year to find the part number.

 

[zed1015]

#40 pilot jets for VM26SS carbs? Those sound enormous...but partzilla should have them. Search by bike/year to find the part number.

Yes! way too big in any circumstance.
Stock 15 or 17.5 will be sufficient.

 

[allojohn]

No. the #40+ jets are for post '79 750's with the BS carbs.

 

[Guest]

Thanks y'all. Appreciate the help. GS850's ran #40 pilots, which is why I ask.

No. the #40+ jets are for post '79 750's with the BS carbs.

 

[allojohn]

Thanks y'all. Appreciate the help. GS850's ran #40 pilots, which is why I ask.

Yes, the one's with BS carbs not VM's.

 

[KEITH KRAUSE]

Zed likes to believe his air correctors replace the need to raise the jet needle position to achieve a good air/fuel ratio at 1/4 to 3/4 throttle positions on the VM carbs.
Some owners might like the idea of installing a jet at the carbs throat instead of what should be done, which is make the necessary adjustment to the jet needle position.
Free flow pods and exhaust greatly lean out the mixture. Raising the jet needle or replacing it with a needle such as from Dynojet allows more fuel to compensate for more air. Zed's "fix" is instead of increasing fuel to balance out the increased air flow, his air correctors actually reduce/restrict air flow to the jet needle and needle jet. This is his way of compensating for more air flow at the jet needle.....by reducing air flow where it first enters the carb. This not only is backwards jetting, it also compromises proper fuel atomization at the needle jet because now you've reduced the air flow. With less air flow into and around the needle jets several small ports, how can proper atomization be achieved?
I don't post here much anymore but when I see something like this I have to add my two cents. I commented quite awhile ago at another thread and Zed got *@%^$*@%^$*@%^$*@%^$ed off because I prefer to re-jet the way it should be done.
I have no experience with re-jetting where you restrict or decrease air flow at the entrance of a jetting circuit as a way of compensating for increasing air flow because you added free flow filters and a pipe. Trying to be open minded, maybe the final mixture could result in no obvious lean or rich mixture issues such as surging or bogging, and a lot of owners would think their bike is running well, but you won't have a properly increased mixture of both air and fuel and you won't gain the performance you should from those mod's.
I'll stick with what I know works and what makes sense. I have no problem with taking the carbs apart to adjust the jet needles. My '79 GS1000 has run great for 42 years now with V&H 4/1 and K&N ovals and a 1085 kit. I've shared what I know with the GSR since 1999. A lot of other 1000 owners have said the jetting that works for my bike works well for theirs too. 850 and 750 owners have made similar jetting changes and replied their bikes run well.
I'm not going to get into another argument with another member trying to make money so please don't bother.
As for JONJONJON, with quality pods and 4/1 pipe, you do not need to increase pilot jet size. The #15's are fine. Even Dynojet says so in their stage 3 jetting kits. As for stalling at 1,000 rpm's, that's the factory recommended idle rpm and your bike, if in good condition and properly tuned, will idle well at 1,000 rpm's. The pilot circuit WILL need richer adjustments at the pilot fuel screws underneath/engine side. Factory setting is generally around 3/4 turns out from LIGHTLY seated. Try 1 to 1/2 turns out and test. Then follow the "highest rpm method" to adjust your side air screws. Start at 1 1/2 to 2 turns out and make small adjustments in either direction to reach best idle per carb. 1 3/4 to 2 turns out often works as a final setting. Poor idling is often a result of the carbs not being vacuum synched well. You must first carefully manually bench synch the slides, then fine tune them with a vacuum tool. Remember, each time you disturb the jet needles, you must re-synch. Also, to avoid fuel starvation, especially when riding in cross winds or higher speeds, REMOVE the two float bowl vent lines and leave the ports open to breath better. Dynojet recommends this on their stage 3 jetting kits. You'll also need to raise your stock jet needles approximately 2 positions richer and test. The jet needle adjustments are the most work but because the bike is most often operated between 1/4 and 3/4 throttle positions, it's important to jet it right. For the main jets, I have not personally re-jetted an 850 but something close to 125's should work or get you in the right direction. Also, be careful to adjust float levels correctly and never mix up the float needle valves and their valve seats because they wear as a unit and if you don't keep them as a set you'll experience leaking.

 

[zed1015]

I have no experience with re-jetting where you restrict or decrease air flow at the entrance of a jetting circuit as a way of compensating for increasing air flow because you added free flow filters and a pipe.
.

And THAT says it all really.
Why keep insisting that main air jet correctors don't or can't work correctly when you now confess to actually having absolutely zero experience of them ?
Maybe you should apply for a position at Mikuni and see how it goes explaining to them how they ( and other major carburettor manufacturers) have got it so terribly wrong in using the exact same method to rectify the exact same issue for the past 40 years and more.

 

[KEITH KRAUSE]

I have no experience with re-jetting where you restrict or decrease air flow at the entrance of a jetting circuit as a way of compensating for increasing air flow because you added free flow filters and a pipe.

And THAT says it all really.
Why keep insisting that main air jet correctors don't or can't work correctly when you now confess to actually having absolutely zero experience of them ?
Maybe you should apply for a position at Mikuni and see how it goes explaining to them how they ( and other major carburettor manufacturers) have got it so terribly wrong in using the exact same method to rectify the exact same issue for the past 40 years and more.

I made that statement because I re-jet the right way. I don't practice backwards jetting and that's why I have no experience with it. If you increase air flow through a circuit, you have to equally increase fuel flow. That makes more power, power that can be used safely and not lean/over heat the engine. If you install pod filters that obviously increase air flow, and obviously lean out the mixture, you don't place an air restrictor at some point to try to achieve a proper mixture. If you did, you just defeated the whole reason to install the pods in the first place. The air flow is then back to where it was and you gain zero power. All an engine is, is an air pump. If you increase air flow, you increase power. If you decrease air flow, at any jetting circuit, you lose power somewhere. Would you install pod filters and then wrap them 90% in electrical tape in an attempt to achieve the proper mixture? That's what your air corrector is doing. The circuit, because you've increased air flow and power, now needs more fuel flow to achieve a proper air fuel ratio so you can use that extra power safely. Your air correctors reduce air flow. Reduced air flow equals reduced power. Get it? Would you also install a 4/1 free flow exhaust and then install a restrictive device so restrictive that it now flows the same as the stock exhaust? Again, that's what your correctors do.
And as far as "confessing" to having no experience with air correctors, what experience do you need to understand your air corrector is no more than a restrictor? You don't install an air restrictor when the circuit in this situation needs more fuel flow.
Again, I'll use what works. If it takes a little more work then that's the way it is.
You go ahead and preach your BS to someone else. You're here because you want to make some money and it makes you mad if someone points that out.

 

[zed1015]

I have no experience with re-jetting where you restrict or decrease air flow at the entrance of a jetting circuit as a way of compensating for increasing air flow because you added free flow filters and a pipe.

I made that statement because I re-jet the right way. I don't practice backwards jetting and that's why I have no experience with it. If you increase air flow through a circuit, you have to equally increase fuel flow. That makes more power, power that can be used safely and not lean/over heat the engine. If you install pod filters that obviously increase air flow, and obviously lean out the mixture, you don't place an air restrictor at some point to try to achieve a proper mixture. If you did, you just defeated the whole reason to install the pods in the first place. The air flow is then back to where it was and you gain zero power. All an engine is, is an air pump. If you increase air flow, you increase power. If you decrease air flow, at any jetting circuit, you lose power somewhere. Would you install pod filters and then wrap them 90% in electrical tape in an attempt to achieve the proper mixture? That's what your air corrector is doing. The circuit, because you've increased air flow and power, now needs more fuel flow to achieve a proper air fuel ratio so you can use that extra power safely. Your air correctors reduce air flow. Reduced air flow equals reduced power. Get it? Would you also install a 4/1 free flow exhaust and then install a restrictive device so restrictive that it now flows the same as the stock exhaust? Again, that's what your correctors do.
And as far as "confessing" to having no experience with air correctors, what experience do you need to understand your air corrector is no more than a restrictor? You don't install an air restrictor when the circuit in this situation needs more fuel flow.
Again, I'll use what works. If it takes a little more work then that's the way it is.
You go ahead and preach your BS to someone else. You're here because you want to make some money and it makes you mad if someone points that out.

You clearly cannot comprehend how main air jets work and you keep calling these air jets mine which they are not.
Instead of continually hijacking other peoples threads to persue this sad little personal vendetta of yours why don't you go do your homework and you might actually learn something or maybe just go join the flat earth society where you should fit right in.
As i've asked previously and you have never given a rational answer to, If they are BS then please explain why Mikuni themselves use them to tune out the same fueling off idle flat spot anomally that occurs on their performance carbs that are designed to run open..
Funnily enough the part number for the Mikuni air jets is BS30/97 so your rantings have actually inadvertently got part of the facts correct.

 

[KEITH KRAUSE]

It would probably be easier to explain the anomaly going on in your head. You'd fit right in with SpongeBob and Patrick.

 

[Guest]

Thanks for this. What is the method to bench sync the slides?

Zed likes to believe his air correctors replace the need to raise the jet needle position to achieve a good air/fuel ratio at 1/4 to 3/4 throttle positions on the VM carbs.
Some owners might like the idea of installing a jet at the carbs throat instead of what should be done, which is make the necessary adjustment to the jet needle position.
Free flow pods and exhaust greatly lean out the mixture. Raising the jet needle or replacing it with a needle such as from Dynojet allows more fuel to compensate for more air. Zed's "fix" is instead of increasing fuel to balance out the increased air flow, his air correctors actually reduce/restrict air flow to the jet needle and needle jet. This is his way of compensating for more air flow at the jet needle.....by reducing air flow where it first enters the carb. This not only is backwards jetting, it also compromises proper fuel atomization at the needle jet because now you've reduced the air flow. With less air flow into and around the needle jets several small ports, how can proper atomization be achieved?
I don't post here much anymore but when I see something like this I have to add my two cents. I commented quite awhile ago at another thread and Zed got *@%^$*@%^$*@%^$*@%^$ed off because I prefer to re-jet the way it should be done.
I have no experience with re-jetting where you restrict or decrease air flow at the entrance of a jetting circuit as a way of compensating for increasing air flow because you added free flow filters and a pipe. Trying to be open minded, maybe the final mixture could result in no obvious lean or rich mixture issues such as surging or bogging, and a lot of owners would think their bike is running well, but you won't have a properly increased mixture of both air and fuel and you won't gain the performance you should from those mod's.
I'll stick with what I know works and what makes sense. I have no problem with taking the carbs apart to adjust the jet needles. My '79 GS1000 has run great for 42 years now with V&H 4/1 and K&N ovals and a 1085 kit. I've shared what I know with the GSR since 1999. A lot of other 1000 owners have said the jetting that works for my bike works well for theirs too. 850 and 750 owners have made similar jetting changes and replied their bikes run well.
I'm not going to get into another argument with another member trying to make money so please don't bother.
As for JONJONJON, with quality pods and 4/1 pipe, you do not need to increase pilot jet size. The #15's are fine. Even Dynojet says so in their stage 3 jetting kits. As for stalling at 1,000 rpm's, that's the factory recommended idle rpm and your bike, if in good condition and properly tuned, will idle well at 1,000 rpm's. The pilot circuit WILL need richer adjustments at the pilot fuel screws underneath/engine side. Factory setting is generally around 3/4 turns out from LIGHTLY seated. Try 1 to 1/2 turns out and test. Then follow the "highest rpm method" to adjust your side air screws. Start at 1 1/2 to 2 turns out and make small adjustments in either direction to reach best idle per carb. 1 3/4 to 2 turns out often works as a final setting. Poor idling is often a result of the carbs not being vacuum synched well. You must first carefully manually bench synch the slides, then fine tune them with a vacuum tool. Remember, each time you disturb the jet needles, you must re-synch. Also, to avoid fuel starvation, especially when riding in cross winds or higher speeds, REMOVE the two float bowl vent lines and leave the ports open to breath better. Dynojet recommends this on their stage 3 jetting kits. You'll also need to raise your stock jet needles approximately 2 positions richer and test. The jet needle adjustments are the most work but because the bike is most often operated between 1/4 and 3/4 throttle positions, it's important to jet it right. For the main jets, I have not personally re-jetted an 850 but something close to 125's should work or get you in the right direction. Also, be careful to adjust float levels correctly and never mix up the float needle valves and their valve seats because they wear as a unit and if you don't keep them as a set you'll experience leaking.