Who can help me out with 79 GS1000E carb sleuthing? VM26SS with Dynojet questions

[oldGSfan]

79 GS1000E. K&N pods and V&H 4/1 - but may try to return to stock(ish). First thing is to try to tune it with what I have. But what do I have?

The main jets are Dynojet #138 which is the base jet per the 'fact sheet' for kit 3304.001 which is all I can seem to get from Dynojet support. Tech sheetd oesn't get into installation, drilling, etc. It just lists it's a 5/32" drill and there is a screw included, as pictured here in Z1's ad.

What would be useful but DJ can't seem to find is the installation guide Part# DI0007 that is specifically mentioned by part number in the fact sheet. Ugh.

OK, so what gets drilled out, the opening under the main jet I assume? And where does that screw go? I see no screw like it anywhere.

I looked at the needles and washers, and the washers at least look stock, exactly like the ones off my 79 GS850G. Pics below. I fear I may have some mish mash but maybe if it's not been drilled out (and needles are stock) it's a good thing, as I can baseline to stock and start over.

So, any gurus out there?

[zed1015]

Ideally you need to put the carbs back to stock.
Increase the main for the pods and pipe and fit air corrector jets to correct the off idle hesitation.
That's all that's needed.
No need for over complicated Dynojet kits with different needles , over large mains and bigger pilots etc that go to elaborate lengths to cure a simple fueling glitch.

[oldGSfan]

That is exactly what I want to do. I just want to be extra sure I'm understanding what the Dynojet changes were/might have been. I got a 5/32 drill, checked it with micrometer to be sure as my eyes are getting bad.... and it is far too large for the opening under the main jet in the carb body. If that is what is supposed to be drilled out, then it hasn't been done, which is great news to me. And if the needles aren't Dynojet ones either (hard to tell but a hint in those washers perhaps), and no funky sheet metal looking screw has been stuck in 'somewhere', all I need to do is what you say.

Edit: I see the spec sheet calls it a 'plug drill' so it may be that is for the 'emissions mixture screw', and the sheet metal screw is to block it off once drilled out? Seems very hack-ish, if so. And mine are not drilled out regardless. Hey, I don't know shine-ola about Dynojet kits but I think maybe the needle has no damage done, as the song says, sorta.

And I could ditch the pods if I can find a stock airbox for a decent price, and slightly mod my nice GS850G pipes to fit the clamp spacing at the head, as they fit fine otherwise.

Ideally you need to put the carbs back to stock.
Increase the main for the pods and pipe and fit air corrector jets to correct the off idle hesitation.
That's all that's needed.
No need for over complicated Dynojet kits with different needles , over large mains and bigger pilots etc that go to elaborate lengths to cure a simple fueling glitch.

[zed1015]

The GS1000E Dynojet kits include larger main jets , Different needles, metal shims a plug drill and THAT screw.
The drill bit and screw is used to remove the anti tamper caps on the fuel mixture screws on the far right of your pic which are not present .
You will need some genuine needles to put it back to stock , smaller mains than those 138's and if keeping pods just fit air correctors which do a nicer job than the Dyno jet.
Dynojet needles are known to be a bit rough and wear the needle jet.
Those plastic needle spacers are original and located correctly with the thin one underneath and the thick one on top.

[oldGSfan]

OK I see, so that screw just is used as a puller to remove the anti-tamper cap then, once the cap has a hole punched in it. That is good to know, I can work with these.

Needle shows up as same part number from the '79 850G which I have a full set of...

Stock main is a Mikuni #95 on the 1000 but the 850G is bigger at #102.5. Interesting, I wonder if trying that combo plus the 'air correctors' makes sense? I have them in hand except the corrector, where can I source those? Oh wait I see you have on eBay.... future sale coming :-)

Thanks for your help, learning a lot.

[salty_monk]

That does look like a Dynojet. You can see when they are stock, the Dynojet is quite a lot sharper and stock is usually a goldish color like a yellow passivate.... Do you have an airbox for it? I might have the set of stock needles and jets mine came with somewhere along with the DJ box & instructions.

I've personally had no issues with the Dynojet stage 3 with K&N pods & 4:1.

[oldGSfan]

No I don't have a stock airbox, wish I did. Let me know if you can scrounge those bits up, thanks!

That does look like a Dynojet. You can see when they are stock, the Dynojet is quite a lot sharper and stock is usually a goldish color like a yellow passivate.... Do you have an airbox for it? I might have the set of stock needles and jets mine came with somewhere along with the DJ box & instructions.

I've personally had no issues with the Dynojet stage 3 with K&N pods & 4:1.

[zed1015]

OK I see, so that screw just is used as a puller to remove the anti-tamper cap then, once the cap has a hole punched in it. That is good to know, I can work with these.

Needle shows up as same part number from the '79 850G which I have a full set of...

Stock main is a Mikuni #95 on the 1000 but the 850G is bigger at #102.5. Interesting, I wonder if trying that combo plus the 'air correctors' makes sense? I have them in hand except the corrector, where can I source those? Oh wait I see you have on eBay.... future sale coming :-)

Thanks for your help, learning a lot.

Good news with having the original needles.
With the air correctors you should end up around 117.5 on the main jet.
Once fitted you should put all carb settings to stock, this includes needle clip position and just increase the main.
Make sure you use good quality free flowing pods such as K&N, S&B, APE and not the cheap Emgos etc as these are often more restrictive than the airbox which will result in rich running and strangled top end power.

[KEITH KRAUSE]

The drill bit and screw have been addressed. They don't apply in your case. Your jet needle pictured is from DJ. DJ needles in your kit have 6 e-clip grooves. Factory jet needles have only 5.
As for properly jetting with the stage 3 DJ kit, with a quality pipe like V&H or Kerker, and quality pods like K&N...Use the 138 DJ mains, place the jet needle e-clip in the 3rd groove from the top, if this results in a little too lean then place the e-clip in the 4th groove from the top and then place the DJ provided jetting spacer directly on top of the e-clip. The thicker spacer (ring) goes on top the e-clip or jetting spacer if used and the thinner spacer goes under the e-clip. That adjustment is equal to "position 3 1/2". I seriously doubt you would need to go richer. Set the float height to .95 which is in the middle of the factory setting range of .90 to .98". Be very careful adjusting them. Be sure all of the float needle valves are in good condition and DO NOT mix the valves with valve seats as the valve and seat wear as a unit. Mixing will result in fuel leaking through. Also be sure to replace the fiber gasket for the seats. The stock pilot jets (15) are fine as is. Initially set the side air screws at 2 turns out from lightly seated. Initially set the pilot fuel screws underneath to 1 1/2 turns out from lightly seated. REMOVE the 2 float bowl vent lines to allow the bowls to vent better. Do not cap the vents. Leaving the vent lines on will result in various levels of fuel starvation, especially on windy/crosswind conditions. Carefully bench synch the throttle valves. Unless you're extremely lucky, the bench synch must be followed by a vacuum tool synch with a quality gauge such as a CarbTune. Synch at 1,600 to 2,000 rpm's by setting the idle adjuster knob. Once synched properly, fine tune the side air screws using the "highest rpm method". Place the bike on the center stand is best. With the air screws initially set at 2 turns out, be sure, as with the synch, to warm the motor fully, place a fan or two to cool the motor, set the idle with the idle adjustment knob underneath to ideally 1,000 rpm's. Start at carb #1. Slowly adjust the air screw in or out and listen for the highest/best idle. Once you find the sweet spot, stop. Re-set the idle to 1,000 rpm's by using the idle adjuster knob if necessary. Repeat to each carbs. ALL basic tuning must be done before synching the carbs. Valve clearances, ignition timing, no intake leaks, proper 5/16" fuel line, proper spark plugs and gapped properly, everything must be right before tuning the carbs and re-jetting.
Be very careful to not over-oil the K&N's. If you follow the directions on the K&N spray can you can easily over-oil them. "Spray each pleat" results in too much oil and the motor will bog when you open her up. Spray about "3 pleats at a time from 4-6" away with a fairly quick sweep of the can.
The real benefit of the stage 3 kit is in the more sharply tapered jet needles. You spend the most time riding at the throttle positions of 1/5 to 3/4 throttle. The jet needle controls fuel flow at those throttle positions with a small overlap from the pilot circuits and main jet. Besides the looks and sound of a quality 4 into 1 pipe and K&N pods, the HP gain is obvious compared to stock, but only at higher rpm's. At about 7,000 rpm's a properly jetted bike will pull away from a stock bike. If you don't really care about that higher rpm performance, then maybe going back to stock is best?
Keep in mind the stage 3 settings I suggest may require fine tuning of the pilot fuel screws and as I mentioned, changing the jet needle position. If you need to adjust the jet needles, you must always re-synch the throttle valves.
If you use the stage 3 mains but you use the factory jet needles, you'll most likely have to place the e-clips in the bottom groove (factory position is #3). The factory jet needles DO NOT mix as well as the DJ needles and often give poor results with intake/exhaust mod's, but not always.
If you go back to stock, the factory mains are #95. Jet needle position is #3 groove from the top on factory needles. Pilot fuel screws setting are impossible to re-set without emissions equipment. Try 3/4 to 1 turn out from lightly seated. Side air screws are as I said earlier. Put the float bowl vent lines on and route them to the sides and near the top of the stock air box. They need to be factory length or close to it. I forget now but about 18" long?
Any short cuts, such as not checking/replacing the intake manifold o-rings, not replacing the o-rings in the carbs, not doing the other tuning, will make a re-jetting inaccurate and frustrating.
Also, I have had bad luck with buying the genuine factory bowl gaskets lately. They are often harder than they should be due to sitting on a shelf too long? They can easily allow leaking. I tried the bowl gaskets from Z1 Enterprises and found that they are softer and seal better against leaks, at least for me. One other note, if you replace the manifold o-rings, replace the stock Phillips screws too. Use Allen screws instead. You can then torque them to about 9 ft/lb. First apply a light coat of high-temp grease to the o-rings to help them last. Be sure the manifolds are in good condition, inside and out.
I have never needed to change any other part of the jetting for basic intake/exhaust mod's, including larger pistons. The "air correctors" are not needed. Only with more extreme mod's would you maybe need to make changes to the air jets or throttle valve cut-away, etc.
Good luck!

[oldGSfan]

Wow, thank you very much Keith. I couldn't have asked for more.

I have new carb and intake O-rings but hadn't thought to go with Allen screws, that's an easy update. I still have my Motion Pro carb stix with mercury that has travelled around the world 3x since I got them in the 80's. Latest use was on my '73 Honda CB750, and I've got that bike running great.

I will read and re-read your advice as it seems spot-on and what I need. I am good at following directions and have been meticulous in cleaning and keeping each carb's bits with the right one (but who knows what secrets the past holds).

The drill bit and screw have been addressed. They don't apply in your case. Your jet needle pictured is from DJ. DJ needles in your kit have 6 e-clip grooves. Factory jet needles have only 5.
As for properly jetting with the stage 3 DJ kit, with a quality pipe like V&H or Kerker, and quality pods like K&N...Use the 138 DJ mains, place the jet needle e-clip in the 3rd groove from the top, if this results in a little too lean then place the e-clip in the 4th groove from the top and then place the DJ provided jetting spacer directly on top of the e-clip. The thicker spacer (ring) goes on top the e-clip or jetting spacer if used and the thinner spacer goes under the e-clip. That adjustment is equal to "position 3 1/2". I seriously doubt you would need to go richer. Set the float height to .95 which is in the middle of the factory setting range of .90 to .98". Be very careful adjusting them. Be sure all of the float needle valves are in good condition and DO NOT mix the valves with valve seats as the valve and seat wear as a unit. Mixing will result in fuel leaking through. Also be sure to replace the fiber gasket for the seats. The stock pilot jets (15) are fine as is. Initially set the side air screws at 2 turns out from lightly seated. Initially set the pilot fuel screws underneath to 1 1/2 turns out from lightly seated. REMOVE the 2 float bowl vent lines to allow the bowls to vent better. Do not cap the vents. Leaving the vent lines on will result in various levels of fuel starvation, especially on windy/crosswind conditions. Carefully bench synch the throttle valves. Unless you're extremely lucky, the bench synch must be followed by a vacuum tool synch with a quality gauge such as a CarbTune. Synch at 1,600 to 2,000 rpm's by setting the idle adjuster knob. Once synched properly, fine tune the side air screws using the "highest rpm method". Place the bike on the center stand is best. With the air screws initially set at 2 turns out, be sure, as with the synch, to warm the motor fully, place a fan or two to cool the motor, set the idle with the idle adjustment knob underneath to ideally 1,000 rpm's. Start at carb #1. Slowly adjust the air screw in or out and listen for the highest/best idle. Once you find the sweet spot, stop. Re-set the idle to 1,000 rpm's by using the idle adjuster knob if necessary. Repeat to each carbs. ALL basic tuning must be done before synching the carbs. Valve clearances, ignition timing, no intake leaks, proper 5/16" fuel line, proper spark plugs and gapped properly, everything must be right before tuning the carbs and re-jetting.
Be very careful to not over-oil the K&N's. If you follow the directions on the K&N spray can you can easily over-oil them. "Spray each pleat" results in too much oil and the motor will bog when you open her up. Spray about "3 pleats at a time from 4-6" away with a fairly quick sweep of the can.
The real benefit of the stage 3 kit is in the more sharply tapered jet needles. You spend the most time riding at the throttle positions of 1/5 to 3/4 throttle. The jet needle controls fuel flow at those throttle positions with a small overlap from the pilot circuits and main jet. Besides the looks and sound of a quality 4 into 1 pipe and K&N pods, the HP gain is obvious compared to stock, but only at higher rpm's. At about 7,000 rpm's a properly jetted bike will pull away from a stock bike. If you don't really care about that higher rpm performance, then maybe going back to stock is best?
Keep in mind the stage 3 settings I suggest may require fine tuning of the pilot fuel screws and as I mentioned, changing the jet needle position. If you need to adjust the jet needles, you must always re-synch the throttle valves.
If you use the stage 3 mains but you use the factory jet needles, you'll most likely have to place the e-clips in the bottom groove (factory position is #3). The factory jet needles DO NOT mix as well as the DJ needles and often give poor results with intake/exhaust mod's, but not always.
If you go back to stock, the factory mains are #95. Jet needle position is #3 groove from the top on factory needles. Pilot fuel screws setting are impossible to re-set without emissions equipment. Try 3/4 to 1 turn out from lightly seated. Side air screws are as I said earlier. Put the float bowl vent lines on and route them to the sides and near the top of the stock air box. They need to be factory length or close to it. I forget now but about 18" long?
Any short cuts, such as not checking/replacing the intake manifold o-rings, not replacing the o-rings in the carbs, not doing the other tuning, will make a re-jetting inaccurate and frustrating.
Also, I have had bad luck with buying the genuine factory bowl gaskets lately. They are often harder than they should be due to sitting on a shelf too long? They can easily allow leaking. I tried the bowl gaskets from Z1 Enterprises and found that they are softer and seal better against leaks, at least for me. One other note, if you replace the manifold o-rings, replace the stock Phillips screws too. Use Allen screws instead. You can then torque them to about 9 ft/lb. First apply a light coat of high-temp grease to the o-rings to help them last. Be sure the manifolds are in good condition, inside and out.
I have never needed to change any other part of the jetting for basic intake/exhaust mod's, including larger pistons. The "air correctors" are not needed. Only with more extreme mod's would you maybe need to make changes to the air jets or throttle valve cut-away, etc.
Good luck!

[zed1015]

. The "air correctors" are not needed. Only with more extreme mod's would you maybe need to make changes to the air jets.
Good luck!

If he did not have the DJ kit then all he would need is the air correctors and increase the main jets.
They do the same job as the DJ without all the unnecessary over complication which is to compensate for the lean condition caused by the higher atmospheric pressure through the venturi at low rpms.
They work on the same principle that Mikuni used on their smoothbore carbs to cure the same issue when running an unrestricted intake.
They are for use from simply removing or modifying the air box on an otherwise stock machine or any state of tune to full race.
Their use is NOT solely confined to engines with extreme mods.

[KEITH KRAUSE]

I'm just giving Tom the same advice that I've used and a lot of others here have used over the years.
If the bike is otherwise properly tuned, I've never had issues of "flat spots" or "low speed fueling problems", etc. The engine is just an air pump. If you increase the air flow, you have to increase the fuel flow to match that increased air flow.
Look at the factory manual for the VM26. Your "air corrector" replaces the air jet. The air jet meters air into the main jetting circuit. That air enters a passage into the needle jets bleed pipe section where it's drawn through the small holes in the pipe. This atomizes the air/fuel being drawn into the main bore.
If you increase the air flow by installing pod filters and a freer flowing exhaust, you must increase the fuel flow for the separate jetting circuits to supply the proper amount of mixture at various throttle positions. For the pilot circuit, that regulates mixture at approx' closed to 1/5 throttle position plus an overlap with the cutaway up to 1/4 throttle position, the air flow increase isn't significant enough to require a larger pilot jet. Even Dynojet agrees the stock pilot jet works well as long as you richen the pilot fuel screw settings and then adjust the side air screws to fine tune the mixture. You should also remove the two float bowl vent lines because with the increased air flow compromises the stock bowl venting. A vortex restriction is created in the vent lines and this causes fuel starvation at various levels and outside conditions. For the pilot circuit, no air jet changes are necessary. There are no significant vacuum issues by going to pods with VM carbs. I hook up my CarbTune gauge. I can easily adjust the vacuums at all carbs literally equal at low rpm's. The bike will hold an idle at 700 rpm's (if I wanted to set it that low) and pull away smoothly without any flat spot or other issue. Removing the vent lines is also necessary for the main jetting circuit to operate properly.
For the main jetting circuit, you have the jet needle regulating fuel flow at approx' 1/4 to 3/4 throttle positions with an overlap at 3/4 with the main jet. At these throttle positions, the tapered jet needle rises up through the needle jet. The gap between the jet needle and needle jet regulates fuel flow. As the tapered needle moves up, the gap widens to allow more fuel flow. When increasing the air flow with pods, the fuel flowing through the needle jet must increase the same amount as it enters the main bore. An way to do that is to raise the jet needle position so the gap between the jet needle and needle jet is increased at this range of throttle position. The air jet only needs to pass the same amount of air to the needle jet to achieve proper atomization. From there the increased fuel flow enters the main bore. The increased air flow enters the main bore. As long as the jet needle is raised correctly, the air/fuel ratio will be correct. Why would you buy "air correctors" or change the air jet when the richer jet needle position is all that's needed? Your "air corrector" must either increase or decrease the air flow. Correct? You wouldn't decrease the air flow in this case. So how would increasing the air flow through the air jet result in a correct air/fuel mixture once the mixture enters the main bore? Increased fuel is needed to match the increased air intake in the main bores, not more air.
I don't mean to argue. Maybe there is another way to achieve a correct, richer mixture but I don't see how an air jet can do it.

[oldGSfan]

Thanks again, interesting stuff!

I have cleaned well in an ultrasonic and gone through all the passages with carb cleaner compressed air etc, put new O-rings including the intakes (greased and replaced with Allen head screws) and mounted them on the bike. I set up as per the info you gave Keith. I just have to mount the pipe, check the plugs, and rig up gas tank on an adjacent shelf and see how it all goes.

[zed1015]

So how would increasing the air flow through the air jet result in a correct air/fuel mixture once the mixture enters the main bore? Increased fuel is needed to match the increased air intake in the main bores, not more air.
I don't mean to argue. Maybe there is another way to achieve a correct, richer mixture but I don't see how an air jet can do it.

I'm sorry that you don't quite understand their operation but fitting the air correctors ( exactly the same way as Mikuni did on the smoothbore carbs with the BS30/97 for the same reason ) reduces the air bleed to the needle jet tube, not increases ( you would have to drill out the existing air passage for that ) which in turn increases the fuel to air ratio delivered at the needle jet.
They compensate for the higher proportionate atmospheric pressure in the venturi at low rpms resulting from running a less restricted intake.
They pinpoint the low end hesitation caused by the lean mixture in that area without any other changes to stock carb settings apart from the usual main jet increase and the normal pilot screw adjustments and there's no need to buy additional alternative profile needles or lift the existing needles to introduce an increased amount of fuel mix earlier throughout the entire rev range .
The stock Mikuni needles remain in the original clip position ..
Their affect on the A/F ratio tapers off as the revs rise which doesn't put additional fuel midrange where it isn't needed which raising the needle does.
These jets have been dyno developed to achieve the correct size and are proven to be more refined and superior in operation to the needle shim/lift and the often used and un-needed larger pilot jet method.
I do know that the needle lift method is the engrained fix when fitting pods etc in most of the world and although it masks the lean spot it isn't the ideal way as it introduces extra fuel to areas in the mid range where it isn't needed and getting owners to move away from the only way they know takes some explaining.
These aren't a recent invention, we have been using these in the UK for over 40 years and the difference between these and lifting the needles etc is a noticeable improvement with average gains of 2 to 6 horsepower overall, a crisper throttle response and increased mpg.

[1948man]

The one and only time I used a dynojet about 10 yrs ago, the drill bit was used drill the bottom of the slide (I think that's the term). I'm not sure why it needed drilling.