1980 Suzuki GS1000E - Help Determining Needle Jet Size

[Phaedrus]

1980 GS1000E / Mikuni BS34 Carbs


4to1
K&N Pods
45 Pilot / 1.5 turns out
137.5 Main


In the process of fine tuning my carbs (BS34SS). At 4 notches down on the needles (half way down), 1/4-1/2 throttle is lean bogging. Only way I can remove the hesitation/bog is by richening the needles all the way + a washer, but then my 3/4-full is too rich and won't pull through redline. I ordered some smaller mains to see if I can get her to appreciate full throttle, but I'm worried about 1/8-1/2 being too rich because of the needle height.


I've tried resolving the issue with a DynoJet kit. No luck. Same hesitation if I don't raise the jet needles. Only way to resolve it with the kit is to richen them all the way +2 washers, but then the bike is a rich slug from 1/8-full.


It seems I'd do well to raise my needle jets 1 size. Stock in these carbs are Suzuki "318 X-7" needle jets--~41mm overall height. Can't tell exactly the inner diameter, but it seems to be about 2.68mm. When looking at the charts I found, it looks like the Mikuni 176/270 P-7 needle jets are a match, but I'm not positive.


Anybody know what the Suzuki 318 X-7 needle jets translate to in Mikuni's world or how to figure it out? Looks like the 176 series to me, but I want to be sure before I throw green paper at anything...


Here's some links for research's sake if anyone wants to play sleuth with me:

 

[1980GS1000E]

CV carbs are never going to operate properly with pods.

 

[GSX1000E]

Too rich on the pilots and mains. I am surprised that it runs. Do you have some kind of air injection pump system hooked up?

 

[Phaedrus]

Too rich on the pilots and mains. I am surprised that it runs. Do you have some kind of air injection pump system hooked up?

Gonna drop back down to 42.5 pilots. Couldn't get her to hold idle with stock 40s.

What sized mains do you recommend? She seems to like 137.5s with the needles @ 4 notches. Was gonna try 132s with the needles all the way up.

 

[GSX1000E]

Those carbs need to be thoroughly cleaned to begin with. If the muffler has any packing at all in it, 40 pilot jets, raise the stock needle with ONE 3mm flat washer and install 127.5 or 130 main jets.
ONLY, AFTER you THOROUGHLY clean those carbs. You can choose to find problems that don't exist if you wish. I prefer to ride them myself. CLEAN THOSE CARBS. (<did I forget that part?)

 

[Phaedrus]

Those carbs need to be thoroughly cleaned to begin with. If the muffler has any packing at all in it, 40 pilot jets, raise the stock needle with ONE 3mm flat washer and install 127.5 or 130 main jets.
ONLY, AFTER you THOROUGHLY clean those carbs. You can choose to find problems that don't exist if you wish. I prefer to ride them myself. CLEAN THOSE CARBS. (<did I forget that part?)

I'll give it a shot. The muffler is part of the old ProSport 4to1, no baffling at all. Upgraded from **** emgo pods to K&Ns when I was building the bike, idle went bye-bye--too much air. After another thorough clean, I'll try the 40 pilots again, see if they'll take.

Now, this is something I've been confused about since I picked up this bike. Never worked with CV carbs before, but the needles that were in my set look like this:

Except, mine are even more tapered. So pointy, they almost look like toothpicks... The PO had obviously been in the carbs before, but it wasn't clear to me what had been changed. I cleaned and rebuilt them, but left the needles not knowing any better.

After so many hours trying to get this bike to run right, it became apparent that I might have the wrong needles and that these 5D50s are what should be in there:

The 5D50s look a hell of a lot more like the DynoJet needles that came with my kit too...

You told me to raise the needle using 1 washer, which again raised a flag--my needle has clip positions. Am I right to conclude that I've been running the wrong stock needle this whole time?...

 

[GSX1000E]

By running it ONE washer higher, I meant to replace the factory plastic spacer with (4) 3mm flat washers which effectively raises the stock jet needle ONE washer or .048-.052mm
Sorry for the confusion.

 

[Phaedrus]

By running it ONE washer higher, I meant to replace the factory plastic spacer with (4) 3mm flat washers which effectively raises the stock jet needle ONE washer or .048-.052mm
Sorry for the confusion.

Got it. Still, which needle of those pictured is the one that I should have in my BS34 carbs?

 

[GSX1000E]

I would start with the factory needle as that is what I was working around with my suggestions. With the various different needles that you currently have on hand,
I would think that you have plenty of fine tuning options besides those.
I have a Dynajet replacement kit that I bought years ago (practically free) to compare what they suggest with what works for me and have yet to have the desire to do a thorough investigation.
Some day I will get out the micrometer and compare the parts myself. I just have no immediate need to do so.

 

[rapidray]

CV carbs are never going to operate properly with pods.

This is flat out a LIE!!! Please have experience before you spout off stuff you don't know about.
Ray.

 

[Guest]

Use stock 45 pilot jets, three up on the DJ needle, (stock exhaust?) 132 DJ main.
Take the idle mixture screws out 3.5 turns out.
If the carbs are dirty none of this will work.

 

[GSX1000E]

You DO realize that he has a 2-valve 1000 engine that came with 40 pilot jets, right?

 

[Guest]

You DO realize that he has a 2-valve 1000 engine that came with 40 pilot jets, right?

Wow
Sorry but saw 1100e

 

[ozman]

This is flat out a LIE!!! Please have experience before you spout off stuff you don't know about.
Ray.

ray is correct its just more of a pain getting CV carbs setup but it can be done

 

[GSX1000E]

The only ones that say it cannot be done without a kit are typically those that have difficulty making a stock bike run.
Remember that often times free advice on the internet is worth exactly what it costs and usually comes from those with NO first hand experience.
"Chose wisely grasshopper".

 

[trippivot]

time for a more scientific approach. I mean, you are having trouble that others have not had with similar combinations.


if you haven't gotten it tuned to your satisfaction by now -- buy an EGT meter.

knowing what the exhaust gas temperature is will point you in the correct jetting direction ... then you won't have to buy 4 of every product in the mikuni catalog.

 

[Phaedrus]

Yeah... I think I need to strip the carbs back down, break the rack and soak again, be more methodical this time... Tried a 42.5 / 132.5 MI / 5D50 (stock needle) combo and I'm getting the same horrendous lean bog in the midrange (1/4-1/2 throttle). Every combo I've tried (at the same needle height) has this result... I'm not sure why I'm getting such a large influx of air/lack of fuel at 1/2 throttle nor why my needles can't compensate for it... There must be something plugged up... Or an air leak. But, what/where?

Why the extra air and/or lack of fuel in that range only? I took out the needle jets (emulsifiers), soaked them, and cleaned the passages--all clear. If there was an air leak, like intake boot gaskets, my idle would be affected... However, my idle is strong and steady with 42.5 pilots @ 2.5 turns out on the air screws. Carb cleaner sprayed around carbs/in intake locations does not result in idle increase. Also, it makes sense that there's a bit of an intake increase @ idle because of the high flow pods and baffle-less 4 to 1.

I know that it's a fuel mixture issue because the bog moves as you raise and lower the needle, and can be eliminated all together by jacking the needle up as high as possible...

I suppose if I re-clean everything and still have the same symptoms, then I should reconsider bigger emulsifiers... But, why out of all the people who have commented and have the same bike, does my particular GS hate the midrange?....



How would an EGT help me discern appropriate jet size?

 

[trippivot]

E.G.T. meter as a jetting tool ? colder exhaust tells a tuner a richer mixture is happening - under 1000F -and hotter is leaner like 1800 -- your temps will move around but you look for a spike or dip where your running problem is - make a jetting change and can compare it to a physical reaction- observe a trend, and tune out your problem ... instinct and the enrichner can get you running good, but this tool will allow you to find the leanest "edge" or keep it all very safely on the rich side.

CV carbs? when you get a good set don't let them go. permanent damage is all too common and usually hidden so well an experienced mechanic can't tell until you get to tuning them and they don't respond to common adjustments.. starting over with known good bank is a tough decision. After the removal of the airbox or even just the snorkel - you got a running problem- I am a believer in dynojet product - don't like the numbering system on the brass jets - but the stage 3 procedure is necessary for most GS's - in my experience.

midrange also is effected by the slide and how quickly it raises -- no amount of needle height changes / main jets are going to cover a mis-operating slide rate.

drilling the EQ hole of the slide makes it lift slower - and keeping the vacuum up just off idle is very important for the bike to pull smoothly- 1200rpm ~1800 rpm at 1/8~1/4 throttle - it is vacuum that draws fuel into engine - that takes time -- micro seconds, it is a fact that there is no pump that squirts gas into the engine -- so a rider cannot treat CV carbs like a holley double pumper - I call it stabbing into the throttle - immediate W.O.T. from a twist happy throttle jockey , that's bad and you can make a good tuned set of carbs malfunction by mis-operating the throttle. - I realize this is not your problem but just so it is said - there is a way to mis-operate CV carbs even if the mechanic says it is fine and you don't believe him.....

 

[1980GS1000E]

This is flat out a LIE!!! Please have experience before you spout off stuff you don't know about.
Ray.

The CV carb is designed to operate with the dead air volume the airbox and connector tubes provide. There is a wider range of jetting that they will work just fine with if fitted with one. Pods do not provide this and turbulence will interfere with the slide operation.

 

[Phaedrus]

E.G.T. meter as a jetting tool ? colder exhaust tells a tuner a richer mixture is happening - under 1000F -and hotter is leaner like 1800 -- your temps will move around but you look for a spike or dip where your running problem is - make a jetting change and can compare it to a physical reaction- observe a trend, and tune out your problem ... instinct and the enrichner can get you running good, but this tool will allow you to find the leanest "edge" or keep it all very safely on the rich side.

CV carbs? when you get a good set don't let them go. permanent damage is all too common and usually hidden so well an experienced mechanic can't tell until you get to tuning them and they don't respond to common adjustments.. starting over with known good bank is a tough decision. After the removal of the airbox or even just the snorkel - you got a running problem- I am a believer in dynojet product - don't like the numbering system on the brass jets - but the stage 3 procedure is necessary for most GS's - in my experience.

midrange also is effected by the slide and how quickly it raises -- no amount of needle height changes / main jets are going to cover a mis-operating slide rate.

drilling the EQ hole of the slide makes it lift slower - and keeping the vacuum up just off idle is very important for the bike to pull smoothly- 1200rpm ~1800 rpm at 1/8~1/4 throttle - it is vacuum that draws fuel into engine - that takes time -- micro seconds, it is a fact that there is no pump that squirts gas into the engine -- so a rider cannot treat CV carbs like a holley double pumper - I call it stabbing into the throttle - immediate W.O.T. from a twist happy throttle jockey , that's bad and you can make a good tuned set of carbs malfunction by mis-operating the throttle. - I realize this is not your problem but just so it is said - there is a way to mis-operate CV carbs even if the mechanic says it is fine and you don't believe him.....

Thanks for all of the great info. I appreciate you taking the time relay it to me.

I like the idea of the EGT. I need to get closer to where I want the carbs to be before I go that in depth with the fine tuning, but that could definitely add the cherry on top.

I wouldn't be that surprised at this point if there was something uniquely wrong with my CV carbs. I'm embarrassed to admit how much time I've put into the tuning process... You should see my spreadsheet (though, mind you, a lot of this has been a "learn-as-you-go" experience). I've inspected them over and over, cleaned out all of the ports, tested, etc. The ONLY consistent issue is the extra air flow @ 1/4-1/2 throttle. HOWEVER, with the stock 5D50 needles raised all of the way, I was able to remove the lean bog this morning. I have 132.5 mains in at the moment, but they're far too rich. Nothing but pops and crackles at full-no pull. I have 127.5s and 130s on their way. I'll try the 127s when they arrive and see if I can get her to like 3/4-full.

This is promising... I think this whole debacle may have been a matter of the wrong needles in the carbs; though, I don't hear any fat ladies singing quite yet...

Again thanks for all of the guidance. I appreciate it.