1980 Suzuki GS1000E - Help Determining Needle Jet Size

[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.

[rapidray]

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.

Yeah, keep telling yourself that & come back when you have jetted over 500 bikes like I have. Again, I have done this LOADS of times, STILL do it currently & you have NO idea what you are talking about.
Ray.

[blowerbike]

it's all in the needle shape aka purchase a jet kit.
if CV's would not function properly and have no HP advantage... dynojet would have been out of business back in the 80's.

[1980GS1000E]

It takes two to argue so I am bowing out. Enjoy your kingdom.

[Izukes]

I have a 1980 GS1000G. Wiseco 1085 Pistons, Freshly rebuilt 2 valve head with stock cams, V&H 4into1, Pods, Dyna S, Accel Coils,
I have fully R&Rd BS34s on it that I'm starting to tune on. I currently have 40 Pilots, 125 Mains and stock needles. I triple checked float levels at 22.5mm and diaphragm integrity. No vacuum leaks. The bike runs like garbage at this point.
I'm getting a lot of help from this series of posts. Thanks for doing all this research for me. Has the fat lady started singing? What were your final jets and needle settings?

[Phaedrus]

Oh, boy did she sing... Had a blast tearing up the CA back roads with her for a season. Ironically, I literally just sold her this morning...

Your jets are wayyyy too lean. These things are thirsty. Final settings were 45 pilots, 2.5-3 turns out on the air scrwws, 130 mains (I think). Dynojet jet needle, clipped 3 notches up from the bottom with 2-3 washers on top.

Caveat is that I ended up getting a clean set of gs1100 cards (I think bs36s??). The oem carbs were either faulty or just a little bit to rich. I'd try my jet setup with your carbs and see how close you are.

[Izukes]

Thanks for the reply! Those numbers are right where I was headed. I'm sorry to hear you sold it, we're fairly close; I live near Gilroy. Now my stock needles don't have the grooves for clips. I will probably try to get the Dynojet ones...

[trippivot]

dynojet kits are fantastic. I get great results with them and cant say enough good about them.

1085cc bs34 = 45 might work with the dj needles but I think 47.5 pilots will cover the fuel flow you want for low to mid transition on a stock needle.

don't be afraid of jumping to - 137.5~142.5 mains.

[Izukes]

That dog'll hunt. So is there a particular needle that seems to work best? My needles don't have grooves for the C-clip. I don't really understand the numbering system for the needles...