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1985 GS550L Jetting and Pilot questions

  • Thread starter Thread starter Doug B.
  • Start date Start date
D

Doug B.

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I have a 1985 GS550L, stock pipes, stock airbox, oem filter.

I recently found it had a flooding concern, and that the PO had pulled or tried to pull the needle valves with pliers, slightly crimping one of the seats, causing an intermittent sticky needle.

I ordered new oem needle valve assemblies, that should take care of that.

What I found and what i am concerned about is that the jets are not the stock spec jets, the bike calls for 95 on the outside cylinders and 105 on the inside cylinders, and what it has is 98.5 across the board (main jet size, havent pulled the pilot jets yet)

Leaner in the center two cylinders doesnt seem right to me, if anything larger throughout would make more sense to me.

I have been looking for dynojet kit 3108, the stage 1 kit for these carbs, but does anyone know what jets are included in this kit? Is there perhaps a kit already installed?

Also, does anyone have a baseline setting for the pilot screws? mine have already been made adjustable, and they dont give a starting position in the book, they just say they are 'preset at factory'
 
Also, does anyone have any experience with 6sigma jet kits?
 
Not so many people here have experience with these 2 barrel carbs I suppose, that or I'm a jerk and no one wants to talk to me about this stuff.. either way..

I pulled the pilot jets, they should be 35 stock and they are 37.5 installed.

So I think Im just going to buy some mains and call it done. I think 97.5s in the outers and 107.5s in the inners should be good, I know this bike was on the ragged edge of lean from the factory, that should richen it up a good bit.
 
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Sorry nothing to add. Just post up your final results where you get it back together.
 
Will do, I figure these carbs are limited to what, 3 years of one model motorcycle? Not too many experts.

I did run my carb bodies through the ultrasonic cleaner at work today, even cleaned it all out and used new fluid, They should be about as clean as can be :)

Hopefully I can find the jets I need at one of the local shops, I should get my needle valves wed., and I'll get a chance to see how my theory works out.
 
Hey there, new here but I have used the online retailer for some other hard to find jets that I needed and only wanted to buy them individually. Not sure if you know about the site but they may have what you need.

http://www.power-barn.com/servlet/StoreFront

Hope this helps you, not sure what type jets your looking for but thought Id mention them just incase.
 
Does the bike run ok now? If so what are you trying to obtain by swapping jets?With no air box or filter mods etc. The reason the inside main jets are larger is to try and get those cyls. to run cooler since they are not exposed to as much air passing through them and sitting between two other cyls. Baseline settings on most of the mixture screws I have seen are between 1 1/2 -2 1/2 turns out.Richer or leaner as per conditions.Any thing above 4 turns out requires a pilot jet change or a pilot air jet change if applicable.I looked up the jet sizes for your bike on the Suzuki fische and I show 37.5 pilots all across and 90 outside and 97.5 inside with optional jet sizes 92.5 outside and 102.5 inside.1985-86 are the sameThe sizes you are looking at may be a tad rich seeing they are larger then the optional jet sizes. As far as the 6sigma jet kits no clue sorry. Dynojet jet sizes are a size of there own and have no relavence to the o.e.m. jet sizes and rarely do they ever change the orignal pilot jet size.At times they change the pilot air jet size which in turn richen or leans the pilot circut. Some times drill and open or restrict the slide lift holes. Repl. the slide springs, and the needles is what I see is what you are really paying for is the different profiles and tapers they use. Poss. since you have a Dynojet part# you may call them and see if they couldn't assemble you another kit if it has been discontinued.Sorry I don't know more about those 2 barrel carbs themselfs,worked on a few over the years but not latley. Happy tuning.
 
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Doug B. said:
I have a 1985 GS550L, stock pipes, stock airbox, oem filter.

...

What I found and what i am concerned about is that the jets are not the stock spec jets, the bike calls for 95 on the outside cylinders and 105 on the inside cylinders, and what it has is 98.5 across the board (main jet size, havent pulled the pilot jets yet)
Click to expand...
A couple of curiosities here. I do not have specs for an '85 bike, only for '83, they might have tweaked the jetting a bit since then.
What I show for '83 is 95 on the outside, 102.5 on the inside. Evidently they saw the need to cool the inside a bit more with larger jets.

I don't know who makes jets with a 98.5 size. Mikuni increases by 2.5, so they would be 95, 97.5, 100, etc. Dyno Jet goes up by 2s, so would be 96, 98, 100, etc., but no .5s. Kehin staggers their numbering, would have been 95, 98, 100, etc., but again, no .5s.

Also, if there are no mods to the bike, why are you adding more fuel with larger jets?

.
 
The first time when I said 98.5 it was a typo, they are 97.5 all across.

The manual from basscliffs site and the bike bandit fiche show that it should have 35 for the pilots, 95s on the outer 2 cylinders, and 105s in the inner 2 cylinders.

I am just concerned about a lean/hot condition on my inner 2 cylinders, and think going down from 105's to 97.5s was a big jump in the lean direction, even with a bump in the pilots to 37.5 (which is where they are)

I would rather be a tad on the rich side.

I just want to go back to 105's or even 107.5s on the center 2 cylinders, the rest im going to leave as it was.

I did have a rideability issue where it felt like it was skipping a bit when at a steady cruise and I accelerated, I do not know for sure if this was caused by the sticky needle valve (it only flooded once, but it could have just as easily been stuck closed or partially closed) or it could have been detonation in the center two cylinders from the lean jetting. I could also have a coil or wire issue but Ill see about that once the carbs are back on.

Thanks for the input, Im a little curious now about where the other jet numbers are coming from, as the manual in the bikecliff site says that is the jetting for all 83-86 550Ls.

The reason to add larger jetting is that the bikes from the 80's were jetted lean, and I've yet to see one that didnt benefit from a little more fuel (epa be damned) at least in the pilot circuit.

I know that leaner than stock is definitely not a good place to be.
 
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So I put it back together last night using the 97.5 (1 size over) jets in the outers, 105's (stock size) in the centers, and the 37.5 pilots (also 1 size over). I set the pilots at 2 turns out and did a bench synch to get it close.

She fired up easily, ran good and had a steady idle. When I took a 20 mile ride it ran good, better than it did with 97.5s all across, with noticably more grunt during top gear roll ons from 55-60mph and no sensation of 'skipping'

It did seem to run a little rough for a brief moment about 15 miles into the ride, but it was just a momentary thing that cleared right up.. not sure if it was ignition or carb related, and I plan on a little longer ride this afternoon. We'll see if it was a fluke or I have some type of further issue.
 
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