3 lean plugs, 1 black plug....

[Big T]

Steve.

The general consensus among those who have rejetted BS carbs is that the adjustable needle is a must have, and that appears to only be availble in a kit

You're correct in that many have successfully run pods and pipe on their BS equipped bikes. Most have long tales of getting the jetting to work correctly.

Others have just gotten ****ed off and went back to the stock airbox

BTW, jets are much cheaper at www.jetsrus.com

Keep us posted on your progress

On your clutch, the fiber plates may be glazed. Pull them out, measure them and scuff them with sandpaper on a piece of glass and reinstall. Your springs may also have worn out after 30 years. I know ,such cheap stuff the Japanese make!

[FlyingSteve]

We'll just have to see how it goes then. I bought this bike with the intention of turning it into a cafe/naked bike, not keeping the silly stock crap.

I know about jetsrus, however it isn't really cheaper after you pay the 7.50 shipping and then have to wait how many ever days it takes to get your jets. I can get OE jets at dealership for 2.75 each and have them in my hands immediately.

As for the needles... Is it just that they are adjustable or is the needle taper actually different as well?

[bwringer]

As for the needles... Is it just that they are adjustable or is the needle taper actually different as well?

Yes, the taper is different.

And I still suspect that your petcock is bad. Just because it doesn't leak sitting on the bench doesn't mean anything. All it takes is a microscopic leak under vacuum to foul the #2 plug.

Might as well get the jetting in the ballpark before riding some more, but I bet if you disconnect and block off the vacuum port and then ride around for a bit with the petcock on "prime", you'll find that the #2 plug suddenly matches the others.

[sparki]

when you say it's black... sooty black or oiled up black?

[FlyingSteve]

Eff me running... I took the right most carb slide out and there was all ready a .5mm washer shimming the needle... The PO must have put it there. Since I don't feel like yankin the gas tank off just yet (Because the custom seat pan I made is a PITA to get off with the stock air filter box on), I'm just going to experiment with shimming the needle on that carb until I get a good plug color and then I know what I'll need for the other carbs and then I can work on the jetting.

[rustybronco]

I'm just going to experiment with shimming the needle on that carb until I get a good plug color and then I know what I'll need for the other carbs and then I can work on the jetting.

Really? how is that going to fix the over rich condition showing up in cylinder #2 ?

[FlyingSteve]

I'm not screwing with cyl 2 right now, just the lean cylinders. I shimmed the needle of one of the lean cylinders with 3 .5mm shims and took the bike out for a run and the plug color didn't change at all. Looks like I'll need larger jets.

[cowboyup3371]

I know I'm a noob and I honestly don't know what I'm fully talking about with this stuff yet. However, I don't undertand why you would have to shim the needle to adjust the leanness. Isn't that just a matter of turning the air needle one way or the other? What does shimming it give you that adjusting it doesn't?

[rustybronco]

I know I'm a noob and I honestly don't know what I'm fully talking about with this stuff yet. However, I don't undertand why you would have to shim the needle to adjust the leanness. Isn't that just a matter of turning the air needle one way or the other? What does shimming it give you that adjusting it doesn't?

There are four major circuits in a carburetor. first is the enrichment circuit, commonly known as a "choke".

second is the low speed circuit, commonly known as the idle circuit. the idle circuit generally covers the throttle positions from from idle to 1/4 throttle. the air adjustment you talk about on later BS series carburetors is really a fuel flow adjustment, used in combination with a fixed air jet which is preselected by the carburetor manufacturer. although, on the early VM series carburetors, the idle air "jet" is a passage in the carburetor which uses a screw to effectively vary the diameter of the passage and it also, like the BS series, uses a fuel adjustment screw.

next is the mid range circuit, or part throttle circuit which covers throttle openings from 1/4 to 3/4 open. the fuel supplied in this circuit is governed by the needle diameter and the taper of the needle inside of the "jet, needle" at a given needle height. if you raise the needle either with the throttle, or by moving the needle higher i.e. shimming the needle, your are effectively creating a larger passage which will provide more fuel to the circuit.

lastly there is the main jet which supplies the fuel needed for proper operation from 3/4 to full open throttle...

[FlyingSteve]

Ok, so I went to dealership today and I got a 102.5 main jet and a 107.5. I put the 102.5 in to the outer most right carb, which I think is cyl 4, right? Anyway, I went for a ride (about 10mi) and came back and pulled the plug... It looked the same. Still white. I even have the needle shimmed up by 1.5mm.

So, do I need to go higher in the jet size? Or is this being caused by something else instead? Tomorrow I'm going to put the 107.5 in and go for another ride.

Interestingly enough, I looked up an 82 GS550M (AKA, Katana) and in the parts fiche it says the main jet is a 92.5... Same as what was in my 80 550E. It even shows the same part number for the needle jet. The reason I bring this up is because the exhaust system I am using is for the 82 GS550M. So if the exhaust flows that much better, than they would have used a larger jet...

*The air jet and the pilot jet are also the same between the two bikes.

[Big T]

Steve,

With pods and a "stock" exhaust you should be at a 100-102.5 main jet.

No change in color or performance?

Sounds like you have some serious intake leaks

[FlyingSteve]

The pods aren't on yet, just the stock intake.

You may be right about the intake leaks. However, the bike idles perfectly steady and rides smooth. What I'm not sure about is why three of the cylinders are showing the same lean condition (Never mind cyl 2 looking very rich for right now).

Tomorrow I am going to rip the carbs off, give them a good looking over, put 102.5 mains in across all 4 carbs with 1 .5mm shim on each jet needle and then put new o-rings on all the intake boots. I'm also going to check the petcock and try to resolve the "rich" mixture issue on cyl 2.

Now those air mixture screws, I should turn those all the way in and then back them out 2.5 turns?

This should give me a good starting point. Since things are fubar right now, I might as well just rip it down and start fresh with my final setup, which is installing the pod filters and new o-rings.

**Also, concerning intake leaks with the stock air box setup... If it was an issue with the stock air box not being sealed up tightly, then the one 102.5 main jet I installed along with the 1.5mm needle shim should have made that cylinder show up rich.

[Dave8338]

YES, lightly seated with the air screws and then backed out 2.5 turns.

Are you doing WOT plug chops to determine plug color? I've only seen you mention the main jet sizing, so I'm a little confuzzzzzed.

Needle shim will help the midrange and do nothing for the WOT, though I'm sure you already know that.

[FlyingSteve]

Yes, I all ready know the purpose/job of the needle. I haven't been doing WOT plug chops because I've just been cruising around at 1/4 to 3/4 throttle (Where most of my riding is done at)... And even with the needle shimmed up 1.5mm, I've seen no difference in the plug color. Perhaps it needs to be shimmed higher?

[Dave8338]

Sorry...I don't know what you already know.

Sounds like you have this well under control.