3 lean plugs, 1 black plug....

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.

[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...

[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?

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.

[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 ?

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.

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

[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.

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?

[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!

Your clutch is slipping when it hits the power band

I hope you have jets or a jet kit if you're going to put pods on it

Sounds like it was never jetted for the pipe, and you are on your way to frying your motor

Meh, I had a bad feeling it was the clutch slipping. Now I wonder if it's just the springs that need to be replaced or if the friction disks are shot. Just another thing to **** my money away on this damn bike. By the time I'm done with it, everything will be new and I'll be broke.

The "pipe" as you so call it is nothing more than the stock exhaust system off of an '80's Katana... Same motor/frame setup as the gs. I just put it on and your right, it's gonna fry the motor, which is exactly why I'm not gonna ride it anymore till I get the jetting resolved. I don't have a jet kit and I'm not going to **** the money away on a DJ kit. I'll get the jets at the dealership.

I appreciate everyone's advice. However if your advice is to keep the stock intake system because you failed at pod filters, then please take a hike from my thread. If you have no knowledge to contribute other than n00b rantings, then don't waste the server space or bandwidth. I don't mean to come across like a jerk but I'm really sick of hearing it. Specially when there are a lot of pod filter users that have no issues. And no, not every person that successfully upgrades their fuel system does it with a fricken DJ kit.

K, thanks.

Hi,

I would tend to agree with the experts' consensus around here regarding the fouling #2 plug. It doesn't take much gas leaking down the vacuum line to foul the plug. (See #13 in your "mega-welcome" list No. 2.) Also, it is "best practice" to first get the bike running well in its stock form, or in whatever configuration you acquired the bike (See "mega-welcome list No. 1) . Then you have a baseline to measure against when you start making modifications.

But, in general, it is possible to install good K&N pods and a 4-n-1 pipe with a Dynojet Stage 3 kit, follow the instructions, and you'll be close as long as all the other pieces of the puzzle are in place (clean carbs, adjusted valves, good electrical/charging system, etc). Keep us informed.

Thank you for your indulgence,

BassCliff

Time for a rebuild. Those are CV's I guess, I've never worked with them. Do Your self a favor and keep the air box no matter how much a PITA it is, and leave the exhaust as stock as possible. A rebuild and hanging yourself out into unknown territory with complete re-jetting is a much bigger PITA. Ask me how I know.

[Big T]

Your clutch is slipping when it hits the power band

I hope you have jets or a jet kit if you're going to put pods on it

Sounds like it was never jetted for the pipe, and you are on your way to frying your motor

They are the BS32's or whatever the number is that came on the 80 550E. I have a feeling that the 3 cylinders are running lean due to the exhaust system. I'm gonna pull it apart tomorrow and I might even just try to get the pod filters on right away. If I'm gonna pull the carbs and screw with this stuff I might as well just "once and done" it. I really don't feel like having to take that stupid air box off over and over. And actually riding along, when I get up to around 5K RPM, if I give it more throttle the RPMs start to shoot up quick but my speed doesn't increase in relation.... Now you'd think that would be clutch related, but at lower RPMs it pulls just fine and it doesn't do this until you get up to around 5K... Making me think that it's really leaning out around there.