A moment for clarification please

[Guest]

Are you running factory intake and exhaust? If so I'd recommend setting the carbs to all factory settings (jet/needle sizes and all) and tune from there.

Like I said. Right now everything is factory except the needles. When I put the factory needles back on the diaphragms the plugs fouled and gas just poured through it was terrible. This is why I'm thinking the Needle Jet valves are worn now.

 

[Steve]

Well, here we go with terminology again. :-k

... air screws lightly bottomed motor idles smooth (no throttle) ...

Your bike does not have "air screws".

The only external adjustment you have is the pilot screw. It controls a mixture, not just air.

Some call it a pilot screw (the proper term), others call it the mixture screw.

.

 

[Guest]

Well, here we go with terminology again. :-k


Your bike does not have "air screws".

The only external adjustment you have is the pilot screw. It controls a mixture, not just air.

Some call it a pilot screw (the proper term), others call it the mixture screw.

.

Steve, I know... and you know which screws we're talking about.. The point is they are screwed in to the point of cutting off fuel (if I've gotten that right).... and the bike was idling at 1000rpm. I've since let the bike cool down and when I went to start it again. It would not start until I cracked the enrichment valves (also called the choke incorrectly i'm told) I opened all 4 air, mixture, pilot screws to 1/2 turn from lightly bottomed and took the bike (motorcycle) for a ride and the only adjustment I had to make was to turn up the idle (using the idle mixture knob between the carbs and the airbox) after the bike (motorcycle was warmed up) to let the engine idle at about 1100rpm (+/- 100) according to my RPM gage. I am going to ride it for a bit and see what changes... As always I'll read comments and because I know so little I will listen to all constructive suggestion...

 

[Steve]

Something is definitely screwy with your carbs. :-k

It is not unusual to use the "choke" when the bike is cool, but the pilot screws are usually about 2.5 turns out from lightly-seated.

There are multiple outlets for the fuel mixture. All of them are at the top of the outlet bore. There is one that is just forward (towards the engine) of the throttle plate, one or two more will be just behind the throttle plate. The last one is closer to the outlet of the carb, that is the only one that is adjustable. In normal operation, the first port mentioned is open all the time, but it can not provide enough fuel for the engine to run, so you have to open the pilot screw to add some fuel (which has been mixed with air). The other port(s) are uncovered as the throttle opens, allowing some transition before the needle circuit takes over. The fact that your bike runs so well without the additional mixture from the pilot screw makes me wonder if you have the correct air and pilot fuel jets.

Here is a side view of the carb so you can see what I was just describing:

.

 

[Guest]

NICE DIAGRAM! .... now.... WHY can't I lean my mixture...LOL

(I really mean that is a nice and concise diagram.. I wonder why that isn't in the manuals that I have on line or in print.... where did you get it? )

 

[Steve]

In the Suzuki manual.

Suzuki GS850G Service Manual

It's page 14-30 in the manual, it's page 301 in the .pdf

.

 

[Guest]

Steve, you called it earlier in the thread. Something is, indeed, fouled up in my carbs.. or something. I went for a ride today and was feeling pretty good about gas mileage and performance... noticed a bit of stutter on deceleration but nothing too drastic... Wanted to tweek down the mixture just a bit more... removed the tank, plugged the vacuum hose to the petcock, set up my temp gas supply and started up the bike... I wanted to see if the exhausts were close in temp.. so I took out my infrared harbor fright (sic) thermometer and while #4, #3, #2 were hot 150 degree range... #1 was cold.. 94 degrees. So I figured I was not getting spark.... Spark is fine with current plug and a couple of others that I tested. No fire in #1... but the plug was wet. Compression is 128 psi....

 

[BigD_83]

NICE DIAGRAM! .... now.... WHY can't I lean my mixture...LOL

Just a thought, but if your bike runs with the A/F mixture screw lightly seated, then I wonder if the tips might have broken off, allowing more fuel through than it should be seeing?

 

[Guest]

Just a thought, but if your bike runs with the A/F mixture screw lightly seated, then I wonder if the tips might have broken off, allowing more fuel through than it should be seeing?

Pulled all 4 screws and they are fine... Right now I need to find out why my #1 cylinder isn't firing while it's getting both gas and spark.....

 

[Guest]

Spark plug cap.

 

[hannibal]

A rich cylinder runs cooler so that would be my guess. It might be so rich if does not fire at all and is getting hot from adjacent running cylinders. Or it may be running fine for a short period of time, then fouling and failing to fire.

I think a cylinder that never fires would be cold to the touch at start up while a cylinder that runs momentarily would be warm, but cooler than the rest.

 

[Sandy]

Pulled all 4 screws and they are fine... Right now I need to find out why my #1 cylinder isn't firing while it's getting both gas and spark.....

Just for giggles and a simple, quick diagnostics swap the coil trigger wires and spark plug wires around. The left coil, if wired correctly, should fire 1 & 4 plugs, the right coil 2 & 3. Switch the 1 & 2 plug wires and the 3 and 4 plugs, then swap the coil trigger wire, not the orange wires the other ones. Fire it up and see if the problem moves to cylinder 2 or stays at cylinder 1. If a coil is very borderline it might dry fire a plug and not fire it under load. What the heck, you've tried everything else, it's easy to do and might tell you something .......might not. At least it's one more thing to eliminate as a source of the mystery.

 

[Guest]

Spark plug cap.

The caps have just been replaced and I swapped an old one (which was still working) Swapped caps, even swapped out spark plugs. ...

 

[BigD_83]

Sandy's suggestion of swapping the trigger wires for the coils is a good one.

I had a situation where, even after swapping caps, I would get spark with a plug grounded on the outside the head, but when I put it all back together it wouldn't fire. Baffled me for the longest time. Incidentally, I was working on the bike as it was getting dark, and I noticed I was getting a lightning show along the entire spark plug lead when it was on the plug, in the head. Of course, that was after I shocked the heck out of myself when my bare hand brushed the lead. Replaced the leads and all was right and good again. Swapping the trigger wires (or even just the leads) might point at whether the #1 lead is bad.

 

[Guest]

Just for giggles and a simple, quick diagnostics swap the coil trigger wires and spark plug wires around. The left coil, if wired correctly, should fire 1 & 4 plugs, the right coil 2 & 3. Switch the 1 & 2 plug wires and the 3 and 4 plugs, then swap the coil trigger wire, not the orange wires the other ones. Fire it up and see if the problem moves to cylinder 2 or stays at cylinder 1. If a coil is very borderline it might dry fire a plug and not fire it under load. What the heck, you've tried everything else, it's easy to do and might tell you something .......might not. At least it's one more thing to eliminate as a source of the mystery.

Shouldn't you swap leads 1 & 4 rather than 1 & 2?? Doing the later would reverse your timing/firing order if I'm following this correctly. Then if 1 heats up & 4 doesn't, you can blame the lead/coil/cap & forgive the plug/carb.

On a side: If you had the air pilot set very lean & the fuel pilot set very rich, would that prematurely foul the plug within say...the first hundred motor revs....to a state where that cylinder would remain flooded and not be able spark until the plug was dried out? And if so, would head temps from the other firing cylinders be enough to ever dry out that soaked plug?? Otherwise you'd probably start leaking fuel down past the valves, diluting your oil to some minor extent, or down the j-tube & into your hot exhaust for 'enhanced surprises'

Thoughts??

 

[Sandy]

The left coil fires 1 and 4 and fires both at the same time and on both the compression and exhaust stroke, the firing on the exhaust stroke is simply a lost spark. Same goes for for 2 and 3 only 180 degrees a part from 1 and 4. So by switching wires as mentioned you are simply moving the left coil and points or ignition pickups to do the right coils and ignitions job and vica-versa for the right side. If the problem follows the existing #1 wire to #2 cylinder then you know the problem is not valves, compression or carburation but in fact something ignition related, plug wire, bad coils, bad plug, pickups, etc. Sort of eliminates one full segment of operation and narrows the possibilities for diagnostics purposes. If the problem after changing the wires stays on #1 then you know it's not liking ignition related. A quick simple test to keep you from chasing your tail so to speak.

 

[Guest]

Ahhh, didn't consider the fact that the coils fire at both compression & exhaust strokes. Paint me automotive minded Thanks for clarifying!
Now, about those pilot screw settings...would a spark plug recover from being saturated during a typical ride?

 

[Steve]

Ahhh, didn't consider the fact that the coils fire at both compression & exhaust strokes. Paint me automotive minded

You had better make that "Old-school automotive minded". :-k
You are thinking of systems that use a single coil and a distributor. With the increase of computers, crank position sensors, etc., many of the cars back in the '90s had a bank of twin-lead coils that fired cylinders that were opposite in the firing order, just like our GSes. I have seen a couple of guys that used those coils on a GS with at least moderate success. In more-recent automotive practice, there is a coil mounted directly to each spark plug.

Now, about those pilot screw settings...would a spark plug recover from being saturated during a typical ride?

It takes a lot less time than that. More like a few dozen revolutions of the engine under load. That short a time will not necessarily give color to the plug, but it will certainly dry out.

.

 

[Guest]

Ahhhhhh....yeah, old school for sure!! Forgot how I learned that my wife's '06 Dodge had a coil 'pack' rather than just a single coil, and thinking to myself 'That's gotta be expensive to replace if one coil craps out'...it never did thankfully .

Thanks to both Sandy & Steve for setting me straight!!

 

[Steve]

We just present facts. The number of curves you take is up to you. :encouragement:

.