Can't figure this out, one cylinder not responding

[hikermikem]

I'm working on a '82 GS650G, 5K original miles. I discovered an interesting problem while trying to get this thing running correctly after several years of outside storage & neglect.

If you need background info, here's a link to a previous thread: http://www.thegsresources.com/_forum...d.php?t=113474

At this point the bike starts right up & idles at 1k well. I haven't synched the carbs yet because I'm still tuning them.

I've just finished adjusting the valves (measured the Suzuki factory way) and I must say, I certainly agree with those on this site that have said the clearance numbers change depending on the "correct" cam position you use. I found this to be the case & was driving myself crazy until I read a recent post from Keith proclaiming the Suzuki factory method to be best. That's the numbers I stuck with.

While adjusting the carbs I noticed a very pronounced "chugging" sound from the engine. I pulled each plug wire off & found the #2 & #3 clyinders weren't doing much because when I removed their wires not much happened. A bad coil I figured & promptly replaced both coils with 3 ohm Dynacoils.

The chugging sound quieted, but now the #3 cyl still seems to do nothing when I pull the plug wire off. I thought maybe a bad plug, but I switched it with #4 & I still had the problem with #3. Please note that #2 seems OK now after the coil replacement - when I pull that wire, it kills the engine (same as with #1 & #4), but #3 still isn't doing much.

If the coil is bad I would think BOTH 2 & 3 would be toast, not just 3.

If the signal gen isn't working, could the #2 fire OK and the #3 not?

What else could be wrong here?? At this point the bike is essentially running on 3 cylinders. It idles nicely at 1K, but doesn't have much low end power. It actually runs quite strong at higher RPM's but clearly it's not running well - and it CHUGS like a train.

Any thoughts??

Thanks in advance,

Mike

[chef1366]

Switch the #2 and #3 wires on the plugs and see it the issue moves to #2. If it does it's a spark plug cap or wire issue.

[hikermikem]

Thanks Chef (BTW, my son is a chef also),

I had switched the plugs already - not the problem.

I didn't switch the 2 & 3 wires though after changing the coils (did that BEFORE chaning the colis & determined the #2/#3 coil was bad)

I'll switch them tonite (hopefully) and see what happens. Thanks for the suggestion.

Mike

[rockford]

Carb

I've been through almost exactly the same thing and checked everything I could possibly think of. I think you're going to find that it's a problem with the carb. Please let us know what you find.

[Thehotbeast]

Had the same problem but with #2.... ended up cleaning the carbs again and the problem went away.

Good luck

[tomm]

I assume that the header for #3 stays cold. If you give it some throttle, is there a point where it starts to warm up? Either way though, it sounds like you have a good chance of a carb cleaning event in your future.

[hikermikem]

NOOOOOOOOOOOOOOO..... not another carb cleaning!!! Is there no justice?

Although, I must admit, I'm getting pretty good at slapping those babies on & off the bike.

I'll report back after i troubleshoot some more.

Thanks,

mike

[hikermikem]

Update - not real good...

I switched the #2 & #3 wires as Chef suggested - no difference, the #3 clyinder still contributes VERY little to the running of the engine.

And yes, the exhaust pipe is relatively cold at idle, as compared to the other 3.

Ohh baby - does this thing CHUG!! It sounds like a train, and i can only assume it's the #3 clyinder going along for the ride.

Some observations:

- bike idles very well at 1k - chug & all

- When I start the bike, I get A LOT of smoke from the stock exhaust on the 1/2 side.

- when I take it around the block, it stumbles slightly when accelerating through the low rpm range (<3K), then it takes off strong and actually seems to pull quite well through the gears at higher RPM's (the neighbors are loving me).

- when I try adjusting the #3 air mixture screw, it's noticable when i lean it out to the max (all the way in), but there's no limit as to how rich i can make it - once past about 2 turns, there's no change.

I did have trouble adjusting the valves, meaning I was getting all sorts of different clearance numbers depending on whether the cams were in the perpendicular or parallel position. I KNOW #1 exhaust clearance is a bit high (~.004") because I ordered the wrong shim, as the one in there was mis-marked (I measured them all with calipers when I took them out. I'm waiting for the correct one to come in now.) That would explain the smoke I guess.

So what's my next step? Do a compression check & see if i really screwed up the valve adjust? Or just check the valves again & maybe put some of the original "tighter" shims back in?

I really don't want to re-clean the carbs AGAIN, but if that's what's needed, then so be it.

Thanks in advance for any comments or suggestions.

Mike

[chef1366]

Is the compression good on #3?

[hikermikem]

Is the compression good on #3?

It was before I adjusted the valves - will check them all again and see where it's at now.

When I received the bike it wasn't running, but after I first got it going I don't remember the "chugging". It didn't smoke either. I'm thinking I messed up the valve adjustment somewhere along the line. The puzzling part is I took extreme care to do that the right way, and in fact verified my work several times. I do recall getting vastly different clearance values when measuring the same cam at the two (perpindicular & parallel) different positions. Do you think I've damaged anything (e.g., burnt valve) at this point, or do you have to run the bike for an extended period to damage the valves?

Perhaps I'll measure again & take an average of the two values to use as the "actual" clearance value - then decide on a shim change from there.

Is it a possibility the #3 carb is the main problem ? The other carbs are problem free.

Thanks again,

mike

[mortation]

You need to balance the carbs and double check your mixture screw. I had the same problem and balancing them made that symptom go away.

I need to rebalance mine this weekend cause I didnt lock down the nut as I was supposed to and I think I lost my sync grrr :P

[Nessism]

I doubt the problem is valve clearance related but by all means verify all the basics like compression.

Cam position prior to valve adjustment must be to the factory position or the adjacent cam lobe will be pushing on the valve spring which skews the cam within the journal clearance and affect the lash value.

Cam position for adjustment:

- Position Exhaust lobe on #1 parallel to gasket surface and check E1, E2

- Position Exhaust lobe on #4 parallel to gasket surface and check E3, E4

- Position Intake lobe on #1 at 90 degrees to gasket surface and check I1, I2

- Position Intake lobe on #4 at 90 degrees to gasket surface and check I3, I4

I don't even bother with looking at the T mark on the crank, just watch the cam position.

Regarding your bike, if the mixture screw is having an effect on the bike running that indicates the bike is firing at idle. Try playing with each screw, turning it in to close, and see if all cylinders are firing.

My 550 didn't run properly until the mixture screws were out to 3 turns (I'm in CA though and the gas is different here).

Stupid question but did you remove the pilot jets and replace all the o-rings in the carbs when you cleaned them out?

Do you have plugs in place over the pilot jets?

Good luck and keep at it. You are getting close.

Ed

[hikermikem]

Stupid question but did you remove the pilot jets and replace all the o-rings in the carbs when you cleaned them out?

Do you have plugs in place over the pilot jets?

Yes, I replaced all the carb o-rings, as well as the intake o-rings too.

Yes, installed brand new plugs over the pilot jets.


I've been holding off doing the carb sync (yes, i have a vac sync gage), until I have everything else optimized. Perhaps I'll do that & see if it fixes all the sins.

thanks,

mike

[hikermikem]

Good News Update !!!

Well, I'll be pickled & jared - I balanced the carbs & my chugging went away. I thought I did a very good bench sync when I cleaned the carbs, but they were WAY OFF.

At first I couldn't get the fluid in the manometer (fancy name for carb sync'er) to register from clyinder #2. Thought it was a dead cly, but when I unpluged the sync adapter & let it suck air, it killed the engine, so I knew it was "working". I slowly kept raising the vac in #3, while lowering the vac in #1 & #4 and eventually #2 showed up. That's when the "chugging" went away. I evened them all out and voila, sounds like a real motorcycle now!

I've been adjusting the air mix screws in the carbs now & the bike runs quite well, although I think the carbs still need to be tweaked a bit better. Still need to do plug chops however, the bike is like night & day compared to yesterday. At this point I think it just needs to be driven for a while, maybe with some seafoam in the gas to make sure the carbs are squeaky clean!

Anyway, thanks to all who offered suggestions - this baby is now on-the-road.

Mike