Two Dead Cylinders on GS550L - Advice Needed

[Anonymous]

I realize I have asked a lot from the forum but continue to have problems. Today I started the bike for a ride after it had been inactive for 2-3 days. When I shut it down the last ride, it was running perfectly now there are two cylinders that are not firing. The bike would start and run but as can imagined had no power with only 2 jugs working. I pulled the plug wire off of the affected plugs with no effect on the engine. The cylinders that are not firing are the two inside ones. I pulled the plugs and they are very black but have no oil on them. The spark plugs are putting out plenty of spark (NEW)...The carbs have just been replaced and overhauled by a certified Suzuki shop. I've had it back twice due to rough running a slower RPM's. Until today it really ran great at anything above about 1500 RPM and really zinged from 5500 on up....What could be causing the problem except the carbs? Got fire and the cyliders have compression.....Your help and advice will surely be appreciated. I guess thats what a 69 year old fart gets for getting a bike this late in life HUH.

[Anonymous]

did the shop syncronise your carbs? or did they just rebuild them. it sounds like your still ritch on the tip in from idle.

[earlfor]

Re: Two Dead Cylinders on GS550L - Advice Needed

Oh Boy, I feel a long one coming on. :-) :-) That it is the #2 and #3 cylinders dropping out points away from it being a carb problem. That the bike when received from the shop after the work was done would still only idle decently at 1500 rpm or more definitely says the "mechanic" did not know what he was doing or was too lazy to look for the actual problem.
Its been my experience with shops that newer/expensive bikes go to the best mechanics and older bikes go the shop help that could use some
on the job training. I doubt the shop did anything other than work on the carbs. Unfortunately, there is a major problem with that. Another problem is that you have no idea or way of knowing what the shop did exactly, what any settings were, or the condition of any of the prequisite adjustments and checks that must be verified before any work on carbs can reliably be done. I think your best choice is to get in there and fix it yourself. These old bikes are 100% mechanical and there are no computer chips or mapping curves or fancy electronics to deal with.
Its a matter of reading a multi meter and being able to turn a wrench, twist a screwdriver and read a vacuum guage. It isnt difficult. You only need to follow an order when looking for a problem.

It could be an ignition timing problem on the 2,3 side of the ignition pickup.
(easy to check advance with a timing light)

It could be an air intake/filter blockage. (easy enough to check to make sure the filter is clean and the airbox is sealed as it should be)

It could be low compression on the 2,3 cylinders. (doubtful)

The carb synchronization could have been done poorly. (likely)
(will also cause idle to be rough, rpm high and increases engine vibration levels when running)

The float heights could be set too high in the 2,3 bowls. (a must check anyway)

The idle jets could still be clogged. (likely) That would also explain why it will not idle smoothly at the normal 1000 rpm it should.

Do you have a factory service manual or a clymer or Haynes book for the bike?

What year is your 550? Factory electronic ignition, after market electronic ignition or factory points and condensors?


Stock airbox and filter or pods?

Stock exhaust system or aftermarket?

Was the bike sitting up for a long time, unused before you got it?

Let me know and we'll try to find whats wrong with the old girl. :-)
Hang in there, it isnt so bad. :-)

Earl

I realize I have asked a lot from the forum but continue to have problems. Today I started the bike for a ride after it had been inactive for 2-3 days. When I shut it down the last ride, it was running perfectly now there are two cylinders that are not firing. The bike would start and run but as can imagined had no power with only 2 jugs working. I pulled the plug wire off of the affected plugs with no effect on the engine. The cylinders that are not firing are the two inside ones. I pulled the plugs and they are very black but have no oil on them. The spark plugs are putting out plenty of spark (NEW)...The carbs have just been replaced and overhauled by a certified Suzuki shop. I've had it back twice due to rough running a slower RPM's. Until today it really ran great at anything above about 1500 RPM and really zinged from 5500 on up....What could be causing the problem except the carbs? Got fire and the cyliders have compression.....Your help and advice will surely be appreciated. I guess thats what a 69 year old fart gets for getting a bike this late in life HUH.

[Anonymous]

Oh Boy, What a great response to my question and thank you Mr. Earlfor.

Response to some of your inquires:
Bike is a 1979 GS550L that I late purchased last summer. Carbs were not correct even though seller advertised " complete new OEM carbs installed" The mechanic at the certified Suzuki dealership says they did not fit my bike. He had a set that would fit, charged me for a complete cleaning and tune up Carbs included of $225.00. I have had it back several times due to rough running at idles speeds. Exhaust is stock and original. I sometime think I hear a rattling in one of the pipes. Could a baffle be loose causing some of my problems. Pipes are in great shape.

When I first got the opportunity to take the seat off after purchase, I found no air filter or cover..Seller said he had the top and filter and would send...He never did (I have him sued in small claims court, trial the 24th of FEB). I fabricated an aluminum cover and we cut pretty good square hole in the top and installed a new filter. Mechanic has had the bike in the shop3 days for another tune up...

I started the bike again this morning, again only 2 cylinders. I took all of the plugs out and they were dark with soot. I cleaned them and then swapped them out (inside to outside etc). I started the motor again and took one of the plug wires off and it pulled the rpm's down. I took the wire and held it about 1/2 inch from the plug and the motor missed a few times and then the rpms drastically increased. I did the same routine on all of the plugs (held the end of the connecter away from the tip of the plug and they all starting firing correctly.. Rode the bike and it will really pull out strong when running correctly. The bike only has 13000 miles on it and I have put about 400 of those. So it would have to have been setting for a good period of time or only ridden 40 miles a month. It also had to be in good storage as the chrome is bright and the paint is original and good..I think it is running too rich so I drilled 5 more 1/4 inch holes in the aluminum cover (I need to find an original and get rid of the plate).
I called the mechanic at the shop this morning and he thought that it might be the coils but I disagree because the plugs look like they are firing okay. When you pull them away from the plug you can hear them fire inside the rubber boot.....Anyhow, I sure appreciate your suggestions and will appreciate any more after you read this long post. I am convinced that I need to get the cover and then get it back to the shop an make them fix the carb right. My total bill for carb and labor was $667.00 and I have told them for that price they would have to make it right. I suspect they will look for other things. What else could cause the black deposit on the plugs (not oil) except too rich fuel??? Gonna go ride it now Earlfor and thanks again....BTW. I flew my airplane (Piper Cherokee) this mornng and it was great 45 degrees, no wind and not a cloud in the sky...Later

Mickey Walker ,. A 20 year old in a 69 year old body

[KEITH KRAUSE]

Hi. It could be any of the things Earl suggested. Possibly a weak spark related to the 2/3 coil or point condition/timing. A weak spark over several miles would eventually foul the plugs. Cleaning them only temporarily helps the spark. Check and adjust the 2/3 point and check the timing.
If carb related, I would suspect the pilot circuits are dirty. It's also possible the pilot screws underneath have been set too rich or may have their tips broken off in the carb body due to someone tightening them down too hard. You may have the needle positions in those two carbs set too rich. With your past carb issues, anything could be possible.
I would check the timing and point gap because it should be checked anyway. But first, because it's the easiest, I would try turning the pilot screws for #2 and 3 IN-CLOCKWISE 1/2 turn, clean the plugs good and see what the bike does. Test ride several miles and read the plugs. Caution, if never disturbed, these screws can be very stiff and the heads easily stripped. Use a very good fitting screwdriver. These screws are underneath and in front of the floatbowls. If this does'nt help, we'll try something else. Any questions, let us know.

[earlfor]

Mickey, the first thing you need to do is put a sealed airbox back on the bike. With stock jetting, it will not run right without a sealed airbox. The open air intake hole in the bottom of the box should measure about 1/2" x 3". Otherwise, the box should be airtight.

To check to see how well your plugs are sparking, remove a spark plug.
Put the plug into the plug wire/cap and ground the plugs threads against an engine cooling fin. While holding it there, touch the starter. (make sure your kill switch is in the on position and your clutch lever is pulled in) If the clutch lever is not pulled in, the interlock will kill the ignition circuit.
You should see a good, blue spark on the tip of the plug electrode.
Check the plugs/wires for all four cylinders. Let me know if you have spark on all four sparkplugs when they are grounded to the engine this way.

Do this check just to humor me if you would please.
Remove the gas tank. (raise seat, remove hold down bolt at rear of tank,
unplug fuel and vacuum lines from petcock.) You will see two coils, one on the left side and one on the right side of the frame. The left coil fires cylinders 1 and 4. The coil on the right side fires cylinders 2 and 3.
The 12 volt positive power feed/supply to each coil will be an orange/white wire. That orange/white wire must go to the terminal on the coil that is marked +/positive. If someone has reversed the polarity of the connections, the bike will run, but it will run like crap. :-)

If you have a multimeter, unplug the wires from the positive and negative terminals on the left coil. Set the multimeter to the lowest ohms scale. That could be X1 or 200 depending on your meter. Connect the red and black meter probes to the + and - coil terminals on the left coil. Any reading between 2 and 5 ohms is within service limits. Average is about 3 to 4 ohms. Make the same check on the right coil.

Let me know what the results are for the two coils. This checks the primary side of the coils.

The secondary side is checked by setting the multimeter to the 200K scale.
You will touch the multimeter probe tips to the metal contact in the spark plug cap. One probe to the #1 spark plug cap contact and the other probe tip to the #4 spark plug cap contact. Resistance should be between 30K-50K ohms. Do the same thing between plug wire #2 and plug wire #3. Let me know what reading you get.

If your primary coil resistance is between 2 and 5 ohms and your secondary resistance is between 30K-50K ohms, then your coils are fine.
If secondary resistance is incorrect, it is probably faulty plug caps.
If you need to replace plug caps, you will need the NGK 5K ohm caps.

A loose baffle in the exhaust will not make any difference other than to annoy you with the noise. :-) I have on in my 750 too. eh eh

Also, set the multimeter to the 20 volt DC scale and tell me what the voltage is at the battery terminals. Then put the multimeter red probe on the orange/white wire that powers the coil and the meter black probe to ground. With the ignition turned on, check the voltage to the left coil and then to the right coil. Let me know what the voltage level is going to the coils.

We have a frequent poster in the forums that is fond of saying things are never balck and white, they are shades of gray. A bike is like that. Everything has to work together. A bunch of small things, that by themselves would be insignificant, when put together will make it impossible for the bike to run right and sometimes not at all.

Not knowing what the shop checked or what condition anything is in is why I am asking you to do these checks.

To reliably do any kind of carb adjustment, you first must know:

1. voltage available at the battery
2. voltage available in the harness to power the ignition system
3. The condition of the air induction system (intake tubes/airbox tubes and filter)
4. verify ignition timing is correct
5. verify ignition system components are working and to spec's
6. Your bike has points and condensors, (if it is still stock) so you will need to set point gaps and at least static time to the F1 mark for the left side points and F2 mark for the right side pointset. If you need spec's and instructions on how to do this and what you will need, let me know.

If any of these things are wrong/faulty, you can adjust carbs until you turn blue and it will do you no good at all. :-)

I suspect you will find very low input voltage or reverse polarity on your right coil. (just a guess at this point) :-) Its also probable your ignition timing is off and if it is, then its a sure thing your carb synchronization isnt quite right either.

Lemme know..........:-)

Earl

[AOD]

sorry these are long to read. if i repeat...my applogies.

with a 79, you have points stock. unless you've replaced those, i'd check there first. make sure you have nice flat contacts gapped to uhm... .014 is ringing a bell (i converted to electronic last summer).

my 550 carbs have a choke circuit problem on full choke. one cylinder will repeatedly not fire until i've gradually let off the choke, and rolled on the throttle. as the choke fades, the cylinder will begin to fire, until it runs normal.

this happened on both my 550's (each had this same carb rack, i swapped em twice) but i've adjusted. try warming your bike up, and running it off the choke, see if it improves.

lastly, hit the airbox with some carb cleaner or starting fluid when its running. see if they fire or it improves.

~Adam

[Anonymous]

Dead Cylinders

Thanks gentlemen for all of the great responses. Only bad thing about them is that they re-inforce my knowledge that I don't know s--t about working on a motorcycle. Most of the suggestions are way beyond my capability but I can sure have a certified Suzuki mechanic follow the recommendations.

As for the airbox. I have the complete box, all hooked up with filter installed etc. except the top cover. Would someone be so kind to take a look at the following ebay auction to see if I will get the cover if I order this item

1979 SUZUKI GS550 GS 550 AIRBOX Item number: 2458558991

I checked the spark as directed and all have spark but I wouldn't say the spark is completely blue on any of them although there is some

Again thanks for the great responses and I will keep you posted.

[KEITH KRAUSE]

The air box lid should be on but without it you would run leaner, not richer, and all 4 carbs would be equally effected if the missing lid was to blame.
I'm not too sure a mechanic will follow other peoples advice.
Do you feel comfortable adjusting the pilot screws as I suggested to carbs 2 and 3? I'm still curious if you really do have the correct carbs on the bike. I have a '79 GS1000E, it has the stock Mikuni VM26SS carbs. I believe yours are VM22SS. These carbs look very similar on the outside.
Visit my website by clicking the WWW symbol at the bottom of my post and let me know if your carbs look like mine. In my photo section I have close ups of the carbs. This would at least prove if you have the correct kind of carbs but to determine if they are 22mm would take some inside inspection.