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Friends bike needs mechanics suggestions

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Hello DRZ friends. You guys are so helpful with my DRZ 400 I thought I would come to you guys for help. I am working on a friends bike an 1980 Suzuki GL 550 I think (rode bike triple) that he had $1200 of work done to it and rode it 6 times and parked it because of this problem. The work he had done was rebuilt the carbs and other things.He has been really good about draining the gas and running it empty ect.(Since thats why the carb rebuild in the first place) The problem is it runs well/nice at half thottle and above but real crappy below half thottle. It is real dead, hesitant and sloggish and barely runs and dies when it drops to an idle. I was thinking carbs but the spark seems weak on on cylinders 2 and 3 witch are on the same coil. It has 2 coils. When I pull the number 2 or 3 plug wire while running at an high idle it makes no difference, if I pull a 1 or 4 it dies. Question #1 Can a coil put out low spark at an idle and work fine in higher rpms? #2 Is there a way to test the coil? #3 Should we buy a new coil? #4 Could it be the voltage going to the coil? #5What else do you guys think it is? I cleaned all the wire connections to the coil. By the way all the plugs look nice after running it at half thottle or above for 5 minutes but dont seem to be loading up at the idle even though I turned the idle way up to keep it from staling. Im stumped and about to find him a new coil.

Thanks alot for your help.

Dennis

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1. A coil can put out low spark at idle if the system doesn't reach full voltage intill it is off idle. (common on older bikes)

2. There are spark testers that allow you to test for spark at varying gaps. With a multiple cylinder engine they are easy to use. (Fairly cheap, look around online or auto parts store)

3. I would say diagnose the problem before simply changing parts.

4. See number 1. And possibly a bad connection.

5. Sounds like no spark in those two cylinders. If you can pull the wire and it makes no differance. Its a dead cylinder.

Good Luck Man.

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Can you swap coils from the good to the bad? Will confirm if the issue is a coil or other electrical issue. May even fix itself because the connections are scraped clean. Might want to make sure the grounds are clean and tight.

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Can you swap coils from the good to the bad? QUOTE]

Sure, tell him the easy way. :lol: We engineering students like to over analyse everything. :applause: Good Thinking. :lol:

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+2 on the pilot circuits being plugged. You can test the coil with an ohm meter if you want to. Check service manual for values.:applause: vanram

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I agree with Eddie,I worked in a suzuki service dept.,never saw a coil go bad.99 percent of the time its pilot jets,you must do the choke test,when it starts to die,pull out the choke,if it runs better its the carbs.jets should soak in a carb tank for an hour or the will varnish shut very quickly. hope this helps.

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ive seen maybe 2 bad coils in my career and both were physically damaged.

Ditto what Eddie had said. I never found a bad coil in the 10 years that I worked at a dealer..

Scooter :applause:

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ive seen maybe 2 bad coils in my career and both were physically damaged.

I guess you guys are on the right path. I first thought pilot circuits but was thrown off the tral when I pulled the plug wires and it didnt make a difference on #2 and #3. Plus he had the carbs rebuilt in the begining of this storie because 0f the varnishing and so my buddy draining the gas and running it dry so well I figured it must be something else??

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1st lets clarify. It is a Suzuki GS 550 4 cylinder not GL (Honda) or 3 cylinder (Suzuki GT) and it is a "road" bike.

Some of the GS550 Suzukis had very strange 2 throat carbs that never worked right. But you say it seems to be ignition so lets start there. Go buy 4 new plug caps. About $3.00 each. Each plug cap has a carbon resister that is suppose to be 5,000 ohm. I can assure you they are all infinity by now (at low voltage). Try the new plug caps and new plugs. It probably as an electronic ignition but still has mechanical advance so check and lube that. If it still has ignition points, those need to be cleaned and set and timing set. Do the ignition first, then check valve clearance and if it still has problems, move on to the carbs.

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just a note, "running it out of gas" still leaves gas in the carbs, and can just as easily gum up a set of carbs as doing nothing before storing it. You really should drain the float bowls.

If this problem started after it sat for a good amount of time, its pretty much a given. Time to pull the carbs and clean them.

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It is my understanding that trying to run the engine out of gas is worse than leaving the float bowls full as the more air around the fuel the faster it will turn to varnish. The best idea for storage is to add the propper amount of a fuel stabilizer such as stabil.

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The only thing that really works is regular use. You can get most of the fuel out by running if you goose the throttle enough to pull fuel from the main jet that is lower than the idle jets. Drain is the best way to get it all out. Then follow by trying it start the bike a few times. There is enough fuel in the circuits to run for about 1/2 sec.

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The only thing that really works is regular use. You can get most of the fuel out by running if you goose the throttle enough to pull fuel from the main jet that is lower than the idle jets. Drain is the best way to get it all out. Then follow by trying it start the bike a few times. There is enough fuel in the circuits to run for about 1/2 sec.

Well I took the cheaters way of cleaning the carbs and took the tops off, pulled out the mail jets and blew carb cleaner down inside and in the fuel line and in the over flow tubes. Still have the problem but seems a little better. I did get it running good enough to take it out for a spin. It runs real poor up to 2500 rpm then runs perfect after that. The battery is weak can that make a difference? I am still guessing its the pilot jets though. I kind of sucks that I haven't narrowed it down to carbs or electrical. Once I know I can tear it apart. It looks like Ill have to clean off the work bench and clean all those carbs unless someone else has a idea. I still didnt check the resistance if the coils yet.

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1st lets clarify. It is a Suzuki GS 550 4 cylinder not GL (Honda) or 3 cylinder (Suzuki GT) and it is a "road" bike.

Some of the GS550 Suzukis had very strange 2 throat carbs that never worked right. But you say it seems to be ignition so lets start there. Go buy 4 new plug caps. About $3.00 each. Each plug cap has a carbon resister that is suppose to be 5,000 ohm. I can assure you they are all infinity by now (at low voltage). Try the new plug caps and new plugs. It probably as an electronic ignition but still has mechanical advance so check and lube that. If it still has ignition points, those need to be cleaned and set and timing set. Do the ignition first, then check valve clearance and if it still has problems, move on to the carbs.

It is a 1980 GS 550. Ill get some plug end caps and see were that leads. I checked the ignition and it is electronic no points. I am not sure were to lube. The thing runs great after 2500 rpm does that weed out the valves with this problem?

Thanks alot for your help guys.

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the problem is the idle circuit. Without fully disassembling the carbs and thoroughly cleaning the idle circuit(s), I doubt you'll get it to work properly.

Sometimes you can get away with doing it half-assed, but it sure isn't a conclusive, ie, you haven't ruled out carb issues.

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divebiker, you have to take apart the carbs to get at the idle circuits/pilot jets. If it runs good at higher rpm, it is unlikely it is the coils. Get the carbs cleaned correctly. ie clean out pilot circuit and if you can't get the pilot jets clean, spring for new ones. If you have access to autobody supplies, try 5717s dupont metal conditioner mixed as per directions to clean the pilot jets, makes carb parts and jets like brand new!!:applause: vanram

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I have had the same problem on older honda's (vintage) even though it this experience does really compare to this bike this info might be helpful. Alot of the times the clueless owner plugs different colored wires together when they remove their tank or head lamp shroud.... check all of your electrical connections, grounds etc. and make sure that they are all connected according to specs I agree with everyone else, It is very uncommon to find a bad coil. Good luck dude.

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