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Coil question

  • Thread starter Thread starter 78550Detroit
  • Start date Start date
7

78550Detroit

Guest
I just picked up another bike this weekend and had a friend come over to help me pull it out of the back of my truck. I started up my 78 GS550 and moved it on the sidewalk. When my friend was looking at the GS he noticed that the right side was cold while the left side was hot on the exausht. I have two coil packs from my 79 GS550E parts bike but the numbers are different can I use these on the 78 To see if it is a bad coil on the right side? is there another way to test that coil I have a new multimeter that I picked up recently at harbor freight.
The numbers on the coil packs are : the 78 has ( 3300TR 12 V 7#) the 79 has ( 333TR 12V 9# ) on the tops.
 
Each coil fires 1 + 4 and 2 + 3 cylinders respectively. So if one coil was bad, either 1 + 4 or 2 + 3 would be cold.
 
Using the diagram are these sparkplug wires run and labeled wrong? The red wire is actually really long and labeled for #4. The purple wire is shorter and was labeled #1. Could this be part of the problem? The bike starts easily every time and seems to run good doesn't have an eradic idle or anything like that. The pipes for cylnders 3&4 are cold while 1&2 will be hot. Am I looking in the right area as the cause of the problem or could it be something else?


sparkplugwires.jpg
 
The two wires that were crossed wouldn't change anything. Except my wonder on how they reached?
Earl's right. You can swap the coils from the 79 bike.
With point type ignition the coils are 5ohms while the electronic ignition coils are 3 ohms.
 
Did some testing and inspected plugs

Did some testing and inspected plugs

In reading some of the posts I tried testing the coils both sets. On the spare ones and the ones on the bike I could not get a steady reading on the primary side. The numbers would move all around then steady out at 0. I did get a reading on one of the spare coils from the secondary side at 23.2 nothing on the other one. The coil on the left hand side on the bike I had a reading of 87.3 from the secondary side. Again nothing on the right side from the secondary side on the right.
I pulled the plugs to inspect them.
#1 Carbon fouled
#2 Normal
#3 Slighty carbon fouled and has gas smell
#4 A little more carbon fouled not as bad as #1 though and has gas smell

Tried to take pics but could not get any to show enough detail on the plugs.
Anyway from the readings on the coils I would assume they are bad? Is there something else that would cause this problem?The bike has 16,500 miles on it. The electric start doesn't work either but it will start up on either first or second kick sometimes maybe three if it is cold. I do need a new battery also. Any help in narrowing down the problem or problems would be greatly appreciated as always. I have found this forum to be a great place to meet people and get good advice.
 
As the others have stated, if #3 & #4 are cold, your problem is not entirely igniton-related. To help determine this, start with new spark plugs. While you have the plug wires off, measure the resistance (with your new multimeter \\:D/ ) from the plug wire teminals on each coil. Resistance from plug wire #1 to plug wire #4 should be almost zero. Same thing for #2 & #3. If you get something higher than that, you may have bad wires. Unscrew the plug caps from the wires, trim the wires about 1/2 inch, re-install the caps.

Another way to try this that may involve a bit less work...swap the plug leads (if they will reach). Swap #1 & #4, then swap #2 & #3. If your problem is in the wires, now #1 & #2 will be cold.


.
 
I forgot to mention that those were new plugs ,replaced them in late april when I did the oil change. I have not ridden the bike very far yet as I do not have a cycle endorsement yet( long story ). I have just ridden the bike through the neighborhood a couple of times when I fix something for a test ride and to practice. I would say there would be about 20 to 30 miles at most on those plugs.

The resistance test on the plug wires showed 0 on 2&3 while it showed 87.3 on wires 1&4. I am going to try to trim up the wires like steve said and get another set of plugs and the new battery today to see if that does anything.

I was just looking in my clymer manual to check if I gapped the plugs correctly and have the right plugs.I just replaced them with the same type that were in the bike when I got it. They are champion RN4c. I think I will get the ngk B-8es like the book recomends. I think I might have had the gap to big also.
 
So let me get this straight, one muffler is hot and the other is cold right? Considering that coil 1 fires cylinder #1 & #4 and coil 2 fires cylinder #2 & #3, the idea that a single coil is responsible for #1 and #2 not firing seems...........highly improbable.

suggestions
1. pull the plugs of the side you think is not firing (hence being cold) with a plug ..plugged into the spark plug feed wire, hold against the block and crank the engine (with the ignition on via the starter button). see if you get a spark, if you do and then checkin all plugs this way find that cylinders #1 & #4 fire together and #2 & #3 fire together, not only are your coils ok but your ignition system as a whole is more than likely operating correctly.

this leads to the next step
2. with the engine running place your hand over the end of the cold side. anything coming out? any pressure. Some GS models have a crossover between the two seperate exhausts. so if one side is plugged its being forced out the other side.
2b. if yes you have (equal) pressure coming off both mufflers check you carbs. if the carbs are gummed up for those two cylinders that may also be your problem.


i do not believe replacing one coil will in any way solve your problem
 
Last edited:
Do you have the equipment to do a compression test? If so do one. Get ordinary readings and then do a wet test.

Have you check the CDI/Ignitor unit or condensors?

How good is the battery?

Air filter OK/new?

This may be giving the signs electrical faults but it could be mechanical.

Suzuki mad

1981 GS1000ET
1983 GS(X)1100ESD
2002 GSF1200K1
 
The air filter is good , the battery I know is weak But I just bought a new one today. I am going to check to see if I am getting spark from the suspected cylinders. My friend had said when I had it running it didn't sound right thats how he figured out that it was only running on two cylinders. Looking at the front of the bike the two pipes coming out of the left side ( 3 & 4 ) are the ones that are cold. It originally had two pipes (no crossover) but the insides were rusted out so I put the ones from the parts bike which has the crossover on. There is exhuast coming out but it is cold on that side. I am starting to think it might be a carb problem? Going to work on it some more tonight and see where I get and what happens.

thanks for all the helpful suggestions so far though. By the way the other bike I picked up is a 73 Honda XL175 dirt bike. The tank and petcock needs attention but it did fire after sitting for 20 some years in a shed up north. It was my uncles who gave it to my brother who just gave it to me.It had almost a full tank of 20 some year old gas and wow did it smell bad :-&.
 
I had one of those yellow $3 multimeters from Harbor Freight. Set it on A/C Voltage and check the voltage in one of your wall sockets. If it doesn't give you a reading of 115 volts, do yourself a favor and toss it in the trash. Using a junk multimeter and getting inaccurate readings is worse than not having a multimeter at all.

I've had good luck with my Craftsman multimeter from Sears (got it on sale for $9.99.)

I love the cheap tools from Harbor Freight, but I can't recommend their multimeter.
 
jayz said:
I had one of those yellow $3 multimeters from Harbor Freight. Set it on A/C Voltage and check the voltage in one of your wall sockets. If it doesn't give you a reading of 115 volts, do yourself a favor and toss it in the trash. Using a junk multimeter and getting inaccurate readings is worse than not having a multimeter at all.

I've had good luck with my Craftsman multimeter from Sears (got it on sale for $9.99.)

I love the cheap tools from Harbor Freight, but I can't recommend their multimeter.
Click to expand...


I didn't check the wall socket but I did check it on some other stuff that I know is good like battery from my truck. It looks like it works fine , but thanks for the tip though.My dad has the same one and he uses it all the time and has never had a problem with it.You must have just got a bad one which happens from time to time. Brand name and more money doesn't necesarily mean that you can't have the same problems.
I bought a Black & Decker Buffmaster Wheel off the Mac truck years ago. I used it for a couple of months and ended up having to pay $108.00 dollars to have the motor rebuilt in it. After that havn't had to many problems with it til I accidently got the cord wrapped up in it so I had to splice that back together.
 
You;re right, I might have just got a dud. The problem was that it looked like it worked. My father-in-law and I were fixing my dryer and getting these weird readings that didn't make sense. Then he tested it in the wall socket and it gave a reading of 102 volts. With a multimeter, close isn't good enough, especially on a bike when a difference of less than one volt can change your diagnosis.

I agree, more money doesn't necessarily mean better quality.
 
Udate on coil question

Udate on coil question

Well I installed the new battery, and checked to make sure I was getting spark on all four which I am. When I put the new battery in my electric start button now works and for now all the exausht gets hot. When I checked the volts on the old battery is was only reading 10.3 volts. So the battery was pretty much toast. I am truly happy that the start button works now even though it would start up within 5 kicks usually on the first or second it still sucked to kick start it.

A friend of mine was having a similar problem on his Yamaha FZR and he just started shutting the fuel off before he would get to where he was going and run it out by the time he parked it. He hasn't had a fouled out plug since doing that. Is there a way to do that on these bikes? I know that the off position is actually on , primer is a constant flow, so I don't know how I could run it out like he does.
 
If your petcock and carb float valves are working fine (and why wouldn't they be?), there is no need to turn the gas off like your friend does.
He has found a way that works for him, but why not fix the problem instead of working around it? :-s


.
 
Steve said:
If your petcock and carb float valves are working fine (and why wouldn't they be?), there is no need to turn the gas off like your friend does.
He has found a way that works for him, but why not fix the problem instead of working around it? :-s


.
Click to expand...
Yeah I hear what your saying I was just curious. It works for him cause he just doesn't have the time to work on his bike. He owns his own buisness which takes up alot of his time and he has a lot of other projects going too. He just converted his snowmobile over to run on the dragstrip so he has been working on that lately.
 
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