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coil problems?

  • Thread starter Thread starter morbidphil0622
  • Start date Start date
M

morbidphil0622

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Well I just replaced my fuel petcock and my gs750 es runs great.. It has a good idle and rides fine but I have noticed that it isnt quite as powerful as it used to be... It once had a really bad sputter/surge type thing on the freeway but a fer new plugs and new wires fixed that. Now the bike runs good but I pulled the #4 spark plug wire off by accident today whilt the bike was running and guess what??? She didnt even miss a beat, just kept on purring like I had done absolutley nothing.. I put the wire to my hand and felt a spark, but it wasnt even enough to make me flinch and move my hand away..
Do you think this might be a problem with my coils?? I have replaced my cdi box before and had no change so I decided to return it to where purchased. Coils would be the only thing that comes to mind right now.. When it gets dark I will check and see what color my spark is but I can tell you right now that it will be crap. My #4 exhaust pipe gets hot like the rest of them, they all warm up about the same. I just dont understand how pulling this wire off could make no difference in how she runs... Any Ideas??? I am going to replace the coils anyways but I would still like some input if at all possible...
Jason
 
So I guess I am on the road to success? I am assuming that is why I have gotten no response, either that or this question has been answered over 1.6 million times before. I searched I did I did I promise I searched the forums...
Sooooooo, I guess I am on the right track then...
 
I found that there is a very weak spark on the #4 cylinder. It is sometimes enough to ignite the fuel/air mixture but when it does you get a backfire and a nice little flame coming out of the tailpipe... So I have come to the conclusion that I am only running on 3 cylinders but amazingly, the bike is running incredibly smooth like this. That is the part that I dont understand, I would think that it would have a crappy idle and try to choke out when you give it throttle but it doesnt... I am in the process of moving right now but I will find time to buy some new coils next week... Does anybody know if I can use coils from a 95 cbr 600 f2? The coils look similar and they are quite cheap on ebay sometimes...
 
Doesn't your bike have two coils? If so, I believe that a faulty coil would cause a problem at two cylinders, and the bike would not purr! Testing the spark in the manner you described is not recommended. Perhaps you weren't grounded to the bike, and so didn't get zapped as expected. Try putting a sparkplug in the cap, and ground the spark plug to the bike. Do you see a spark (hard to do in bright sunshine). Maybe you've got a spark wire problem on that one cylinder.

Regardless, remember that if two wires come off each coil, the juice will follow the path of least resistance. If the plug/wire you're testing (off the engine) is not properly grounded, you won't get a spark.
 
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I understand that the coil effects both cylinders, but also must at some point split to feed spark to each seperate cylinder and I have already replaced wires, caps, and plugs with brand new out of box ones... Regardless I am going to replace the coils because they are 23 years old and I am sure they would like to retire soon and buy that big house in florida somewhere... Thank you for the input though... I do appreciate it.
 
I will retest the spark tonight with your suggested method
 
I do not mean to scare you but I had the same problem. Turns out I had almost no compression in all the cylinders of my bike. Now I am in the middle of a rebuild.
 
coils

coils

If you can take the spark to your hand and it doesn't even tingle, I'd suspect you've got a bad coil.

- Tim
 
That is about what I figured.. I gan pull the boot off with my hand and touch the engine block with a finger on the same hand and almost not even notice... Now correct me if I am wrong but normally that would make just about anyone throw thw boot and jump back a foot or 2, at least I would think...
 
morbidphil0622 said:
That is about what I figured.. I gan pull the boot off with my hand and touch the engine block with a finger on the same hand and almost not even notice... Now correct me if I am wrong but normally that would make just about anyone throw thw boot and jump back a foot or 2, at least I would think...
Click to expand...


Negative ghost rider. The electricity is too far inside the cap to effectively shock you. Stick a key inside of the boot and hold the end of the key close to the block and look for a spark. DO NOT HOLD THE METAL PART OF THE KEY. Hold the rubber boot or you'll be shocked. If it does shock you but not enough to cause a lttle pain then YES you coil is weak.
 
I do have a somewhat weaker spark than the rest, I ordered some new ones off of ebay anyhow so if it isnt the problem then its all good.. I did manage to get the cylinder to fire last night while i was playing around in the garage.. I took my pod filters off and played around with the jets right inside of the carb. I am pretty carb stupid so I dont know which jet it was but I was sure to record positions so I could resort back to them if I screw up... Now I am thinking that I am not getting enough fuel into the cylinder... I really dont want to start adjusting things though just in case it is the coil... We will see what happens in about a week or so...
 
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