Suzuki GSX-R Motorcycle Forums Gixxer.com banner

1 - 13 of 13 Posts

·
Registered
Joined
·
1,934 Posts
Discussion Starter #1
Both of my coils are only firing one spark plug each. The resistance between the two connectors is 3.0 ohms on each coil. I've replaced the secondary wires, but I had to reuse the boots. Each boot measured around 10K ohms.

I thought this was a wasted spark system, in other words...I thought each coil was supposed to fire both spark plugs connected to it at the same time, one spark is used and one is wasted. My f'n clymer manual doesn't show the internal wiring of the coils, so I'm not sure.

Is there something I'm over looking...or are the coils bad even though they have the correct primary resistance? Seems to me that if the primary is good then either both plugs or no plugs should fire. I don't know how the secondary windings could fail in a manner that would only fire one plug.

Firing was checked with an o-scope, I'm using a Fluke 105 with a single secondary lead. I see a good pattern on one plug and coil oscillations on the other. This is the same for both coils. Am I measuring them wrong?

[ 05-11-2002, 07:38 AM: Message edited by: Rbike ]
 

·
Registered
Joined
·
17,099 Posts
the coil doesn't make a distinction between the two outputs - it fires both at once. there is something wrong with yours (seeing as how you've replaced the high tension leads), unless you're using the scope wrong. try swapping plug boots just for kicks to see if the problem switches over.

as i've said before, a resistance test for coils isn't a 100% guarantee of anything....except if the primary resistance is way off from 3.0 ohms (on a 3 ohm coil), then there's something definitely wrong. otherwise, a coil could check out fine on a resistance test but still be defective somehow.

have you checked the resistance across the secondary (high voltage) windings? again, if it's way off (i think spec is something like around 25-35k ohms), then there's something definitely wrong.

[ 05-07-2002, 07:59 AM: Message edited by: jeff ]
 

·
Registered
Joined
·
1,934 Posts
Discussion Starter #3
I did check the secondary resistance of each coil, it is in spec around 30-40K. I thought it was odd to spec the reading through both leads and boots. So I checked everything independently by takin apart the leads. I also know understand about the coil failing under a load, yet measuring fine otherwise.

I replaced the wire sections with good quality Belden solid core wire. I would have bought new boots but I could only find 5K boots.

I swapped plugs but I didn't try swapping the boots. I'll do that before I spend the $$ for the new coils. I just don't seem to be convinced by what I'm seeing on the scope. Since the same secondary winding is used for both plugs, how could it always fire one plug correctly yet never fire the other plug? Seems like that kind of a problem should be in the wires or plugs.
 

·
Registered
Joined
·
17,099 Posts
5k boots will work fine....the resistance in the boots (and on some bikes, the plugs and/or ignition leads) is for emi noise suppression. you could even run an unsuppressed ignition if you wanted, but the ignition would just throw out a lot more interference (shouldn't affect the stock ecu, though, as i ran an unsuppressed ignition for years without interference problems with the stock ecu....car radios are a different matter).

was there a reason why you're testing the coils? were you getting a bad misfire? if so, then i'd be more inclined to believe that the coils are bad than you using the scope wrong.
both coils failing at the same time in the same way is fairly unlikely, but still possible....
 

·
Registered
Joined
·
1,934 Posts
Discussion Starter #5
Whole thing started because the bike will sometimes run great then will suddenly be barely able to increase the rpm's...then bingo start running like a raped ape (normally). It seemed to happen only after the engine got warmed up, like after being on the track for a few sessions. Then it slowly progressed to happening sooner after starting the bike...until now when it won't start.

Only lately did I get the problem to act up when I had some test equipment around. I should be capable of running a scope...and if I can tune it to see a good pattern on one lead, the same setting should be showing me the pattern on another lead.

I'm just wanting to be sure pior to laying out the $$ for new coils and my findings seem odd. I may go home and see if the coils off my VFR will swap in, I don't have a manual here to verify. I have loads of cdi coils here at work but thats not any help.

Thanks for the info on the caps...I know that some modules are more prone to emi problems than others. Since the bike didn't come with a radio I figured the resistance was there to protect the ignition module. But if you've run without it for an extended time I guess it's not needed.
 

·
Registered
Joined
·
17,099 Posts
that intermittent misfire does sound like a coil problem. i've had that happen to me once or twice....bad misfire when warmed up (although in my case it was both outputs from a single coil). eventually it will get to the point where they'll stop firing altogether.

i believe the vfr uses a coil for each cylinder, so you'd have to rig up a pair in series (parallel would probably draw too much current from the ecu - although it'll really depend on the primary winding resistance) to get them to work on the gsxr.

[ 05-07-2002, 09:35 AM: Message edited by: jeff ]
 

·
Registered
Joined
·
1,934 Posts
Discussion Starter #7
Well since the high tech aproach has been raising questions in my mind...I ran home during lunch and watched each coil fire a test plug, the kind that has a ground clip attached.

I could see a regular timed blue spark out of one output, and an erratic orange spark out of the other. I swapped the leads and boots and the outputs remained the same. I guess I have a lot of doubt since both coils went bad at the same time. I just need to go ahead and replace them.

Thanks for your help...and the VFR does use 4 coils.
 

·
Registered
Joined
·
434 Posts
on my 86 I run 4 individual coils wired 2 groups in series with solid core wires and no resisters in the plug boots with the stock ecu and do not have problems. The coils are I think from a yamaha rd-rg 350 they are about 3/4 the size of an old style car coil and 4 fit in a flat configuration above the carbs and between the frame rails. Mine has the stock airbox removed.
 

·
Registered
Joined
·
106 Posts
Keep us posted I have the same problem with my coils. I was wondering if I can take them to a parts store and have them tested? well let me know what you come up with. Thanks
 

·
Registered
Joined
·
1,934 Posts
Discussion Starter #10
I replaced the coils with a used set from a local shop. All four now seem to fire correctly when viewed with a test plug. I got two test plugs and put one on each output of a coil. Both sparks are fine when viewed that way. But when hooked to the real spark plugs installed in the cylinders, the scope pattern doesn't look so good. It's always hard for me to read a wasted spark system, but I pulled out two plugs and they are both black and sooty from all this testing. They fire when grounded to the head, but who knows what is happening under pressure in the cylinder.

Got some new non resistor NGK C9E plugs since they are cheaper than the dual electrode models. I am gonna put them in tonight and hopefully be up and running. The stock plug was a CR10EK, I wanted to go a little hoter and can't see any harm in eliminating some of the circuit resistance if you guys aren't having problems going with no resistance.

The odd thing I found in testing was that I could view the trigger pickup waveform fine, but the bike would stall when I put the probe on either of the wires coming from the coils (white or black/yel). In fact I ended up blowing the 10 amp ignition fuse doing this. I can't figure why the scope is putting too much of a load on that circuit.
 

·
Registered
Joined
·
1,934 Posts
Discussion Starter #11
It's Alive


Yes it was the coils...the low tech approach was the easiest way to find it. You can buy a test spark plug at any auto parts store. Some look like a spark plug with a clip on the side, others look like a thumb screw with a clip. Either one works fine, but the screw style allows you to change the gap.

Get two of them and hook one up to each output of a coil. Crank the bike over and the sparks should be equal and blue is better than orange. Repeat this for both coils. I was getting one good blue spark all the time, while the other was orange and sometimes didn't fire. A used set of coils solved the problem.

I then had a second problem throw me for a loop. Once I got the ignition working, the bike was still hard to start and would only run poorly. Always had to have the choke on and couldn't increase the rpm's.
Solution: It ran out of gas during all the testing and such
I think that every time I took the tank on and off it would splash some gas around, just enough to get it to sputter and kind of run. Once I switched it to reserve...it went back to being it's old scream'n meany of a bike
 

·
YAAFM Mod
Joined
·
3,016 Posts
Good to hear your back up and running! I hate electrical problems they are just so hard to track.
Bones
 

·
Registered
Joined
·
1,934 Posts
Discussion Starter #13
Damm gixxer is running like a hardly


After installing the used coils evrything was running fine for a while. I took the bike out to the track and it ran fine for a couple of sessions then started misfiring. I didn't have a scope with me but I had a device that measures the peak KV, a Sheffield TA 100. The same cylinders were misfiring as before. It was 1 and 2, while 3 and 4 were doing fine.

The peak KV on 1 and 2 was down below 6K, usually around 2K or 3K, and sometimes 0. Cylinders 3 and 4 stayed consistenly above 17K and usually around 24K, seems slightly high but the plugs also look slightly lean. Yet 3 and 4 never misfire, and 1 and 2 have the same symtoms as before installing the used coils and wires with new plugs.

Not sure what to try next? Replace everything
 
1 - 13 of 13 Posts
Top