No spark

[ssco156]

I replaced the stator and reg/rec on my 1981 GS450 a couple of months ago and only had the chance to try it out last week. The bike wouldn't rev past 5000 RPM and seemed like it was only working on one cylinder. I confirmed that the LHS cylinder was not firing. Checked the spark on both cylinders, the RHS was OK but nothing on the left. It turned out that the LHS spark plug cap was giving infinity resistance reading while the other one gave 5Kohms. So it looked like I needed a new set of caps but before replacing then I thought I might swap caps and confirm that the LHS would produce a spark using the known good cap. To my surprise, got the same result (no spark). I connected the good cap back to the RHS and this time, no spark on this side either. Both coil resistance readings seem fine (app 3 ohms on the primary) and about 8K between the secondary and ground (with the coil connectors plugged in). I'm beginning to think that the igniter might now be the problem. How can I check if this is the case? Thanks

 

[tom203]

Have you removed the plug caps and snipped off about 3/8 inch of plug wire to expose fresh copper for cap to bite into ?

 

[ssco156]

Have you removed the plug caps and snipped off about 3/8 inch of plug wire to expose fresh copper for cap to bite into ?

Tks for your reply. I have cut off the end of the wire and I could try cutting off another bit again. The thing is though, that the wires are already just about the shortest they can be, any shorter and I will have to replace the coils themselves. Seems that I will have to cut the end of and see if that solves the problem. If it does, then I'll either get new coils or work out how to replace or lengthen the wires.

 

[tom203]

If both sides were firing months ago when you replaced stator and r/r, suspect connection issue from signal coils up to ignitor and ignition coils. Ignition coils are very durable

 

[ssco156]

If both sides were firing months ago when you replaced stator and r/r, suspect connection issue from signal coils up to ignitor and ignition coils. Ignition coils are very durable

I've done a few more measurements. What I got is 17KΩ between both spark plug wires and the Orange/White wire (that's the total for the secondary winding, the 5K cap resistor and the resistance of the wire) so that part of the system seems OK. The static (not cranking) voltage at the battery was 12.5V while it was 12.3V on the Orange/White wires. It seems more and more likely that the igniter is the issue.

 

[tom203]

Yes, could be ignitor - challenging to test reliably. But you didn't say if it was running on two when you replaced the stator and r/r. Did you have high voltage condition?

 

[ssco156]

Yes, could be ignitor - challenging to test reliably. But you didn't say if it was running on two when you replaced the stator and r/r. Did you have high voltage condition?

To be honest, I didn't ride the bike after replacing the stator and R/R but just started it and let it idle. So I'm not sure if it was only working on one cylinder then as the symptoms are only obvious when riding. The old stator was outputting a very low voltage so it was not a high voltage that could have caused the present problem. I've read somewhere about a way how an igniter can be tested. I'll have to look it up and see if it helps.

 

[fastbysuzuki]

Something on igniter testing here http://members.dslextreme.com/users/cbsaunders/gs/Repair_and_Fault_finding_GS1000G_Ignitor.pdf

 

[ssco156]

Something on igniter testing here http://members.dslextreme.com/users/cbsaunders/gs/Repair_and_Fault_finding_GS1000G_Ignitor.pdf

I fell for the oldest trick in the book. Didn't have a fully charged battery so not enough juice to produce a spark

. My fault for not taking notice of all the posts that emphasize this point. I've ordered the spark plug caps on line (not available locally) and see how it goes from there.