Question regarding No Spark on Cylinder 4

[Thex12]

Hello all,

I am currently having an issue with a no spark condition on cylinder 4 (R/F) and I am wondering if there might be something simple I am overlooking. The bike is a 1988.

I suspected bad wires or a bad coil so I swapped a known good coil and wires from Cyl 1 to 4 and the problem still persists.

In addition the coil/wires that I originally suspected being bad works fine in the new location.

When testing for spark on the #4 cylinder I noticed it would occasional spark once or twice right after the engine turned over, then nothing.

While researching the issue I read somewhere that disconnection/bypassing the side stand switch could cause issues with the computer cutting spark to one of the cylinders, but I don't know if there is any truth to that statement.

The voltage seems to be ok, and with my most recent test I had the battery on a tender overnight. The bike has no other issues starting and seems to run decently on 3 cylinders. So in all honesty I dont know if I've ever experienced it running on all 4 as I only purchased the bike a few weeks ago and ridden it a few times.

(Long story short) Cylinder 4 has no spark, swapped a known good coil and still no spark. The "bad" coil functions normally in the new location. Not sure where to go from here.

Thanks for any information you may be able to provide!

 

[sdt354]

Test for voltage at the coil connection at cylinder 4. One side should be hot whenever the key is on. The TCI could very well be the issue. Try to borrow a know good one. Swap another in it's place to test.

 

[MaxMidnight]

Forgive me if I am wrong about this but it is the grey wire that feeds the rev counter which is also the return from the O/S/F coil?
If that assumption is correct then if the rev counter works then the coil is being switched by the ICU.

As there is no spark then I would think the issue would lie with either the HT lead, plug cap or spark plug. But as you have checked that by substitution....????

Have you checked continuity of the red/ white (+ 12 v.) and grey (if assumption is right) or white/ yellow/ orange* if not?

I think you will find that the side stand cut-out affects all cylinders.

* select as appropriate.

 

[Donny Daughtry]

I got help from here---:clapping:

http://www.ebay.com/itm/1985-2007-Y...ash=item2f0710cce6:g:dwMAAOSwuAVWwqjT&vxp=mtr

 

[Thex12]

Thanks Donny, I have been looking into switching over to COP, but wasn't exactly sure what was required. This looks like it would be a good start to replace my old wires and eliminate that as a possibility

 

[Thex12]

Thanks Max, I will test the continuity of the red/white and Gray leads and see if that all checks out. I've been reading through the shop manual so I'm getting a better idea of what to be testing for. It was weird that when I substituted the coil/wire/plug assembly to another cylinder it seemed to function normally, but I certainly could have overlooked something.

 

[Donny Daughtry]

Thanks Donny, I have been looking into switching over to COP, but wasn't exactly sure what was required. This looks like it would be a good start to replace my old wires and eliminate that as a possibility

I wonder how far you are from radley-another member on here who has been trying to get his vmax running for more pages than i can remember-He is in the same city as you---:confused2:

 

[Jan Bee]

Hello all,

I am currently having an issue with a no spark condition on cylinder 4 (R/F) and I am wondering if there might be something simple I am overlooking. The bike is a 1988.

I suspected bad wires or a bad coil so I swapped a known good coil and wires from Cyl 1 to 4 and the problem still persists.

In addition the coil/wires that I originally suspected being bad works fine in the new location.

When testing for spark on the #4 cylinder I noticed it would occasional spark once or twice right after the engine turned over, then nothing.

While researching the issue I read somewhere that disconnection/bypassing the side stand switch could cause issues with the computer cutting spark to one of the cylinders, but I don't know if there is any truth to that statement.

The voltage seems to be ok, and with my most recent test I had the battery on a tender overnight. The bike has no other issues starting and seems to run decently on 3 cylinders. So in all honesty I dont know if I've ever experienced it running on all 4 as I only purchased the bike a few weeks ago and ridden it a few times.

(Long story short) Cylinder 4 has no spark, swapped a known good coil and still no spark. The "bad" coil functions normally in the new location. Not sure where to go from here.

Thanks for any information you may be able to provide!

I got cops from jon harris-free of charge-we are very close though.