#4 Cylinder Not Firing Properly

[Mutashio]

Hey Guys,

Could use some help with a weird issue im running into with my 83 Gs650GL. The issue is with #4 cylinder and regardless of which boot I try on it, #1 or #4 it does the same thing. With the boot fully on #4 doesn't fire, if I pull the boot off and just place it on top of the spark plug the cylinder starts to fire! It's almost like something is shorting out my ignition coil??? Any thoughts?

[pdqford]

I suspect #4 spark plug is bleeding current to ground.
With the boot pulled back, it acts like a resistance gap.
When the current jumps the gap, it hits the spark plug too fast to bleed off.
Try swapping another plug into #4 and see if it still happens.

[Mutashio]

I suspect #4 spark plug is bleeding current to ground.
With the boot pulled back, it acts like a resistance gap.
When the current jumps the gap, it hits the spark plug too fast to bleed off.
Try swapping another plug into #4 and see if it still happens.

It wont cause any problems trying to put #2 or #3 on it?

[pdqford]

Remove the spark plug from #3 and put it in cyl #4.
And put the spark plug from #4 into cyl #3.
Then see if cylinder #4 fires correctly and if the issue moves to cyl #3.

[Mutashio]

Um. I could see putting 2/3 wires on 1/4 to see if the problem follows, as 1/4 fire from the same coil and 2/3 fire from the same coil. Moving wire 4 to plug 3, wouldn’t that cause things to be out of order?

Thats what i was thinking! Wouldn't moving just one plug cause any problems or damage?

[Mutashio]

Remove the spark plug from #3 and put it in cyl #4.
And put the spark plug from #4 into cyl #3.
Then see if cylinder #4 fires correctly and if the issue moves to cyl #3.

Oh geez! Sorry just realized you're talking about the spark plug itself not the coil cable!

[Mutashio]

Remove the spark plug from #3 and put it in cyl #4.
And put the spark plug from #4 into cyl #3.
Then see if cylinder #4 fires correctly and if the issue moves to cyl #3.

So I tried your suggestion and the issue switch to cylinder #3! Swap the spark plug and it helped. Now I think I just have a carb issue as #4 gets hot but not as hot as the other 3. Also with my colortune I'm not able to get proper bunsen blue flame on #4. Back to tearing apart may carbs to clean it again!
Thanks for your suggestion! It amazes me the how much you guys know about these bikes and are able to help with issues like this! This forum is a lifesaver!

[Rich82GS750TZ]

Forget what I wrote above, I got confused then wrote something that couldn’t possibly help. That was silly. Carry on.

[Mutashio]

So was able to get things going pretty good...#4 is still slightly off, so i guess once i park it for the year the carbs are getting a nice bath! Also had time to get my new mufflers one, exhaust wrap and the windscreen i ordered a while back!
Suzuki5.jpg

[Mutashio]

Got everything back together today after giving the carbs a complete spa treatment 😅 and she is running great! Was a cold and windy day so didnt get out to test ride it but its idling beautifully and everything heats up evenly! I hoping for at least one more decent day to ride and test it properly before I have e to park it for the year, fingers crossed!
I appreciate all the insight from everybody! Helped a lot!

[steve murdoch]

It's always nice to get sorted out before the hibernation.
Congrats!

[Mutashio]

It definitely is! Thanks!