Cylinder 2 & 3 aren't firing

[Guest]

Hello!

I started noticing that the tune of my bike change and exhaust pipes 2 and 3 were cold. After cleaning carbs, installing new ignition coils, new points and condensers, new spark plugs, and new ground wires... 2 & 3 pipes were still cold. The only other thing I could think of/find online was to get new piston rings. I've got the new rings on and along with a new piston jug I got on ebay (mine wasn't in the greatest condition after taking it off and looking through it) installed back onto my engine (also putting all new gaskets). Now I am currently putting the cylinder head back together after cleaning and replacing valve seals and cleaning valves. If all goes as planned I'd like to put the head back on this Sunday and start measuring for new shims. My plan is to have everything put back together before June gets here and see if cylinders 2 & 3 run . If push comes to shove... and this doesn't work... Does anyone have any other information as t what it could be? Any help will be greatly appreciated!

Thanks!

-Seth

[Big T]

Spark, fuel, air
Which one is missing?

Sounds like a electrical problem

[greg78gs750]

wow, went in deep right off the line. Make sure the valves are in spec when you reassemble, make sure the carbs are actually clean, it takes more than most think. As said above, spark, air, fuel.

[canuckxxx]

New spark plug caps.

[Baatfam]

Did you check for spark....I am bettin' the 2/3 coil isn't firing.

[greg78gs750]

he stated he replaced the coils, buuuut....seems like a parts-swapping approach rather than systematic troubleshooting? We are going to need some additional info......

[SB3]

he stated he replaced the coils, buuuut....seems like a parts-swapping approach rather than systematic troubleshooting? We are going to need some additional info......

Not necessarily, I did not do all of this at once. Started with the carb clean out, still cold. Then checked both ignition coils and noticed the one 2 & 3 ran on had a crack, replaced both with new plugs, still cold. Swapped a brand new petcock, still cold. Went through my timing and that's when I replaced my points and condensers, still cold. Keep in mind I've done all of this in the span of 5 months.

I noticed that whenever I would start the bike 2&3 would stay cold but after riding the bike would change tune and I would feel 2&3 and they would be warm. I read online that this is because my rings wouldn't release from my piston walls till after it warmed up and set them free. Hints why I changed for new piston rings and I just finished up lastnight going through my top end and cleaning my valves and putting new valve seals on because I could tell I was burning oil whenever I did ride.

Thoughts?

[Baatfam]

Thoughts?

Yes....
Did you actually check for spark?

[SB3]

Yes....
Did you actually check for spark?

Yes, I checked for spark. It has spark.

[tas850g]

igniter???

[Nessism]

Did you ever check the valve clearance? The valves tighten with mileage and after enough neglect they won't close anymore and the compression goes way down.

[SB3]

Did you ever check the valve clearance? The valves tighten with mileage and after enough neglect they won't close anymore and the compression goes way down.

I am planning on putting the cams back on this weekend and measuring valve clearance accordingly and order new shims. Lets hope this solves it.

[748cc]

Curious to know how this panned out...I'm chasing down a cold cylinder too.

[Steve]

Thoughts?

Sure. (in reference to the original poster)

The fact that #2 and #3 fire off the same coil tells me that it's likely igntion-related.

The fact that you replaced points and condensors tell me that it's a '79 or earlier bike.

Because it's a '79 or earlier bike, it won't have an ignitor.

The fact that you are on a GS forum might hint that we are considering a GS, but we REALLY need some clues.

In the words of one of our more illustrious members:

Please provide details. The GSR Hive Mind is nearly omniscient, but not yet clairvoyant.

.