High compression and non-firing cylinder

[Guest]

#4 is dead and I can't figure out why. It has freshly cleaned carbs (same problem before cleaning), gas is getting there, strong spark, but it won't fire. I checked the compression and came up with 150-145-145-170 (on #4). I got exactly the same numbers about 2 years ago, except that #4 was 150.

I think the big increase must be carbon build-up on the piston, right? What else could cause it? Would that keep it from firing or did it result from it NOT firing? I'm stumped. Thanks for any suggestions.

EDIT: The plug has a strong spark when it's OUT of the cylinder and placed against the side of it but I put in a new plug and it looks like it's not sparking when it's INSIDE the cylinder. Could the high compression keep it from sparking?

 

[SqDancerLynn1]

I would swap #1 & 4 plug wires and see if anything changes. Have you changes the plug caps? Maybe at least remove the plug cap and trim the wire back 3/8" & reinstall the caps. If this doesn't help You may still have a carb problem.
Yes 170 lbs is probably due to carbon buildup, Just run a few tanks of cleaner thru it

 

[Guest]

Mahalo

Mahalo

Thanks for the suggestions. I've done them all. I payed special attention to #4 when I rebuilt them this time and it appeared to be perfect.

I'm wondering if the high compression could prevent it from firing? I also wonder if the carbon built up because it wasn't firing?

 

[tkent02]

If it's not firing at all it can't be growing any carbon deposits. Does the exhaust pipe stay stone cold? or does it fire sometimes? randomly?

How long has it been doing this?

What did you do to it right before it started doing this?

Has it ever hit on all four?

 

[Guest]

If it's not firing at all it can't be growing any carbon deposits. Does the exhaust pipe stay stone cold? or does it fire sometimes? randomly?

It does get hot but since it's connected to the engine, there's no way it could do otherwise. The bike seems to run fine at high speeds so it seems like it must be hitting on all 4 then.

How long has it been doing this?

A couple of months but it hasn't been ridden much during that time.

What did you do to it right before it started doing this?

I rode it.

Has it ever hit on all four?

Yes, for years. It's almost always seemed to run perfectly. One of the major problems (aside from rust) here is that you can't go very fast. I'm going to take it down to Waianae and back and try to run it fairly hard in the lower gears.

 

[Nessism]

Sounds like the pilot jet is clogged or there is no fuel in the floatbowl. I'd pull the drain plug do see if fuel is in the carb and if so, you might want to check the pilot by holding it up to a light to make sure it's open.

 

[Dave8338]

Problem in the pilot circuit or a weak plug/wire.

 

[Guest]

Back from down the road

Back from down the road

Sounds like the pilot jet is clogged or there is no fuel in the floatbowl. I'd pull the drain plug do see if fuel is in the carb and if so, you might want to check the pilot by holding it up to a light to make sure it's open.

Jet's were clean when I removed the carbs to rebuild them and clean when I put them back together. Plenty of fuel in the float bowls.:|

 

[Guest]

Sparky

Sparky

Problem in the pilot circuit or a weak plug/wire.

Good looking, clean carbs and a really strong looking spark; at least as good as the other 3. #1 and #4 wires were switched, as already mentioned.

 

[tkent02]

How about the tiny passages these pilot jets feed?
They are very small. Did you spray carb cleaner through each one to ensure that they are all clear?
The tiny holes in the choke pickup tube clear too?
And did you ensure the passage in the float bowl itself that feeds the choke pickup is clear?

 

[Guest]

Good job

Good job

How about the tiny passages these pilot jets feed?
They are very small. Did you spray carb cleaner through each one to ensure that they are all clear?

And did you ensure the passage in the float bowl itself that feeds the choke circuit is clear?

I think so. I'm satisfied if I'd paid a shop to do it they wouldn't have done as good of a job. I've done it about a dozen times in the past on this bike and others and I'm really good at it. I'd be amazed if the carbs are the problems but I may stick on a second set if I can't figure it out. (Yes, I have another perfect set all ready to go, but I refuse to think that's the problem.)

 

[tkent02]

I think so. I'm satisfied if I'd paid a shop to do it they wouldn't have done as good of a job. I've done it about a dozen times in the past on this bike and others and I'm really good at it. I'd be amazed if the carbs are the problems but I may stick on a second set if I can't figure it out. (Yes, I have another perfect set all ready to go, but I refuse to think that's the problem.)

So spend ten minutes swapping them out and know for sure.

 

[Dave8338]

I think so. I'm satisfied if I'd paid a shop to do it they wouldn't have done as good of a job. I've done it about a dozen times in the past on this bike and others and I'm really good at it. I'd be amazed if the carbs are the problems but I may stick on a second set if I can't figure it out. (Yes, I have another perfect set all ready to go, but I refuse to think that's the problem.)

Try the second set and report back... :-$

 

[Nessism]

Wish I had a dollar for every time someone says their carbs are "clean", only to learn they weren't.

Fuel or spark. You tell us.

 

[Guest]

10 minutes?????

10 minutes?????

So spend ten minutes swapping them out and know for sure.

You've obviously never switched out a set of carbs on a motorcycle.

 

[Guest]

Clean

Clean

Wish I had a dollar for every time someone says their carbs are "clean", only to learn they weren't.

Fuel or spark. You tell us.

You may be meticulous but I wouldn't swap my carb rebuilding experience for yours. I think that's a mean comment but not unlike some other flippant comments that I remember seeing from you. You must be quite a guy! Do you do a better job than anyone else? Are you the only one capable of cleaning carbs the way they should be cleaned? How do you know? Being a self-confident know-it-all is no reason to be rude.

I wish I had a dollar for every time someone made an mean, uncalled for, foolish, self-gratifying comment.

As far as your "fuel or spark" question, if you weren't so quick to kick out a smug response, you might know what was stated.

 

[Nessism]

You may be meticulous but I wouldn't swap my carb rebuilding experience for yours. I think that's a mean comment but not unlike some other flippant comments that I remember seeing from you. You must be quite a guy! Do you do a better job than anyone else? Are you the only one capable of cleaning carbs the way they should be cleaned? How do you know? Being a self-confident know-it-all is no reason to be rude.

I wish I had a dollar for every time someone made an mean, uncalled for, foolish, self-gratifying comment.

As far as your "fuel or spark" question, if you weren't so quick to kick out a smug response, you might know what was stated.

Dude, it's simple...Fuel or Spark. You have shot down every suggestion made saying all the bases are covered. Well, something is obviously wrong and and you have not stated how you verified the pilot jets are open. Did you stick a wire though them? Hold them up to a light to make sure you can see a hole though the center? Also, regarding the carbs did you replace all the various O-rings? The old o-rings turn hard and brittle with age so did you get a kit from Cycleorings.com to make sure all the various parts are properly sealed? Where are the mixture screws set? Did you sync the carbs? All these details matter yet you have not provided any information.

About 7500 of my posts here have been in the Tech forum helping the newbies that come to the GSR, and I'm serious about all the people that say their carbs are "rebuilt" when they are not. I don't know you from Adam, and sorry to offend, it's just that we have seen this thing go on hundreds of times before from people that shoot down suggestions without providing reasonable evidence as to what they have done to their bikes.

Yea, I'm coarse. Guilty and non remorseful.

Oh, and 170 psi is not high compression on a GS engine. It's within the normal spec range for your bike that's in the factory service manual.

 

[tkent02]

You've obviously never switched out a set of carbs on a motorcycle.

Three sets this week.
Fix your own fvcking bike.

 

[Guest]

Poor you!!

Poor you!!

There's no reason to stick a wire through something I can see through. If it were clogged, I'd be most willing to point that out. All of my "O" rings are new and I've cleaned my carbs as best I know how. So much for bikes, you fellas have bigger problems.

OK, so one of you can "swap out" a rack of carbs in 10 minutes? Who, in his right mind would believe that?

Now, the other one's importance in life is based upon 7500 posts which often simply parrot answers already provided? At the same time, you know how good of a job others do cleaning their carbs? Is this your life's work? God, I hope not.

I'm not in the 'clique' and I don't miss it a bit! Your foul self-important attitudes have led to this forum losing so many people who once had a lot of enthusiasm. You don't have any interest in GS motorcycles; you only have interest in your selfish desire to be appreciated.

 

[first timer]

when you rebuilt your carbs did you dip them or spray them?

slides moving freely? no pin holes in the diaphrams?

are the plugs new? sometime plugs just go bad and will drive people nuts with bad running bikes carbs will be spotless but still run like crap until new plugs are in.

None of your fuel mix needle tips are broken off in the little hole are they?
Did you stick a fine wire in every hole you could find? Includeing the 3 little holes in the carb body by the butterfly valve?

you swap your #1 and #4 plug wire?

I know you may feel like you are running in circles right now but we have to start some where when promblem solving. and each thing you can check off helps us think of other things it could be.

Like said your engine only needs air, gas and spark, and one of those three is out of wack so it's just a matter of eliminating things.