1972 CL350 Running on one cylinder

[fluke12]

Brief history here: Oversized, pistons and new valves went into the engine a few years back. Everything was running well and then sat for almost a year without fuel in the tank. Filled it up, and did some light riding. All was good for a while (20ish minutes). Then it got a little choppy and i'd twist the throttle and rpms would actually drop. I assumed the carbs needed a good cleaning. Tore them all apart and replaced o-rings. Synced the throttle cables and was beginning to try to adjust mix and idle screws. When I'd turn the mix screw on the right cylinder, and nothing changes. From all the way in, to almost falling out, no difference. I do the same thing on the left and exactly the same, no change. I put my hand behind the pipes and realize one is blowing warm, the other cold. So I pull the plug wire from the left cylinder and nothing changes. I put it back on, and pull the right wire and it immediately dies. I also checked both plugs to make sure they're firing and they are. They both look pretty much the way they should as well.

So it's clear to me that something is wrong with the left cylinder. I also notice that there's a few drops of what looks like oil/liquid dripping from the right breaker contact bolt. It seems like it's making the area above and around the spark plug a little wet and oily. I Know a compression test is probably in order along with some timing things. I've never had to adjust the timing, so that'll be new for me.

My Questions: Which do I do first, mess with timing or check compression? If I should start with a compression test, i'm supposed to do it with the engine more than just idle warm right? So do I just ride around on one cylinder for a few minutes to get the temp up? Any and all help for this is greatly appreciated.

 

[Maritime]

Check valve clearances then do compression, cold is fine WOT or carbs off bike. If you get the 120+PSI cold that means it will run. It sounds like fuel starvation on the one cylinder so make sure the float height is right and the needle/seat passage are nice and clean. turn on the fuel and open the float bowl drain on the offending side and see if fuel flows out well. Then if fuel is flowing check the timing to make sure it's firing at the right time. I had one dead cylinder on the GL and it came down to one O-Ring not fully seating on the float needle preventing fuel from filling that carb. took a bit of trial and error to find that.

 

[fluke12]

...It sounds like fuel starvation on the one cylinder so make sure the float height is right and the needle/seat passage are nice and clean. turn on the fuel and open the float bowl drain on the offending side and see if fuel flows out well. Then if fuel is flowing check the timing to make sure it's firing at the right time. I had one dead cylinder on the GL and it came down to one O-Ring not fully seating on the float needle preventing fuel from filling that carb. took a bit of trial and error to find that.

Thanks for the suggestion! I’ll give it a shot. I did clean out the petcock when I did the carbs too, so I know that’s not clogged. Unfortunately, the side pipes make it a little tricky to get in there in the left side but I’ll probably start with that before I do the compression test.

 

[fluke12]

Still haven’t been able to run a compression test but I’m definitely getting fuel to both carbs and also all over my engine. I tore my tank crossover line with my valves open and dumped about half a tank of gas on the engine so I had to replace that. Valves were just a tiny bit off, but now they’re right where they should be.

Any other ideas or suggestions? I’m guessing IF my compression is good, the next thing to check is timing?

 

[irk miller]

Pull the plug on the cold side and see if it's getting wet. If it's dry, it's not getting fuel and it could be float level or idle jet, or that the float bowl isn't getting fuel at all. If it's getting wet, then you know you're getting fuel and then move on from the carb. I would've done compression right after I checked to see if the plug is getting wet. Messing with valves is the last thing I would check.

 

[fluke12]

Definitely wet plugs, so I know it’s getting fuel. I adjusted the valves because that’s something I have the tools for, I’ve gotta borrow the gauge for compression. Wouldn’t it have read off anyways because the valves were slightly more open than they should be?

 

[Maritime]

Definitely wet plugs, so I know it’s getting fuel. I adjusted the valves because that’s something I have the tools for, I’ve gotta borrow the gauge for compression. Wouldn’t it have read off anyways because the valves were slightly more open than they should be?

Yes, that's why I recommended a valve check before compression test. a slightly tight clearance can cause a valve to stick open and give you low compression. too lose and same won't let enough air in to get full compression. My CX wouldn't run on one cylinder when I got it. I did compression first and the cylinder in question was like 50 PSI, I set the valves and it went to 150. Tight exhaust valve was sticking open just enough to not allow compression to build. I opened the carb on that side and it was gross. PO had run it for a while on only one cylinder and that carb built up so much crap from unburnt fuel it was bad. I got the bike cheap as the PO couldn't get it started anymore, he never even thought to check the valves at all.

 

[irk miller]

Yes, that's why I recommended a valve check before compression test. a slightly tight clearance can cause a valve to stick open and give you low compression. too lose and same won't let enough air in to get full compression. My CX wouldn't run on one cylinder when I got it. I did compression first and the cylinder in question was like 50 PSI, I set the valves and it went to 150. Tight exhaust valve was sticking open just enough to not allow compression to build. I opened the carb on that side and it was gross. PO had run it for a while on only one cylinder and that carb built up so much crap from unburnt fuel it was bad. I got the bike cheap as the PO couldn't get it started anymore, he never even thought to check the valves at all.

Then why did you do a compression test first on the CX? You literally told him to check valves first, then gave him a reason why you should do a compression test first and an example of you doing the compression test first. That compression test told you to adjust the valves. No one is saying not to check the valves, but it's not the first thing you do. Compression test and leak down will at least lead you down the path to adjust valves, or tell you if you have damaged valves, nicked valves seats, bad rings, etc.

 

[Maritime]

Ha, I suppose when you put it that way. I was equating the none running cylinder to mune being valves so if you check/set you re starting from the righf baseline.

 

[Sonreir]

Is it running on both cylinders at idle or not at all?

 

[fluke12]

Is it running on both cylinders at idle or not at all?

It’s not running on the left at all. I completely cut power to the left plug and nothing changes. I pull the right with the left plugged in and it dies.

I DID finally do a compression test tonight on the cold engine. It took a whole hell of a lot of kicking but both sides sit at a little over 150, so either I’m blindly missing something with the carbs or my timing is off, right? I mean, I’ve got spark, I’ve got fuel, I’ve got compression... what am I missing?

 

[irk miller]

In your original post, you say you feel cool air coming out of the left muffler. Is the left header also cold? A loose connection can cause it to create spark until the engine runs and causes vibration. Timing being way off on the left would do this, but you time it to the left first, then you time the right. Usually, when people have the left way off it doesn't run at all. This is feeling so much like a sync problem. I want to know if the left header is at least warm. If it's firing, but way out of sync, then you'll get a cool side and a hot side and the same deal where when you pull a plug the idle drops or even dies.

 

[teazer]

Looks like a couple of different approaches and both are valid. Just different. One says check compression and then if it's low, determine what's wrong and then fix it. The other approach was to check that all the settings were correct and then test.
The advantage of the test first approach is that it shows up an error in measured results that should be investigated. That way if you see low compression and then check and fix valves and compression improves, so you know what was wrong. Checking and fixing everything and then testing could leave an owner confused as to what changed. For most situations though it's a personal preference as long as the end result is a running motor.

Doing a compression test first confirms/measures the symptoms before diving into possible cause. Checking settings first approaches the problem for the other end. It checks that all the details are right and if so, things should work as specified. Top down or bottom up. I tend to do both. Check all the settings and if it still doesn't run, look at the symptoms and drill down from there to work out what measurable outcome is out of spec.

But it this case, I didn't read anything about checking timing yet. We approach things differently, but before I messed with jetting or float levels, I would check the timing on both sides to identify if that is the issue. If timing is spot on, I would go ahead and check FUEL levels on both sides and if that's OK I would focus on primary air circuits. Test one side and then the other to compare them. I spray WD40 through one circuit and compare with the other side and then move on to the next circuit. That way I can see how much/hard it sprays and can compare one side to the other.

WD40 is less obnoxious in the garage than spraying lots of carb cleaner. Finish off with compressed air to dry it out.

 

[fluke12]

In your original post, you say you feel cool air coming out of the left muffler. Is the left header also cold? A loose connection can cause it to create spark until the engine runs and causes vibration. Timing being way off on the left would do this, but you time it to the left first, then you time the right. Usually, when people have the left way off it doesn't run at all. This is feeling so much like a sync problem. I want to know if the left header is at least warm. If it's firing, but way out of sync, then you'll get a cool side and a hot side and the same deal where when you pull a plug the idle drops or even dies.

Ok, so when I start it up, the header is warm, just not hot like the right side. By the time it comes out the back, it’s cool. Trying to ride, it jerks like I don’t know how to smoothly let out the clutch. I pulled the left carb and went through it again just to see if that would do anything. I’ve never adjusted the timing so I’m gonna have to learn how to do that next I guess??