Dead Cylinder

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Tre Lapole

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hey guys,
So I’ve run into a bit an issue. I’ve seen threads around the forum about this issue been never any real answers.
So what I have is a 1979 xs650 with
Cam from Gary, Re-Phased by hugh
Crank directly from hugh Re-Phased
JE piston and jug set up from Hugh
Pamco 277 ignition from mikes xs
New timing chain and guides
All new gaskets around the motor
New Mikuni 34VM Roundslides from tc bros

My current issue is I have a dead cylinder one cylinder one

I’ve tried the following to correct it
Compression test which came back fine
Swapped ignition coils to check for back coil
Checked ohms of coils for weak spark

Any answers would be appreciated, I’m thinking maybe the cam is slightly out of tooth but wanted a second opinion before I tore down into the motor

Thanks guys!
 
Have you tried swapping plugs wires to opposite to see if problem switches sides? Could be as simple as a bad spark plug.
 
If it doesn't follow swapping igntion sides or plugs, and compression is ok, then it's probably the carb on that side. float valve stuck open or closed, or blockage on that side. or set up extremely rich or lean. Does it never hit on that cylinder at all, or just sometimes?
 
It runs extremely rich on one side and lean on the other, it seems to hit at times but no throttle response from that side at all. I am getting a bit of pressure coming from that pipe though
 
The pressure likely as not could just be air pumping through. With carbs in general if it won't hit at idle and low revs but does with more throttle then the pilot (idle) circuit is the problem. Unfortunately the only carbs I know about are the BS34. Somebody will chime in on 34VM carbs probably. Maybe 5T or Griz.
 
After it's been running disconnect the fuel keep running it, see what happens. If it cleans out and runs for a bit before it quits, it might point to a flooded condition in the rich cylinder. The VM34's can be a bit fussy about the float valves and a sliver of fuel line or tank rust, paint chips anything really, can stick one open. A very common issue on build start ups.
 
gggGary said:
After it's been running disconnect the fuel keep running it, see what happens. If it cleans out and runs for a bit before it quits, it might point to a flooded condition in the rich cylinder. The VM34's can be a bit fussy about the float valves and a sliver of fuel line or tank rust, paint chips anything really, can stick one open. A very common issue on build start ups.
Click to expand...
I’ll give that a whirl once I get the motor back together. I’m stripping it back down to the pistons and am going to degree The cam in hope that will show me any issues or fix any issues. As I said everything is brand new and messing with carbs has yet to solve any issues for me but I’m always down to give stuff a try.
 
So I’ve degree’d my motor and nothing came up as off at all, and I also went through and did a cleaning of my carbs and resynced just in case with no advantage to this at all. I’m still sitting at square one with a cold cylinder and can’t seem to find an issue. Has anyone ever had any issues with the pamco 277 ignition? I’ve read a few threads where folks had my symptoms and it turned out being that, and nothing else.
 
Got spark on both sides? checked with a light to be at the right time? You can use a timing light with the electric start and the plugs out. Or an enthusiastic friend can kick if this is a no battery bike. have you tried a battery to power the pamco?
 
hey guys, so I took my bike apart to freshen up the internals (clean carbon build up out of the engine) and now she’s back together and won’t start for me. All it’ll do currently is backfire after a couple kicks. Ran completely fine before tearing it down, rephrased engines seem to be a nightmare for me every time.
 
Try swapping coil wires? Might have left pamco firing right cylinder.
Check cam/crank are "in time"
 
gggGary said:
Try swapping coil wires? Might have left pamco firing right cylinder.
Check cam/crank are "in time"
Click to expand...

Even if I’m a tooth off on the cam or something stupid like that I’d still get a start right? Sorry odd question but I was under the assumption even if I was a tooth off I’d get a start and kick back, but it’d start non the less lol
 
Check compression? doesn't take to far off to keep it from running. Dry your plugs and try again. Are you capacitor, kick only? Try a battery to the ignition to get it running.
 

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