Z1 Leak Down Test

You guys keep suggesting a major mechanical issue, valves, rings, etc, and the comp test, even if inacurate, shows a normal engine. Start from the outside in. No sense in ripping the top end off for a carb or electrical problem.

Pics of the plugs. I was thinking valve guide seals. The plugs tell a lot.
Steve

Valve clearance;
Fuel level per clear tube test.

Good Fortune!

I'm with KidKawie on this one. Don't learn to swim by jumping into the deep end. Check the easy stuff first. Your compression readings are at the low end, but they are also consistent. I suspect your procedure was flawed. Did you remove the carbs or hold the throttle wide open while taking your readings? Regardless, don't worry about the compression readings to start. You didn't mention any exhaust smoke, so your rings and valve seals are probably fine. Is the plug wet or dry? Oil doesn't evaporate. An oil fouled plug will be wet and shiny. Touch the electrode and oil will wipe off on your finger. Most likely it will be dry. This also indicated rings and valve seals are not the problem
First, check your valve adjustment. This is just routine maintenance that should be done anyway. Check your points gap and timing while you've got the points cover off.
Next, Swap plug wire from the same coil (in this case 1&4). Did the issue follow the plug wire, or stay with #1 cylinder? If the same, swap plugs. Still no change, you've got a fuel issue. You can check #1 carb individually, but since they come off as a set, I would just clean all 4 and carefully follow the adjustment procedure in the manual.
Don't worry about internal engine problems (compression) until you've eliminated the (relatively) easy external fuel and spark.

I've done bundreds of compression tests, yes the theory has a base in reality; about 10% of the time tho it is way off base or wet will even read normal with bent valves in play. Best to skip that and just go to your typical tuneup items first.

Also lower compression can be remedied with heat cycles (run the motor) as long as every thing else is in spec and things arent too far off

A fouled plug can be (less or more depending) low compression but before I would get all wrapped up in that as there are a couple of things to check. Has anything been done to the bike lately? Carb Adjustments?

First I would unscrew the plug wire cap and cut 1/4 inch off the end of the wire. Then screw the cap back on. Also be aware the spark plug caps can and do go bad even when they look just fine. I’ve had both the 90 degree an straight caps go bad. OEM replacements are available at Bike Bandit.

You are correct in the fact from left to right the cylinders are number 1,2,3 and 4. Switching the coils to see if it follows is an excellent idea.
The valve adjustment does have an effect on compression. If I were going to do a compression check I would make sure the valve adjustment was in spec. Your valve check is done every 4,000 miles anyways. When was the last one?
Another thing no one has brought up is when cranking the motor over to get compression the throttle must be held wide open.

Thinking about what you are saying the distance is from new to fouled plug seems to me like weak spark could very well be the culprit.

good luck. Tim

MDZ1rider wrote: I'm with KidKawie on this one. Don't learn to swim by jumping into the deep end. Check the easy stuff first. Your compression readings are at the low end, but they are also consistent. I suspect your procedure was flawed. Did you remove the carbs or hold the throttle wide open while taking your readings? Regardless, don't worry about the compression readings to start. You didn't mention any exhaust smoke, so your rings and valve seals are probably fine. Is the plug wet or dry? Oil doesn't evaporate. An oil fouled plug will be wet and shiny. Touch the electrode and oil will wipe off on your finger. Most likely it will be dry. This also indicated rings and valve seals are not the problem
First, check your valve adjustment. This is just routine maintenance that should be done anyway. Check your points gap and timing while you've got the points cover off.
Next, Swap plug wire from the same coil (in this case 1&4). Did the issue follow the plug wire, or stay with #1 cylinder? If the same, swap plugs. Still no change, you've got a fuel issue. You can check #1 carb individually, but since they come off as a set, I would just clean all 4 and carefully follow the adjustment procedure in the manual.
Don't worry about internal engine problems (compression) until you've eliminated the (relatively) easy external fuel and spark.

Thanks for the excellent suggestions, Gents.

I spent a little bit of time investigating the problem last week then was out of town for the weekend. The plug seems dry to me. I thought of switching the plug wires. I actually left the wires on the plug and switched them at the coil. The fouling problem did not move to the #4 cylinder. I got a new spark plug wire and that did not solve the issue. So #1 cylinder is still fouling the plug. The plug looks and feels dry, not oily. I did not swap plugs as you suggested. I'll do this tomorrow. Trying to eliminate a spark issue.

Misc. notes:

1. I did hold the throttle wide open when doing the compression test.
2. My bike no longer has points, Dyna-S ignition.
3. I will check valve clearances while chasing this fouling issue.
4. If I can eliminate spark being the issue, then I will move to fuel. One note, if I forget to close the petcock, fuel will leak out of the carb. It's done this since I first got the bike 2-3 years ago.
5. Guy at parts store told me to throw away a spark plug that has been fouled because he said I wouldn't be able to clean it well enough for it to work right. I dunno, it didn't sound right to me.

Oh, one question... the coil has two wires that come from it. Can one end of the coil have a weak spark while the other end is normal? This would cause one cylinder to have weak spark while the other cylinder (in this case #4) could be normal. I guess this is what MDZ1rider is implying.

I think I'll get a chance to look more at the coil tomorrow.

Thanks again for your help.

bugsinmyteeth wrote:

MDZ1rider wrote: I'm with KidKawie on this one. Don't learn to swim by jumping into the deep end. Check the easy stuff first. Your compression readings are at the low end, but they are also consistent. I suspect your procedure was flawed. Did you remove the carbs or hold the throttle wide open while taking your readings? Regardless, don't worry about the compression readings to start. You didn't mention any exhaust smoke, so your rings and valve seals are probably fine. Is the plug wet or dry? Oil doesn't evaporate. An oil fouled plug will be wet and shiny. Touch the electrode and oil will wipe off on your finger. Most likely it will be dry. This also indicated rings and valve seals are not the problem
First, check your valve adjustment. This is just routine maintenance that should be done anyway. Check your points gap and timing while you've got the points cover off.
Next, Swap plug wire from the same coil (in this case 1&4). Did the issue follow the plug wire, or stay with #1 cylinder? If the same, swap plugs. Still no change, you've got a fuel issue. You can check #1 carb individually, but since they come off as a set, I would just clean all 4 and carefully follow the adjustment procedure in the manual.
Don't worry about internal engine problems (compression) until you've eliminated the (relatively) easy external fuel and spark.

Thanks for the excellent suggestions, Gents.

I spent a little bit of time investigating the problem last week then was out of town for the weekend. The plug seems dry to me. I thought of switching the plug wires. I actually left the wires on the plug and switched them at the coil. The fouling problem did not move to the #4 cylinder. I got a new spark plug wire and that did not solve the issue. So #1 cylinder is still fouling the plug. The plug looks and feels dry, not oily. I did not swap plugs as you suggested. I'll do this tomorrow. Trying to eliminate a spark issue.

Misc. notes:

1. I did hold the throttle wide open when doing the compression test.
2. My bike no longer has points, Dyna-S ignition.
3. I will check valve clearances while chasing this fouling issue.
4. If I can eliminate spark being the issue, then I will move to fuel. One note, if I forget to close the petcock, fuel will leak out of the carb. It's done this since I first got the bike 2-3 years ago.
5. Guy at parts store told me to throw away a spark plug that has been fouled because he said I wouldn't be able to clean it well enough for it to work right. I dunno, it didn't sound right to me.

Oh, one question... the coil has two wires that come from it. Can one end of the coil have a weak spark while the other end is normal? This would cause one cylinder to have weak spark while the other cylinder (in this case #4) could be normal. I guess this is what MDZ1rider is implying.

I think I'll get a chance to look more at the coil tomorrow.

Thanks again for your help.

You can clean plugs pretty much an unlimited number of times by holding the end in the flame of a propane torch long enough for it to glow red, then allow to cool and clean off carbon/ash with a wire brush.

The fouling of one plug will affect the other plug on that coil as the circuit goes out of the coil, over the gap of one, through the engine, over the gap of the other, then back to the coil.

If fuel leaks out of the carb then thats prob your issue. You need to reset the float and/or replace the valve.

Only if it's on the same cyclindr being fouled. My over flows pee once in awhile too.

If the fuel levels won't stay consistent, the idle won't ether.
Steve

He said "the carb" so I'm assuming we are all talking about cyl. #1.