plugs bad?

I had a plug foul on cyl. 3 so I replaced all my plugs. I have driven around 100 miles and I tried to start my bike for the first time of the year and it didn't want to. I finally got it started but it wasn't running right. It was running just on 2 cylinders. 2 of my 100mile plugs wasn't fireing. I put 2 of my used plugs back in and they fire great. The plugs look a little black but not excessive. Can carb cause these plugs to foul out? this is on a 80 1000ltd
Do you think I got some bad ngk plugs?

yes carbs can cause them to foul double check your enrichener make sure it is closing all the way if it isn't closing properly it can cause an excessive rich mixture which will foul the plugs in a freaking haert beat also what cylinders did you have to replace the plugs on.

terry s wrote:

I had a plug foul on cyl. 3 so I replaced all my plugs. I have driven around 100 miles and I tried to start my bike for the first time of the year and it didn't want to. I finally got it started but it wasn't running right. It was running just on 2 cylinders. 2 of my 100mile plugs wasn't fireing. I put 2 of my used plugs back in and they fire great. The plugs look a little black but not excessive. Can carb cause these plugs to foul out? this is on a 80 1000ltd
Do you think I got some bad ngk plugs?

Would also check ---
Voltage reaching coils;
Spark quality on plugs (remove each and visually inspect spark);
Compression and valve clearances;
Fuel level (clear tube test);
Clean air filter;
Nothing under seat obstructing air intake.

Good Fortune!

Also make sure your plugs are the correct heat range. What NGK plugs are you running? Ed

I had trouble in the 1,2 and 3 cylinder. I just rebuilt the carb. middle of last summer.I put the stock NGK plugs in. It ran great after that. My air filter is fine. I will do the voltage check.

another problem that can occur is the plug caps can and do loosen up on the wires them selves they just screw on so give them a pull and if they come off,cut the wire back about 1/4" and rethread them back on also you may as well check the resistance of the caps at the same time the resistance should be 5kohm. try that before you lose your mind.

I just checked voltage at the coil. I have 11.31 volts at both coils. I have 12.33 volts at battery. I lost 1 volt. It that enough for my problem? I am going to go ahead and track down where I am lossing that 1 volt. I checked at kill switch and have 11.31 also. Now I am going towards the ignition switch.

I found the voltage loss. It was at the 20 amp fuse. The fuse was good but the connector was making a bad connection where the fuse pushes in . I replaced with a spade type fuse holder. I am going to replace all 3 fuse holders. I also cleaned all the connections going to the coils. I hope this takes care of the fouling plug problems. It gets to be a pain in the a@@.

terry s wrote:

I just checked voltage at the coil. I have 11.31 volts at both coils. I have 12.33 volts at battery. I lost 1 volt. It that enough for my problem? I am going to go ahead and track down where I am lossing that 1 volt. I checked at kill switch and have 11.31 also. Now I am going towards the ignition switch.

i would be very surprised if the minimal voltage increase
solved the problem....sounds like a carb problem...i get less than 11.3 at the coils and my bike starts within 2 secs cold and the plugs look good.....let us know how you make out.....

I just got back to working on the bike. I checked the voltage at coils at idle is 6.7 volts .At 3 grand 7.5 volts.
Is this voltage a problem? I also checked my compression cold.
150,110,115,130

I then put oil in cylinder.
240,200,175,210

So this just about doubled my compression. I presume this means a tired motor.
Do I need a rebuild motor? Do I have 2 problems? Think I could just rering?

those first numbers aren't to bad for a low compression stock machine. the second set of numbers sound a bit out of whack to me does your engine smoke or have a lot of blowby out the breather. cause if doesn't i be running the the engine for a while and recheck the valve clearances sometime down the road, by the voltages at the coils are way to low.they should be as close to battery voltage as possible.

No it does not smoke and no blowby. I just adjusted valves 500 miles ago. I may go ahead and run them again. My main problem is the sooty foul plugs in 100-200 miles. I checked and cleaned all connections from battery to coils. I think I am going to do the wire mode with relay and try that. thanks for your input.