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Discussion Starter · #1 ·
I just bought a 1981 El Tigre 6000. It is 500cc, liquid cooled, dual carbs. The previous owner stated that he had a problem while running wide open once where the sled died. He was able to restart and ride it back to the truck. Upon inspection he found 1 piston that showed signs of detonation (said it was melting a hole through the top). He figured he had a carb ice up and that caused it???? He then replaced both pistons and said it worked fine for some time. When I bought it he complained of loss of power when it warmed up. I found that the same side piston as before had lost most of the rings and a part of the ring land. I rebuilt it and checked carbs for dirt, fuel pump flow, ignition. All seemed OK. Now it seems great when started , idles at 2500 as plenty of pep. But after a trip around the engine seems to want to die, like it's running rich. The cause seems to be it is running on one plug. One plug looks very clean. If I pull one spark plug wire and ground it and leave the other connected it starts. Now do the same with the other wire, it will not start. If I check for spark with the plugs against the head both show spark. Last check is with the good side wire connected to the bad cylinder and the other wire grounded, I get no start. Are these engines exhaust stroke firing fom 1 double ended coil? If so that cylinder should also start the enginewhen connected to the known good plug wire unless it is not ignition. Any ideas on what to check next

Thanx
 

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I am Spartacus
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What does the non firing plug look like? Completely soaked? It could have great speark, but flooding so badly it won't start. Do a compression test again to see what you've got.
 

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Discussion Starter · #3 ·
The plug is soaked when it does this. Compression still good @ 90psi. The thing is, I removed the wet plug and put in a fresh one and again tried to start on just that cylinder and it will not. And the plug is dry. It is like when you get it started on the other one at higher RPMs the "bad" cylinder does fire some of the time.
 

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I am Spartacus
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90 is low. Should have minimum of 110, 120 to 140 is good. That could be affecting the cylinder. When you rev it it builds enough compression to fire the fuel cleanly. Do you have an actual spark tester? That's a much better indicator than resting the plug on the engine.
 
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