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Rear Cylinder not firing

W

Wiedyk

Member
On my Evo, every since I brought it, it ran bad. It would back fire through the carb and it seemed like the rear cylinder would cut out. This winter, I redid the top end and got a different manifold and a CV carb. Once I completed the rebuild, the back firing stopped but now the rear cylinder still seems to either not fire or cut out. While idling my front cylinder is HOT and the plug is burning correctly, but the rear cylinder is warm and the plug in burning rich. I tried a coil off another bike with the same results. I still have the stock igntion. Could it be the ignition module or something else?
 
It could be plugs, wires and a few other things. Highly unlikely that it is the module on that bike. It's a process of elimination to isolate the problem. Have you checked for intake leaks after the installation of the new parts? How about a compression test?
 
You could try plugging in an automotive type in-line spark tester to determine whether it is an electrical problem or not
 
Have you done a compression test or are you just saying that it's good? What were the numbers for both cylinders respectively ?
 
I used a compression tester and rolled it over a few times. The tester isn't a screw on type you have to hold it in the spark plug hole.
 
What I would suggest is to use a quality screw in tester and do it again. Look in the self help forum in the engine section for the proper way of doing the compression test and come back with some accurate numbers so maybe we can put an answer to this. 100lbs is not a good reading, the minimum for that motor is about 90 lbs.
 
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