Twin Cylinder engine lacks power/runs on one cylinder

The following information applies to opposed Twin and V-Twin engines.

1.Spark is going to one cylinder only. This problem can only happen on V-Twin engines. The problem could either be a bad magneto or a bad diode. There is one diode for each cylinder.

2.Fire is going to both cylinders, but one is still dead. To find out which cylinder is “dead” start it up and remove the spark plug wire from the cylinders one at a time. If you remove one spark plug wire and it does not phase the engine any, then that is the bad cylinder. The causes of a dead cylinder are the valve seat coming out, valve stuck open, low compression, or even a bad spark plug!. Pull the head off and see what happened. If a valve seat came out, then you must take the engine to an authorized service center and have them repair it.

You will not usually notice the power loss until you put a load on the machine that requires both cylinders to be putting out power. A twin cylinder engine will run with no problem on one cylinder, just as long as the load is not greater than what the good cylinder can put out.

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3 responses to “Twin Cylinder engines lack power”

  1. James Dawson says:

    I have a riding mower with Honda gxv 620 v twin its running on one cylinder I pulled the plug wire on left side it will keep running the same. pull on right the mtr. quits running. I replaced the magneto on the left side now its getting fire still running on one cylinder I have a good spark plug on the bad side. I can pull the head and check the valve seat if the valve seat came out can I bring the mower to you for repairs I live in Oklahoma I don’t mind making the drive if you will work on it could you send me an address and phone # thanks this sight is great my phone # 580 513 7729 email any help would be great thanks for your time

  2. tony says:

    have 24hp briggs and Stratton engine bend rods replace heads they are (used) start it up overloaded up gas can u tell me what to check ??? do you set bottom and top both on 4?

  3. ronald moody says:

    I have a two cycle two cylinder engine that runs on one cylinder runs the same no mater witch plug wire I have on it but will not run on the other cylinder no mater witch plug wire is on it good compression on both it has one coil for both plug wires change carb no difference what do u think

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