wireman

My Feedback: (13)

I recently have obtained a JC Evo 100 cc engine that was in a fatal crash this spring but was running fine at the time. I have installed it on my Carden Extra and after starting it and it warms up I lose a cylinder at low speed and cannot get to a higher speed to see if it clears out. When it is cold and first started it will run up to full throttle fine but after about 2 min it will cut out one cylinder. I put new spark plugs in, changed the ignition module, changed the sensor, bypassed the ignition switch completely to direct battery to module connection to no availe. I am using Stihl Ultra at 50 to 1 and the previous owner used something different so I am going to flush the carb out and see if that helps but it seems weird that it only effects the running after several min, I have had bad luck switching oils in the past but the issue occurred immediately and not later.
Any thoughts out there that might suggest an area to look at would be very much appreciated.

ahicks

My Feedback: (2)

Know nothing about your engine, but reading your note has me wondering about your ign. battery. Have you checked it's voltage while under a load, after it's displayed this problem?

w8ye

My Feedback: (16)

How is the compression on the bad cylinder?

wireman

My Feedback: (13)

The battery was fresh charged and then I changed it out with all the other things up to this point. Compression seems good, I do not have a gauge but the curious thing is it runs good until it warms up and then the cylinder falls off totally.

JohnB96041

I would check the spark plug gap. Make sure they are the same.

JRgraham

My Feedback: (1)

Did the engine get serviced after this fatal crash?

I would inspect your plug caps for any sort of damage, big or small. Even a tiny dent in a cap can disrupt the electrode flow and make an erratic spark.
If you can, try another ignition. Also try a different battery to be certain its not an ignition or battery problem. Plug gaps should be equal to each other.

You should check your carb filter screen as well, if not already.
And a final thought, inspect your reed cage and reeds for any sign of damage or rough mating surface the reeds lay on.

*You might also inspect your piston ring.
Something is happening when the motor heats up and/or rev's up, judging by your description. Fuel flow or battery is likely.

earlwb

Well, in my opinion, it sounds like the engine is too lean. Thus the one cylinder isn't getting enough of the air fuel mixture to run. The problem with all of the boxer twin engines is that one cylinder will have a tendency to get more fuel than the other cylinder gets. Usually the left cylinder tends to run more rich and the right cylinder more lean. So you have to compromise and have the adjustments made to take that into account.

1QwkSport2.5r

Rotating one of the cylinders and pistons 180* will alleviate the cylinder charging problem if both cylinders share the crankcase volume. I know some models won't allow for this, but it would certainly help I'm sure.

w8ye

My Feedback: (16)

Crankshaft seals typically leak more when hot than cold.

Sounds like you have a crankcase leak when it gets warm?

earlwb

Yes that is a good point, in that the crankshaft bearing seal may be leaking. One could probably grease it up good and see if that helps or not. Although you may have to pull the drive hub off to get to the bearing seal. But maybe just dribbling on some oil behind the hub onto the bearing seal might do the trick too. You can use something to apply the oil with there. I am reluctant to say to use starter fluid (the ether based stuff) but it would work if you are careful.

JohnB96041

A trick that I used on a Saito .90 twin that was really throwing oil from the front bearing was wrap a strip of bed sheet about 2" wide and a foot long around the hub and soak it with marvel mistery oil. I kept it soaked for about a week and it has not leaked since.

coralcape

My Feedback: (4)

Swap the plug wires around, to prove if gas or ignition problem. Good luck, red

wireman

My Feedback: (13)

Thanks for all the input, it turned out this weekend when I finally got around to getting the plane back out and found that both batteries that cycled OK last fall have gone to the dark side over the winter. A new 2700 mil cell cycled 3 times and installed ran perfectly!! Again, thanks for input as I did not suspect the batteries initially at all.

JRgraham

My Feedback: (1)

Awesome, love it when the problems turn out to be one of the simple things