Had the old Jag out for the 3rd time this year. I knew we were playing with fire going out just a couple of days before Waconia...
Anyway, it ran great yesterday. Put on about 25 miles with the kids around the lake. Then this morning it started up normal. Let it warm up a few minutes and we drove out on the lake. After about 4-5 minutes my son drove up and said it won't go fast even when you are wide open. I tried it and it was running on one cylinder.
Drove it about a half mile back to the cabin and my oldest and I started checking things out. Here is what we found:
Mag Cylinder was Cold - PTO Hot
Pulled the spark plugs and it was hard to read because it was really bright outside but it had spark. Plugs were cardboard brown about half way down the insulator. Plugs were only 3 weeks old.
Put in a new set of plugs. Fired it up and ran great for about 30 seconds then dropped the Mag cylinder again.
Pulled the exhaust manifold - no scuffing, rings look great.
Pulled the intake manifold - piston skirts look great.
Pulled the head - piston wash looked great.
Put it all back together - snipped the plug wires 1/4" at the boots. Tried swapping the plug wires which caused it to run worse. Swapped the plug wires back and it still ran bad.
It's a single carb 340 so we pulled the carb because I wanted to jet up some based on the plug read. When I did that the carb was clean - everything looked good. Plus with a single carb if one cylinder is running the carb shouldn't be the problem right?
At this point it will idle but not rev high enough to engage the clutch. Just bogs. After feathering the throttle I got it to rev once more to go down the road 100 yards and back but then it would just bog again.
So we loaded it on the trailer and finished the day on the XLT. When we got home it was dark but we checked the compression - 122 / 122 which seems good. Checked the spark again now that it was dark and it is blue and good on both sides.
So I'm stumped. Any ideas of where to look next?
Anyway, it ran great yesterday. Put on about 25 miles with the kids around the lake. Then this morning it started up normal. Let it warm up a few minutes and we drove out on the lake. After about 4-5 minutes my son drove up and said it won't go fast even when you are wide open. I tried it and it was running on one cylinder.
Drove it about a half mile back to the cabin and my oldest and I started checking things out. Here is what we found:
Mag Cylinder was Cold - PTO Hot
Pulled the spark plugs and it was hard to read because it was really bright outside but it had spark. Plugs were cardboard brown about half way down the insulator. Plugs were only 3 weeks old.
Put in a new set of plugs. Fired it up and ran great for about 30 seconds then dropped the Mag cylinder again.
Pulled the exhaust manifold - no scuffing, rings look great.
Pulled the intake manifold - piston skirts look great.
Pulled the head - piston wash looked great.
Put it all back together - snipped the plug wires 1/4" at the boots. Tried swapping the plug wires which caused it to run worse. Swapped the plug wires back and it still ran bad.
It's a single carb 340 so we pulled the carb because I wanted to jet up some based on the plug read. When I did that the carb was clean - everything looked good. Plus with a single carb if one cylinder is running the carb shouldn't be the problem right?
At this point it will idle but not rev high enough to engage the clutch. Just bogs. After feathering the throttle I got it to rev once more to go down the road 100 yards and back but then it would just bog again.
So we loaded it on the trailer and finished the day on the XLT. When we got home it was dark but we checked the compression - 122 / 122 which seems good. Checked the spark again now that it was dark and it is blue and good on both sides.
So I'm stumped. Any ideas of where to look next?