1978 xs400 2e
So it appears my top end rebuild has not been successful. As it stands right now I have about 90 psi on the left side and 60 psi on the right. Prior to the overhaul everything was fine.
The first start went well; it ran on the second kick after the rebuild (near freezing temperatures as well), but only for about 15 seconds before it died. Everything sounded normal and the idle was steady at about 1,500 rpms.
I thought it was a carb problem at first because I saw some flooding, but I took a look through the plug holes and what looked like droplets of water were scattered over the piston heads. I really didn't want to believe it was oil because it looked so thin (like water droplets) and 20w50 at near freezing temperatures is very thick. Unfortunately I took a sample with a swab and it won't burn easily or at all. Obviously if it was gas it would flare up vigorously. I cleaned the piston heads with long swabs, but the droplets come back after turning the engine over.
I replaced all the gaskets, seals, and torqued everything to spec in the proper pattern very slowly. Literally, I spent 20 minutes each tightening the head and cam cover. Everything was generously lubed with motor oil and I lapped the valves.
One mistake I may have made was to not clean all of the lapping compound out of the intake/exhaust port area below the valve sealing/seating area. Honestly, I think I forgot to look through the ports and not just through the seat. I can see how this could ruin the valve seal and cause a loss of compression, but is it likely that the valve seals are toast as well? Both would have to be damaged in order to explain the oil and the loss of compression.
What seems most likely? The carbs were flooding a lot; could I have washed out the cylinder walls?
If I pull the motor again and open it up will I need a new head gasket and cylinder block gasket? I have no idea of these can be re-used.
So it appears my top end rebuild has not been successful. As it stands right now I have about 90 psi on the left side and 60 psi on the right. Prior to the overhaul everything was fine.
The first start went well; it ran on the second kick after the rebuild (near freezing temperatures as well), but only for about 15 seconds before it died. Everything sounded normal and the idle was steady at about 1,500 rpms.
I thought it was a carb problem at first because I saw some flooding, but I took a look through the plug holes and what looked like droplets of water were scattered over the piston heads. I really didn't want to believe it was oil because it looked so thin (like water droplets) and 20w50 at near freezing temperatures is very thick. Unfortunately I took a sample with a swab and it won't burn easily or at all. Obviously if it was gas it would flare up vigorously. I cleaned the piston heads with long swabs, but the droplets come back after turning the engine over.
I replaced all the gaskets, seals, and torqued everything to spec in the proper pattern very slowly. Literally, I spent 20 minutes each tightening the head and cam cover. Everything was generously lubed with motor oil and I lapped the valves.
One mistake I may have made was to not clean all of the lapping compound out of the intake/exhaust port area below the valve sealing/seating area. Honestly, I think I forgot to look through the ports and not just through the seat. I can see how this could ruin the valve seal and cause a loss of compression, but is it likely that the valve seals are toast as well? Both would have to be damaged in order to explain the oil and the loss of compression.
What seems most likely? The carbs were flooding a lot; could I have washed out the cylinder walls?
If I pull the motor again and open it up will I need a new head gasket and cylinder block gasket? I have no idea of these can be re-used.
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