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Dirt Bike Mods & Maintenance
coolant in the engine
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[QUOTE="rmc_olderthandirt, post: 1173447, member: 68872"] okay, let's get a couple of terms straight here: The cylinder head is the top "cap" of the cylinder and is where the spark plug is. On a two stroke that's all there is, on a four stroke the head will also have the valves, cams and associated valve train mechanics. Down underneath the cylinder is the crankcase, which has the crank and connecting rod (oftened referred to as just the "rod"). The crank wil have seals where it extends through the case on each side. There will also be two bearings for the crank, often referred to as the "main" bearings. There will be another bearing for where the connecting rod attaches to the crank, often referred to as the journal bearing. A third bearing will be found up where the rod connects to the piston, at the "wrist pin". Hubert said that there was about 5 hours on a new top end. This suggests to me that the head was either not torqued (tightened) down properly or it was warpped from the previous failure. When I ride I load up all the camping gear and drive 6 hours to my favorite spot so I want to make sure my toys are in good working order before I go. In this situation I wouldn't take any chances, I would take the cylinder head to a shop and have them check it to make sure it was flat. If you ride next to home and missing an opportunity to ride basically means more time to mow the lawn then I would just buy a new head gasket and make sure it was torqued down properly and see if it was okay. As for the water in the crankcase ruining the bearings: I don't think so. I have had a bunch of motors, both two stroke and four stroke that have been completely submerged in water. I have hauled them out, drained the water, dried everything out and got them running again without any bearing issues. I sure wouldn't start a complete bottom end rebuild just because a little water got in there. If you have the cylinder head off then you should at least inspect the cylinder and make sure there are no signs of siezure. It is possible that you basically siezed it again which made it overheat and that is what blew the head gasket. With only 5 hours on the top end rebuild you should be able to clearly see the faint crosshatch boring pattern onthe cylinder walls. If you see any vertical marks at all then you will need to pull the sylinder and redo the top end. Just out of curiosity, who did the top end last time? Rod [/QUOTE]
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MX, SX & Off-Road Discussions
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coolant in the engine
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