Manx Club

Well, after putting maybe 400 miles on my newly rebuilt engine, it locked up on me. I was screwing around in some gravel and the RPMS probably got a bit high when it happened. I took it all apart and apparently the main bearing welded itself to the crankshaft. Why would this happen? Did I over-rev the engine and this is a natural effect of that? Lack of oil? I checked the reading on the dipstick after it happened and the oil level was fine. Does having an oil filter affect what the level should read on the dipstick? Why else wouldn't that bearing have been getting oil? Before I fix everything I need to figure out why it happened in the first place. Now, as far as fixing it, is my crankshaft shot or should a machine shop be able to save it for me? Also, when it locked up it stretched the little pocket for the dowel pin in the case. does this mean I now need a new case as well?

How trajic............Did you plastic gage the bearings when you did the assembly?

If you were hanging continuous doughnuts you could have pushed the oil to one valve cover and the pickup ran dry. Once you stopped the oil level would be back up when the oil drained back. Bummer. Hope you get it going again.

[quote="fubar;12938"]How trajic............Did you plastic gage the bearings when you did the assembly?[/quote] Uh, what? I guess that means no. I just followed the Muir Manual. It was just a stock rebuild.

What was the original reason for the rebuild? Did you have the case align bored before the rebuild? What parts were replaced?

Plastic gage is a small piece of plastic wire that you put inbetween your bearing and bearing surface, when you assemble it smashes out. Then you disassemble and measure the smashed width and that will tell you what your actual bearing clearance is. Usually only a few thousanths, but you need something or it will sieze. I thought it even came with the bearings?

Plastigauge will only measure 1 main journal because only one bearing is split. The main bearings must to be measured with a bore gauge when they are in position in the case with the case properly torqued. The crankshaft journals need to be measured with a micrometer. Subtract the crank size from the bearing size and divide by 2 and you have an accurate measurment of your bearing clearence on all journals. It's too expensive and time consuming to take shortcuts when you build an engine.