hi guys can anybody help regarding the tollerance on the big-end journal of the crankshaft? what is the maximum material that can be cut before crankshaft is deemed as a paperweight? also does anybody know the sizes of the different colour bearing please e.g, thickness.
big end bearings come in different sizes.if too much clearance the bearings pound out and if too littl they seize. also need to be round and not oval. an engine rebuild shop should be able to put a micrometer on and measure.then correct bearings can be sourced or the crank reground and alternative bearings fitted.the bearing runs on an oil film which is compressed by the rotation and pressure.no oil then seize, too much clearance means drop in pressure of film and seize.too little clearance the oil film cannot build up ands same result. racing motors usually have slightly lager clearances but bearings replaced after each race and aa fuellers drag racing have the motors stripped after each quarter mile run.most engines in cars will now last 450 k but bikes should do 100k at minimum
hi risky im aware of the different sizes but what im asking is if someone knows the thicknes off the different colours? to reground the crank is not a problem. e.g the bearings i have now is 1.60mm thick, and my big-end journals are 27mm in diameter, the #2 journal is the 1 that ran a bearing and the journal measured in at 25.50 so you see there is a difference of 1.50mm. with a difference of that much on a cars crank i would scrap the crank but still new to bikes so i dont know the tricks of the trade.
you could get the jounal metal sprayed or welded and reground. with welding there is a chance of cracking the crank. another crank could be cheaper.
i was thinking of just getting a bearing made up and then run a thicker bearing on that journal. will see what the bearing agent says.
never heard of that being done.hot metal sprayed and reground to standard or another crank probably best solution. also con rod will likely need resizing as a flogged bearing would damage that too.
