How lucky have u been with crank rod bearings?

Lately my bike (yamaha XJ400 4 cyl) wont past 3K RPM & if the throttle was opened further then 3K the engine would literally stall as if it has seized, after going through all the obvious parts such as valves, cam, pistons, carbs & realizing they are fine i was assured there is something wrong with the crank so i dismantled the bottom case & found one crank rod out of the four with alot of clearance & play, enough that if i would have rode it for a little longer the crank rod would simply burst out of the block tearing the engine into pieces. so after removing the faulty crank rod i noticed the plane bearings inside the crank rod were sitting on top of each other (not good) & the bearings were simply unusable & needed to be replaced. leaving aside the fact that they are not produced anymore.

I've heard when this happens the crank shaft also takes some hammering & needs to be checked through a meter, since i did not have that particular meter i decided to remove the good crank rod bearings & install them on the damaged one to see if there was any play, fortunately when i installed them the crank rod had no up & down play & the side play was almost the same as it was on the other 3 good crank rods.

Now since i havent been able to start the bike due to a TCI problem i don't yet know if the crank will run fine & last, the engine turns over fine with a wrench though, anyway im just wondering if anyone's been lucky enough to do such a repair, also if there are any precautions i need to take before using the engine to it's limit.

 

Hi
Let me start by saying I have not seen or heard of a yamaha XJ400 4 cyl. All the 400s are 2 cyl. Now to the crank and rod problem. I can think of a few problems that could cause this. In order for the rod bearings to stack there had to be 1 a temporary lack of oil pressure to that rod causing the bearing to seize to the crank thus spinning the bearing. 2 over revving the engine witch hammered out the bearing and possibly the rod. Bottom line What you should do is replace the crank and rod

 

GWH57:

There was an international XJ400 4-cylinder, we just never got it in the states.

Herb