125 connecting rod bearing

[kevin kaester]

I replaced the connecting rod bearing on my 1987 force 125. the motor ran great for 4 days without horsing it than it started to knock sprayed some WD 40 in the carb the knock went away put some extra oil in the gas ran good for another day.than it went. this is the top piston on a rebuilt power head the piston appears to be an oridgenal one.I plan to replace the piston connecting rod and bearing. but when I took the carbs off to look inside the top bearing and cylender looked dry no oil on the bearing not like the other ones. Does anyone know what might cause this.
Kevin

 

[Frank Acampora]

Re: 125 connecting rod bearing

Top carb was set too lean, or partially clogged causing it to run lean. On dual carb, four cylinder engines, one cylinder of a pair serviced by one carb always runs a tad leaner and it shows damage first when a carb goes lean.

Changing the rod bearing without checking the crankpin or wristpin surfaces was poor judgement. If the crankpin is damaged, then the whole crank needs to be replaced. No new bearing will last. If the wristpin was damaged, then it will need to be replaced.

 

[kevin kaester]

Re: 125 connecting rod bearing

Thank You Frank I'll do a closer inspection of the crank this time around.I am changing the piston , connecting rod and bearing this time.
kevin