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I have a 21’ yz125 with 65 hours on it and the water pump has started seeping coolant from the weep hole. Looking at the parts diagram I’m just wanting to know which parts I should replace to do it right. I know they sell aftermarket rebuild kits but I’d prefer to keep it OEM and I don’t see yamaha selling a kit anywhere. Thanks for any info!
You will need part numbers 1,7,8,9 and 13.
Replace the waterpump impeller shaft (part #1) as it will have a small grooves in it from the seals wearing into it.
Take your time and take pictures at each step of disassembly to make sure you know which direction the seals are oriented. You will need a new bearing (part # 9) as it will be damaged when you pound it out. This is also a good time to make sure you have a service manual to guide you along.
One other note. Be very careful when reinstalling the right side clutch cover after servicing the waterpump. When lowereimg the right side clutch cover onto the engine, take the flywheel cover off and rotate the flywheel while lowering the right side clutch cover on. This will rotate the crank primary gear and will help the waterpump gear and powervalve governor gear mesh properly so the clutch cover will fully seat.
I have seen people not to this step and smash the clutch cover on without the gears meshing. This can cause the powervalve governor to compress allowing the shear pin to fall out and cause damage to the engine.
Take is slow and good luck!
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