As part of the engine rebuild for my project Honda XR125L, I need to recondition the oil pump. There's no point rebuilding the engine just for the oil pump to not be up to spec and ruin all my hard work.
Can't find the correct Honda o-rings for love nor money at the moment. These however are very very very close to the correct size (they may even be the correct size as the fit the casting in the engine casing perfectly. OD 14mm, ID 9.2mm thickness 2.4mm. Bought off AliExpress. A pack of 20 cost less than a single one of the (unavailable) Honda part.
A perfect fit.
Getting ready to recondition and refit the oil pump, oil filter (centrifugal), clutch, and gear shift drum detents.
Taking the oil pump apart to inspect the gear rotors, one of the two machine screws that hold the back plate on it jammed. So I'm drilling it out. I taped up the other orifices on the pump, but as I'm going to be fully disassembling it anyway, this wasn't really needed. I guess it stops any swarf wrapped around the drill bit from scratching the machines surface.
Head of the machine screw removed.
I always use some cutting compound. Keeps the drill bits in good condition and keeps them sharp for longer.
Removed. The "washer" is actually the head off the other machine screw.
The shaft of the machine screw is still in the pump. I had hoped the shank would have been proud of the pump so I could get some locking pliers on to it, but sadly no.
My plan is to drill the screw out from the rear (the hole isn't blind). I don't have a left handed drill bit so can't drill from the front. Using a right handed drill bit from the rear of the bolt will have the same effect of unscrewing the remains.
Carefully clamped the pump in the vice. I made sure to clamp it only tight enough that it doesn't move and not tight enough to distort the housing.
Barely touched it and the screw came out. Nice.
Pump fully disassembled.
The machine screw I had to drill out. Need to replace that.
It measures as 3.90mm, so an M4 thread.
For countersunk screws the length is the entire body of the screw which includes the head. For most other screws and bolts you exclude the head. This is 11.62mm long, so 12mm. I'll order some replacements. I think I'll go with Allen head instead of JIS.
Next I need to clean all the parts. I used Bilt Hamber's "Surfex HD" for this. Amazing stuff. Cleans like a solvent but is water based and non-toxic. Really amazing stuff.
A rinse with water and then careful drying of the steel parts to make sure they don't rust whilst I'm waiting for parts.
There is light scoring on the two rotor parts. I'm sure it would be fine to reuse them, but these are parts I already ordered before prices went through the roof and availability dried up (as I expected to have to replace them). So I may as well use the new parts. No sense not to at this stage.
All the parts clean and dry. Bagged up waiting for the replacement machine screws to turn up, then I can reassemble and fit to the engine.
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