Failed Mikuni oil pump

[Alain2]

I found that part in my stash and I want to share what a failure of the mikuni oil pump could look like. I think the pump ran without oil and shewed the plunger cam. I couldn't find the plunger, but I'm sure it was not pretty.

[SUPERTUNE]

Generally Yamaha oil pumps don't fail, but any mechanical parts that depend on oil to use them, of course it will fail.

Oil injection pump don't wear much due to brand new oil is all it ever sees, never any oil get recycled back through it.
The main failures are running them out of oil, cables breaking, and on the early RD350 pumps with the roll pin did have issues of coming loose and falling out and shutting down the pump stroke to 0.
RD400's were fixed with a screw in pin. When oil pumps get tired, it's because the seals are old and they leak out, but still work and isn't a issue of pumping, just making a mess. Very rarely I do see check ball issues, it's they hang open and can loose some oil pumping volume and can flood engine with 2 stroke oil when sitting from gravity feed from the oil tank.

Properly rebuilt and setup they are really fail proof and do get a bad fear rap most of the time.

Chuck

[Alain2]

I run the oil pump on all my bikes except one because the oil tank leak too much. I think they are very reliable.

[RdsOnly]

I don't think Mikuni made the Yamaha pump. Yamaha patent on the pump.
I have pumps and part if you are rebuilding.

Like any mechanical device they should be serviced from time to time.

I have seen many pump failures, plastic blocking pump feed, wrong internal parts.Most just leak at the pump seal,

Economy cycle has rebuild kits for them.


JT

[quocle603]

I found that part in my stash and I want to share what a failure of the mikuni oil pump could look like. I think the pump ran without oil and shewed the plunger cam. I couldn't find the plunger, but I'm sure it was not pretty.

Time to pre-mix!!! 32:1