2000 SX200 oil pump replacement

[Dragon11]

Hi there. Been searching everywhere for a comparison on oil pumps. Question to anyone that knows oil pumps. Will the SX150 oil pump work on a SX200? They both are identical on the exterior but cost difference and part numbers are different. Curious if there is a different volume output or what? I know Mikuni does shim them but can't seem to find any real specs.

[boscoe99]

Let's think about this for a minute.

An SX200 is going to be drinking about 5 gallons more gasoline at wide open throttle than will the SX150. Using the rule of thumb that fuel flow is ruffly 10% of the rated HP when the motor is being operated at wide open throttle. 10% of 200 being 20 whereas 10% of 150 is 15.

Now the pump is designed so that it can vary from ruffly 200/1 gasoline/oil at idle to 50/1 gasoline/oil at wide open throttle. Doesn't it stand to reason that the pump for the SX200 would have to provide more oil to the gasoline at any throttle setting than it would for the SX150, given that the fuel flow rates are going to be different for all throttle settings?

I suspect that the SX200 pump could be used on an SX150 with maybe there being just some more smoke and maybe greater carbon build up. I suspect that if the SX150 oil pump were used on the SX200 then some adverse stuff related to under oiling may occur. There is a reason that the pump part numbers are different. So as to make sure the right pump is used with the appropriate model motor.

Oil flow specifications would be found in the applicable service manual.

Each pump may have a different prefix identity cast into the pump housing to make sure the correct pump is being used.

[Dragon11]

That seems to be logical but.... regardless if the motor is at idle or wide open it'll have pretty close to the same mixture... Oil pump pushes 6 outlets into 1 outlet and then into the vst which is than mixed, pressurized, and injected. Not sure how that can meter the oil that percise as you said. Further, out of curiosity, I was able to find the oil pump off a year older 150. Pulled them both apart and began measuring every orifice, bore, diameter, depth, ect.... both were identical with in + - .0015" and that I believe was due to wear. One thing I did notice though was the actual arm. Stop points were a bit different. ?? Maybe that's the reason for the extra $$ who knows. Next step is to do an actual flow from both first with each their own arms and than both with one arm. I'll post if anyone is interested.. Doesn't seem to be much interest.

[boscoe99]

It is designed to have the same mixture. But with more gasoline means the need for more oil from a higher HP model to keep the mixture the same.

Each model has a specification for oil flow. Motor is to be run at X RPM with the pump control rod wide open. Oil flow is measured over a three minute time span. Specifications are met or not.

We need and welcome experimenters. Run the pumps on your motor using premix and see for yourself what the difference is in the oil flow output. Let us know. Then try the 150 oil pump on your motor and let us know how it works out. Might make ole smokey a bit less so. That is one way for all of us to learn.

Yamaha has many many models that are rated to run on 100/1 gasoline to oil. Most folks want to add more oil and run with 50/1. In your case you will be going in the opposite direction, using less oil. Will it make a difference? Maybe, maybe not. Will that difference be able to be seen? Maybe but maybe it would only mean the cylinders/bearings wear out in 4000 hours versus 5000 hours. Is this a good trade off? Only individuals can say for themselves.

Waiting to hear from you. I am interested.

[99yam40]

yes others would be interested.
maybe you are correct on the arm just moving farther on the same oil pump, but seems strange it would cost more