Stock Oil Pump Delivery Ratio

[Wheelman-111]

Greetings:

A Forum question arose about the ratio of oil delivered by the stock pump. In a previous post, I submitted my own "Formula" for adding premixed oil while retaining the pump, based on some assumptions. Naturally the models with a throttle-controlled pump deliver a variable ratio that depends on throttle position as well as RPM. One would think that the highest-performance Hondas would require the most oil. For Honda, that means the CR motocross bikes, whose recommendation is for 32:1.

It'd be pretty easy to calculate the pump ratio if you have the energy and inclination:

Fill the oil tank to a marked level. Fill the fuel tank all the way. Carefully measure the gasoline consumed over a few tankfuls. 2 or 3 gallons consumed would be a pretty good interval. Next carefully measure how much oil it takes to refill the oil tank to your mark.

For example, say you ran up a gasoline burnt total of 3 gallons = 384 oz. If it takes exactly 12 ounces to refill the tank, 384/12 = 32:1. Plug in your actual numbers to obtain the real pump rate.

I'd have done this myself, but I refill from a gas can with my premix, and I'm too lazy to measure the gas I pour in... I should, but I haven't yet done it. First one to post actual results gets a free used Spree engine mount. I pay shipping. "Actual" results must be documented, preferably with a pic of that gorgeous Brunette from Bee-Tee's website astride the scooter.

[odinxxix]

if anybody has done this or even knows what it is i think this should be sticky cause this could prove to be great info.!

[maddog]

pull the oil line off the oil tank, clean the oil screen which gums up with bacteria, the oil flow should be a steady thin stream, the oil pump takes over from there.

[odinxxix]

we know how it works, we want to know if anybody knows what the mix ratio is from the pump.

[maddog]

We don't need to know but if you blow your engine we can tell you why

[noiseguy]

Jeez. What's bugging me is that I know I've seen this delivery on a chart somewhere in one of the technical documents. It had a graph of output vs RPM. For one of the Elite models.

There it is! In the '83/'84 service manual. Only one I've seen it for, but I doubt it's changed much over the years. And it's not RPM, it's control angle.

Thing is, this isn't really tell you what you want to know, which is the oil / fuel ratio. Oh well, it's a pretty chart anyway

83 oil pump.jpg (104.18 KiB) Viewed 43986 times

[Wheelman-111]

Greetings:

'84-'84?! Is that for the 1st-generation Aero??

[noiseguy]

Yep, right in the factory service manual for those years Aero. Odd, really.

[Wheelman-111]

Greetings:

I thought I'd give this a bump as there have been a couple of questions regarding Elite S vs Elite SR pump delivery lately. At least this graph gives us a ballpark from which to extrapolate. Keep in mind that the pump stroke is RPM-dependent, and there is every reason to believe that the relationship is linear: at 9000 RPM the cc/minute would increase five-fold.

Careful measurement of oil Vs. Fuel consumed over a few hours of operation could allow us to reset the data for a later-generation oil pump. If someone were truly determined, (and running premix) one could reinstall the pump and hook it up to a catch-can consisting of a graduated cylinder and measure the dribblage over a 10 minute span of operation.

Or is that too anal-retentive? Anyone seen my Thorazine?

[maddog]

Yes you are anal retentive, there is no flow rate for an oil pump

[Wheelman-111]

Greetings:

Thanks for the validation, 'Dog. I was beginning to think I was the only one! It appears JonSteffen is planning some Science. I may be in a position to do it myself in a couple of weeks.

How do you figure "there is no flow rate"? Seems to me if there is flow, there must be a rate of flow, or a range at least.

[S4Patrick]

Good post here...Some great thoughts for sure....

Since there's a different part # for each pump, I'm very curious as to what the differences of the S vs. SR pumps are...

May have to do your suggested oil container line draw technique....

[bartle90]

Hi all,
I just bought a 1998 elite sa50p and the guy I bought it from disabled the oil resivoir because of some sort of modification he did to it. He told me I had to premix the oil at the gas pump and I was wondering what the best ratio would be... he said 50:1 but one of my buddies said to do more like 40:1. Let me know what you think...

[Wheelman-111]

Greetings:

A stock SA50 should do fine at your choice of 40 or 50:1 with Honda's own GN-2 or SP-2 synthetic oil. There are a number of brands of hi-po 'smoker oils to choose from at your nearest Moto-performance shop, too. Just avoid the Wal-Mart brands of yard implement stuff and also outboard motor oils designed for liquid-cooled engines.

You might be wise to examine exactly how the PO "disabled" the oil tank. If he left the pump in place and just didn't fill the tank, there is a risk that the pump can seize if it is run without oil going through it. Should that happen, it might strip the worm drive on the crank and wreak havoc inside your engine.

Pop the oil pump out and examine that the gears have been ground off completely so that the pump isn't being driven. Better still, call VTCycles or Limp for a proper replacement plug.

If you plan to mod the scooter with a big-bore kit, pipe, etc., then a thicker premix ratio of something like 32:1 is the norm.

[bartle90]

The PO told me that he made these mods to the scooter:
72cc polini corsa top end kit
Pg long exhaust
28 mm carb
New main and pilot jet
UNI air filter
Throttle cable
Chrome intake manifold
New reed valves
9.1:1 final drive gears
High speed variater


Would you say a 32:1 ratio is more appropriate? He told me he would only put in about 2 tablespoons of oil for every gallon but that just seems like its way off...
Thanks for your input