The Enigmatic Oil Pump

[Wheelman-111]

Greetings:

Aside from the vicious interpersonal attacks, here's what I've learned so far:

1. The NB50 Aeros built after 1985 had throttle-controlled oil pumps. The pump is geared to the crank, so it IS RPM-sensitive, as well as responding to increased lube demand occasioned by opening the throttle. The stock engines seemed to run indefinitely and trouble-free, for the most part, using Honda oil and pure gasoline in the tank.

2. A Polini 65cc bore kit (47mm piston and cylinder) ups the ante in terms of heat production and (perhaps) lubrication needs. The main jet included in the kit (a #80?) addresses the engine's mixture needs. The stock fan/shroud may or may not suffice. To compensate, many feel it is necessary to increase the supply of lubricating oil.

3. There are three ways to achieve that: A. Adjust the pump to maximum opening, B. Leave the pump alone, and pre-mix at a dilute (say, 50:1) ratio, or C. Defeat/plug the pump and run a straight 32:1 premix.

I just resurrected my Aero, which had sat untouched for 7 years. My old OMC outboards ran on 50:1 premix, so I decided it might be prudent to mix such a batch to re-"break in" my stock engine with a little "insurance". I put a few miles on it - with the pump connected. It smokes just a little - no vapor trail, but visible smoke out the exhaust at all times. I'm assuming the pump is still working. I believe this because otherwise I would not see this much smoke and probably would have had a problem by now using only 50:1 in this air-cooled application at South Texas temperatures.

This week I should be installing my Polini 65. I still have about a gallon of 50:1 in my fridge left.

Once I consume my current supply however, I would prefer to avoid the chore of pre-mixing. Some have indicated that they have adjusted their pumps to open sooner/wider with their bore kits. I would like to hear from them.

Specifically, how they set the pump to deliver the maximum - or at least sufficient - oil supply to provide a bit more lubrication than the stock "50cc" adjustment delivers.

[roadcapDen]

Guy,
I don't see why the amount of oil to gas ratio should go up with a larger bore?
Enlighten me...y'all don't really need too...
RCD
Swarm & Asteroid

[Wheelman-111]

Greetings:

The unproven assumption - that increasing the piston diameter from 41 to 47 requires more oil to be injected - has been asserted. The ratio is fixed if you eliminate the pump and premix the fuel in the tank. Otherwise, unless it's adjusted the pump will deliver the same amount of oil to the engine at a given RPM and throttle opening with the big-bore kit as it did with the stock piston, causing consternation and trepidation about under-lubrication. And an online conflagration about tuners' qualifications.

[Kenny_McCormic]

Im on crack but 25:1 will be even better. Oil pump is easily defeated, grind teeth off pump and then some and install with all nipples capped off.

[Wheelman-111]

Greetings:

Thanks KM! You're the Bill O'Reilly to Bear's Katic Couric. I truly appreciate you're trying to help.

However since I've heard it can be done without incurring the eternal wrath of the Scooter Deities (or is that DIO-ties?), I intend to keep on pumpin' my oil. No messy premixing for me. Anyway it seems a shame to put all that fine Honda engineering to the bench grinder.

I'd be grateful to anyone who can suggest a starting point to adjust the pump cable.

[Bear45-70]

I would just disconnect the cable to the pump and wire the lever full open. It will smoke more at idle and that's the primary reason they have it adjustable. The only reason that comes to mind as to why more oil would be required is that the big bore creates more heat, but the only way to tell is to use a infared heat gun and measure the temp stock and after the kit install check it again. If it was me for the breaking period of the kit I would be running premix along with the pump. That was pretty much standard procedure. Say 2 to 4 tanks worth depending on how paranoid your are.

[maddog]

the oil pump will only work to a certain rpm unless you lower it with a gear change which you can't, premix is safe.

[Bear45-70]

the oil pump will only work to a certain rpm unless you lower it with a gear change which you can't, premix is safe.

Your statement state defies physic!

[scooterwerx]

there are two 12mm lock nuts where the cable attaches to the bracket, loosen the outside one then crank the inside one in. i found on mine that at WOT, the oil pump cable still had a bunch of throw to go. so i maxed it out at full beans on the grip, full beans on the oil pump. it moved about a half inch more on mine.

[Wheelman-111]

Greetings:

I found I could set mine to prevent the carb from reaching WOT. The oil pump hits its stop before the throttle! Kind of like a "Kiddie Control" for big boys . I still buried the speedometer last night. That's never happened while it was stock.

[noiseguy]

Engine failures from lack of oil on big-bore kits is commonly reported. Option D: Guys that sell the bore parts recommend wiring the adjustable pump wide open and thowing a capful of oil into the tank to compensate. I think this last step (cap of oil) is meant for operation at WOT for long periods of time (island riding), vs. stop and go city driving (most of mainland), where wiring open the pump would be least effective. Wiring the pump open would tend to overoil at idle, leaving a nice thick coat for short WOT runs.

Why more oil? Typically one upjets the main carb with the bore change; you need more oil to maintain the oil-fuel ratio. Running a larger carb or drilling out the stock carb would have the same effect.

[Kenny_McCormic]

Engine failures from lack of oil on big-bore kits is commonly reported. Option D: Guys that sell the bore parts recommend wiring the adjustable pump wide open and thowing a capful of oil into the tank to compensate. I think this last step (cap of oil) is meant for operation at WOT for long periods of time (island riding), vs. stop and go city driving (most of mainland), where wiring open the pump would be least effective. Wiring the pump open would tend to overoil at idle, leaving a nice thick coat for short WOT runs.

Why more oil? Typically one upjets the main carb with the bore change; you need more oil to maintain the oil-fuel ratio. Running a larger carb or drilling out the stock carb would have the same effect.

Guys that sell the bores will tell you to walk the line on oil and jetting. If you keep it a lil on the rich side(which is not noticeable)and lubed up good you wont be back soon for a piston when you try to ride your bike in weather 10* cooler than you set it up for.

[scooterwerx]

wheelman! if you take apart the gauge cluster, there is a pin that limits the speedo needle, mine with the bore kit and variator pegged it out. if you cut the little peg off, the speedo goes all the way into the e!!! haha i saw this website about this dudes aero that did 90mph!

[Skeeve]

Something to bear in mind:

with a modern synthetic 2-smoke oil, the big bore kits won't be able to under-lubricate at the pump's max capacity; the oils available now are just that much better than the dead dinosaurs available before the turn of the millennium...

More to ponder: oil burns hotter than gasoline. oil produces more carbon, that clogs up the exhaust, that causes that much more back pressure, that builds up that much more heat.

Truth: more people have seized their newly hotted-up 2smoke engine because of a lack of proper jetting than any inadequacy of lubrication. Do the math: if you can melt & seize a 4stroke engine with it's positive lube system due to inadequate attention to jetting, what's the more likely culprit on a 2smoke, with it's fuel- & air-cooled system?

[Kenny_McCormic]

More to ponder: oil burns hotter than gasoline. oil produces more carbon, that clogs up the exhaust, that causes that much more back pressure, that builds up that much more heat.

Testing seems to show enignes running more oil have less carbon?