oil tank fuel tank question

[jokim00]

Before I begin asking my questions, I would like to apologize ahead of time if I annoy or anger anyone with my lack of knowledge regarding mopeds. I've been reading these threads and it's been scary haha.

I was reading on premixing and jetting and also on oils in general. I also read the service manual for the honda spree.

I saw that there is a fuel tank and a oil tank.
1) Can someone clarify for me the relationship between these two tanks the the role of premixing?
2) As clarifying questions, if you were to premix, which tank do you fill with this premix?
3) If you were to premix, do you then install an oil plug?
4) If rich/lean talk is in the service manual, does that mean that the spree can only run with premixes?

Let's say you're completely stock. Do you just fill the fuel tank with gas station fuel and the oil tank with two stroke oil?

If you get a BBK and a bigger carb, do you have to run a premix?
Premixing is more controlled than filling both tanks and having the moped manage itself right? or are these two things completely different?

My questions seem like they're all over the place.

I guess I just need a run down on all the relationships between the two tanks and premixing.
Thank you for all your help and patience.

[Wheelman-111]

Greetings:

Excellent question!

This issue is why not manyTwo-strokes like these remain on the market in 2011. In the old days, the only way to run a 'Smoker was to "Pre-Mix" fuel with oil in a catch can and use that to fill the tank. Outboards, lawn mowers and early 'cycles had to be fueled this way. Then clever manufacturers like Yamaha developed the AutoLube systems to keep users from having to sully their manicures with the messy process of measuring and mixing oil into their fuel.

Whether pre-mixed or oil injected, all 2-strokes are "Total Loss" lubricated. Unlike 4-Strokes with crank cases or dry sump/Oil tank setups, the oil you pour into a 2-stroke doesn't come back at maintenance time. It all goes out the tailpipe.

Here is where Uncle Sam has been poised with his Emissions sniffers since the late 1960s. The standards tightened more and more over the years, but basically too much hydrocarbon in the exhaust and the EPA would put the Kibosh on the whole design. If that happened, the maker would be prohibited from selling the vehicle in the U.S. and A altogether! Thus Honda had to be sure the engines got just enough oil.

So Honda-san's engineers designed pumps that deliver oil at a calculated ratio to "match" the fuel consumed. The faster the engine spins, the more oil is pumped. Some higher-performance models add a throttle-controlled lever that increases the pump output for higher throttle settings, where the engine is expected to produce more heat and thus more lubricant demand, while decreasing the oil supply at idle and coasting. (This did create some problems - more later...)

The oil and fuel come together in the intake tract. Some oil pumps dump into the carb, while others feed the manifold. Wherever the oil enters, it is dissolved by the hurricane-force stream of vaporized fuel and carried along in the form of micro-droplets into the crankcase. There much of it condenses on the walls, to be captured by channels and trickle onto the main bearings as well as dragged by the piston skirt up the cylinder wall. Some of the oil makes it to the combustion chamber where it furnishes the intoxicating 2-Smoke smell we love so well. It's not all good, because the oil's combustion also leaves an ashy residue that cakes things with carbon that eventually needs to be cleaned off, particularly if the oil supply ratio is overly generous.

When a Big-Bore kit is installed, suddenly the pre-set oil pump supply becomes overmatched by the increased displacement and fuel consumption. Remember the pump is set to be "just enough" for 49cc's worth of fuel per cycle. When that volume increases to 66, 72 or more, there's no longer enough oil to keep things lubricated.

This is where some add a little additional oil - "Pre-Mixed" into their fuel tank. One problem with this strategy is the issue of coast-down, where the pump output drops as the throttle is closed on some models, but the engine contains a lot of heat and is still revving pretty high. This is one reason why most modders will ditch the pump altogether and plug its hole, and then begin to run totally pre-mixed fuel in their preferred ratio. Lots choose 32:1 of whatever brand to which they're loyal. Actual homicides have resulted from the Great Oil Brand Debate.

So if you're running a stock scooter, the answer is yes. Fill your oil tank with recommended Honda oil and the fuel tank with your favorite gasoline. Then let the Magic of the oil-injection system sort it all out for you. Honda ensured this will result in reliability and long life.

[jokim00]

Wow...
Thank you so much for that history regarding the fuel and oil as well as answering all my questions!

Alright, I will keep all this in mind when I begin modding my spree.

That was some awesome feedback from you.
Thanks again wheelman-111

Jeong

[Mystic]

I agree, very informative article wheelman

[PimpinSpree]

People like to think that the oil injection system is just waiting to fail, but it has proven to be very reliable. No reason to ditch the system on a stock system.