fuel ratio

[JJ Joseph]

all my bikes have oil pumps removed and i run premix

That sounds totally retarded to me, but what do I know. The oil pump supplies oil during closed throttle operations. It's a brilliant 2-stroke idea so your engine doesn't seize during part-throttle descents. So why would anybody remove the engine-saving oil pump from a 2-stroke scooter?

The oil pump supplies oil during closed throttle operations.
So does premix

so your engine doesn't seize during part-throttle descents.
That is not why oil pumps were invented

So why would anybody remove the engine-saving oil pump from a 2-stroke scooter?
To choose a different oil gas ratio. The stock oil pump is 70:1 (not enough for bigger bores)

Oh, please! Where are you getting the bogus info? Those of us who have been riding 2-strokes for 50+ years know something about this stuff. During closed throttle ops, there's LESS fuel/oil going through the engine because the throttle is CLOSED. The throttle slide comes DOWN, and the needle drops into its little hole shutting off the fuel. Less pre-mix going through means LESS oil. The engine becomes oil-starved. That's exactly why oil pumps were added to 2-strokes. Less blue smoke is just a side benefit. The real benefit is end of scorched pistons. Do some homework before giving out gobs of bad advice. Maybe this will help you: http://en.wikipedia.org/wiki/2_stroke_engine

[Bear45-70]

Oh, please! Where are you getting the bogus info? Those of us who have been riding 2-strokes for 50+ years know something about this stuff. During closed throttle ops, there's LESS fuel/oil going through the engine because the throttle is CLOSED. The throttle slide comes DOWN, and the needle drops into its little hole shutting off the fuel. Less pre-mix going through means LESS oil. The engine becomes oil-starved. That's exactly why oil pumps were added to 2-strokes. Less blue smoke is just a side benefit. The real benefit is end of scorched pistons. Do some homework before giving out gobs of bad advice. Maybe this will help you: http://en.wikipedia.org/wiki/2_stroke_engine

Not only have I been doing 2 strokes as long as you but anyone using Wikipedia to prove their point is playing with a bogus deck. To put info into Wikipedia only requires that you submit it. No proof required. *, Wikipedia tells you the the Spree Special was only available in Europe and is worth $20,000....... NOT! FYI, I was a professional factory trained (several in fact) 2 stroke mechanic, plus a 2 stroke racer, National Champion and speed record holder until I retired and guess what no factory school will ever teach that BS. 2 strokes have a fairly large quantity of oil floating around in the crankcase to deal with any deceleration, or thousands upon thousands of premixed 2 strokes would have blown up in the last century. Since they did not, your theory is full of holes.
.

[JJ Joseph]

Not only have I been doing 2 strokes as long as you but anyone using Wikipedia to prove their point is playing with a bogus deck.

You seem to be afflicted with the same ailment as the other gentleman. It's called "going off on a tangent." I wasn't using WP to prove a point, I was simply trying to clue him in to the use of oil pumps in 2-strokes. If you were racing 2-strokes, you're probably as clueless about Sprees & Elites as he is. We engineering types always suspected that drivers didn't have much of a clue about anything other than driving. There's no similarity between a racing 2-stroke and a Spree, other than they both have 2 wheels. And that doesn't provide any explanation of why Sprees & Elites have oil pumps. I respect your driving experience, but it's time for you to go back to school and learn about the oil pump in 2-strokes. Then you could apologize to the oil-pump engineer who wrote the WP article (no it wasn't me).

[Bear45-70]

Not only have I been doing 2 strokes as long as you but anyone using Wikipedia to prove their point is playing with a bogus deck.

You seem to be afflicted with the same ailment as the other gentleman. It's called "going off on a tangent." I wasn't using WP to prove a point, I was simply trying to clue him in to the use of oil pumps in 2-strokes. If you were racing 2-strokes, you're probably as clueless about Sprees & Elites as he is. We engineering types always suspected that drivers didn't have much of a clue about anything other than driving. There's no similarity between a racing 2-stroke and a Spree, other than they both have 2 wheels. And that doesn't provide any explanation of why Sprees & Elites have oil pumps. I respect your driving experience, but it's time for you to go back to school and learn about the oil pump in 2-strokes. Then you could apologize to the oil-pump engineer who wrote the WP article (no it wasn't me).

Well, then you must be right about everything then because I couldn't have won several National High point Championships and set several speed records because all my motors blew up because I was running premix, in fact when I started racing oil injection did not exist by any manufacturer so everyones motor blew up on decel. Get real will you. Your pet theory flies in the face of fact.

Oh and why isn't there a similarity between a racing 2 stroke and a Spree engine? Are they not both 2 strokes with a requirement for both fuel and oil being induced into the crankcase? Are the both not very sensitive to exhaust tuning (all 2 strokes are BTW)? Do they both spend a lot of time at WOT? Should I go on?

Oh I'm supposed to apologize to the claimed oil pump engineer that wrote the Wiki article, not likely. I found out a long time ago that most engineers know engineering but know very little about the real world application of their engineering. That's why there are testing crews in experimental departments that have to show engineers the errors of their ways, been there done that at Beechcraft Aircraft Corporation.

[evilone]

I found out a long time ago that most engineers know engineering but know very little about the real world application of their engineering.

I don't want to join this circus but that is so true Bear.

[zuphilius]

I found out a long time ago that most engineers know engineering but know very little about the real world application of their engineering.

I don't want to join this circus but that is so true Bear.

X2. Most engineers (not all) would ask us lowly aviation mechanics what we thought should be done and then they would write it up that way and take all the credit. This also applies to the automotive assembly world, not as important as Aviation, but it still happened.

[Trafficjamz]

The oil pump supplies oil during closed throttle operations.
So does premix

so your engine doesn't seize during part-throttle descents.
That is not why oil pumps were invented

So why would anybody remove the engine-saving oil pump from a 2-stroke scooter?
To choose a different oil gas ratio. The stock oil pump is 70:1 (not enough for bigger bores)

Oh, please! Where are you getting the bogus info?
Bogus info??

Those of us who have been riding 2-strokes for 50+ years know something about this stuff.
Just because you have riding 2-strokes for longer than I have been alive does not make you an expert on Honda scooters.
If you want to modify a Honda scooter beyond the stock displacement, the stock oil pump can not keep up!
Therefore you must premix some oil in with the gas to compensate for the larger displacement engine.
You can do this by adding oil to the tank to supplement the oil pump, or by bypassing the oil pump all together, and premixing all the oil and fuel.


During closed throttle ops, there's LESS fuel/oil going through the engine because the throttle is CLOSED. The throttle slide comes DOWN, and the needle drops into its little hole shutting off the fuel.
I am very aware of off throttle heat spikes that 2 stroke engines have, especially modded scooter engines.
Larger pilot jets can take care of those pretty easy, because the pilot jets flow even OFF throttle.

Less pre-mix going through means LESS oil. The engine becomes oil-starved.
The elite oil pumps deliver less oil at closed throttle too. They are attached to the throttle cable


That's exactly why oil pumps were added to 2-strokes. Less blue smoke is just a side benefit. The real benefit is end of scorched pistons.
Oil pumps were invented for ease of use at the gas pump. No ratios or fractional math to do when filling up.

Do some homework before giving out gobs of bad advice. Maybe this will help you: http://en.wikipedia.org/wiki/2_stroke_engine
There is some good info on that wiki link.....But nothing that HELPED me, since I am not the one asking for help or advice.
My "Gobs of bad advice" have helped many people on this forum. But if you don't like my advice.....don't follow it.

[fastplastic]

i bet this guy believes in Santa too..... maybe Santa can bring him a clue this year

[808BMW]

Wow, lots of varying opinions here. Personally I believe in premixing, my taiwan bore has about 2500 miles on it and hasn't had a problem. I just tell all my friends to blip the throttle down hills or after high speed runs.

My only question: If the pump is mainly designed to save your engine on decel, why is it hooked to a cable that pumps less oil as you let off the throttle?

[Trafficjamz]

My only question: If the pump is mainly designed to save your engine on decel, why is it hooked to a cable that pumps less oil as you let off the throttle?

Very good point.

[Wheelman-111]

Greetings:

I'm late into this discussion and haven't read every word, but here goes:

The Pump is calibrated to supply a low-ambition, underachieving 49-point-som'n ccs. When you increase displacement the dearth of oil will immediately become apparent. Supplementing the pump with something like 70:1 premix worked for me on a 65cc Contessa and a Malossi, with both engines in a mild state of tune and pipe.

Going to larger bores and higher outputs, the strategy no longer worked for me with Honda's pump. Perhaps a higher oil output could be achieved from the stock pump, but the simplest course and that recommended by virtually every experienced builder is to premix. Each has his favorite ratio. Mine's 32:1.

[mousewheels]

My only question: If the pump is mainly designed to save your engine on decel, why is it hooked to a cable that pumps less oil as you let off the throttle?

-- For discussion's sake - oil pumps under overrun conditions (deceleration & downhill)--
I'm thinking the variable oil pump ratio is mostly for low speed and idle use - see Rotax oil injetion advantages near the bottom.

On the other hand during deceleration - the oil output is still tied to engine RPM. It may not be a lean as it looks at first look.
Whatever the output is at idle (1800 rpm), when decelerating rpm is higher. When coasting down at double the rpm there will be twice as much oil, but the pilot jet will flow only so much. Thus the oil mix changes toward richer. If the hill is steep or at the start of decel from top speed, the oil to fuel ratio would be yet higher.

-- What is the true fuel/oil ratio during overrun?
What is the *best* combination? We could study an oil pump wired for full output + pre-mix vs straight pre-mix. That is - if the end user want's 32:1, yet fusses over the off throttle decel or downhill side: The oil pump + pre-mix might yield a higher oil percentage in that operating region.

-- Rotax pro/con for oil injection
Rotax sells engines with and without oil injection. Aircraft probably have less of the 'downhill' syndrome with lean oil mixtures. But they there are pro/cons for oil injection pumps on Rotax engines here Rotax oil injection pro_con

[PimpinSpree]

That sounds totally retarded to me, but what do I know. The oil pump supplies oil during closed throttle operations. It's a brilliant 2-stroke idea that's even used in 2-stroke ultralight airplanes, so your engine doesn't seize during part-throttle descents. So why would anybody remove the engine-saving oil pump from a 2-stroke scooter? It's like going back to the 1930's. So convince me . . . show me that you know more than Honda-san about oil pumps.

There's no similarity between a racing 2-stroke and a Spree, other than they both have 2 wheels. And that doesn't provide any explanation of why Sprees & Elites have oil pumps. I respect your driving experience, but it's time for you to go back to school and learn about the oil pump in 2-strokes. Then you could apologize to the oil-pump engineer who wrote the WP article (no it wasn't me).

The spree is more similar to a race bike than it is to an ultralight airplane. When your talking about with the airplane descending, it could take a LONG time to come down out of the sky, 20 minutes. When talking about a spree descelerating, it happens very fast. Here is a hard concept for people to understand. A 2 stroke motor will have a lot of oil in its case. The fuel gets burned off and leaves some of the oil. That excess oil is what lubricates the motor. The fuel coming into to the case is what replenishes the oil. I run premix because i want 32:1. If i left the stock oiler in. I would have to premix anyway and then id have to figure out how much oil to put in to make it 32:1. I did the math and came up with 68:1 being the correct ratio with the stock oiler......... its easier just to put in 32:1 in the first place

[Trafficjamz]

deja vu?
viewtopic.php?f=3&t=15492&hilit=oil+pump