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Post by typhoon on Sept 24, 2010 18:10:26 GMT -5
same setup on cylinder and piston - new iridium spark plug - same air box
I hope it is a carb tuning issue and not the new top rebuild .
How does oil/gas mix ratio affect performance?
I added a little more than the 30:1 to tank for breakin period
It also has automatic oil pump so could be rich on oil
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Post by 90GTVert on Sept 24, 2010 18:42:41 GMT -5
Oh wow. Yeah, you might just be losing power from all that oil. 30:1 with no oil injection is plenty of oil. 30:1 plus injection is too much. Now knowing that, I'd say don't change anything untill you have used up that tank and put in a fresh tank of gas with no or much less oil.
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Post by Fox on Sept 24, 2010 19:56:41 GMT -5
I run 40:1 premix in my scooter all the time. I heard that running too much oil will actually cause a lean condition because the oil takes the place of the fuel in the mixture. Sounds feasible but to me it seems that too much oil would likely cause poor combustion, lack of power, plug fouling and excessive carbon buildup in the chamber.
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Post by 90GTVert on Sept 24, 2010 21:15:23 GMT -5
I heard that running too much oil will actually cause a lean condition because the oil takes the place of the fuel in the mixture. The carb's jets have orifices of a given size. Only a certain amount of fluid (gasoline in most cases) can pass through this orifice. When you mix oil into your gas, you are diluting the fuel in a way. A mix ratio of 30:1 means that 3.33% of the fluid passing through the jet is now oil rather than fuel. If you are using the oil injection system, nothing but gas is in the bowl and oil is being injected elsewhere. That means that 100% of the fluid passing through your main jet is gas. If you are premixing with a 30:1 ratio, only 96.66% of the fluid in the bowl that is drawn through the main jet is gas, the other 3.33% being oil. So if you have a 100 main jet (just an easy number to work with), and pre-mix with a ratio of 30:1, your 100 main jet is only delivering as much fuel as a 96.66 main jet would. The other fluid being delivered is the pre-mixed oil. Hopefully that makes sense. I'm kinda tired for some reason. lol |
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Post by 2strokd on Sept 25, 2010 1:11:46 GMT -5
Makes so much sense... I even used oil instead of jetting a little leaner at the track last month. Seemed to work fine. I just looked over the posts again and realized you have an aftermarket top-end. You may have a different layout of the ports on your new top-end causing it to be a little lazy on the bottom end  ? Just a thought :2cents: .... Too much oil will cause it to be lazy too, past a certain point. |
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Post by typhoon on Sept 25, 2010 16:21:46 GMT -5
 I heard that running too much oil will actually cause a lean condition because the oil takes the place of the fuel in the mixture. The carb's jets have orifices of a given size. Only a certain amount of fluid (gasoline in most cases) can pass through this orifice. When you mix oil into your gas, you are diluting the fuel in a way. A mix ratio of 30:1 means that 3.33% of the fluid passing through the jet is now oil rather than fuel. If you are using the oil injection system, nothing but gas is in the bowl and oil is being injected elsewhere. That means that 100% of the fluid passing through your main jet is gas. If you are premixing with a 30:1 ratio, only 96.66% of the fluid in the bowl that is drawn through the main jet is gas, the other 3.33% being oil. So if you have a 100 main jet (just an easy number to work with), and pre-mix with a ratio of 30:1, your 100 main jet is only delivering as much fuel as a 96.66 main jet would. The other fluid being delivered is the pre-mixed oil. Hopefully that makes sense. I'm kinda tired for some reason. lol This could be the issue. those new rings are getting plenty of oil I did not realize that the injected oil does not pass thru the carb as pre-mix does. Where exactly does it get injected? Anyway, I assume that low end torque is where a high ratio oil mix would first affect performance and not at WOT? I checked plug and looks good - no fouling although it has only been 1 / 2 tank since rebuild.
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Post by Fox on Sept 25, 2010 19:55:03 GMT -5
This could be the issue. those new rings are getting plenty of oil I did not realize that the injected oil does not pass thru the carb as pre-mix does. Where exactly does it get injected? On my scooter the oil goes in here. (If I didn't pre-mix) but I do mix so it's not an issue. The link is to a replacement with clear pics. www.partsforscooters.com/Carburetor_50cc-2 |
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Post by typhoon on Sept 25, 2010 20:00:06 GMT -5
Makes so much sense... I even used oil instead of jetting a little leaner at the track last month. Seemed to work fine. I just looked over the posts again and realized you have an aftermarket top-end. You may have a different layout of the ports on your new top-end causing it to be a little lazy on the bottom end ? Just a thought  .... Too much oil will cause it to be lazy too, past a certain point. The new cylinder and piston are identical as far as i could tell. They matched upin size and exhaust etc. |
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Post by typhoon on Sept 25, 2010 20:04:28 GMT -5
:itshere: This could be the issue. those new rings are getting plenty of oil I did not realize that the injected oil does not pass thru the carb as pre-mix does. Where exactly does it get injected? On my scooter the oil goes in here. (If I didn't pre-mix) but I do mix so it's not an issue. The link is to a replacement with clear pics. www.partsforscooters.com/Carburetor_50cc-2That looks like it does go into the carb bowl like pre-mix? |
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Post by 90GTVert on Sept 25, 2010 20:09:35 GMT -5
With oil injection there is a seperate port where oil in allowed to enter the path of air and fuel. What Fox showed you is where the oil source enters the carb, but there is another port inside the carb. To be perfectly honest, I've never paid enough attention to oil injection systems to tell you exactly how they work and how much, if any, bearing engine vacuum has on the amount of oil being drawn in or if it's nothing more than metering by the pump and cable.
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Post by typhoon on Sept 25, 2010 22:41:58 GMT -5
With oil injection there is a seperate port where oil in allowed to enter the path of air and fuel. What Fox showed you is where the oil source enters the carb, but there is another port inside the carb. To be perfectly honest, I've never paid enough attention to oil injection systems to tell you exactly how they work and how much, if any, bearing engine vacuum has on the amount of oil being drawn in or if it's nothing more than metering by the pump and cable. So injected oil enters carb but not in combustion chamber? Maybe that is why people say not to trust the oil-injected system and pre-mix as added saftey factor. The ratio of 30:1 should be ok. |
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Post by 90GTVert on Sept 25, 2010 23:15:24 GMT -5
Oil enters the carb, but not the bowl. It still gets drawn into the engine.
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