So I’ll do my best to explain this problem but it is strange. I am just looking for some ears to bend in hopes someone will have a solution or an idea I have not tried and I promise I have tried everything. Originally the motor started out is it 04 Yamaha 40 stroke. I have since then converted it into a 50 hp via new 50 tuner and a set of 50 hp carbs. This are the only differences in the two hour ratings of this year. With the 50 carburetors on it idles perfect and runs on the top end perfect but from idle to accel it just bogs. While looking into the carbs the fuel doesn’t seem to want to flow through the emulsion tube at first throttle twist. Long story short replaced everything fuel system wise all brand new. Rebuilt and sonic cleaner the 50 carbs at least 4 times complete breakdowns. Decided to throw my 40 carbs back on and just like that the problem went away. I’ll begin process of illumination by taking my 40 idle circuits off and putting them on the 50 carb bodies. In this elimination process I also got rid of the prime start sooooo all I can think now is something is wrong with the body of the 50 Carbs I have. also when I was testing the 50 Carbs while they were bogging I could put my hand over any one of the three carbs I wanted in the motor would proceed to pick up and get better sometimes pumping the bulb would help as well but usually that would cause more of a bog. Timing is in spec plugs are new CDI box is new what in the world in a car body could be bad causing this and why would I be able to Palm any one of the three carbs to get it to create enough vacuum to suck fuel. Seems like the carb body could be clogged in an passage but I feel like it wouldn’t be all three. Oh and my reeds are brand new ccm fiber reeds.
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04 Yamaha 50 two stroke acceleration bog.
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if the 40 carbs work fine, just change out the jets with the 50.
I believe the jets and tuner are the only thing different
are you sure the timing is advancing as it should?
why the new CDI?
is it aftermarket also?
not sure how you could swap idle circuits as the jets and passages are in the carb bodies
and I am not sure how you got rid of the PS.
I hope you blocked off the passages into the intake and crankcase
may want to put that all back togetherLast edited by 99yam40; 04-10-2021, 06:48 PM.
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Originally posted by 99yam40 View Postif the 40 carbs work fine, just change out the jets with the 50.
I believe the jets and tuner are the only thing different
are you sure the timing is advancing as it should?
why the new CDI?
is it aftermarket also?
not sure how you could swap idle circuits as the jets and passages are in the carb bodies
and I am not sure how you got rid of the PS.
I hope you blocked off the passages into the intake and crankcase
may want to put that all back together
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