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1991 130, precision blend. long post, but i feel it necessary to be plentiful with details since it is a weird problem.
my family yamaha tech went through the engine a few weeks ago changed waterpump, poppet valve, t-stats and generally gave the engine a checkup; compression, spark ect. everything was fine, and said the engine ran wonderful, as far as he could tell with the flush kit. it idles smooth as a 2 stroke can and does not miss a beat. it has great smooth power all the way until WOT (not that i run there..lol), but after about 5 seconds of getting to WOT the rpms drop down. sometimes they will drop down to 4700, sometimes 4300. first time i give it the throttle it goes up, if i try it again it usually goes up but for even shorter. a few tries later i usually cannot get those extra rpms at all. the engine still runs strong at those rpm's once it drops down and shows no sign of stalling or anything. its just annoying to know it has more balls i just cant use. wouldnt hurt to have it limited with these gas prices, but want those extra revolutions for outrunning a surprise thunderstorm.
the o-ring on the fuel filter was missing; we initially thought this could be the problem-- sucking in air at that high fuel demand. i have replaced the oring and repaced all filters, still no luck. the plugs are fresh, and mechanic (ours since late 80's) says the engine is healthy.
isolated the issue to the engine; by using an external fuel tank. basically the carbs were incorrectly installed from his opinion (gaskets on backwards causing restriction) so it was our thought to take them off, dissasemble clean and rebuild--if someone messed putting the gaskets on imagine how they assembled the carb. orings on something inside the carb were junk, as was the float adjustment (not even close to level), whitnessed by myself, the orings disintigrated in my hands. needless to say, i would think it safe the carbs needed service anyways.
however, after this service the problem has not gone away, but it seems to possibly gotten worse. now it holds the rpms even less, and loses power to an even lower power...so instead of the usual 47 where it would level out it will drop all the way down to 38 at "WOT."
he should be looking at the engine and running it again tomorrow night (no lack of water tests at problem speed/rpm's) to hopefully figure it out. he admits he is stumped for the most part, although i continue to suspect the fuel pump. the pump was replaced in the fall before winterizing the engine. since the pump is new, he does not think it is the problem. basically i'm just looking for an opinion whether defective pumps exist or not. like any other part i am sure they do exist, but is it feasible within normal odds to actually end up with one?
if not the pump to suspect anymore, any other thoughts?
fresh fuel, filters, clean/adjusted/gasketed carbs, tight fuel lines, problem isolated to engine with external fuel supply.
thanks for any help.. we appreciate it.
my family yamaha tech went through the engine a few weeks ago changed waterpump, poppet valve, t-stats and generally gave the engine a checkup; compression, spark ect. everything was fine, and said the engine ran wonderful, as far as he could tell with the flush kit. it idles smooth as a 2 stroke can and does not miss a beat. it has great smooth power all the way until WOT (not that i run there..lol), but after about 5 seconds of getting to WOT the rpms drop down. sometimes they will drop down to 4700, sometimes 4300. first time i give it the throttle it goes up, if i try it again it usually goes up but for even shorter. a few tries later i usually cannot get those extra rpms at all. the engine still runs strong at those rpm's once it drops down and shows no sign of stalling or anything. its just annoying to know it has more balls i just cant use. wouldnt hurt to have it limited with these gas prices, but want those extra revolutions for outrunning a surprise thunderstorm.
the o-ring on the fuel filter was missing; we initially thought this could be the problem-- sucking in air at that high fuel demand. i have replaced the oring and repaced all filters, still no luck. the plugs are fresh, and mechanic (ours since late 80's) says the engine is healthy.
isolated the issue to the engine; by using an external fuel tank. basically the carbs were incorrectly installed from his opinion (gaskets on backwards causing restriction) so it was our thought to take them off, dissasemble clean and rebuild--if someone messed putting the gaskets on imagine how they assembled the carb. orings on something inside the carb were junk, as was the float adjustment (not even close to level), whitnessed by myself, the orings disintigrated in my hands. needless to say, i would think it safe the carbs needed service anyways.
however, after this service the problem has not gone away, but it seems to possibly gotten worse. now it holds the rpms even less, and loses power to an even lower power...so instead of the usual 47 where it would level out it will drop all the way down to 38 at "WOT."
he should be looking at the engine and running it again tomorrow night (no lack of water tests at problem speed/rpm's) to hopefully figure it out. he admits he is stumped for the most part, although i continue to suspect the fuel pump. the pump was replaced in the fall before winterizing the engine. since the pump is new, he does not think it is the problem. basically i'm just looking for an opinion whether defective pumps exist or not. like any other part i am sure they do exist, but is it feasible within normal odds to actually end up with one?
if not the pump to suspect anymore, any other thoughts?
fresh fuel, filters, clean/adjusted/gasketed carbs, tight fuel lines, problem isolated to engine with external fuel supply.
thanks for any help.. we appreciate it.
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