Intermittent Problem with my motor
 

So was wanting to get some direction on where i need to be looking for a problem i am having with my 50hp Yamaha 2 stroke motor.

It's a 2007 model (believe it was last year they made the 2 stroke)

It starts up fine, I try to only keep ethanol free gas in it.. (and am mostly successful with that) and it runs fine.

However, sometimes AFTER the engine is warm (has never done this when i first start engine) when giving it gas it bog's down. It does not happen every time, only some of the time.... if i keep giving it gas as it's bogging down the engine will die... I will restart and it will run fine. If i let of the gas as it's bogging down it will start running fine again and usually i can then give it gas and it will hop up on plane and run fine.

I do my own maint on the motor and am have just recently changed out the plugs and pulled and cleaned all the carbs. The problems were occurring before i did this, and to be honest it seemed to do it more often then (but that's just a feeling) it has continued doing it since i cleaned carbs and replaced plugs.

My first thoughts are that something is going on with the fuel solenoid thing that helps with cold starts and once its warmed up it cuts off... I am thinking that's it's officially referred to by yamaha as a prime starter (or auto enricher)

What other things should i check out to put out of the picture... (I also just replaced my fuel hose with a ethanol safe one, and put a new spin on fuel filter) (i still do need to remove the engine fuel filter and clean that out as well)

Anything else it could be???? am i missing something??? any advice from an expert appreciated.

Check and drain your water seperator. Sounds like its full and cant filter the water out. My motor does this when it gets full. Dump the water out and im usually good to go. Never overlook the simple things. You can get water in even if u use non ethanol all the time.

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When you say water seperator i am thinking your talking about the fuel filter inside the hood of the engine that has clear tube around it right?

I had trouble similar to what you are having and it was fuel lines on motor changed all hoses and fixed problem. Just a suggestion! Good luck

Change the fuel filter on your engine.

When you cleaned the carbs what did you use to clean it? I have a ultrasonic machine I clean carbs with along with a strong carb soak chemical. Sometimes you actually have to clean the jets with a small brush made for cleaning jets. If the fuel filters and gas is good I would say the high speed jets have some restriction. The auto enricher rarely gives trouble on those motors but nothing is impossible. Also how old and what brand is your primer bulb? Only use OEM products,the check valves inside of the aftermarket one's suck.

Had the same thing happen to me a couple years ago. Thought it was a gas problem, ti ended up bing the power pack was going out. might check that. good luck

Montauk, When i cleaned the carbs I just pulled the bowls and the top plates and used carb cleaner in a can to shoot thru all the holes, didn't take out or adjust any jets etc. They are very very simple carbs.

I think i am going to clean out and drain the fuel filter first and see if that helps. I don't think the primer bulb is OEM, but was having the same problem when i had an OEM bulb on it.

I have never drained / cleaned the fuel filter on the engine so i'm thinking that's probably the problem.

I hope it is not a power pack.. :(

well pulled/drained the engine fuel filter. there was a little bit of gunk inside the bowl, but nothing that i would have thought would have caused an issue. have to wait till i get on the water to see if that resolved things.

the odd thing with this is that it does not happen all the time, it only occurs sometimes when the engine is warm...... and I also notice that if i quickly advance the throttle it does not happen either.

Its possible you could have a little piece of debris getting stirred around in the high speed jet every once in a while, you let go of the throttle and it breaks free from the jet then you get going again and later it may suck it up once again. May have a needle sticking also.

alright also pulled my fuel water seperator filter mounted outside the engine (looks like an oil filter) and dumped the contents into a glass jar. Gas looks clean as a whistle no seperation after 30 minutes and no debris on bottom.

filled filter back up with fresh gas and put it back on.

Wouldn't it then bog down again once i was on step?

once i get past half throttle... and up on step it doesn't bog down... honestly since cleaning the carbs about a month ago it has been running better than ever.

If the last couple things i did are of no help, i am gonna do a full cleaning of the carbs again.. might even see if i can get my hands on a ultrasonic cleaner to do it. and will probably also replace all the fuel lines on the engine with some of that tygon fuel line.

Sounds like some small trash thats getting hung up in the jets.

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Sounds like the progression holes are partially plugged in the carbs. If you don't completely disassemble and soak for 3 hours, you are wasting your time. Save your money, spraying carb cleaner does not clean the carbs. They all have simple carbs, but, they must be clean to operate properly.

My procedure is:
1. COMPLETELY disassemble the carbs
2. soak all metal parts in carb cleaner for 3 hours
3. Remove from carb cleaner and rinse with water
4. Check ALL passages, jets, pickup tubes, EVERY hole in the carbs with compressed air to insure cleanliness. Blow air through ALL passage and holes, including screw holes.
5. Reassemble and adjust air idle mixture screws CORRECTLY.
6. Reinstall carbs on intake.
7. Synchronize the carbs.
8. Add water and enjoy.

I usually also remove the intake to make sure there are no split, cracked, or broken reeds.
I have never had to "re-clean" the same carbs in over 30 years of doing this. Maybe at a much later date, like after the unit sits up for months, but never had a problem after following this procedure.
The ultrasonic cleaner is second to none, but, we don't all have them.
D