4hp Yamaha, need a little help.

[RC56]

On my 3hp Yama ha there is a little pencil thin filter on I think the outlet of the gas valve that got plugged. It is not much bigger than a pencil lead. Look close take out and blow out the filter. Mine had this issue and once I did this there were no issues. Regards

[Lambretta]

Originally Posted by TJ D

Final update:

VICTORY IS MINE.

Nothing was outwardly wrong, but when I took the carb back off, I unscrewed the low speed/idle jet a bit, and that did the trick. It had been fully in previously, and I don't really see how this would solve things, but I'm not complaining!

The engine runs like the day it was new now.

Thanks for the assistance, gents. I didn't expect this to take all day, but the sweetest wins are the hardest earned, I guess.


TJ

Well done

I guess the beer at the end of the day tasted twice as good

[CSY Man]

Glad you got it sorted out.
What year is your motor?
Mine was a 2009, strong as a bull, it would push my 310 dink along at 10.9knots
With 225 lbs of swinging beef onboard. (Me)
Previous 4 HP, the 2-stroke, 2 cylinder Evindrude could only do 7-8 knots.
No idea there was a big difference from one 4 HP to another..

[TJ D]

Originally Posted by CSY Man

Glad you got it sorted out.
What year is your motor?
Mine was a 2009, strong as a bull, it would push my 310 dink along at 10.9knots
With 225 lbs of swinging beef onboard. (Me)
Previous 4 HP, the 2-stroke, 2 cylinder Evindrude could only do 7-8 knots.
No idea there was a big difference from one 4 HP to another..

This one's from 2005. We bought it in Panama a few years ago for $300. I was totally sick of lugging the 100 pound 9.9 on and off the dink. I'm happy enough to go a bit slower, anyway.

We've got it on a Zodiac compact 300 RIB. I go about 240 and it'll get me and the dog on plane, just barely. I didn't ever check the speed, though.

[Mango51]

I have similar problem. With my yamaha f4. I took apart the carb cleaned it. Runs Only high rpm. Won't idle. Took apart a second time took it to my shop. I'm a watch maker. After cleaning the carb in a very strong ultra sonic the jets under microscope were still full of varnish. Used a small bronze wire dipped in oil covered in diamond dust. Came out perfectly clean and polished. Same thing won't idle. 😡

[onavegador]

Had the same problem with my Yamaha 4HP 2stroke. Cleaned the carburettor and the jets several times, no better result.
Brought the motor to an mechanic, he could not resolve the problem (he was steadely asking "I do not know what it is?")
Back in Fort Lauderdale I brought the motor to an other mechanic. He disasembled the carburettor and let the jets in a cleaning solution for about a day. After the motor worked like it never had a problem before.
Good luck.
James

[TJ D]

Originally Posted by Mango51

I have similar problem. With my yamaha f4. I took apart the carb cleaned it. Runs Only high rpm. Won't idle. Took apart a second time took it to my shop. I'm a watch maker. After cleaning the carb in a very strong ultra sonic the jets under microscope were still full of varnish. Used a small bronze wire dipped in oil covered in diamond dust. Came out perfectly clean and polished. Same thing won't idle. 😡

Well, I was truly stumped too. So, you can try what I did. Take the smaller jet (the one that has the brass screw under it, not the rubber plug), and loosen it up until the lower screw is basically touching it when it's tightened down. I don't have any explanation for why this did the job, but it's the only thing I changed between the extremely high idle and working properly.

[Mango51]

Originally Posted by TJ D

Well, I was truly stumped too. So, you can try what I did. Take the smaller jet (the one that has the brass screw under it, not the rubber plug), and loosen it up until the lower screw is basically touching it when it's tightened down. I don't have any explanation for why this did the job, but it's the only thing I changed between the extremely high idle and working properly.

I'll try that. Thanks

[buzzstar]

This is one of the few threads that mainly stuck to solutions, and where the OP kept us informed. While I have not experienced the exact problem, I have actually copied most of the thread as a reference. BTW, the indicated locations, from SE Asia to Europe, plus outliers such as Florida () all pulled together well. What a happy day. Thanks!

[Mike Banks]

Mine did the same thing. Reed valves were sticky from lav=ck of use--while at it I also discovered the waterway was blocked. Cleaned both and now runs well.

[sazarac]

Originally Posted by TJ D

Hi guys,

My little 4 is giving me fits. It starts and runs ok, but if I turn off the choke and give it some gas, it gets starved for fuel and dies. A little choke on and it runs again, but I can't get full power out of it. Basically, it seems like the high-speed jet isn't working.

I've taken both jets out of the carb, and they're clean. Obviously I'm missing something here. What else should I be looking at?

Thanks much, TJ

Air leak between the carb and the head.