suddenly too lean?

[larsfis]

So I have this wonderful Yamaha 4hp 4 stoke (2003) that I bought last year to push my dinghy around. Just the other day, I could not get the engine to continue to run when I pushed the choke knob back in. It starts - no problem - with the choke out, but every time I push it back in, it stalls. <br /><br />Figured maybe the mixture went bad somehow and that I was running too lean - but I can't find a mixture adjust screw anywhere on the carb!<br /><br />Any thoughts?<br /><br /><br />P.S. Not to be a Yamaha basher... this thing has been anything but reliable since I bought it. I thought that maybe I didn't pamper the engine enough, but in comparison, a friend has a honda 2hp 4stroke that he treats like an old dish rag and the thing starts on half a pull and arguably has more power than my 4hp.

 

[WillyBWright]

Re: suddenly too lean?

Welcome to iboats.<br /><br />It sounds like there's some jet blockage in the carb, usually varnish. Small motors don't use-up gas very quickly and the supply can go bad before it gets used. Use a fuel stabilizer all year and that should help prevent that. But for now you probably have to disassemble and clean it.<br /><br />The nice thing about starting a 2-stroke is that every revolution pulls in some gas and fires it. On a 4-stroke it's every-other revolution. And I agree that the small 4-strokes are kinda poochy.

 

[larsfis]

Re: suddenly too lean?

Yes, thanks!<br /><br />I pulled it all apart today and sprayed it down with gumout. Works like it should now. <br /><br />I'll keep fuel conditioner in the gas from here on out!!!<br /><br /><br />Thanks again,<br /><br />Lars.

 

[rodbolt]

Re: suddenly too lean?

so it wasnt a junk yammy problem after all . was a consumer neglect issue <br /> no worries. its the cause of most small motor problems. especially on blow boats. blow boaters seem to think that 20 gallon fuel cell should be good for the life of the engine .<br /> take my advice. use a 3 gallon gas tank and keep it dry and toss it every 2 months.<br />a few weeks ago I pumped 80 gallons of trash fuel from a boat that sat 2 years. they started with 40 gallons and added 40 more so I pumped 80 gallons of trash. cost 3.10 a gallon to dispose of .