How to tune Yamaha 2 hp carb?

[steviecops]

Hi<br />I've just got my little 2B running after having it completely stripped down. Serial number is 6A1 102994.<br /><br />Could anyone tell me a rough starting point on tuning the carb using the top and bottom screws? How many turns out should they be? I've messed around a bit with then, and it doesn't seem to make much difference where they are!<br /><br />Thanks in advance<br />Steve

 

[jim dozier]

Re: How to tune Yamaha 2 hp carb?

I don't know the number of turns to start on that particular engine but I'm guessing 1.5 turns on both the main and idle would get you started. If it has an adjustable main always adjust the main first, get the engine running at load first then play with the idle mixture. If adjusting the screws still don't seem to affect the engine it may be that crud is doing the metering for you and you need to clean the jets and orifices before you attempt to tune the mixture.

 

[Yepblaze]

Re: How to tune Yamaha 2 hp carb?

Being as it's only 2HP, the carb is going to have some pretty small orifices. Sometimes there are some small bypass slots or idle air bypass holes near the butterfly in the venturi that can need a blast of carb cleaner or air.<br /><br />Also make sure you have removed the main jet and the tube above (if applicable) While noting orientation and any small holes that may be plugged.<br /><br />Generally 1 1/4- 1 1/2 should be good enough to get it to run.

 

[steviecops]

Re: How to tune Yamaha 2 hp carb?

Thanks for the very quick responses.<br /><br />The engine is running under load, but when you slide the throttle back too far it'll cut out. I adjust it as you suggest and go from there.<br /><br />Also, could anyone tell me what year this motor is? The numbers are; 2B 6A1 102994.<br /><br />Thanks again<br />Steve

 

[Jammu]

Re: How to tune Yamaha 2 hp carb?

The motor is an 1986 model.<br />Starts from # 091437->

 

[Johnnyboy454]

Re: How to tune Yamaha 2 hp carb?

Does anyone know how to make my 2hp yamaha idle better?
It runs great but will only start at half throttle if I give even the slightest bit less its cuts out I turned the little screw on the carb a couple times and it didn't help? I thought about taking the whole carb apart but I didn't really know if that was the way to go or not? Im 16 and pretty mechanically inclined so I wanted to try to do it myself before spend all my money at a marine mechanic any help would be appriciated! Thanks Johnny.