Fuel not fully burned, everything working - WTH?

[RAD]

EA81 with Hitachi carb, good spark plugs that look like they should; newer, quality wires, all cylinders firing, but a lot of un-burned fuel going out the tailpipe...

I don't understand, how does that happen? Don't know what to fix....

[Sapper 157]

Probably just needs a float adjustment. Look at the little sight glass on the side of the carb while it is running at idle and look where the fuel level is... above middle of glass = too rich. Below middle of glass = too lean. At center of glass = just right. To adjust, take the top off the carb and pull the float off needle valve. bend the little foot on the float either up or down to adjust. I THINK its Up = rich and Down = lean.... but cant remember exactly. Have you rebuilt the carb recently? make sure you did not flip the jets by mistake. I did that once and got 14 MPG. haha! Also, are the plugs/wires NGK? Replace them if not. You will see a jump in performance just by switching to NGK plugs

[RAD]

Probably just needs a float adjustment. Look at the little sight glass on the side of the carb while it is running at idle and look where the fuel level is... above middle of glass = too rich. Below middle of glass = too lean. At center of glass = just right. To adjust, take the top off the carb and pull the float off needle valve. bend the little foot on the float either up or down to adjust. I THINK its Up = rich and Down = lean.... but cant remember exactly. Have you rebuilt the carb recently? make sure you did not flip the jets by mistake. I did that once and got 14 MPG. haha! Also, are the plugs/wires NGK? Replace them if not. You will see a jump in performance just by switching to NGK plugs

 

Thank you. I have done a couple carb rebuilds in the past, and all I probably need for this then is maybe a new gasket to be almost pro about it.

More than one person has told me that, so seems pretty obvious, but did not occur to me.

Now that I look back on it, the problem seems to have been progressive, not all at once necessarily - would that indicate anything in itself? I might apply Murphy's Law and wonder if the float itself may be compromised or going bad or something.

 

 

 

[Sapper 157]

and all I probably need for this then is maybe a new gasket to be almost pro about it

....the problem seems to have been progressive, not all at once necessarily...would that indicate anything in itself? ...wonder if the float itself may be compromised or going bad or something.

It is good that you have done rebuilds in the past... you will need to call upon all your carbureation expertise in order to take on the Hitachi. They are hellishly picky and incredibly complicated for a two barrel carb... You will need to purchase a rebuild kit. The cheapest I have found them is on carparts.com for about $25ish. Or sometimes ebay has a good deal on them. I would try to get a Walker kit as they have always been good to me. 

 

You pretty much nailed the problem on the head... or at least a potential problem. The fact that it was slowly getting worse tells me that the float itself may have a leak in it and is soaking up fuel, thereby making it run richer. Or it is possible that your throttle needle just needs to be replaced... You could just replace the float for good measure. They typically run about $6 — $10.