Yamaha 150 Carburetors

[edgutgesell]

I have a 1985 150 Yamaha V6 (150 ETLK). It has been running lousy since going to ethanol fuel. I decided to pull the carbs to clean them. As suspected, there was alot of crud in the float chambers. I soaked the three carbs overnite and then blew out the circuits with compressed air. Reinstalled the carbs and the engine seems to be running much better.<br /><br />My question is:<br /><br />I have two manuals for my engine. One is the Yamaha factory manual and the other is a Sealoc manual. For the initial setting of the air adjusting screws in the Yamaha manual for my model carb (Takei), the adjustment is 1 1/4 turns out from fully seated. The Sealoc manual says that the air adjusting screws should be 1 1/2 turns out from fully seated. One of the manuals and I am not sure which, said that these air adjusting screws are not to be adjusted and the 1 1/4 or 1 1/2 turns out are the final setting, no tweaking. I set my carbs to 1 1/2 turns out from seated because I didn't want to set the carbs to run too lean. Even though my engine seems to be running better, it seems to be burning more fuel than before the carb cleaning. Can you tweak the air adjustment? Is the turns out from fully seated the absolute setting?? Turning the screws in leans the mixture, right? I would like to believe the factory manual however I have found some mistakes in several areas of the factory manual. In some cases the same mistakes appear in the Sealoc manual. Who do I believe for these carb air adjusting screw settings? I have a tendency to believe Ray N. or Rodbolt before believing these manuals!!!

 

[rodbolt]

Re: Yamaha 150 Carburetors

the air valve setting is a start point. occasionally I will be 1/8-1/2 turn from specs. on that carb I believe the air fuel is mixed by the idle fuel jet and the pilot air jet. all that screw does is allow more or less of the mix into the intake track. but its old enough I may be off.<br /> it happens. but if your carbs have a pilot air and a pilot fuel it works as above.

 

[Ray Neudecker]

Re: Yamaha 150 Carburetors

As rodbolt says it is a starting point. 1 1/4 was correct as far as the factory. I go 1 1/4 on those as a rule. The springs have gotten old and you will have to check more often. They will vibrate out of place over time. The adjustment only affects idle. Be sure you got the float levels correct. It was important on those carbs. At that age I hope you replaced the needles and seats.

 

[edgutgesell]

Re: Yamaha 150 Carburetors

Thanks again guys!! I think you have given me the information I needed once again!! My concern was to get the engine running with the correct setting, not too lean, not too rich, particularly not too lean. Don't want to burn pistons!! Needles look good with no visible wear or signs of being tightened down too much causing needle and seat damage. I am going to order new springs asap.

 

[edgutgesell]

Re: Yamaha 150 Carburetors

One more thing. I didn't replace the float needles and seats because I couldn't see any wear on the needle point. Also the float level was right on. If I could not see wear as shown in the manuals, is not replacing the float chamber needle and seat very risky? Carbs seem to be performing OK in metering fuel into the float chambers. Also, I suppose you guys use a tach at the engine to adjust the idle. Will a cheap automobile tach be OK. If not, what should I get to check rpm? The tach on my helm panel is inop. Are there some other tools or process needed to determine the correct idle mixture or is the final tweaking only accomplished by the experienced ears, eyes, and brain?