Yamaha 40Q Carb. adjustments

[ogspiller]

I have a cleaned the fuel system from tank to fuel filter however, at mid range I get a sputter and almost backfire. I put new spark plugs and after running for only a few mintues (using flush kit) the number one plug was fouled a little, the number two fouled a good bit and the third none at all. I believe the carbs need setting but I have no clue how to do this. I also pulled the carbs and cleaned then. I have fresh gas however I've not put in new oil. (oil injected) When I cleaned the carbs the brass vent to the side of the adjustment screw was clogged. (the number three crab.) The adjustment may not be the problem are my only problem so I accept any and all help I can get.<br /><br />Thanks<br />Glenn Spiller

 

[jim dozier]

Re: Yamaha 40Q Carb. adjustments

Exactly what did you do to the carbs when you worked on them.

 

[ogspiller]

Re: Yamaha 40Q Carb. adjustments

I removed the top and bottom plates and cleaned the bowls and floats. I sprayed carb cleaner in any port hole I saw. The motor ran the same afterwards as it did before.

 

[jim dozier]

Re: Yamaha 40Q Carb. adjustments

Get a manual.<br /><br />You need to remove the jets and clean them thoroughly with solvent (remove all non metal parts and soak overnite) and then blow them out with compressed air. You need to clean both the main which probably is sticking down into the bowl and the idle circuit. You should have removed the idle mixture screw. Install new float valve and reset float adjustment then reset idle mixture adjustment. It sounds from your description like you are running lean on take off from idle. Also, check for air leaks, especially at hose connectors like the one that connects the fuel line to the engine.<br /><br />The idle mixture should be set to 1 1/2 turns out from lightly seating unless the book says different. Set the idle speed to recommended rpm, probably ~700rpm. Then adjust 1 carb at a time to optimum idle + 1/8 turn. Reset idle speed if necessary between carbs. You may have to repeat another round.<br /><br />Your manual will tell you how to synchronize timing and carb.

 

[ogspiller]

Re: Yamaha 40Q Carb. adjustments

Captain #18514<br />Thanks for your help I'm almost there. I've ordered the parts and looking for a manual. Know where I might pick up a used one? <br />I did reclean the carb's as you advised and did some adjustments and she is running great, thanks to you. Hope you don't mind if I call on you again. Any other advise you my have would be great. <br />Sorry about not getting back to you sooner but I couldn't login. Today I thought I would try again and bam up she pops.<br /><br />Glenn Spiller