slight carb issue

[hurleyt]

I have a 93 Yamaha 30 HP very low hours. It starts right up idles ok while warming up, goes in gear fine runs very well. The problem I have is after I run it for say 10 minutes or so and return to slow (no wake speed) it is bogging down some, and I have to give it a little throttle to keep it from stalling. Also when I do gradually throttle up to go it bogs slightly and then instantaneously takes off when I get to the transition spot from the low speed jets to the main jets (say 1/4 throttle) I'm thinking I need to maybe adjust the pilot screws (3 carbs) some but am not sure how to go about it. They are at the factory settings now. The carbs were removed and cleaned about a month ago. Of course if you think I'm off base please let me know, you won't hurt my feelings! Any advice would be appreciated. Thanks

[hanksvilleman]

It sounds like you are running a little rich if it runs good when cold and then wants to die after warmed. With the set screws what you might want to try is turning them all the way in one at a time until they lightly seat and then back them out 3/4 turn each. I'm not sure if that is factory setting, but your motor should run with them set there. Then, run the motor until warm. If you have the same problem back each screw out another 1/4 turn each. Do that until you get idle. Then have fun trying to fine tune it.
What you can do is buy a carb vacume kit (usually motorcycle used) for around $75 and fine tune with the vacume and that is usually very accurate.
Also, Have you done a compression check? That might cause your problems also.
Hope that helps,
Dave

[hurleyt]

Thanks for the info Dave. I agree I think I'm running a little rich. Do you know which way to turn screws to lean? I think its in but wanted to make sure. I believe I'm only a slight adjustment away from fixing the problem. Also I like the vacuum idea, just not sure where I would pick up a vacuum source. Once I figure that out I assume you adjust each carb until you get max vacuum at idle, correct?

Thanks again Dave
Tom