Question about Motorcycles
Hi, Mark, you need to repost your question under the Yamaha F40 outboard category, not Motorcycles. Thanks, Gregg
Posted on Aug 06, 2020
The carbs need to be cleaned.There is a high speed jet in the carb that is more than likely stopped up. Jim OMC retired mech.
Posted on Jul 07, 2009
Since there is no background to this, I assume at some point in time, the motor ran ok for you...
The first thing to do is to drain one of your carburators into a glass jar to check for water. If there is water, you will see it separate from the fuel in a couple of minutes. The water is on the bottom. If there is water, you will need to flush the motor with good fuel, one carburator at a time and probably will have to pump your tank.
If there is no water, the easiest thing to try is the following...when the motor starts to bog down, activate the choke. (If you have a side mount box that activates the choke when the fast idle lever is all the way up), you will have to have someone go back to the engine and manually pull the choke lever out. If the motor picks up, the motor is most likely in need of a carb job.
You can then do a cylinder drop test while motor is idleing, momentarily pulling the spark plug wires off of the spark plugs one at a time. If you pull one off and the engine speed does not change, listen for spark at the spark plug connector to the engine. If you hear the clicking of spark spark is probably ok. The issue with that cylinder is probably fuel related...probably a clogged carburator. If one carb is not functioning correctly, they all probably need some work. If you are not into mechanical stuff, you should have a dealer do the work. After the carbs are cleaned, they need to be adjusted for proper idle and idle/air mixture as well as vacuum balanced . If you are going to attempt it yourself be sure to by a manual either from Honda or one after market.
Before the carb job, a good dealer will always do at least a compression and spark check to be sure there is not an internal issue. The spark plugs should be checked at this time and changed out if they look questionable. Only use NGK DR7EA spark plugs not a substitute.
Also, check your oil and be sure it is clean and at the proper level.
There are several other things that it can be, but this is the most common.
Posted on Aug 10, 2009
You need to pull the cover and track where the trottle cable goes to on the motor. If you have someone open and close the throttle while you're watching you will find the linkage that it controls. There should be some kind of an idle ajustment screw there that you can readjust to increase your idle.
Posted on Oct 18, 2009
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