BF50A3LRTA High Idle speed when warmed up.

[jakedaawg]

So, we have what we believe to be a 2003 BF50A3LRTA. Motor starts and runs fine cold or warmed up. The problem happens after you put it back ito neutral after having run it from a cold start. It idles too high to want to atempt to put it back into gear once the engine is warmed up to normal operating temp.

Nobody has messed with any linkages. All the paint and such marking the placement of the various adjustments are unbroken and still lined up.

The cables appear to be working properly. When it is warmed up and goes into this high idle the cam follower roller is free in the slot of the throttle cam. The throttles are closed.

What I am thinking is that for some reason when warm this engine is advancing the timing. I have not put a timing light on it yet to verify but am pretty certain it is not a carb/fuel issue.

My question are: How does this timing system on these hondas work? I am primarily an evinrude and yamaha tech. This is for a friend. What determines idle timing and how does it work? Am I going to need to hook this up to software that I do not have or is there a mechanical timing advance that I can check? There seems to be some sort of vacuum operated throttle control but it is not activated as far as moveing the cam and hence the throttle plates. I have visually verified that they are all closed at idle both when cold and when warmed up and the issue is occurring.

 

[hondam]

The timing is mechanical set by the knotches in the timing belt Its just like any other, there is a T on the flywheel and a 1 on the cam pulley just line them up with their corresponding indicators. I know that is vague but its fairly obvious when you look at it. The ignition timing is controlled by the sensor under the cam pulley and the CDI unit. It is not adjustable. There is no computer hookup on that engine.

The vacumm throttle control is just a dashpot, its for even deceleration unlikely effecting the idle.

There is one screw on the bottom carb that shouldnt have any paint on it. That is your idle speed adjustment. That engine needs to idle at 950 rpms in nuetral.

 

[jakedaawg]

Thanks for the description. This will help. Do you happen to know what degree the idle ignition timing should be?

 

[MattFL]

I have the same motor, but the 1999 model. The timing is electronic, there is nothing to adjust on the timing.

I think your problem is plugged pilot jets. What happens is the pilots get partially plugged and idle becomes unstable, especially when the motor is cool. Someone will turn the idle speed up to try to fix it. As a result the idle will take off when the motor is warm, but be slow and unstable when the motor is cool. The proper fix is to disassemble and clean the carbs. The quick and dirty fix is remove the intake silencer and blow carb cleaner through the pilot circuit. With the intake silencer removed, there are 2 holes on the top of the intake bell on reach carb. The bottom hole is the air inlet for the pilot circuit. Stick the carb cleaner straw in each one and give it a couple long blasts. Have the motor tilted up a little and the throttle open so the cleaner runs out the carb and not into the motor. When finished, see how it runs. You might have to adjust the idle, which is the screw on the bottom carb as described in the post above.

That should do the trick, but if it doesn't for some reason then check the valve clearance. Overly tight valves can also affect idle.

This is not like your old 2 stroke with a mechanical timing advance, there is nothing to do on the spark timing on these motors.