1997 Honda BF75AT Carb Flooding

[USAF Montauk]

I just cleaned (three times) and put new o-rings and gaskets in the carbs of my 1997 Honda 75 four stroke. I didn't notice any leaks in the floats or bad needle valves/seats and the floats are free moving. At high rpm the motor is fine but coming off high rpm and back to idle the carbs start leaking fuel out of the vents. the only thing I haven't done is replace the fuel pumps. can anyone help me figure this out, i am stumped.

 

[Flakeys]

Re: 1997 Honda BF75AT Carb Flooding

I have a Honda carburetion manual and in the troubleshooting section for the BF75 engine (7.5 HP) which I assume is your engine, under the flooding causes as you have, it says the following:

1. Varnish on float valve and/or float valve seat, and 2. Worn float valve tip. The correctives for each in order are: 1. Clean or replace float valve, 2. Replace float valve and adjust float level.

Float level on carb is 9.85-10.15mm and mixture screw adjusted to the highest rpm at 1200 +/- 100 at idle.

IF you have the 75HP engine, I can give you the information for that engine also.
Hope some of this helps.

 

[USAF Montauk]

Re: 1997 Honda BF75AT Carb Flooding

Thanks. I do have a 75 HP motor. What can you tell me about that?

 

[Flakeys]

Re: 1997 Honda BF75AT Carb Flooding

Are all 3 of your carbs flooding out through the vent holes or just one of them? Here's the specs for the 75HP engine: Causes, 1. Worn float pin bores in carb body. Fix is replace the carb. 2. Varnish on float valve and/or float valve seat. Fix is Clean or replace float valve. Clean and polish float valve seat bore. 3. Worn float valve tip. Fix is replace float valve and adjust float level.

There are 2 vents in each carb also. The float height on the carbs is 11.5mm and the mixture screw adjustment is 1-7/8 turns out. Idle speed 950 +/- 50 rpm.

The last item you need to deal with is the synchronization of the 3 carbs after they are reinstalled on the engine. You need a special set of gages and a tach to properly do this, so no one carb will be hogging more or less load as the 3 work together through the various speed ranges. You may have to have that done by a dealer or someone that can do it properly.

 

[USAF Montauk]

Re: 1997 Honda BF75AT Carb Flooding

unfortunately i have four carbs. i guess i am going to order four needle valves today and polish the needle valve seats and see what happens. the engine is a 97 but it only has 70 hours on it so i am hoping the pivot pin bores are fine. thannks for the reply, i will let you know as soon as i find out what happens.

 

[Flakeys]

Re: 1997 Honda BF75AT Carb Flooding

I forgot the 75 hp is like the 90 hp with 4 carbs.

 

[USAF Montauk]

Re: 1997 Honda BF75AT Carb Flooding

I cleaned the carbs again! Polished the valve seats and valves and checked float leveles. They looked good. Put it all back on and the #2 carb is still leaking when I pump the bulb. AHHHH. I have brand new needle valves coming tomorrow and I hope that they might fix it, if not I dont know what is going on.

 

[Flakeys]

Re: 1997 Honda BF75AT Carb Flooding

Are you sure the float is set properly on that carb? Other than the float valve, i can't think of anything else that would cause it to overfill and spill out a vent.