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2006 BF90A Cylinder Problem

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burch1975

New member
First time needing some help with a problem with my Honda. I have a 2006 BF90A. I was having what I thought might be fuel problems. But now I am stumped due to the following:

Motor is not running on all 4 cylinders. At first it was 2 and 3 not working and thought maybe a coil. But then it jumped to 2 and 4 not working. Then it went to 1 and 3 not working. I am thinking this must be electrical but I am not sure as to where to start checking.

Any help would be greatly appreciated.

Thanks!
 
Not sure how you checked to see what cylinders are failing...but....

As the motor is idling, do a cylinder drop test. Pull the spark plug wires off, one at a time (with an insulated pliers) and see if the rpms of the engine reduces. If it does, then that cylinder is firing. If it does not, hold the spark plug cap close to the spark plug and listen for the tick, tick, tick of the spark. If it is ticking, then you most likely are getting spark.

If your cylinders are firing or getting spark, then remove the choke linkage (part #17) http://www.boats.net/parts/search/Honda/Outboard%20Engine/2006/BF90A6%20LRTA%20/CARBURETOR/parts.html. Then manually close the choke on the cylinders that are not firing one at a time. If that cylinder picks up, then it is a fuel problem.

Drain a couple of your carburetors into a glass jar and see if there is any water in your fuel.

Also, be sure that you have good spark plugs....NGK DR7EA ...do not use anything else.

That should give you a start. Once you figure out if it is spark or fuel, then you can go from there.

By the way, if the coil is bad, you will have 1 and 3 fail or 2 and 4 fail in that combination, unless there is an internal short to ground (which seldom happens).

Mike
 
Mike,

I will give you a full update of what we have done so far to reach where we are:

Drained all fuel and put in 91 octane today. Also changed out fuel filter and tested the fuel pumps (by pushing in the bar to make sure it is staying hard as well as checking for leaks on all fuel lines). Changed out line from motor to tank and replaced bulb. Changed out all spark plugs (with NGK DR7EA) and tested compression for them. Took apart carbs and did rebuild replacing the following:
11-16010-ZV4-005 : GASKET SET
11-16011-ZV4-005 : VALVE SET, FLOAT
11-16221-ZW1-000 : GASKET, CARBURETOR
11-17384-ZW1-000 : GSKT, MUFFLER PLATE
11-17151-ZW1-000 : GASKET, IN. MANIFOLD
All other parts were fine and we couldn't see any dirt but did do a full cleaning. Put all back together with specs from manual and still having changing problems.

We have tested the spark plugs with the motor idling by pulling wire and to see if engine rpms reduces and checking for spark. This is where it has me stumped. At first it was the #1 and #2 carb not reducing the engine rpms. So we tried opening up the air fuel mixture screw (from the standard 2 1/4 turns) and could hear it kick in that cylinder. So we tested the plug for that cylinder and it was firing and then reduced rpms when we pulled the wire. So we thought after replacing all of the fuel things that we would take it out for a drive to see if it might be in the last carb not firing. But after about 5 minutes of driving we noticed a loss of speed so we stopped the boat and opened the cover to now find that the 1 and 4 carbs are not firing and rpms remained the same when we pulled off the plug wire. So we decided to go back to the drawing board. But before we took it back out of the water we decided to check the plugs for rpm loss again and found that 2 and 4 are now not firing but 1 and 3 are.

Any suggestions would be greatly appreciated. I am about done guessing and coming up empty handed. But on the plus side I do have some extra parts for future use now.

Thanks again for your reply,

Jason
 
Try removing the choke linkage, like I suggested, and manually operating the choke on the failing cylinder. If that cylinder kicks in, you have proven it is fuel and not spark.

You did not say that you changed out the jet set Part #18 http://www.boats.net/parts/search/Honda/Outboard%20Engine/2006/BF90A6%20LRTA%20/CARBURETOR/parts.html

They clog easily and are the path of fuel for idle. They also, sometimes development very small cracks in them.
If clogged, they are almost impossible to get cleaned thoroughly, due to their internal construction. They also are easily clogged if the internal pieces of the fuel lines come loose.

So, if you find that it is a fuel issue, it is time to pull the carbs again and carefully see where it is clogged. If you find black debris and you can get all passages flowing, then change the fuel lines on the engine at least to the filter. Changing those from the filter to the fuel tank would be good to do, but at least do it to the filter.

Also, check to be sure that the small pin holes at the top of the carb throat pass fuel properly. There are three sets, varying from one hole to a set of 3 or 4 (can not remember the exact number). The three sets provide fuel to the cylinder for idle then transition to midrange. If you have the idle mixture screw partially screwed in, take some brake clean and stick its straw up through the hole where the jet set seats in the top of the carb. When you spray the brake clean, it should come out of the pin holes in a smooth stream. If not, the passage or holes are partially or completely clogged. You may have to stick some very small pieces of wire in the holes and shoot with compressed air to clean out. Do not put the carbs back together until you get those holes to flow. The carb will not work right if you do not.

Mike
 
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