BF90 Honda rough idle problem

[cjerzak]

I have a 1999 BF 90 with a rough idle. Here are the symtoms:<br /><br />1. Idles at about 950 RPM very rough. It will cough(backfire)Once in a while. <br />2. After running hard for a while it will run better but not good enough to stay running. <br />3. After I get it past Idle there is full power as far as I can tell.<br /><br />Here are the things I have tried:<br /><br />1. Changed fuel, complete fuel line, fuel filter, and spark plugs.<br /><br />2. I adjusted the valve clearance, which was very little. <br /><br />3. I then syncronized the carbeurators. This engine has 4 carbs, one for each cylinder. It helped but I think it should be better. <br /><br />4. As a last resort I tried SeaFoam carb cleaner to see if my carbs were plugged. I have not noticed any help.<br /><br /><br />After all I have done I have noticed that the primer bulb does not stay hard like I am used to on a two stroke motor. Is this normal? However, when I pump it up it doesn't seem to make a difference. With a carb float it shouldn't matter, right? Could it be the Fuel pumps?<br /><br />Do you guys know of a good parts supplier for Honda motors? I have a hard time finding parts.<br /><br />Thanks in advance

 

[MajBach]

Re: BF90 Honda rough idle problem

Two things:<br />I have the same motor and have not yet experieced your symptoms. However, I have noticed that after running a good 15 minutes or more at cruise, the idle seems to not be as 'steady'-like the carbs are out of sync; it seems to correct itself after several minutes.<br />Anyway... have you checked the service bulletins (TSB) for this motor? There are several for 1999.<br />One has to do with the flat brass looking thingy - looks like a diaphram would be inside(I forget the actual part name). This part is faulty and will cause the motor to die under quick acceleration. I don't know if it affect the idle. However, there is a recall on a wire mesh inside the intake manifold. It can fall apart and become trapped in the carbs. It is replaced with a coarser mesh. Perhaps this is the problem.<br />I assume you have checked the idle screw. Have you also ascertained that the fuel line is oriented in the correct direction? I believe it is possible to hook it up backwards.<br />When you changed the fuel line, did you also change the fittings? PErhaps the O-ring is gone on one of them. I know with mine, if i build up pressure with the bulb, it takes only the slightest jiggle (or wave) on the fitting that attaches to the motor to cause fuel to spray out.<br /><br />By the way, there are also TSBs for the gaskets and O-rings on the lower end. Have you had any water seepage into the gearcase?