Logo
FULL SITE MENU

93 honda 9.9 fouling plugs

M

mewillia1

New member
replaced the carb as well as the ignition coil (which tested bad). the compression is 120 and 125 psi on the cylinders. new plugs will run good for a couple of outings. then it wont start and the plugs are black. Has anyone had similar problems?
 
Last edited:
Compression should be 156 plus/minus 14.....with throttle plate open on the carburetor. You will have to hold the throttle plate open at the carburetor.

Three things come to mind...

1. Oil could be too high. Should be 1/4 below the full mark.

2. Thermostat stuck open and engine is running cold.

3. Could have jumped time by one notch.

And some questions....

Did you replace the carb with a carb for a 9.9?

Are you doing a lot a idling?

Are the spark plugs ....NGK DR5HS?

Are you using synthetic oil?

As usual, more questions than answers.

Mike
 
Thanks Mike,

I didn't hold the throttle plate open when doing the compression test.
I'm not running synthetic oil and the level may be too high.
thermostat hasn't been addressed
I replaced the carb with a 9.9 from boats.net. The parts description claims that it came with the standard main jet #102
I am running NGK DR5HS plugs
I do idle alot to warm up because she tends to flood if i go into gear too soon. I think the idle is set pretty high.
I'm not sure about the timing, I'll read up on that and you've given me some other things to try as well.

Thanks again

Mark
 
ohm tested the CDI unit, suspecting that the spark was weak. I don't have the meter that is called for in the book and got some strange readings. When I reinstalled the CDI unit, no spark at all! I ordered a new CDI unit and the motor cranks right up every time! I have read that a CDI unit is either good or bad, no in between, but I have to differ! I struggled with this flooding issue/fouled plugs for several seasons but motor ran great as long as it would start. I tried every thing else to no avail. incidentally, the book specs for the coil ohm test are around .4 across the low side and around 8 across the high side. The low side tested good but the high side tested at 28 ohms on both old and new coils. They both work!

Mark
 
Back
Top