1988 Johnson 120 hp idles to high and misfires

[ermess]

1988 Johnson 120hp Idles to high and misfires. Checked compression, spark, idexed flywheel, checked idle timing, - what should idle timing be on this motor? Is this a carb issue?
Thanks
Ed

 

[HighTrim]

Re: 1988 Johnson 120 hp idles to high and misfires

Get yourself a spray bottle and put some premix in it. Throttle the engine up to the point where it starts runnin' ragged and then give the carb a little shot of the premix. If the engine smooths out and runs like it should for a few seconds, you've got a fuel problem. If it floods out immediately, the problem is probably an ignition breakdown. My bet is you have a partially plugged orfice in the carburetor. Do the deal with the spray bottle and post back (on this posting, not a new one) and tell us what ya found out

Also might wanna run some carbon cleaner thru it. Then change the plugs. I doubt it is a fuel delivery problem, but maybe.The timing may be out. A reed may be staying open too long. It may be a bad plug wire (best detected visually on a dark night--look for arcing)...But do the cheap stuff first.

Also, check the fuel pump filter.When idling ruff, try a shot of WD40 in the carb to see if it picks-up slightly.At least this may help you determine which carb is giving you grief.

 

[ermess]

Re: 1988 Johnson 120 hp idles to high and misfires

HighTrim thanks for the reply, also failed to mention - fuel bulb will not get hard. Any idea what timing should be on this motor, customer had the screw backed out so it was reading 20 degrees, I backed timing screw in so it was about 4 degrees.
Thanks
Ed

 

[hoeser]

Re: 1988 Johnson 120 hp idles to high and misfires

Something in my brain is saying 8 degrees. I am probably wrong though. 20 degrees is way excessive.

 

[reeldutch]

Re: 1988 Johnson 120 hp idles to high and misfires

idle timing is 8*

max spark advance 18*

if you have a bulp thats not getting hard and your motor has faster idle and coughs.
chanses are there is a air leak in your fuelsystem.
or float stuck open.
check for leaking fuel somewere.
get a vacuum gauge and a clear vinyl hose.
put the ose between the carbs and the fuel pump and t in the gauge there to.

if there are any bubles pressant and you have high vacuum that means there is an opstruction.

if there are any bubles presant and there is a low vacuum you have air leaking in the system.

did you unplug the vro system?

my guess is you have an airleak between your primer bulp and your fueltank.

 

[ermess]

Re: 1988 Johnson 120 hp idles to high and misfires

Someone had already bypassed the oil on the VRO with a short piece of hose and a screw clamped to the end of it. When engine is running I can see air bubbles coming from this hose thru a clear plastic fitting?
Don't you just love these South Texas modifications!
Thanks
Ed

 

[reeldutch]

Re: 1988 Johnson 120 hp idles to high and misfires

so make shure thast the oilside is capt of airtight.
it will blent the air in the gas from the oilside.


still your bulp should be getting hard .

could be the checkvalve inside the bulp is bad or airleaking in and out.
make shure your needles are closed.


im just giving you suggestions to look at.

the looper should easily idle at 1000rpm on mufs in the driveway or at 900rpm
in the water it should idle 600/700 rpm in gear.

 

[Walker]

Re: 1988 Johnson 120 hp idles to high and misfires

Idle timing for your motor should be 8*ATDC