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90 120hp Johnson idle awry

T

terry

Member
" Started motor on hose today.

" Started motor on hose today...last time run was last week in last week in Feb. when it ran fine.
Started right up as usual but idled very high, between 1800 and 2200 rpms. It would miss about every 2 seconds where it would go from 2200 to 1800rpms. Took plugs out they all looked somewhat like it was running lean. Upon further inspection I found a fuel leak in the vro oil intake, which I have plugged off...I like to premix the fuel. I will find another cap, and fix the leak...thus to my question...will that cause this eratic idle situation? It was very small leak, I only noticed it when I touched the plug when inspecting the filter and fuel lines. I assume now that I uncapped the fitting on the vro it will only drain the carbs. I put a hose on it to keep the raw fuel contained. Thanks for whatever information you can share... "
 
"Terry.... First, check the ob

"Terry.... First, check the obvious such as: Is the timer plate stuck in the advance position under the flywheel (not likely). Is the throttle cable out of adjustment for some reason. Always a good idea (regardless of whatever problem) to check the compression and ignition (spark) first also.

You say that you like to pre-mix the fuel (50/1 mixture in the tank), but you don't say that you have the oil side of the VRO plugged off whereas you would be using the VRO strictly as a fuel pump only. But at any rate, a air/fuel leak could have an effect on the idle, but usually it is due to slightly clogged jets that result in a slightly lean mixture.

You may have had experience with the older single carb engines whereas one would disconnect the fuel line to run the carb out of fuel..... and as the carb ran towards the dry/lean side, the rpms increased.

At the beginning of your message, you stated
"last time run was last week in last week in Feb".
I assume that was a typo, but was it supposed to read "last time run was last week in Feb". or was it to be "last time run was last year in last week in Feb".

I've never seen a carb foul/clog between the last week of the previous month (a two week span), but if the span of time was a few months or more, I'd strongly suspect that the carbs are slightly fouled, resulting in a slightly lean mixture (fuel/air, not fuel/oil) which would cause the increase in rpms and the spitting back (slight backfire effect) that you mention.

That engine has four carbs. Remove the carburetor face plate, Remove the brass screw you'll see at the lower front of the carburetor float chambers (have a rag ready to catch the fuel that will escape). If the back of any of those screws are fouled, gummed, etc, that's a fairly good indication that that the carb(s) are fouled.

This may not be the cause of your problem, but it where I would look first. Keep us informed.

Joe
"
 
"Terry.... I meant to mention

"Terry.... I meant to mention that many of the later model engines have the "Fast Start" feature. This will cause the engine to have an high idle rpm until the engine reaches a normal operating range. Should the engine (for some reason) run unusally cold, the rpms will stay higher than normal. I believe that your engine has this feature.... check your owners manual.

Joe
"
 
" Joe...I last ran the motor a

" Joe...I last ran the motor about a month ago with fresh gas...same fuel, but it smells ok. Spark, control cable and, timer base were ok...did not check compression. The only problem I found was that fuel was leaking out of the plug I put in the oil pickup line from the vro. I replaced but havn't started yet,no time. Yes this motor does have quick start, which is likely that I did not run long enough to deactivate...will try again and if problem persists I suspect carbs will be the next place I go...Thanks Joe "
 
Joe..I did as you suggested a

Joe..I did as you suggested and checked under the brass screws in the carbs...free and clear. Hose and bulb are good. I'm still having the problem...maybe I should take it to the boat ramp and start it on the trailer. Any other suggestions? Thanks
 
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