2nd cylinder has spark but no change when plug wire is pulled

jhotch

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Jul 4, 2020
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Motor idles well and runs fine until 2000 rpm and then starts surging after 15-20 seconds. Redid entire fuel system. Set linkage as per manual. Jumps right up onto plane and then starts surging. Today I started investigating ignition. Idle timing is at 4 atdc . All plugs had good spark. Dropped each cylinder in idle and the second cylinder had no change, in fact if anything it ran a little better. Changed the plugs between middle and bottom cylinder and the middle cylinder still did not change idle when pulled. Any ideas?
 

jhotch

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Model is J70tlesb I checked the compression when we started working on it last month 120, 118 , 121
 

boobie

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Squirt some fuel in that cylinder that is dead and see what happens.
 

jhotch

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Boobie, Where would I squirt the fuel in? into the carb or directly into the cylinder through the spark plug hole?
 

jhotch

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Jul 4, 2020
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Find out anything ???

Thanks for checking in. Planning on working on it tomorrow and will post results. Here’s my plan of attack
pump primer bulb to see if it stays hard for 1 minute




gap all spark plugs




compression test




clean carb of # 2 cylinder




squirt fuel into second carb




switch coils




switch wires




test powerpack
 

racerone

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Dec 28, 2013
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Once the primer bulb has been used to fill the carburetors it does NOT need to stay hard.
 

jhotch

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Jul 4, 2020
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Ok. compression was good and equal, spark was good on all cylinders. Switched the coils betwwe the 2nd and third cylinders and the second cylinder still caused no change when I pulled the plug at idle. Squirted fuel in the second cylindee and the idle immediately smoothed out. Pulled the second carb, cleaned it, checked the float setting. put it all back together and voila. idled great on muffs in the driveway. I took it to the lake, started and opened it up, ran great for about 2 minutes and then started surging again at about 3500 rpms. I think I’ll pill the othwr 2 carbs and give them a once over and then redo the linkage. Thoughts?
oh also Timing at idle on muffs in the driveway was 4 btdc
 

jhotch

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Jul 4, 2020
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Now I’m thinking I am going to test the coils resistance and focus on getting the timing back to spec at 4 ATDC .
 

jhotch

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Jul 4, 2020
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‘90 Johnson 70 2 stroke Bad timing caused by fuel problem?

90 Johnson 70 Would one carb not working when I adjusted the linkage be the cause of having my Idle screw all the way in and subsequently the timing advanced from the spec 4atdc to 4 btdc?
 

GA_Boater

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Please don't start another thread about the same problem or you get asked all the same questions again.

In answer to your question - No.
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
36,047
Fact-----You adjust / set maximum timing advance only.-------Idle timing is where the throttle plates start to open !!!----Where timing is when engines idles properly does not matter and looks after itself.
 
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