on 1 cylander sometimes

[ace420ace]

Hi all i recently bought a 1981 johnson 15 hp, it runs good intermittantly i am pretty sure one cylander is working than quitting seems to run better cold, i just did a decarb and put new plugs was running good on both cylanders for 15 min, then bog down to 1 after some hesitation got it back to two off and on, checked new plugs after 15 min and both were white/tan. too lean but gas is mixed 50 to 1, carb just rebuilt, idles fine problems come at wot or close. any info greatly appreciated.
thx

 

[ace420ace]

could this be caused by float height?

 

[ace420ace]

and does richening the slow speed adjust knob affect half throttle or wide open?

 

[racerone]

Run with a timing light and observe behaviour of spark.---Test each cylinder to full throttle on the lake.

 

[kbait]

Check coils/plug wires for arcing (easier at night). Also, check the bundle of wires coming from under the flywheel for cracked/frayed - especially where they flex due to armature plate movement w/throttle. Check both cd box plugs (pull apart and make sure the pins are in place correctly and not corroded. Make sure coil grounds are both clean/tight.

Good luck and welcome aboard!

 

[ace420ace]

ok will check for arcing i looked at all wires looked good, not sure what a timing light is,if electrical what cause to run lean? also before decarb went to full throttle and died after rinning wot for a min like wasnt getting fuel but hasnt done lately its seems like second cylander is sputtering trying to work at half throttle. thanks

 

[ace420ace]

there is also a red wire that is not doing anything it just loose, i figure was for electric start.

 

[ace420ace]

ok I have a timing light and was told how to use but is it ok to hook up to a 12 volt battery or do u have to hook to motor to get power? I checked the spark with spark tester both jump 7 16. thanks

 

[ace420ace]

ok guys I took it out on the lake tonight with a timing light spark is normal on both from idle until half throttle from half to wot bottom cylinder missing and spark erratic as well. the bottom cylander kicked in a few times but when slowed down and went to speed up again it was erratic again. also the bottom plug was wet top good. is this a coil problem?

 

[ace420ace]

maybe i blew a piston and its pieces of rings? can a plug melt?