88 Johson misfire on idle.

[inohv8]

I sent some info last week and got some feedback.. here is some new findings..<br />my 88- 50 horse johnny was completely rebuilt from a scrapper, so I don't know if it ever ran properly., re-done crank,, bored out, new pistons etc.. I took out the VRO unit and replaced it with a regulare fuel pump and mixed fuel, (shouldn't be a problem should it?), the charge coil, either connected to the ign. module or unplugged from the module, reads max 80 volts, the manual says 150 plus.. the resistance reading of 480Kohm are proper but still no proper voltage, It runs very rough, I can't set the timing without it running better.. the timing light does not miss a beat on either of the cyl.. so spark is getting to the (new plugs), gapped at .030. thoughts on voltage being an issue? or is there something else that I am missing? oh yes, the carbs have been done as well.<br />feedback appreciated...

 

[Joe Reeves]

Re: 88 Johson misfire on idle.

Compression should be 100+ psi and even on all cylinders.<br /><br />Spark plugs removed.... spark should jump a 7/16" gap with a strong blue lightning like flame, a real SNAP!<br /><br />Spark plugs should be Champion QL77JC4 plugs, gapped at .040 (not .030).<br /><br />Timing can be set at cranking speed (not running) as follows:<br /><br />(Timing At Cranking Speed 4°)<br />(J. Reeves)<br />The full spark advance can be adjusted without have the engine running at near full throttle as follows. <br /><br />To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary). <br /><br />Rig a spark tester and have the gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4° less than what the engine calls for. <br /><br />I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28°, set the timing at 24°. The reasoning for the 4° difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4°. <br /><br />If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4° which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place. <br /><br />No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting. <br /><br />Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes.

 

[inohv8]

Re: 88 Johson misfire on idle.

very valuable info many thanks.. however what about the voltage output of 70 volts compared to 150 according to the manual? I will put it all back together and re-check spark with eye rather than timing light..