I have a 1993 vj40tletf that has been a work in progress. I finally had it running at full RPMs end of last season after dialing in prop pitch and changing out my ignition coil. It's always had a very hard start unless I raise the throttle (in neutral) to at least 1/2. Doesn't like to idle very long (without stalling) without raising the throttle, but I've been told this is common for 2 strokes. Tends to cut out sometimes when shifting from forward to reverse (navigating to the boat launch). Biggest issue: This year it has been progressively losing rpm at WOT, to where I'm now at about 2600rpm (from 5000 beginning of the season). It will rev to full RPM in neutral, but from what I've read this doesn't really mean anything since it could be running on 1 out of 2 cylinders and still get full rpm in neutral...
What I've checked so far:
Fuel system was losing prime, so I've replaced all fuel lines, filters, pickup, and primer bulb. Pumping fuel bulb during low rpm condition does nothing.
Rebuilt both carbs, no change
Pushing in enrichment (choke) button changes nothing
Replaced plugs and wires with proper champions and sierra wires
Performed throttle sync and linkage adjustments
Set proper timing at idle, timing light loses signal at higher rpm
which had me check spark gap...
With my spark tester, it did produce a 7/16" spark on both cylinders, but at varying strength. How strong looking is a good spark?
Video of spark test, harder to see on video than in person but it's the best I got...
https://youtu.be/ii3VrCsaBzg
The spark seemed to come in and out, could this be an indicator of something deeper in the ignition such as the power pack or timing base? I've read the timing base can specifically cause this type of issue, and that may explain my timing light losing signal on either ignition wire at elevated rpm.
Is there an easy way to test these components since they are under the flywheel?
I've also read of a pinhole in the vro fuel pump diaphragm causing problems like this, I purchased a rebuild kit but haven't dug into it yet.
If anyone has any insight on where to go next, I would really appreciate the help.
What I've checked so far:
Fuel system was losing prime, so I've replaced all fuel lines, filters, pickup, and primer bulb. Pumping fuel bulb during low rpm condition does nothing.
Rebuilt both carbs, no change
Pushing in enrichment (choke) button changes nothing
Replaced plugs and wires with proper champions and sierra wires
Performed throttle sync and linkage adjustments
Set proper timing at idle, timing light loses signal at higher rpm
which had me check spark gap...
With my spark tester, it did produce a 7/16" spark on both cylinders, but at varying strength. How strong looking is a good spark?
Video of spark test, harder to see on video than in person but it's the best I got...
https://youtu.be/ii3VrCsaBzg
The spark seemed to come in and out, could this be an indicator of something deeper in the ignition such as the power pack or timing base? I've read the timing base can specifically cause this type of issue, and that may explain my timing light losing signal on either ignition wire at elevated rpm.
Is there an easy way to test these components since they are under the flywheel?
I've also read of a pinhole in the vro fuel pump diaphragm causing problems like this, I purchased a rebuild kit but haven't dug into it yet.
If anyone has any insight on where to go next, I would really appreciate the help.