New 23 Hp Vanguard - Check Timing w/light?

Is there any way to check the timing of a 23.0 Hp Vanguard model 386447-3079-G1 engine using a 12V powered timing light? I understand the timing can’t be adjusted, but I was hoping the timing could be tested to determine if the flywheel key may be partially sheared.

Last fall I installed the new engine to repower a John Deere 318 Lawn Tractor with 44” mower deck. The engine now has about 7 hours on it, and the tractor has about 1500 hours. Last fall everything ran just fine. It started good, accelerated quickly and had power to spare while under full load.

I noticed over the winter when I was pushing snow it started running rough, seemed to be somewhat lacking in power & top RPM, would occasionally stall out and have to be restarted. I attributed a lot of that to the cold conditions and the “push till you spin out” loads I was moving.

This spring after I put the mower deck back on, it now runs rough, struggles to run above 1/3 to ½ throttle, will only accelerate while SLOWLY advancing the throttle lever to full speed, barely has enough power to move the hydrostatic tractor at creep speed, dies repeatedly, and occasionally backfires up through the carburetor. Even with the engine running at maximum governed speed, it will die when the electric mower clutch is engaged. All of the mower blades & idler bearings seem to be turning freely, so I don’t think that’s the issue.

I have the complete Vanguard OHV Repair Manual, but I am stymied as to what is causing my issue. My in-line neon spark tester shows I have consistent spark on both cylinders at all RPM. I’ve replaced both Champion XC92YC factory sparkplugs with NGK BKR5E-11 (Stk 6953) plugs. I did find one of the factory plugs was black and wet when removed.

I have cleaned the air filter & foam, and the engine performance does not change even with the air filter absent from the engine. When I did the repower last fall, I removed the fuel tank from the frame, and attempted to remove any sediment by turning it upside down & shaking the remaining fuel out of it. I also replaced all fuel lines inside and outside of the Deere tank, and cleaned & re-attached both submerged fuel pickups inside the tank.

I’m willing to try any suggestions from the group, but I’m leaning toward the possibility of a partially sheared flywheel key. Again -> Is there any way to test the timing of the engine using a timing light? Unless someone has a better idea, the only way I can see to inspect the flywheel key (in this application) is by completely removing the engine from the tractor frame; approximately an all-day project for the out & in.

It’s not something I’m looking forward to doing AGAIN and I’m too cheap to pay someone else to do it, but if you say I have to........!

No way to check timing with light because there is no reference marks to compare it to. Without knowing the exact moment the spark plug is suppose to fire and be able to measure that and mark it for reference there is no way to know. Sheared flywheel keys on rider engines are rare because they are not subject to the high impact loads like push mower engines.

I would say you could have a carb issue and possibly running rich, One cylinder not firing due to dropped push rod, or plug not firing under compression.

ILENGINE - thanks for your reply & suggestions!

Your suggestion/observation the engine was running rich on one cylinder proved correct. After finding a good video at YouTube on how to remove a Welsch Plug, I discovered one of the Idle Mixture Screws was approximately 0.75 turns from fully seated, while the other was 1.50+ turns from fully seated. Of course the screw that was open further was the side I was having firing and fouled plug issues.

Once I corrected the settings, performance has improved enough that I could get my lawn mowed!

I do have an additional question regarding the correct Idle Mixture Screw setting, but I'll start another thread so it will be easier for others to find & follow.

By the way, the YouTube video on removing the Welsch Plug is - https://www.bing.com/videos/search?...67B8E53402A41B67D51067B8E53402A41B6&FORM=VIRE

You can set a TDC mark with a little work. If you can get a dial indicator extension down the spark plug hole (better yet with the head off. Rotate the piston before TDC and mark, after TDC and mark. Half way is TDC, then paint mark . This is an old hot rod trick familiar to many. We have discussed timing here before. since the 4 strokers "run at fast idle" most agree there is no advance curve unlike the 2 stroker trimmers etc running to 7000 rpm. The later ones have a "solid state" curve built into the "shoe" of the coil magnet givng up to 20 degrees advance, I believe. (corrections please , you pros)

Once I did check timing on my old Intek V with a 12v auto timing light. The spark is very weak compared to car output, but in a darkened garage I did see an orange pulse. The engine must be turning over at starter speed.