Sounds like a Full crank Victa 160 motor Norm.
It's probably worth 🔍 Checking the list below just to make sure you haven't missed anything.
Kickback on a 2-stroke engine like the Victa 160cc in your 24" slasher—especially with a vacuum-controlled decompressor and V-belt driven blade plate—typically points to ignition timing or decompression issues. You've already fully retarded the ignition, which is the first and correct step. However, since the engine is still kicking back, here are the most likely causes and solutions:
As we know even a small failure in the vacuum-operated decompressor can cause excessive compression during cranking, leading to kickback.
Valve operation – it should open during cranking and close as the engine runs.
Carbon build-up or sticking in the valve seat area also the small port that the decomp connects to the combustion chamber can become
blocked with carbon.
I've had a few motors where the exhaust port is restricted with carbon so I usually remove the muffler to check the ports not blocked
if there is a problem with starting or running.If it's blocked you can use a screw driver if your careful to remove the carbon.
Also you can temporarily remove or disable the decompressor and test cranking to see if kickback is reduced.
that will tell you if the port is free or decomp is blocked.
Fully retarded ignition might still be too advanced at low cranking RPMs, especially if:
The flywheel key is partially sheared.
The ignition module (if electronic) is faulty or triggering early.
I've had bad spark plugs that advance the spark.
Check:
Is the belt tension correct?
Any drag on the crankshaft? If the bearings on the blade plate shaft aren't free ,example grass jammed in the rotating assembly then the preloading the crank on start up will cause kick back.
Lean mixture or a bad plug can cause pre-ignition which leads to kickback.
🔍 Check:
Plug heat range – should be cold enough (e.g., NGK B6HS).
Plug gap.
Fuel condition and octane – stale fuel is notorious for causing detonation.
âś… Fix:
New plug with correct gap.
Fresh, high-octane 2-stroke mix .I'd try 98 ron see if it makes a difference on start up.
Another thing I try, just to see what happens is to remove the decomp and put a short plug in the decomp hole as this will
lower the comp slightly.
If this is a full crank motor they don't usually kick back and on the 24 they usually use a high comp head.
Another thing that might effect the kick back is if you chose an earlier motor the crank is heavier and this can help reduce kickback as we know.
Any problem and I like to replace the coil with a good known coil as it saves time if it fixes the problem as a faulty ignition coil can cause kickback on a 2-stroke engine
Cheers
Max.
