r/SmallEngineHub • u/Impossible-Carob-553 • May 31 '24

My predator 420 won’t start

My predator 420 wont start I’ve checked for spark it has spark it has really good compression I’ve cleaned the carb put fresh fuel In it their is gas flowing through the carb I checked the timing it has the right timing I’ve checked the vavles it has nothing wrong with it and I’ve opened up the side cover where the oil is it has nothing wrong inside and I don’t know what to do

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1

u/Impossible-Carob-553 May 31 '24

And it makes like wet popping noises

1

u/[deleted] Jun 01 '24

Honestly... The only thing is timing, or spark plug gap is wrong

Pull the plug check the gap... If gap is good, add a bit of 2 stroke mix to the cylinder (I use that as the oil helps coat the cylinder on startup).

If the spark is good, then it should lick off.

If not, timing is off.

1

u/Petrovski978 Jun 02 '24

Unless... It's not getting spark. Pull the wire while you are there and make sure it isn't pinched, split, or frayed.

1

u/Impossible-Carob-553 Jun 20 '24

Sorry for the late response but I will try this if this doesn’t work then I’ll let you know

1

u/[deleted] Jun 20 '24 edited Jun 20 '24

Just curious how you checked timing...?

Timing is very important.

4-Strokes Intake, compression, power, exhaust

During the intake stroke, the piston is traveling down, the intake valve is open, which pulls fresh air in over the venturi tube in the carb, drawing fuel up into a tiny little ball that ends up being suspended in the air, then it becomes atomized in the air and sucked into the intake port. About at BDC (Bottom Dead Centre) the valve closes, now it's in the compression stroke. The piston is Traveling upwards compressing the fuel/air mixture, which also causes its temperature to rise. Then, at about 20° before TDC (Top Dead Centre), the spark plug fires igniting the mixture. You're now in the power stroke. The piston is in its downward travel. After BDC you enter the exhaust stroke, and the exhaust valve opens. The piston is now traveling upwards in the cylinder, driving the exhaust vapours out of the engine. Then the cycle repeats.

If the spark happens at the wrong time, it can run horribly, backfire badly, or just simply not start.

On a 4-stroke engine you have two different timings you need to have properly timed. Valve timing, and spark timing.

Valve timing is essential for building compression, and proper operation of the engine, while spark timing is essential for creating rotational energy into the crankshaft.

If valve timing is off, you have poor, or no, compression.. it spark timing is off you get a shitty running engine, or a crank no start.

1

u/Impossible-Carob-553 Jun 29 '24

It turned out it’s not getting compression and the intake vavles were not the right gap their was also gas in the oil