Outdoor Power Equipment and Small Engines - 2 Stroke Starting Problem

Hello,

I have a 160 cc 2 stroke Victa lawnmower that has just suddenly become difficult to start. What's happening is that as I'm pull starting the engine it initially spins the right way before suddenly reversing direction as though I'm suddenly pulling against the compression. I have observed this by removing the catcher & watching the baseplate as I pull start the engine. This reversal does not occur if I take the plug out & operate the pull start. I've replaced the decompression diaphragm assembly but this does appear to have made a difference.

Any hints?

Thanks in advance.

Is the blade on and tight?

I replaced the blades (4 of) on the mower. I thought the idea was (& I'm pretty sure it was also noted in the instructions) that the blades should rotate freely once they were tightened.

I spent so much time trying to start the mower, checking spark, fuel, changing the decompression unit etc. that in desperation I actually removed the new blades & tried to start the mover without any blades. The same thing happened - the motor spins the right way before suddenly springing back in the opposite direction.

I see this is an Australian mower and the website isn't very informative but, I'll assume this is similar to the old Jacobsen rotary's with a very heavy hub that has four, short blades attached. Take a look at the flywheel key for shearing. This would retard the ignition timing and give the symptoms you have. In other words, the ignition is firing well before top dead center and trying to kick the engine backwards from the force of the ignition.

Ah, I see the 160cc now. I was thinking of some kind of push-mower engine, lol. I have never hear of that brand, but the flywheel key Puey61 mentioned would be a super place to look.

You're right in that this is an Australian brand motor mower & while I'm not familar with the Jacobsen rotary, it sounds a similar arrangement - 2 stroke mounted on the top of the base driving a horizontal disc with 4 blades mounted on the periphery. I'll have a look at the flywheel key as you suggest on the weekend.

Many thanks from the land downunder!!

The nut holding the blade disc onto the bottom of the mower is most likely loose. When you pull the cord, the engine turns but there is a delay before the blade disc turns. Once the engine encounters resistance and the blade disc turns the timing is stuffed up and the mower misses a beat or turns backwards and rips the cord violently out of your hand. The mower therefore cannot start.
To tighten the nut you need to insert a long 9.5mm diam piece of steel into a slot in the sleeve above the blade disc (to stop the engine from turning). Then you can tighten the nut. I cut the end off an old large screwdriver as I couldn't find an appropriate piece of steel.
(The Victa 2 Stroke does not have a flywheel key.)