OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Powertorque overrevving

Hi guys,

i have a power torque that has me miffed.

The mower has no throttle response (apart from all or nothing) and is over revving.

I have changed all 3 o-rings (2 manifold o-rings and the one under the starter) and its still over revving.

I thought there might be a crack in the carby somewhere drawing air so i replaced the whole carby and that did not solve the issue.

I then thought the governor might be playing up so i unplugged the governor hose from the chassis end and blocked the governor intake to the carby to check if it will make a difference.... no difference!

All i can really think of now is that the bottom seal is shot, but im not sure if it would produce those symptoms. Could the decompressor valve be leaking air into the carby somehow?

HELP!!!! im really out of clues!

You cant just unplug the govenor hose from the back of the carb onto the bottom of the block. Its air pressure vs spring, that governs the high rpm. The air sucks on the diaphragm to pull the poppet in lowering the RPM.

So you can hook a long hose on there and suck and see if that alters RPM.


Air leak.
O-rings on the manifold.
O-ring under the starter.
Theres also an O-ring in the centre of the pull starter.
Bottom crank bearing.

Faulty decomp. Wont shut under suction or diaphragm split letting it suck air through.
Leaking head gasket/warped head.
Rubbed through hose.

You said you swapped the carb so it shouldnt be these.
Crack the the black cover on the carb.
Split in the diaphragm in the carb.
Diaphragm not seated propperly. If they have been like this for ages they can be stretched back out.


To see if the bottom seal/bearing is bad, grab the blade plate and see if its got any movement/slop in it.
If the seal has been leaking look in the side of the block to the top of the flywheel, it will be dirty greasy.

Hi guys,

i have checked through just about everything and im down to the bottom seal. I have managed to remove the lower bearing from the engine assembly but im a litle stuck on how i go about replacing the lower bearing seal......


Im not even sure if the lower bearing is an original one (its made in japan).

How do i go about disassembling the bearing to get to the seal so that it can be replaced?

G'day Johno,
The bottom bearing has the seal in it, it is a sealed bearing.
I tap it out with a socket on an extention.

The one on the left is the top bearing.
The other two are bottom bearings, showing each side.

thanks mark!

i did get to that stage but then i was stuck as to how to remove the seal from the bearing

i ended up sticking a flat screwdriver in between the inner bearing and the seal and prying the old seal out.

Just wanted to know if that sorted your problem as I'm in the same boat as you with an over reving power torque and wanted to see if it was worth the time trying.

I've got the same problem ,Engine over reving and no real throttle response , I done all of the above with the "O" rings the only thing i have'nt done is change the bottom seal ,so i think doing that i might as well give the engine a recondition and see how i go ,

Have you tried adding the brass washers under the throttle cam that are available in the online store? as the carb body and throttle cam wear down it can cause overrevving and minimal throttle response, generally 1 or 2 of the thin brass washers fix it.

Sounds like a good idea , i have some of those washers in my spare parts box ,will give that a try tomorrow night ,