OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Over revving P/T engine

Hello all,

I picked up a Victa P/T and have gotten her running nicely. Unfortunately, it is still revving its arse off on run (though it comes down to idle well).

So, I have changed the head gasket, replaced the rings for the manifold (2), the starter ring (small ring on starter was fine though), and the carby ring. I checked underneath with oil on the bottom of the crank and no leaking. I cannot see any holes in the snorkel pipe, and it all looks to be attached firmly. New filter in the air filter housing fits fine.

So, are there any areas I have missed here?

Hi Sapper,
I don't know how to fix these without doing the carby mod, only way I have been able to control the revs at a set point

Hello Sapper,

I had a problem with an overreving Chinese Powertorque and seeing it was a late model straight manifold engine, I figured it was not likely to be either of the inlet manifold o rings, so I decided to check the governor diaphragm and as I suspected, it wasn't seated right when I pulled the cap off. One side was folded into the body. Once positioned right and forming a proper seal around the perimeter before replacing the cap, problem was cured.

Thanks fellas,

I will check that diaphragm out tomorrow MF. If that doesn't work, I will see what is required for your fix Norm.

Hi Sapper,

Do you have a spare carburettor? For a whole unit replacement, you're only looking at about $60, P/N: CR03773A. With that, you'll get a couple of jets and springs which you can use to adjust the full RPM speed.

The only reason I mention this is it's often the fastest way to determine if the issue is the carburettor or not. Also, if you're going to do this professionally or as a hobby, it's a good idea to keep a "known good" carburettor around for testing purposes.

Moving on from replacing the whole unit, consider:

- Fuel blockages/restrictions - Over-revving may be a result of running lean at full RPM. Check the fuel tap filter, the needle, the main jet, and the poppet valve position

- Vacuum leaks - To determine if the issue may be vacuum related, there are 3 easy things to do. 1, spray around the engine with Nulon's SYB. If there's an air leak it will be plugged temporarily and the engine will return to full RPM. To that point, if you want to determine if that's the case under the engine, your best bet is to try to spray SYB through a hole in the chassis if you have one, DO NOT ATTEMPT TO SPRAY UNDER THE MOWER WHILE THE ENGINE IS RUNNING. Sorry, not assuming, but I had to say that. 2, check the vacuum from the carburettor to the body. Remove the hose connecting the top of the carburettor to the engine. Connect an extended piece of fuel hose to the carburettor and start the engine. You should notice the RPM's change as you block the hose, suck on the hose, etc. If you notice no change, the issue should be fuel or carburettor related. 3, test/check the decompressor valve. You can remove the decompressor and replace it with a spark plug, then block the decompressor hose connector on the carburettor. If the engine runs better, there could be an issue with the hose or decompressor.

- Configuration - If you have the wrong main jet or spring configuration in the carburettor, that could cause the issue. Consider changing the main jet and spring to see how the engine responds. You can also try servicing the carburettor by adding washers, P/N CRO3619A, before you put the cam back on. Remember though, this will reduce the RPM's when the engine is idling too, so I'm not sure if that's the solution for you.

I hope this helps.

Cheers,

pau13z

Have to dig up an old thread saves me making a new one
Just wondering if my airbox) has a hole in it would this count as a vaccume leak? One of my PT victas has a 50cent coin hole in the airbox.

Thanks

Hi Tjames1991,

I've never heard of anyone refer to an air hose hole being referred to as a vacuum leak, the vacuum hose goes from the top of the carburettor housing (The opposite side to where it connects to the engine) to the engine block (Near the flywheel), and looks the same as the fuel hose. It's thin Black plastic.

What you will experience, however, is your carby and possibly engine getting full of gunk and junk, possibly causing wear to the internals of your engine if it gets in, due to contamination. The airbox has a filter in it, so that only clean, filtered air enters the carby and engine. If you have a hole in it, who knows what's getting in your carby/engine, or what damage it's doing.

I'd replace or at a minimum patch the hole ASAP.

Cheers,

pau13z

Hi TJ, not sure what you are referring to?

Thanks for the info
I think the beers on the weekend took its toll at 5am in the morning asking this question 😂

Yep, that will do it haha

I figure your last sentence meant took its toll

Yes that's the one.
Thanks for your help got some handy info in this thread. I also have ordered some gasket sealer to seal all the carby from any air leaks. Mine definitely needs a couple spacers, having it full throttle scares me a little