OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines engine cutting out

i have a victa commando with a powertorque engine which i inherited. a couple of parts needed replacing, which i did, reassembled the whole thing, it starts fine and runs at idle fine but when i push the throttle to full it cuts out, i've pulled it back apart and tried to find the fault but i have no idea! if i pull thye throttle back to idle it continues to run .

any ideas? i'm pulling my hair out!!!!

cheers in advance
martin

Sounds like its starving for fuel. You might try removing the fuel pipe between the tank and carburetor then turning on the fuel tap briefly to observe the flow rate. Make sure the engine is cool, you are outside, and you catch the fuel, for safety reasons. If the fuel runs slowly, you have a blockage in the tank outlet. If it runs fast, you may have a blockage at the carburetor fuel inlet, such as the needle-and-seat. You'd need to dismantle the carburetor to check that.
Having said all that, there are people on this board with much more recent experience than I have. My two-stroke carburetor experience was gained in the days of Villiers engines. It was easy then: you just held down the "flood" button and checked how far the fuel squirted out through the drain hole in the side of the carburetor top. It took a few seconds to check, and only a minute or two to fix. Yes, we old guys get nostalgic. But I wouldn't have one of those lousy old engines in a fit, now.

What was it you replaced?

Pull the fuel line off the carburettor and turn the tap on and let it run into a jar. What is the fuel flow like?

What is your air filter like? is it fitted securely the right way up?

GO with the basics first then dig deeper.

far out, beat me to it grumpy

Joe, when he comes back and asks how to service a Victa two-stroke carburetor I'll just fade into the sunset and leave it to you people who've actually done it.

cheers, i'll check that.
the replaced perts were the o ring on the fuel chamber and a part in the carb which adjusts the mixture(not sure of the name) its a disc with a pointed piece coming off it which connects to a diaphragm. i've remover the air filter whilst i've been tinkering

the fuel coming out of the tank i would describe as a "reasonable trickle" for want of a better description probably 100mls in 20 seconds

That is a litre in 3 minutes, so if the engine needed all of that the tank would run dry in about 10 minutes at full throttle. It doesn't, so you have enough fuel flow into the carburetor. You may have loused up the internals of the carb, hopefully non-permanently. Alternatively, there is garbage in the carb, blocking something up. I'm sure someone will tell you how to put it together so it works.

this was my carb guide!

Seeing that it's a Powertorque engine, I'd check to see if the starter O ring is not stuffed......in which case it'd be pulling in heaps of air leaning the mixture.

I haven't heard the way the engine sounds when you go back and forth across the cut-off point. Lean mixture is usually accompanied by a 'lean spit' as you gradually increase to the cut-off, and perhaps a bit of a hiccup when you reduce the throttle and it starts firing again. If you don't have anything like that, there is a possibility that the kill-switch is malfunctioning rather than it being lean mixture. If it is running fast and is killed by the switch, if you let it stop completely with the throttle wide open then take out the spark plug it should be wet. If it died of lean mixture the plug would be dry.

Brainwave I had while out at the shop this morning, is your needle valve the right way up or missing?

Is the line on the carby plate horizontal?

Is the valve in the carby lined up with the A position marked on it.

if i push the throttle to full and let it stop the spark plug is wet.(when starting from cold it runs on full throttle for about 5-10 seconds then spins down as if killed by the switch and gives one last cough just before dying)
the little o ring between the plastic gooseneck tube and the cylinder inlet port had been seated wrong and was misshapen, have reseated it the best i can until i get another.
needle valve is pointed end up,round end down. plate is horizontal, will go and check the valve now.

edit- it is now lined up with a-no change

just had a thought-does it matter which way around the metal plate behind the diaphragm goes? it seems fairly obvious that it has to be the way i have it now but obvious isn't always the case?

If it runs longer cold than hot, and if it coughs before it stops, seems like it is mixture not ignition. I'm not familiar with that carburetor but I have the impression there is a priming bulb which shoots fuel into the intake manifold when you pump it. Perhaps you could try pumping this when it is in the process of cutting out, to see if it comes back to life? That won't fix anything, it just confirms it is purely a fuel shortage that is causing the problem. Once we confirm that, I'll retire to the sidelines.

tried-makes no difference

also checked the kill switch contacts when i had the carby off, they only touched in the normal off position.

If the bulb makes no difference, but the problem is fuel starvation, that would mean there's no fuel in the bulb when the problem occurs.
1. Does the bulb squirt fuel when the engine is not running? (I think you can see the fuel squirting by looking in the open end of the carburetor, where the air cleaner would go).
2. If you squirt a little fuel into the carburetor air opening when the engine is running and is in the process of quitting, does it enable the engine to rev up briefly? Naturally you need to do this test carefully, not getting any part of yourself in front of the open end of the carburetor, and using an oil can or something similar to control the fuel delivery safely. If you don't feel comfortable you can do this test safely, don't do it.

running better?!?

not sure what i've done but it seems to be running a lot better, wanted to cut out 3 times during cutting the lawn, but quickly kept going after a throttle change. the only thing i did was starve it of air.
for no good reason i can think of i pulled apart the plastic flexi air hose from the rubber air hose to see how much air it was drawing, i put my hand over it, it cut out,i put the hose back together and restarted it and it seems to be running fine(better)
i checked the carburetor hose connection and there was no obvious crap that had been drawn through.

i'm happy that its running but i'm still curious as to what it could have been!!
any ideas?

probably a bit of crap in the jet, starving it for air will make it suck hard on the fuel dislodging the muck. I do this sometimes with dry briggs motors.

I agree with Joe - if briefly choking it hard clears a lean mixture problem, it has sucked some crud out of somewhere, almost certainly the main jet.

Ahhhh the gremlins at work again; isn't it amazing how a minute piece of crap can stop a well engineered piece of machinery.
Great to see all is well with it now.

I used to put my hand over the air inlet to clear the old G3 type carbies as a quick fix years ago but what I would be doing is taking out the main jet and giving it a good clean as well.

Hi Guys,

I know that this thread is now a bit old but thought that I'd share my experience!

I've just got a 160cc engine and mower going, with help from Bruce and this forum. See "160cc engine-ring gap ?".

I used the mower on a very overgrown "lawn" (about 3 months overgrown-some of the weeds were 1.2met. high!!!).

What an incredible machine!!

The Victa chewed the grass and weeds up like they were not even there!!

Then, suddenly last night it "coughed, spluttered and died". This was after about 3 hours use-not continuous. (1 hour the first night and probably 2 more 1 hour sessions.")

The symptoms were identical to the first post in this thread. On high revs it died but I could keep it running by using the throttle cable moved to "idle".

This screamed "Fuel starvation".

Tonight I stripped the the tank off and took the "main jet" (that's the brass "screw" that holds the float chamber cover in place on a G4 carby) out and inspected it with a high powered magnifying glass - sure enough there was a small "bit" of dirt in it - so small that I would not have seen it "by eye" (but then my eyes are not that good :-)).

I cleaned the jet and re-assembled it (the "new" O-ring I had installed 3 days ago was "stretched" so I carefully re-fitted the original (old) O-ring and it fitted. (the petrol and other solvents had probably evaporated off and it had returned to it's original size).

I also used the opportunity to sort out a fuel leak where the "on-off" tap fits into the tank. (Fuel was dripping out there and landing on the mower body!

I also discovered that the "spring clip" (hose clamp)holding the rubber part of the "air inlet pipe" had slipped off (or maybe I had not put it on correctly in the first place) the carby body and that there was a gap there where the pipe met the carby body. This IS WHERE the dirt got in as it was "sucking" air (and grass cuttings & dirt) through this gap (the area of least resistance !

I then started the engine (on a bench) and it ran perfectly - first pull - I adjusted the idle speed with that grey button/wheel on the diaphragm cover.
(I know that the cable can also be adjusted by loosening the screw just after the air filter but mine is rusted solid into the plastic and I do not want to force anything!)

Thereafter I took it out onto the "lawn" and gave it a real "workout". (My neighbours probably confirmed their beliefs that I am MAD as it was well after 10:00 pm.)

The "Victa" 160cc proved it's worth - I pushed it relentlessly through some seriously overgrown grass & weeds and it never even gave so much as a "hiccup" - it just took all I could throw at it in it's stride. This engine/mower is a credit to it's Aussie designers.

Moral of the story:
1) Dirt (especially)in the Main jet is a definite "No No"!.
2) Check your air intake connections.
3) If it does not work "right" it is probably because because you did something wrong. It is a great engine and does a really good job of what it was designed for!