Victa carby questions

[Guiseppe]

Prologue:

The Victa mower is now about 18 years old and has started over-revving and does not respond properly to the throttle lever. A fix for the over-revving, if there are no air leaks, is to dis-assemble the carby and place some spacer washer(s).

Did this with a washer about 0.3 - 0.4mm thick and re-assembled the carby. Started first pull but now idles so slowly that the motor dies. Throttle response improved but is not completely to my liking either.

Further research reveals that the carby should have been assembled with the "C" on the poppet valve where it is currently "A".

Questions:

(a) If the poppet valve is simply turned to the "C" position what are the likely repercussions?
(b) will the diaphragm be "twisted"/"distorted"/"what-ever"?, or
(c) dis-assemble/re-assemble with the poppet valve in the "C" position?

[wotnot]

C - dis-assemble/re-assemble with the 'C' pointing towards the primer cap

[Guiseppe]

This was relatively easy. Take the carby off the motor. Click the cap off the carby. Rotate the diaphragm, etc. until the poppet valve points in the correct direction. Reverse the above to assemble. Mower started first pull - marvellous what a difference a new plug makes. Two strips up and back to check and all seems well. Three cheers for wotnot.

Fast forward to this morning. Mower starts first pull but hang on what is this? Revs increase just sitting there. Mow the back yard anyway with one hand on the throttle to keep the revs in check.

After lunch pull the carby off and replace the kill switch boot. Pop the cap off and notice that the diaphragm is not sitting correctly. Correct that and reassemble. Starts first pull and seems to run correctly. Try to shut down. Motor revs increase and no shutdown. Move throttle to get minimum revs and eventually motor dies. Pull the carby apart again so that I can see the kill switch wire in the carby and connect the other wire through the boot. Reassemble and you guessed it - exactly the same. Motor revs increase and no shutdown.

Scratch skull and ponder the problem.

[wotnot]

..seriously, as they get old they go stupid/warp etc...especially the bowl piece...

[lsemmens]

Two stroke?

[Guiseppe]

..seriously, as they get old they go stupid/warp etc...especially the bowl piece...

From one dis-assemble to the next in about a week?

[wotnot]

From one dis-assemble to the next in about a week?

Yep, can happen ...if you're sure you installed the diaphragm correctly, and it's subsequently moved, something's awry -- the cap should seal/locate the diaphragm in the body, it shouldn't be able to go anywhere.

Is the O-ring ok between carby body and inlet port?

[wotnot]

Two stroke?

I believe it's on of these ->

[Guiseppe]

(a) Yep, can happen ...if you're sure you installed the diaphragm correctly, and it's subsequently moved, something's awry -- the cap should seal/locate the diaphragm in the body, it shouldn't be able to go anywhere.

(b) Is the O-ring ok between carby body and inlet port?

(a) When I took the cap off to turn the poppet valve the diaphragm was not seated properly. That has been rectified but something else is "not quite right".

(b) It was replaced a short time ago as part of the high revving scenario.

[wotnot]

If you needed to install a washer as you say, it means the throttle cam/lifter are worn -- how worn, is the question (badly worn are near impossible to fix). There's also a chance the engine crankcase seals are leaky, which will also pull it lean/fast idle. If you have a block/leak in the vacuum line to top of diaphragm, that can also cause these issues.

You'll pretty much have to work your way through the doc I linked to above ; you'll find the problem =)

[Guiseppe]

There's also a chance the engine crankcase seals are leaky, which will also pull it lean/fast idle.

That was replaced as part of (b) above.

[wotnot]

That was replaced as part of (b) above.

What colour is the poppet valve?....black or white?

Also, exactly which model victa is it?

[Guiseppe]

White.

Corvette Series 400.

I am planning to take the carby apart, yet again, so that I can see that the throttle cable, kill switch, etc. is working as it should. No rain forecast for a few days so Builder's Bog, sanding and painting has priority ..

Thank you for your continuing interest and input.

[wotnot]

White.

Corvette Series 400.

I am planning to take the carby apart, yet again, so that I can see that the throttle cable, kill switch, etc. is working as it should. No rain forecast for a few days so Builder's Bog, sanding and painting has priority ..

Thank you for your continuing interest and input.

Last of the (chinese made) Victa 160cc powerstroke engines at a guess, and likely it's a LM carby type.

I'm thinking the vacuum control button is somehow buggered. That comment assumes a good diaphragm.

Also, my bad -- that model may have the 'vortex' cutting disc on it, and if so, proper position of valve is with the 'A' towards primer (makes them idle a bit richer/slower)

No worries....been around 2strokes for decades, the old tech still holds my interest =)

[Guiseppe]

Good news, at least in the short term!

While the Bog was curing stripped it so that I could see the throttle cam and the kill switch wires. All good. The diaphragm didn't seem to be quite right though.

Very carefully re-assembled - with "C" towards the primer - and a satisfying click as the diaphragm cover snapped on (Maybe that was part of the problem?).

Started first pull, revved up and down and the kill switch did its job. Yay! Time will tell. Seems that my previous assembly efforts left something to be desired.

As an aside and something that I am not going to interfere with again, unless absolutely necessary, is the kill switch wires. I thought I would check with an analogue multimeter whether the pins were shorting or not. In the run position there was no or little resistance and in the stop position ,again, no or little resistance - I didn't look for absolute values. Hmm!

[wotnot]

Very carefully re-assembled - with "C" towards the primer - and a satisfying click as the diaphragm cover snapped on (Maybe that was part of the problem?).

Yeah, that's likely it...as for kill switch, I wouldn't worry to much about it ; turn off fuel tap or fit a pushbutton kill switch.

[Guiseppe]

Kill switch works so ..

Thanks again. Much appreciated.

[wotnot]

[lsemmens]

Quick! Sell it while it is still working....................{/hides}

[wotnot]

Quick! Sell it while it is still working....................{/hides}

LoL....nah, hang onto it until they pass environmental legislation banning the use of 2stroke lawn mowers...-then- sell it as an antique =)

You can keep these machines going ad-infinitum otherwise ; as soon as Victa outsourced a lot of their production to CN, was the moment spare parts became aftermarket plentiful and cheap ~ you'll prolly still be able to buy new old stock for these into the next millennia B)

Remember the old square framed 'mini bikes' of the 70's?



You could blow away those 4HP B&S motors embarrassingly with a moderately tuned Mk4 160cc victa ...in fact, you could easy wrangle 8hp out of the victa, which was enough to turn that little bike into a widow maker =)