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My rare Victa Two Stroke Twin Cylinder Mower

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My rare Victa Two Stroke Twin Cylinder Mower

Postby Swift » Sat Nov 24, 2012 6:57 pm

This is my Victa twin cylinder mower and it still runs. It has two cylinders opposing each other in North South direction. Certain parts haven't been available for years as Victa gave up on this concept in the early 1980s and stopped producing parts specific to this engine.
It has a wider cutting width than other Victa models which is why I use it in my large area of lawn. I have not been able to source a catcher that fits this model so far.
Surprisingly, it doesn't sound any different to a regular single cylinder Victa. I love the look of it though.
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby Albatross » Sat Nov 24, 2012 7:41 pm

Two cylinders opposed to each other? So they are like a small version of a Subaru boxer engine basically?

One of my former Industrial Arts teachers at school had one of these and he said the reason they sound virtually the same as as a regular lawnmower is because both of the two cylinders fire at exactly the same time, instead of at alternating like a regular engine.
I was told to think of them as two 1 cylinder engines sharing a crankshaft rather than a 2 cylinder engine, although I am sure that's oversimplifying it too much for any real technical analysis of how they work.
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby Derwent » Sun Nov 25, 2012 6:36 am

I have wanted to get my hands on one of those for ages!!!!
The lovely Victa 170cc twin....
Only ever seen a couple.

What I do have is the 85cc Victa Compact which was a smaller base with basically one half of the twin motor.
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby simonl » Sun Nov 25, 2012 1:05 pm

Albatross wrote: both of the two cylinders fire at exactly the same time, instead of at alternating like a regular engine.
I was told to think of them as two 1 cylinder engines sharing a crankshaft rather than a 2 cylinder engine, although I am sure that's oversimplifying it too much for any real technical analysis of how they work.

That makes sense to me. Two stroke without forced induction needs to have a sump chamber for every cylinder. Having them fire at the same time means the crankshaft can look like this:
Code: Select all
   ___
__/   \__      __
         \____/

Having them fire at different times, the crankshaft would need to look like this:

Code: Select all
    ____     ____
___/    \___/    \___


Which would need much bigger counterweights.

Sorry for the ASCII art
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby Bedford-29 » Sun Nov 25, 2012 1:38 pm

The Victa twin cylinder was called the Victa 500 built in 1974 and at 38 years old no wonder they rare but I`d say if you look around you bound to dig up a Victa 500 somewhere.
members.optusnet.com.au/~rarelawnmowers/
www.vintagemowers.net/Victa_Twin.php
http://www.youtube.com/watch?v=Sh36-4Evhk8
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby Jeff » Tue May 14, 2013 1:50 pm

Hi.
I am lucky enough to have two of these.
One I found in the bush many years ago (discarded and not complete, but repairable), and I was lucky to get one from eBay last year.
This one is a goer, but it did require some work before it would run.

It doesn't sound like most single cylinder mowers. I am not sure why. Theory is, it should, but at speed it has a unique note.
It is MUCH smoother than any single cylinder mower I have used, and as mentioned has a wider cut than most.
Also, it is a lot more powerful than any mower I have used. I can mow by lawns as fast as I can, without it even slowing down when it gets to a thick/deep patch of grass.

Problems? Yes. Very hard to start because of the G4 carburettor! And I dont have a catcher. Anyone who wants to sell one, please let me know.

PS, I use it instead of my B&S powered mower, even though that has a catcher. The Victa is MUCH faster!
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby chewtah » Tue Sep 08, 2015 4:25 pm

I asked about this twin cylinder engine. I think it does spark both cylinders at once, but one piston is right down, and one right up each time it sparks. According to the parts diagram the crank has a separate opposing journals for both rods, which is good. I think when it sparks both at the one time is has to be sparking on some fuel in the pot that is at BDC, which is not ideal, but it seems to work. I dont think is making two power strokes at once, but one, then the other.
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby Swift » Wed Sep 09, 2015 1:20 pm

An earlier post explains it well.
Albatross wrote:One of my former Industrial Arts teachers at school had one of these and he said the reason they sound virtually the same as as a regular lawnmower is because both of the two cylinders fire at exactly the same time, instead of at alternating like a regular engine.
I was told to think of them as two 1 cylinder engines sharing a crankshaft rather than a 2 cylinder engine, although I am sure that's oversimplifying it too much for any real technical analysis of how they work.
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby chewtah » Thu Sep 10, 2015 1:48 am

Having thought some more about it, yes he's right, fires both at once, and now I dont think it fires at the bottom of the stroke as well,someone else told me that.
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby chewtah » Thu Sep 10, 2015 7:27 am

I am convinced now the motor fires both cylinders at once, I was told it fired at the bottom of the cylinders too, but it doesn't.
But I think it should have been designed to fire one then the other, and have two coils, one for each plug, and both leads the same length, maybe then they wouldnt need to have altered the next model to fix the ignition problem.
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby Swift » Sat Sep 12, 2015 1:37 pm

For years I had a black Victa catcher I found in near new condition sitting in my shed. Only thing wrong with it was the push button used to secure it was missing. I recently got around to scavenging another push button assembly off a cracked catcher from a 1970s Victa Mustang to fix it. When I tried to attach this catcher to the Mustang, the mouth was too wide and the penny dropped when I discovered it fitted the 500 base :!:
Now I just need to replace the badly corroded handles (from being stored outside under a tarp!) and give the very temperamental carby a clean out and hopefully have myself a decent useable Victa 500 twin.
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby eddy » Sat Sep 12, 2015 3:10 pm

Now this is very interesting and I am still trying to get my head around it

Here is another theory that perhaps like a GM two stroke truck motor that sounds like it is really revving it may only be going at half the revs of a conventional Victa with both conrods connecting to the same big end?

PS
That did not seem right either so i checked it out further and simonl is right with the crankshaft http://www.vintagemowers.net/Victa_Twin.php

Click on engine assembly
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Re: My rare Victa Two Stroke Twin Cylinder Mower

Postby Swift » Tue Nov 15, 2016 10:27 am

I had to move my collection out of the shed to dry the floor so took the opportunity to take some pics.
I managed to get a replica decal off Ebay for the engine cowl of the twin.
Note: all the mowers pictured run. Some need more persuasion than others, but still turn grass into lawn.
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