OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk Self propelled Victa power plus

Someone's been busy looks awesome!. The hole in the muff is just a part number in a way,its all on the inside they are a high flow muffler...

Thanks Chris, I've seen some of the restores other members have done, I call this one a refurbished mower.

Have to put it aside for a few days, I will work on the engine next week.



At some point this mower was a dogs toy with the catcher, starter & height adjust handles all chewed had to do some plastic welding.

The hole in the muffler does nothing in itself, I am pretty certain its just to designate it as being a power plus muffler, as they have different baffling..

Do you Have Any Pictures of the Finished Product?


Kori

G'day Kori, no, this project is on hold for a while, shuffled down the priority list.
I will get back to it though, cheers
Here are some shots of 2 self propelled victas
1. grey one is victa vulcan 2. red one is a 550 22 inch - both are driven by power torque engines.

G'day thanks for the info on the muffler fella's, I have not had much time to play with mowers lately.
Here is an update on this one.
I have done the engine this weekend.
It had no spark, so I replaced the points.
The piston had a stuck top ring and bore had a small amount of scoring, I honed the bore and cleaned the ring grooves, then reassembled it.
Cleaned magnet faces, serviced decompressor more.....
Tomorrow I will do the carby & hopefully get it all together to see if it runs.

That's looking good,but you should paint the engine it would really set it off then.

She's Come up a treat mate!

But I agree With Bumbly, Paint the Engine And Muffler, It will look factory then.

But All Around Top job there!


Kori

Thanks for you ideas's Blumbly & Kori, I will paint up an engine one day. Not this time though :-)
I have it all back together and running, the hi-comp muffler was rusted out where it meets the port, so I have fitted a standard one. Seems to run fine.
Took a few pulls to get it started, but it is running well.

I love the fuel cap with the stepped prism, so you can see the fuel level without removing the cap.

By the look at the fuel gauge it needs some. Good work non the less still would be better in my garage though. It's got the same clutch cable I need for my auto drive.

She's a Beaut mate!

Really nice job!


Kori

I am sure you have read it elsewhere on here but do not let ethanol fuel touch that fuel cap, it will melt it, along with the other seals, but the fuel caps like that are harder to find unbroken, even harder to find at tiny's after I have been shopping.....

Any chance of grinding the rim around the edge of the old power plus muffler to open it up so we can see the internals of the power plus type muffler? It might clear up some recent conjecture. (I reckon it might have an extra hole/s inside or bigger than STD holes, if any different)

I have a rusty std one I can cut open and post pic here for a comparison. What you guy's think?

Edit: Like so.....

The 3 Holes are 3/8" in Dia. you can see how the dimple would lower the flow/increase backpressure.

Inside HI-COMPESSION MUFFLER.
Do the extra holes mean more flow?
I'm not sure I understand back pressure?



To finish this mower, I just have to sort out the self propelled arrangement with the idler wheel and how the cable makes it tension the drive belt.
If someone could put up an image, that would be much appreciated.
Thanks from Mark

Thanks for the photo Mark, good stuff!

I guess the best way to describe back pressure is to do a little experiment: take a deep breath, close your mouth, close one nostril and breath out as fast as you can. Then repeat with your mouth and both nostrils open..... a self evident answer to both your questions (and make sure the bushmans blow doesn't make a mess)

Mark, two of the three steel stampings are the two halves of the outer shell of the muffler. I'll call them the back (which has the hole for the exhaust port near the bottom, and also has the rectangular exit port at the top left) and the front cover (which has no external holes in it). The third, flat piece sandwiched between the back and the front cover is the baffle. The exhaust gas enters through the single large round hole at the bottom, which is clamped across the exhaust port. On the inside of the muffler, the perimeter of that hole is pressed against the matching hole in the baffle, and probably welded to it. The exhaust gas that enters the muffler is then on the wrong side of the baffle: there is no external port in that side of the muffler, because there is no hole in the front cover. To reach the only exit (the elongated exit hole at the side of the top of the back pressing) the exhaust gas has to go through the small holes in the baffle. On the standard muffler, those holes are positioned as far away from the exit hole as possible, so the gas will have to bounce around a lot before it leaves. The bouncing around breaks up its pressure pulses (which are sound waves).

On the high performance muffler, a whole bunch of additional holes have been punched or drilled right near the exit, so the gas doesn't have to bounce around much getting there.

Back pressure is a crude measure of how restrictive a muffler is. If you have a simple muffler - say an old jam tin stuffed with steel wool - the back pressure will increase as you stuff more steel wool in there, and the exhaust sound will get quieter as well. More sophisticated mufflers use "interference effects", not back pressure, to damp sound waves. The Victa muffler effectively consists of two expansion chambers, with a restrictive damper (the baffle) in between them. Simplistically, if you make the expansion chambers bigger, you can use a less restrictive damper and get the same sound level. In practice you usually find tricky ways to make the expansion chambers effectively bigger without making them physically bigger, because of the space requirements. If you crawl under a dual exhaust V8 from the 1960s or 70s, you are pretty sure to find a very short "balance pipe" approximately at the transmission support mount, joining the two pipes (which come close to each other at that point). That way, each of the two exhaust systems is able to use the whole of the other exhaust system as an expansion chamber. (It only works because there cannot be two pulses arriving at the balance pipe from opposite ends at the same time, since the engine fires each cylinder at a different time from all the other cylinders). The system has to be tuned to work properly: the engine's output power changes slightly as you vary the position and length of the balance pipe.

Designing exhaust systems is an interesting blend of science, experience, and experimentation.

Good stuff guy's...Here is one more muffler off an old 125 I got but not sure what its off..Ive not seen one like this before so had to have a look in side.

The design of that one seems pretty awful. It relies on the packing material, which has migrated to the exit hole and become choked up with carbon. In the end, there would have been lots of back pressure: it had turned into a jam tin full of fibrous material, caked up with crud.

Mark for painting the barrel and muffler plain old matt black out of a spray can works great and will last a long time no need for heat paint...The power plus looks great I will have to keep my eye out for one Ive not got a self propelled mower....

Your right there grumpy awful looking thing that muffler..When I open it up and seen that fibrous material I wet it down it could even be Asbestos for all I know....