OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Victa Super 24/600 - PowerTorque decompressor issues

I think there is something I'm missing and love for you all to explain it for the "noob", sorry.

You've tried 4 engines on this 600, and they've all had the same issue. However, they all work perfectly fine on non-pulley bodies? I.e. anything but a 24", right?

So knowing that the engines work perfectly fine on other bodies, why are you looking at the engine as though it's the problem?

Or if it's the problem because of the design of the body and how that affects the engine, but Victa still sold it as a complete kit, was there something different about the original engines used? Is there documentation about the 600 series specifically that states part numbers used?

If not, I would imagine a lot of people would be having this issue with any 2-stroke 600 series, yeah?

Maybe the issue is something to do with the body? Maybe it's something to do with an engine component that's different?

To me, it sounds like the solution is to take some pressure off the crank while the engine is starting, almost like you need some sort of clutch for the belt, rather than attempting to modify the engine?

hi Pau13z
yeah you are more than likely correct BUT not many people have the skills to modify the mower in such a way as to build some type of clutch or belt release. So if mucking around with the decompression valve works as suggested. i think all of us could manage that mod.
and another thing if you remove the belt then you will need a flywheel like the blade disc.maybe?
I reckon its worth trying your idea.
I haven't actually tried starting the mower without the belt.but i have bench ran the same size engine and having no flywheel on it it ran perfectly fine.
Its just a weird anomaly that i for one after reading this thread found out about.
as i said before, until now i thought my 24 just had higher compression .
this makes me really curious now to see how she starts without the belt on.
So your Noob question is perfectly relevant here mate.and i also thought a spring loaded slipping pulley tensioner as a ride on mower has may also work.

Don't try starting it without a belt , it will break your fingers. It is all to do with how the decompressor works for some reason on these belt machines. Never had a problem with a full crank one but obviously some people have. After trying several decomp valves I finally tried one with the brass restrictor in it and so far not one kickback.

Hi Gizmo, curious about the above comment. My understanding is that the engine needed the blade disk and blades to balance correctly, or it won't run correctly? I'm not positive, but I'm pretty sure I have both read that here and experienced it myself. Does that sound right? If so, how do you run a PT on a bench? Just curious as to your setup.

Moving on from that, as far as I'm aware, and this is why I suggested checking the parts/owners/service manuals, the engine is the same. For example, on the MSP602, MSP562, and MMX482, my understanding is that they all run the VEX60. They're all the same generation, they're all the same engine. So the way I'm looking at it, if you took the engine from any one of those and swapped it with the other, unless a specific component was different, such as the decompressor, they're all running VEX60's and should be compatible with each other. Same carby, throttle, same compression, etc. The only part I'm aware that would or may be different is what's on the end of the crank. The blade boss, disk, pulley, blades, etc.

So this comes back to... how can something further down the line affect the function of the decompressor all the way up the chain? And, if every mower had this issue, how could Victa sell it? Wouldn't they have endless complaints and returns? Wouldn't we know about it here?

Hi NormK,

I know this might sound like a silly question, but do you need to yank the hell out of the starter when starting these? Or is it a nice gentle easy pull?

Hi pau13z.
pull is maybe a little harder but not much more than normal

Hi NormK,

I was referring more so to your technique. If you'd call it that? Do you need to pull the starter hard and fast typically? Or is it a gentle easy pull? See the video below:



Note how he doesn't need to yank at the starter super hard or fast. I know with my engines, if everything is calibrated correctly, you shouldn't need to yank it's guts out, it should be a steady easy pull, and often, slow. It shouldn't need to be super fast.

The reason I mention this is if the engine is more difficult to start, possibly because of the additional components under the engine, pulley, etc, you may be pulling the starter harder than it needs to be pulled? If you pull the starter slowly, regardless of if it starts, does it kick and buck? Does the starter snag like normal if you go really slowly? If it doesn't, then that could be a clue?

And please, of course, don't take any of this the wrong way, I know you know about PT's and what to do with them, just a suggestion/thought, it's good to cover all bases, even pros forget sometimes.

The full cranks seem to start about the same as they do on a normal base, but the PT's do seem more difficult to start on a 24 than they do on a 24 for some reason

pretty simple really. i have a large piece of steel beam that has pre drilled holes in it to accommodate victa and villiers engines.

and they run just fine without the blade disc attached. i haven't ran a powertorque on it though. but the engine i am talking about is the victa engine on my 24 which is a full crank.
i test all my engines this way without a blade disc. honestly haven't had an issue with it. if you are referring to a powertorque well i don't know, never tried it.
I forgot the origin of this thread was referring to powertorques, but i was experiencing very hard to pull starting with my full crank also .
which is why i sought the same solution.
as for an explanation as to how they are to start,( imagine it has no decompressor).

NormK,

I would suggest that's balance and stability added by the FC. Without that, in a way, you could refer to the PT's as more "flimsy", with nothing to hold them on the other side. This would give rise to flex, shift, etc. Though it should be nominal, and I personally find the PT's good engines.

I must confess, I've never worked on a FC. Now, with the PT's more difficult to pull-start, that could have something to do with the weight under the mower, coupled with the fact that it's a HC and doesn't have anything on the other side to hold it stable. My thoughts are that, while you may need additional force to start the PT, you shouldn't need additional speed. So you need to compensate for the weight of the components under the 600 by putting your weight behind the pull, but the pull shouldn't be fast. If the pull is fast, coupled with that additional weight, could that be causing the decompressor to be pushed closed before the engine fires? Could the solution be to try to pull it slower but with more force/consistency?

Gizmo,

I've never worked on anything but PT's, maybe NormK or someone else could chime in here?

Does the PT need the boss/carrier/blades to function normally? Will it run without them?

If trying to pull-start the engine feels like there's no decompressor, I would suggest that there's too much force with which the piston is moving up. As such, the valve is closing. That could be because the engine is spinning too fast and with the force behind it of the heavy disc, when the valve closes it's like the disc/blades stopping instantly, causing the whole mower to buck. Pulling the starter slower but more consistently may be the answer, but the engine/carby would need to be functioning A1, as per the video in the previous link.

That's why I originally suggested, try starting it on level, firm ground, and note that it should start with an easy slow pull. if it's much more than that, I'd suggest the valve would close and the issue would present itself.

I have been building all sorts of motors and working on them for 60 years now, I sort of have some idea how things work. I know what works and what doesn't

Hi NormK,

As I mentioned, these are just suggestions, I'm spitting out whatever comes to mind here lol. Please don't presume that I presume you don't know what you're doing, I know you know what you're doing

One test that may? if it's quantifiable? provide a result to my suggestion, is to have the engine bolted to one mower and rotate the blade disc to feel compression and resistance, then, move the same engine to the 600 and do the same test, see if there's a different feel to that compression/resistance from the disc?

Another random thought, don't even know if this will work/fit but I imagine it would and it would be a good test... Do you have an electric start PT? Could you try that and see how it responds? I'd be interested to see the results of that.

Plenty of electric start PT's here but I'm not spending any more time on it. I have found the fix and will wait till I end up with another PT 24 to try it again. In the meantime I have 3 here with F/C's that need rebuilding so I am moving on to those. I have an Ariens I want to get finished and another 3 PT bases painted up that need to be put together

hey NormK
when i get time to play with my full crank 24 i will try your suggestion. I know my prob isn't exactly the same cos its not a PT but its still a bugger to pull.
have you ever tried to pull start a PT with a spark plug in the decompressor hole. I have and it's impossible unless your name is schwarzennegar. don't ask me why i did that. nearly broke my arm. he he.

anyway thanks again 👍😎

Hi all,

Now I want to see what decompressor is fitted to my 24 with or without the restrictor. Unfortunately the mower is in Eden and I am in Brisbane. Certainly impossible with Covid and difficult enough at any time. I might be able to persuade my brother to have a look if no disassembly is needed.

The motor I fitted was off the green steel base PT utility. Late-ish model I would think but not the black one. It does seem to be a very good motor.
Anyone know what type of decompressor is fitted to those? It is the one with the 4 short hold down bolts not 3 short and one long.

I still have the utility but with an earlier engine. Still a good mower but not quite as good as previously. A bit of rattle in the bottom end somewhere too but not serious.

Norm is the rattle noise that you noticed in PT 24 s an issue with this current one as well.?I never had that in ours.

This has been a good topic just what this forum is all about.

Jeff

Hi Jeff,
I have never taken any real interest in the decop valves they either worked or they didn't . The first 24 I had with a with a PT was the yellow one and that was the one with the odd noise. Never found what it was but it had to be something with the belt/bearing/blade carrier because I swapped 3 motors on that one and the third motor was the one that made the least noise. It was still prone to the kickback but it wasn't too bad and I haven't heard from the bloke who got it so hopefully all is good. Next one was a red one and that suffered badly from kickback and difficult starting. That one wasn't mine it was just one Big Ted had referred to me to fix it. I swapped 2 motors on that one and got it reasonable but it still was prone to kickback if it didn't want to play ball. The bloke sold it shortly afterwards and wanted me to build another one with a 4 stroke on it. I didn't build one because the cost of a new 4 stroke was going to be too costly.I also had a grey one but I ended up putting a full crank on that one but I had to make up an adapter plate for it and that caused a few problems with the F/C bolts clashing with the PT slots in the base.Wouldn't bother going that way again. Then I have the current one , I do want to try a modified carby on it to see if that improves the starting ( it is taking 3/4 pulls to start it) but with the restricted decomp it has not kicked back once so that is what causes that problem

OK I just tried NornK s solution.it works on full cranks like mine.real easy to pull.at least it was cos I just blocked 2 holes with hot glue ( just wanted to see if it worked) yep that's definitely it. The hot glue only lasted 1 pull.now I can do a proper fix..so I guess as Norm says it slows down the operation. Of the decompressor giving it time to Work. Or release some of the pressure before closing.
I love using this mower but I never did like starting the thing
Brilliant

What about blocking three?