Apparently the flywheel is different in the S600. Curious. Does anyone know the difference? As mentioned, I've never owned or worked on a 600 so I can't comment.
I have been looking through part catalogues from 84 onwards, all 600s use the same flywheel as everything else - even the TAC edger.
I heard the FC TAC used a heavier flywheel, but the 1982 catalogue has it with the same as everything else. Having been thrown on my bum starting a TAC without a belt, I know how it feels
I did find some interesting things, which I will make new threads for in a few days - mainly relating to carby and why the PT is stated as so weak in Nm tests
That's interesting Paul - the latest full catalogue I had was mid 90s - and all said they were the same. Thanks, have saved it for future reference
Maybe they were starting to have issues as the 600's got older and had to do something.
It was the second doc that I saw about the governed speeds - no wonder they reckon a briggs 550ex (7.5nm) has nearly as much power as a PT (8 nm) - the PT is barely spinning over at 2600 rpm -
I've never tried modifying the carby to the extent of changing springs or jet, but I could only imagine the power you'd get from installing the higher output jet and heavier spring, coupled with the correct poppet valve position. That said, another component which may relate is the flywheel. If the different flywheel generates a different amount of vacuum, that would affect the suction to the top of the carby and subsequently how the rest of the machine runs.
That's why I keep suggesting knowing exactly what was supposed to run on what mower in the first place. With that information, we may be able to tell the cause of the initial issue. Is the PT from an 18" designed to run on a 600 correctly? Are there required changes to the flywheel, carby, etc.? I don't know, but as I keep coming back to here if the mower didn't work... if everyone had that issue... wouldn't Victa have known about it? Addressed it? Why would they keep selling it if they knew it didn't work? Wouldn't every person who has ever purchased one reached out to Victa or reached out here with the issue?
I believe the stock power of the VEX60 in the last generation of PT's was 8.5Nm? I always laugh when I see massive 4-stroke engines, twice the physical size of the VEX60, boasting 10Nm. I often just think... if we kept going with the PT, if we got those figures where they could be with the mods listed above, they'd blow it out of the water.
That said, that may actually be a reason for the 8.5 rating. That may be with those specifications, so as the engine has max power while keeping under the old emission restrictions. If you scrap the fuel efficiency and fuel economy, who knows where the PT would be at. Put in a Green spring, plain face jet, correct poppet valve position... mmmmm haha.
This is the older doc I downloaded somewhere a few years ago
Everything appears the same except for the jet
I don't think I will need to do the hi-po mods to a PT - they aren't too highly stressed on any of the lawns I put them over. Slashing duties go the the old Big Bob with gxv120 - which really shows the benefit of having a large reciprocating mass (blade disk) as it punches way above its weight
I can see the benefits of the correct jet, poppet, etc on a 600 or pro550 expected to cut 4 ft tall weeds though
Slightly off topic, but I happened across this in an old briggs document
It begs the question "who would copy a briggs"
Answer - "Probably the same person who would eat a bat"
That manual is so old but it's going straight in the bank because I don't have it and they're always useful haha.
You know how when you get something made in china they ask what quality level you want? B&S.. hehe.. probably just said to the factory... Can you make us a 2 that we can compare to the 6 we normally get you to make us? Then put the two against each other lol.
That's wonderful. So if the decompressor is black it should have the restrictor.
My brother should be able to see that without doing any disassembly
Interesting also the post about the different flywheels
I wonder if ODK have any of both types in stock so they could see any differences. May not be weight at all just something to do with the blade boss. If they were different I would like to get hold of a heavier one.
Norm
I wonder if that one you have has the original 24 engine. If so it should have the different flywheel.
There are a couple of flywheels anyway. Doesn't the electric start one have teeth.?
Hi all. As NormK seemed to have found a solution to his problem shouldn't this be a new topic. As far I I was aware that smaller hole restricted version is part of the suction vacuum caused once engine is up n running. Similar to a cars brake booster. This keeps the decompression valve shut during operation. Changing g the size of this hole changes the strength of atmospheric force. So my point is at initial start up before any vacuum can start happening is the point where these engines are difficult to start.
Last edited by Gizmo; 16/04/2010:23 AM.
If my collection is complete ( then how come i keep buying stuff ? ) 🤔🤔🤔🤔🤔
Hi all. As NormK seemed to have found a solution to his problem shouldn't this be a new topic. As far I I was aware that smaller hole restricted version is part of the suction vacuum caused once engine is up n running. Similar to a cars brake booster. This keeps the decompression valve shut during operation. Changing the size of this hole changes the strength of atmospheric force. So my point is at initial start up before any vacuum can start happening is the point where these engines are difficult to start.
No, it doesn't, actually.
What it does do is, to lengthen the time it takes for the deco system to reach either of the two possible 'static states' it has; i.e. of a fully closed, or fully open, valve. The actual system pressure, that above the decompressor diaphragm, basically reaches a 'constant value' as either of these 'static states' is attained.
No criticism or 'dissing' intended here, in any way; it's just that to comprehend fully what's happening here, you really need to have a decent understanding of Fluid Mechanics, and the difference between 'static pressure' and 'dynamic pressure' - not to mention the Bernoulli Equation.
Thanks to my 'misspent past' , I do have the 'disadvantage' here, of having a Chemical Engineering qualification [our Forum Historian CyberJack can confirm this, if there's any doubt]. Which included the study of Fluid Mech, as it incorporates 'essential concepts' for Chem Eng...
Cheers, Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
I lost interest in chemistry when I couldn't understand if the german lecturer was saying alkanes, alkenes or alkynes haha
Flow momentum, conservation of mass for steady flow, Bernoulli, The Application of Hydrostatics in the Hydraulic Jack was at least interesting - however I know SFA in the scheme of things
OK so here's the bit where I get really curious. According to Victa, the current parts catalogue, which I don't have, unless the last one they released for the PT's was the Feb 07 one, which would make sense, considering the engine and other components haven't been changed since then, but I'm not a Gold dealer so I don't have access to their back-end stuff. If, according to Victa, which was confirmed by a Victa technician when I called up previously for assistance on something, all of their current parts for those engines should be backwards compatible and whole unit replacements (I.e, if you want to replace part of the carby, buy the whole carby, it will be the only replacement part they officially sell), which would include the decompressor. So... If the current decompressor is the model which should be used as a whole unit replacement for any of the previous models, and the current model decompressor does not have that restrictor valve... Is there something else we're missing? Or does someone need to reach out to Victa and let them know they may have made a whoopsie..?
My belief with the restrictor is not that it slows the suction down, what it is doing is slowing down the rate that the compression with the piston coming up can push the valve closed, that slight delay allows the piston to go over the top on the first rotation and by the second rotation it has enough momentum
My belief with the restrictor is not that it slows the suction down, what it is doing is slowing down the rate that the compression with the piston coming up can push the valve closed, that slight delay allows the piston to go over the top on the first rotation and by the second rotation it has enough momentum
Well,sort of!
The main point here is, that having that 'restrictor orifice' in the system, is going to slow down the speed of movement of the poppet valve, in both directions.
Cheers, Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
We tried it. Got the the restrictor nozzle , Installed it. It made absolutely no difference. Kick back still there. Not that it ever has been very bad on this one. It can be lived with.
He does have a very slight needle valve issue at the moment. Probably flooded slightly. That's when I noticed it.
Hi Jeff, Sorry to hear that, was so convinced it was the fix. At least it fixed the one here, never one attempt to kick back once I fitted that decomp. Before that it wasn't something you could consider living with, it was absolutely brutal. So were the other PT's I had but they were not quite as bad, but they were not good starters either for some reason, bit temperamental for my liking. As you say bit floody then difficult to start. I still say the F/C is a much better motor in this situation. I will probably have a play with another PT but I won't be going out of my way to get it.
![[Linked Image]](https://www.outdoorking-forum.com.au/images/Product%20images%20directory/040503-3053.jpg)
, I do have the 'disadvantage' here, of having a Chemical Engineering qualification [our Forum Historian CyberJack can confirm this, if there's any doubt]. Which included the study of Fluid Mech, as it incorporates 'essential concepts' for Chem Eng...
