I have an old Victa Mustang, I believe with the V40 engine, that's over revving.
I did the typical test and changes with seals, etc, but couldn't figure out what was going on.
I thought it might have something to do with vacuum, so I connected an extended hose to the diaphragm cap. When sucking I did feel pressure building up, and the top of the cap pulling down, so I'm happy there. I then connected the hose to the chassis port and confirmed, no blockages.
I then tried running the mower with that extended hose connected to the diaphragm cap and sucked while the mower was running... the revs dropped. I thought maybe the neutral spring in there was too much for it, swapped it for a Red spring.. no change. I shortened the length of hose between the cap and chassis, no change.
The only things I can think of are something to do with the 2nd spring in the carby, or something to do with the flywheel not creating enough vacuum?
Paul, it's more than likely the bottom bearing seal when all other checks have been completed and nothing appears wrong. If that is the case a full strip down will be required.
Interesting BT, I have never had to replace a lower seal, I don't think in my pile of dead PT's any of them suffer from a lower seal problem. When I test these motors I always check the top seal to be sure and I run a wipe of silicone around the "O" ring and then if it doesn't fire with a puff of starter fluid it goes in the scrap pile because I believe it has been straight fueled. I don't even bother pulling the head off, because the ones I have pulled the head off have always confirmed my suspicions of a scored bore. Another way I check is when I pull the starter off I look at the skirt of the piston that is just visible and if it shows signs of any scoring it usually confirms my suspicions I do have a couple of F/C's here that I believe a seal is the culprit, but they are a long way down the must look at list
Paul, it's more than likely the bottom bearing seal when all other checks have been completed and nothing appears wrong. If that is the case a full strip down will be required.
Hi BT,
Do you know of a way to test this without disassembling everything? I don't want to disassemble most of the mower before realising that I did it for nothing lol.
Hi you can probably try the easier things first then get on the harder things like checking/changing the bottom seal etc.
It's not hard to get the carby off these things and give them a quick check, clean, rebuild and put them back on again, there is a rubber seal on the carby neck you never know you might also have a leak from there and that's easy to change when the carby is off.
Just try the easier things first to see if it makes any difference.
Can you still adjust the revs to fast and slow speed with the throttle control lever?
Some years ago I did come here for an issue on my mower where the idle speed was too fast on my older full crank Victa with the G4 carby, I got some great help here and added a few brass washers in the carby and it fixed my fast idle issue. I also did change the top and bottom seals on my full crank engine but I don't think they were leaking and causing the fast idle problem but I changed them anyway, but when I added the 2 brass washers in the carby it fixed the fast idle problem perfectly. I can post you a link to the thread but as I said I am not sure if it's exactly the issue you may be having as this was for a full crank with a G4 carby and a faster than normal idle speed. Not a powertorque with a LM carby.
There is a rubber seal on the carby neck you never know you might also have a leak from there and that's easy to change when the carby is off.
Hi Converse,
Ref the attached "Carburettor Exploded". I have replaced (For different reasons as well), 3, and swapped 14 with the Red spring. The diaphragm appears to be functioning normally. If it weren't, when I sucked on the vacuum hose connected to the diaphragm cap it shouldn't create a vacuum, which it does.
Ref the attached "Manifold Exploded", I've replaced 31 & 33.
Ref the attached "Starter Exploded", I have replaced 52.
Originally Posted by Converse
Can you still adjust the revs to fast and slow speed with the throttle control lever?
Yes, but only to a very small degree, there isn't a very big difference here between the start, idle, and full positions, but there is a difference.
Originally Posted by Converse
Some years ago I did come here for an issue on my mower where the idle speed was too fast on my older full crank Victa with the G4 carby, I got some great help here and added a few brass washers in the carby and it fixed my fast idle issue.
Ref the attached "Carburettor Exploded". You're referring to the washer, ref 8, is that correct?
I haven't tried anything here, unfortunately, I don't have any available to me at the moment, but I can try this. I have always been curious about it though... why does this make a difference? I understand mechanically why, but I'm assuming this isn't something that occurred initially but came about after production and after use. So is the cam rotating on the carburettor body and wearing it down over time, causing the seat on the carburettor body to wear and therefore requiring repair essentially?
Paul I believe the washers are not needed due to wear, I think there is about 20 different shaped cams out there all tried by Victa to try and solve the governor problem, some may have been successful others not so good. So far I have never heard of anyone offering a successful fix on the governor problems, if anybody can offer any advice I would love to take it on board and try it. I have repaired over 150 of them and they work fine once I modify them
In my case on the G4 which I know was factory original was I added in those 2 brass washers to fix up the fast idle problem and it definately fixed it perfectly, I haven't modified the carby or changed any springs at all. I did this back in 2011 when the mower was 29 years old. So in my case I guess it was the wear on the carby and the 2 washers fixed it up and gave me fully adjustable idle again.
Like I said I had all new seals for the engine and carby also, but these 2 little brass washers fixed up the fast idle on my G4 that's for sure.
I haven't yet started working on my own powertorque engine but I will be soon and I think it may have similar problems to your mower pau13z. When I got mine started the other day, I also didn't have much between the idle position and full throttle. But this thing has been sitting unused for 10 years and it had a seized engine. So when I really start working on it I am sure there will be a carby rebuild involved for me also.
Yes the washers that I added is the number 8 on your diagram, so it seems that this was also a service fix maybe on these LM carby's?
I don't know about the spring you have changed also? Maybe if this spring tension is too much it can make it idle/run faster?
Because on the G4, where that spring sits which you have changed it's where the idle adjustment screw adjusts from on the G4's. When you screw it in it pushes onto the poppet valve and opens it a bit for a faster idle, screw it out and it closes the valve a bit for a slower idle.
I hope another user here that's more familiar with these LM carby's on a powertorque can give you more help and advise mate. I do like NormK's modified LM carby though. I might end up doing this mod on my Victa powertorque mower if I can't get it to run reasonably well as a original rebuilt LM carby.
Wish I could help you out more Pau13z but I am more familiar with the older full cranks and the G4 carby than the powertorque and the LM. But i'll soon be rebuilding and working on mine so we'll see how it goes.
Cheers!
Last edited by Converse; 15/02/1904:11 PM.
Zip a dee doo dah, zip a dee ay, another trash picked Victa, hip hip Hooray!
OK, so I think it's wear. I think it's the cam rubbing against the body/resting point of the carby and over time wearing it down, hence the washer to lift the cam higher, which is also why the washers are so thin.
Unfortunately, I only had one and figured that with the problems I'm having I wouldn't have been able to resolve the issue with just the one. That said, I wanted to test it quickly and didn't have any other brass washers. So, I grabbed a steel washer which fit but was probably as thick as at least 4 of the brass washers, and the issue appears to have been resolved; There are now issues with the throttle moving and cut-off, I'm assuming because of the super thick washer, which I'm not worried about because I'll replace it with the correct brass washers when I get them.
The poppet valve was originally set to C but I moved it to A to try to reduce the amount of fuel coming in. I did that before as one of my troubleshooting steps too but obviously, it didn't make a difference, though worthwhile noting.
Thanks for your help everyone and if I swap out the washer for the brass washers and find I've got more issues or it doesn't resolve the issue after swapping out, I'll be back... from outer space!!.. haha.
It's not 100%. The throttle cable is now sticking a bit because the washer was a bit thick. The washer also has some sharp edges and the last thing I want to do is do more damage to the body. Finally, I think they use brass because it's a softer metal and shouldn't promote additional wear of any plastics, where steel, even if smooth, could slowly wear out the plastic more than the soft brass.
I have boxes of bodies if you ever need one, cams are the thing I hang on to because if they get forced the cable can pop out and this splits the plastic where the ball fits so it is bin material and they are expensive to replace
You have probably checked these but you never know. Is your decompressor and the rubber line all sealed and working properly? I don't know if it will make much of a difference to the fast running and idle, but this does have a vacuum line that connects to the neck of the carby. If you did have an air leak here somewhere it may make it run a bit faster? Also the wires and the rubber peices that go in to the carby for the kill switch, maybe they can also leak air into the engine if they are not inserted and sealing properly?
I am just thinking about what other items may cause this over revving problem on your mower. Apart from the last resort and stripping the engine down to change the crankcase seals.
On mine I did put a new decompressor on it years ago and I also got new rubbers for the kill switch wiring. I figured that they don't cost all that much and there not hard to change, considering I had my engine rebuilt by a mower shop I just replaced alot of things that might have worn out with age, and I also was trying to get my idle speed down so I wanted to make sure I didn't have an air leak from anywhere.
Cheers!
Last edited by Converse; 16/02/1902:15 PM.
Zip a dee doo dah, zip a dee ay, another trash picked Victa, hip hip Hooray!
I have never had a problem with an over revving PT or FC once I modify the carby and I never have any problems with seals leaking or whatever. Lifting the cam with the washers solves the problem by closing the poppet, cutting the cam is only to get rid of the lumps and bumps Victa put on them to give smooth cable operation
Have you ever tried to plastic weld them back together? I haven't looked at a broken one and it would depend on where and how the break etc, but that could save quite a bit.
Hi Converse,
At this point, I believe the issue has been identified (The brass washers need to be put in place), I just need to get the correct parts to troubleshoot further. I changed the decompressor to one that does not have an O-ring on the cap, the one I'm using is pressed on so it shouldn't come loose, and to further test for vacuum leaks when I was troubleshooting I was spraying SYB around the engine and at no point did the revs change, except when spraying it in the throttle/air filter housing.
When you have an air leak, something that you can try doing is spraying starter fluid (Like SYB) around. If all of a sudden you notice the revs drop down, it's because while you were spraying the starter fluid where the air leak is, fuel is being sucked in instead of air through the leak, getting the mix back to where it should be. Try if yourself if you'd like, with your mower running at full revs, spray some starter fluid into the air filter (Not a lot, just to test), and you'll notice the revs will drop down. Just a tip
Paul I haven't tried welding them, I don't really have any way of welding them and it is fairly delicate to work on it in that area. Araldite may work on it but it is in contact with fuel so I'm not sure. I use steel washers under the cam as they are not going to rust with the oil in the fuel in there
