Yes should of figured that. I still think it is worth fixing don’t you. What else’s can it be it has to probably be an oil seal or crank case seal. Hopefully I can test it tonight.
I have 50/60 of them here that are worth fixing, usually a hone and a new set of rings, but I also have 50/60 that I have tested and are running fine. The ones that have been straight fueled will probably not be repaired in my lifetime as I keep coming across ones that run fine but bodies are stuffed
im trying to get a seal on the muffler and carburettor port. when I pump air in and the piston is at the top, air still goes past the side of the piston rings so they may be leaking
If the engine fires up or and doesn't run, make sure the starter o'ring is fine. Even a tiny leaks on the crankcase is negligible compare to the amount air/fuel drawn into the crankcase during up stroke direction and the engine should run. Assuming the carburetor is working fine with diaphragm, governor vacuum line working properly, best to check the main jet or replace the main jet with a known good one or new one. When main jet is partially blocked, the engine will fires up then dies straight away like fuel starving. Note: 79psi is a good compression.
The starter o ring seal looked like it was pinched when put in stretching it. I took it out and fit it on the starter and it is larger then the starter so this may be the issue. Hopefully as I really don't want to be replacing bearing seals and pulling out the crank shaft. it concerns me that when I compress air in through the head, it leaks past the piston when the piston is at the top.
Put a bead of silicone around the starter ring and put it back on. I can't see why the starter "O" ring would be a problem if it was running and just stopped. I'm thinking now it has been straight fueled, usually the only way they stop like that and can't get started again
it concerns me that when I compress air in through the head, it leaks past the piston when the piston is at the top.
Yes it's perfectly normal for pressure to leak past the piston With a pressure test ,the piston should be at bottom dead centre with a pressure test ,you are checking for leaks in the complete engine not just the top end and remembering piston rings have a gap at the ends so by design will always leak ,as we know the bigger the ring gap the more the rings will leak.
I was thinking it may have been the starter O ring as some o rings won't fit in properly when installing unless you give them a coating of rubber grease before installing.
The pressure test would have confirmed a crankcase leak and the starter is the easiest part to check first.
Buy a new O ring and put some rubber grease around it, if it's a good quality O ring and you don't have rubber grease Vaseline can be used to lubricate the O ring ,then fit the O ring in the starter and then install the starter evenly.
I never use silastic anywhere near fuel as it's not compatable ,everytime I put fuel on silastic the fuel just disolves the silastic ,not sure how Norm gets silastic to work with petrol as the silastic always breaks up for me . There are a lot of different grades of silastic ,it's just the ones I've tried haven't worked with fuel. Cheers Max.
One time when I pulled a starter off, the I couldn't refit the O ring as it had enlarged and wouldn't fit tight around the starter and was impossible to reinstall, so I grabbed a spare and put it aside. The next day I had to pull it off again and decided to see if the original seal had shrunk and it had shrunk overnight enough to fit nice and snug again and reused that!
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!
I can't even get the clear silicone to seal oil ,when I look up the specs it says the clear silicone resists oil but it's not oil resistant, The black silicone works fine for me for sealing oil and the specs are it's oil resistant .Both don't mention being fuel resistant.
Silicone can .work very short term for sealing fuel but when I see clear silastic on parts that are in contact with fuel or on sumps and rocker covers it never lasts well.
When removing silicone ,I always wash the silicone in fuel and it orange peels and breaks up.
Originally Posted by Mowerfreak
What about when you need to open it again? Do you have to remove all the old silicone and reapply?
I don't think there would be a problem removing the silastic it should fall off in a fuel / oil environment.
A good test although a little dangerous would be to put silicone on a leaking fuel tank ,it won't take long for the tank to be leaking again.
I would use the o rings as they are fuel resistant. Silicon peels away over time. I put sillicone on my other 70 series utility 160cc. When I pulled that part and cleaned it with petrol, the sillicone comes right off. Apart from that starter Irving seal, there is only the bottom seal that is part of the bearing unless I have missed something else? It was pinched when I removed it so it could be the issue. I don’t see how it could of run on straight fuel as the compression looks fine?
They will have compression but the bore is damaged, I have 50 here to prove it. As for the silicone you can use it for testing purposes because I can be pretty sure you won't have an "O" ring sitting in your back pocket
I had to cut the grass. I made a complete mower out of spare parts. rebuilt a carburettor, starter and decompressor. new gasket and rings. I had an old o ring but it was good enough to use. no issues, it started first go.
I replaced the o ring n the starter as it was not in right. I go to start it and it is like it almost starts but does not start. I am thinking there is not enough compression to get it to start?
I don't know how good your decompressor is ,I would remove it and put a spare spark plug in the decompressor hole, then try and start the mower at least then you will feel the compression when it turns over.
Make sure the blade plate is tight to the crank but if it's not kicking back on the starter it should be good.
Just in case the carby primer isn't working ,take the spark plug out and pour a small amount of fuel into the plug hole before starting it should run for a few seconds off that fuel if there is a carby problem.
Take one kill switch wire out off the carby when starting in case it's shorting out from movement.
If it almost starts take the plug out to check that it's not wet ,if it's flooding the wet plug stops it from starting.
thank you. I will work on it tomorrow. the decompressor and spark plug are new. the carburettor was working as I tested it on my other mower I built out of spares when I found a good chassis on the side of the road with a briggs and Stratton on it that I throw out as it was rubbish.
it is all scored up. I really think the compression is low. maybe I should change the rings as the scored piston should not matter if the rings are new. I dont think the cast iron block would be that bad.
enough is enough. it must of been run on straight fuel before. the whole case is toast and good for the trash. I will keep the carby decompressor cowl and chassis for another mower if I build one. like I said before, I made a new mower out of a chassis I found on the street, and my spares I had. It worked first go. This is a waste of time. also I wont be honing it as I can be bothered wasting any more time on it.
Exactly, I have 50/60 of them here exactly like that. Keep the pull starter, coil, decomp, snorkel, maybe inlet manifold and keep an eye out for another one dumped on a nature strip. I find about 85% of the motors are ok but the body is toast
I took the lower bearing, and bearing seal out. they dont look to leaked however they must off been the the reason the mower is not starting. 79 psi in the cylinder should be enough however the case must have a vacuum leak. I will look around on gumtree for mower parts or bulk part cheap. I really want to make a plate to block the inlet and exhaust for vacuum testing.
Nothing to do with the piston, it is the bore damage is why it won't start, nothing to do with the seals. If you hone out the bore marks and fit a new set of rings it would start . We have been doing this for a long time
