thanks I will do a vacuum test tonight. don't ask how I even own a vacuum tester. I think it was when I was rebuilding my still blower or edger. I could first try to start I with out the muffler outside on the concrete so I don cause a fire in my garage but that will hopefully annoy the neighbours if it starts. I will just take some phots of the muffler port
My way of testing them is a squirt of starter fliud in the plug hole, and if it fires or gives an attempt to start you can be fairly sure the problem is carby related or possibly as Max said the seal on the pull starter. I doubt this would be a cause because as you said in your first post that it was running.. Putting it in the plug hole means it doesn't have to suck fuel in through the crank, If no attempt to start as Tyler? mentioned, remove the muffler and look in at the piston and if you see any scoring then we have to consider it may have been straight fueld
Yes it is a quick easy first check , to look at the bore, rings and piston in the port hole as Tyler and Norm suggest.
The only other things to check would be the spark plug as I've had a lot that work one minute and misfire the next so I like to use a plug out of a mower that I know runs well or try a new plug.
I would also check the head gasket isn't leaking but that will show up when doing the vacuum test.
yes I have have poured a bit of fuel/ oil in the spark plug hole. I pulled it many times to start it and it would not start. I could smell the exhaust so the cut of switch is correct and it is getting fuel in the carburettor and I could still smell the exhaust from trying to start it even without pouring some fuel in it. This is still a great tip. would you pull out the piston and rings even if they are scored since the compression is 79 psi?
So correct me if i'm wrong please. from what I gather from the videos, I block the muffler port, carburettor port, spark plug and decompressor port. To pressurise or create a vacuum, I attach a hose onto a nipple to a backing plate I make up and attach it to the carburettor. If it does it not matter any where I place the nipple, I can get a brass threaded fitting and braze a nipple on to it and attach it onto the spark plug port as it would be easier to braze a nipple onto a brass thread fitting then to a steel plate. Do I have to move the piston around or place it anywhere? Finally, what result should I get for the pressure and vacuum. It could be a top or bottom seal or the case seal. Thanks for you help.
I would attach the nipple to an old plug as long as you smash out the porcelain .
Block the intake and exhaust port ,rubber hose and wood plugs / plastic etc and hose clamps would work. for the intake.
The exhaust you may need to g clamp a flat plate over the exhaust port with a gasket or flat rubber inbetween the plate and the port.
The piston is at bottom dead centre for testing and you can rotate after you have vacuum applied.
I don't think the bore etc will be scored at 79 psi. but is easy to check.
To see where the leak is if you have one ,you would need to use soapy water where you are checking for a leak so if head gasket and the 2 port block offs aren't leaking then you know it must be crank seal with a pressure test.
With the vacuum test you will know there is a leak if the needle falls.
It looks like it would have to be a leak in the crank case. The compression is good enough, I have a spark and I get combustion with the carburettor and even with fuel in the head. I canβt think of anything else. I will test it tonight and let you know and hopefully find the leak. What pressure should I pressurise the crank case to?
Just keep an eye on hard rubbish piles you can often find a PT there with buggered chassis or wheels and 98% of the time the motor is in pretty good shape, not worth spending too much time and money trying to get one running
Yes should of figured that. I still think it is worth fixing donβt you. What elseβs 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!
