I was reading your spray test again. Is it possible it increased rpms because the spray was being sucked into the carb by the air injection horn? If so, the spray test is a red herring.
254xpg help please
- Thread starter Welder56
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Welder56
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Sorry muffler side. Corner of the cylinder on flywheel side.
Used mityvac 8500. 6 psi for 10 mins. Both pressure and vac no a movement.
Used mityvac 8500. 6 psi for 10 mins. Both pressure and vac no a movement.
Welder56
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Is it possible my carb is malfunctioning??
backhoelover
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i have seen where if the unit has a rubber intake boot it would not leak when the pressure tester plate on it or rubber piece between carb and intake. I was a ms 180 doing the same thing your was i changed the rubber intake and it ran perfect
backhoelover
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does the 254 have a rubber intake
backhoelover
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nope intake is plastic
Welder56
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Plastic. With fresh gaskets.
I've heard that 10psi on pressure tests and anywhere from 10"hg to 16"hg on vacuum tests is considered valid. Maybe you are not applying enough of each? Personally I use 10 psi pressure and 10 in-hg for the vacuum.
I use a MityVac 8500 too - great unit.
backhoelover
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you need to reline up flywheel and make you some marks so you know if it is jumping timing
Welder56
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I already made the marks and have checked twice. Starts on the first or second pull usually.
I will apply more pressure and try again! Thanks!
Welder56
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I did use scotch Brite to clean it all up. Can try the sealer on the surface. Gonna loctite all the bolts and seal holder
Did you put sealant around the bore that the seal sits in before pressing the seal in? Those three screw holes that are used to force the seal out can bugger up the seal bore if you get too enthusiastic with the screws you are using. Ask me how I know. 
This is the first I have heard of using sealant on the surface of these. The o-ring should really be all that is needed but obviously some people have had different experiences.
Welder56
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Can't remember if I put a little bit on. Don't think I did on the flywheel side. Just installed dry.
I greased the new o ring before installing.
I'll try 10psi for pressure when I test again. I will report back.
I would think if I had an air leak in the crankcase it would show up on pressure or vac testing. But obviously I have an air leak somewhere.
If I can't determine where it is I'll loctite every bolt that goes into the case and see what happens
I greased the new o ring before installing.
I'll try 10psi for pressure when I test again. I will report back.
I would think if I had an air leak in the crankcase it would show up on pressure or vac testing. But obviously I have an air leak somewhere.
If I can't determine where it is I'll loctite every bolt that goes into the case and see what happens
If the rpm's go up when you spray, your problem is not pressure, it is vacuum. As I said earlier, the seal is one of few things that can pass a pressure test but not pass a vacuum test.
Threaded holes and decompression valves usually will fail both a pressure and vacuum test and therefore are easier to find with pressure and soap.
Threaded holes and decompression valves usually will fail both a pressure and vacuum test and therefore are easier to find with pressure and soap.
Welder56
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Lol I've done both tests without issue. I had the vacuum up quite abit and left it. Came back 20 mins later and it didn't move a hair.
Welder56
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I left it at 7 psi (vacuum) and came to the inlaws for supper. So when I check it tonight I will let you know
There are three tapped holes near the mounting holes on the seal holder. You can use the seal holder mounting screws, thread them in those other holes and they will push the seal out part way. They will NOT push it out all the way so don't force them after the seal starts moving. Treat them like you would head bolts and tighten each one a little more in series so that the seal is pressed out evenly. Usually once they are started they will pop the rest of the way out with a pick or similar tool.
