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Case Tractors Discussion Forum

Compression Test / VAC

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Mike Beeker

11-30-2019 20:47:39

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Still having issues with engine backfiring through carburetor, blowing the oil from air filter up through breather tube. Have had local Case dealer boil and rebuild carb, checked gap on the rocker arms, they are in spec. and working fine. Was considering doing a compression check, but need to buy the equipment for that procedure first. Does anyone know what is a good reasonably priced test kit to buy, and what reading on each plug should I see.? Also thought I could have a stuck valve causing problem. Any help would be greatly appreciated.

Thanks ,Mike

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12-01-2019 15:13:22

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 Re: Compression Test / VAC in reply to Mike Beeker, 11-30-2019 20:47:39  
I do almost all my compression tests with a simple push-in "cone" gauge. What you are looking for is not an exact number, but look in the manual for a ballpark. Make sure you check with a good strong charged battery and starter, choke & throttle both wide open, crank until gauge quits going higher. Look for all cylinders above 100psi and within 10% of each other. Misfires start occurring around 90 and a cylinder with 60psi or less is effectively dead. A very high number usually indicates oil leaking around piston rings or valve oil seals, 140 or more. These are all rule-of-thumb generic-gas-engine ballpark figures that vary with many things including weather. Oh yes, and if two adjacent cylinders are low you may well have a bad head gasket leaking between them, this could also cause your symptoms.

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12-01-2019 09:46:32

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 Re: Compression Test / VAC in reply to Mike Beeker, 11-30-2019 20:47:39  
O'Reilly's rent them out. You go in pay for it and then when you done you bring it back and they give you your $$ back simple as that. By the way it also only costs around $20 at O'Reilly's

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Case Nutty 1660

12-01-2019 04:54:46

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 Re: Compression Test / VAC in reply to Mike Beeker, 11-30-2019 20:47:39  
Mike, a bad valve/sticky will make a more constant "pop" you hear through the air cleaner and or breather,, easy to see if that is happening,, pull the valve cover and let her idle and watch the valves work,, you will also here a push rod rattle if you do have one sticking, a bad seating valve will make a "Hiss" sound, does the backfire stop with some choke or at least change/ does opening the load jet? make any change? does it backfire at more open or wide open throttle or does it do it all the time idle or wide open?,, with out hearing it I am shooting in the dark so I am trying to cover the bases. I am thinking you have either a carb or electrical issue,, it can be a valve/ exhaust/intake leak,, if you like give me a call when you have it by you so I can hear what you are fighting maybe will help

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12-01-2019 04:37:30

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 Re: Compression Test / VAC in reply to Mike Beeker, 11-30-2019 20:47:39  
Mike, come over and you can use my compress set. Jerry

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Chuck machinist

12-01-2019 03:20:55

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 Re: Compression Test / VAC in reply to Mike Beeker, 11-30-2019 20:47:39  
All right Mike, I found a snap on compression tester at a yard sale for 20 bucks. I built my own leak down tester from parts I had in my junk drawer . I used 300 pound gauges for my leak down tester, they seem to be sufficient for the testing I do. The first gauge gives me the actual psi per cylinder and, The second gauge gives me the actual leak down on the cylinder . I hope you will find this useful. CMIf you require some clarification, my email is open

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Mike Beeker

12-01-2019 23:48:47

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 Re: Compression Test / VAC in reply to Chuck machinist, 12-01-2019 03:20:55  
Thanks for all the ideas guys, it'll be couple of days before I get back to it, will keep you posted on results.


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