The CORRECT Way To Do A Compression Test - Avoid These Mistakes!

[@spelunkerd]

That's a good point about the Shrader valve. Both of my automotive compression gauges have removable Shrader valves, so you can use the adapter for measuring real time pressure. As you say, with no Shrader of course a small cylinder will appear to have a much greater volume and lower pressure if the length of the hose is significant.

[@VintageEngineRepairs]

Spot on! Thanks for watching and sharing :)

[@niconine268]

Yes great tip right there so I won't fall down on that error

[@kevinjohansen8149]

Very glad you pointed out that the Schrader valve is not a common tire valve. It has a very light spring and is specific to compression tester's 0:22

[@VintageEngineRepairs]

Yep, quite right Kevin! Thanks for watching :)

[@niconine268]

Yes very useful to know this truth.

[@jcondon1]

I ended up getting a mityvac compression tester with the Schrader valve. The other one I had without the valve I used for years on 420cc engines without issue, but on small engines like chainsaws it did not cut it.

[@VintageEngineRepairs]

Fantastic James! Good to hear it :) thanks for watching!

[@treecycle4631]

Just tried mine on a whipper snipper and found I only got about 20PSI. Definitely wrong as it runs perfectly. Time for a new one with the valve for small engines. Thanks for the heads up Tom.

[@KensSmallEngineRepair]

Another lesson from Mr Two Stroke. Good info Tom!

[@theautodidacticman_]

Sometimes we don’t always have a compression checker with us so a shade tree way of knowing if the compression is good enough is place a finger on top of the plug hole. If your finger pops off when turning it over, then you know it’s good enough to operate.

[@VintageEngineRepairs]

Thanks for sharing,

[@neverclevernorwitty7821]

Your channel deserves so many more subs, really great stuff, I keep coming back to your content to learn more, thanks!

[@VintageEngineRepairs]

Thank you! :)

[@obbiebeal3060]

👍👍👍👍 10,000 Times. You are helping me survive in the bush in West Africa.

[@VintageEngineRepairs]

Awesome mate! You’re welcome :)

[@treecycle4631]

Got my new Mityvac today and the Whipper snipper I tested a couple of days ago with the other non valved tester has gone from 20PSI to 160PSI. Great info.

[@VintageEngineRepairs]

Fantastic, there we go :)

[@SeriousSchitt]

@treecycle4631 So, how do you know which one’s correct, if any? I mean, obviously you’d wanna believe more the 160 over the 20, but how do you know that even the 160’s correct? Compression testing seems highly hit and miss to my way of thinking.

[@VintageEngineRepairs]

If you use a small engine compression tester they’re all very accurate within 5 psi of each other.

[@treecycle4631]

@@SeriousSchitt Plug a compressor into each and compare the readings.

[@raymondthompson4222]

Another great video Tom.

[@VintageEngineRepairs]

Thank you Raymond!

[@ringsidejudge4302]

Another very well informed video .

[@VintageEngineRepairs]

Thank you! :)

[@mowtoegee7049]

Well thank you so much for mentioning the part about the schrader valve. My kit had a schrader valve that you can screw into the end of the line, so it can do automotive and small engine. No other youtube video mentions this important step so I was about to throw the tester out wondering why I was getting 15psi!!

[@VintageEngineRepairs]

Awesome! Glad it helped!! :)

[@mowtoegee7049]

Gone from 15 to 150psi! and able to see that my other machine is reading around 100 and probably needs a rebuild. So helped heaps, thanks again :)@@VintageEngineRepairs

[@VintageEngineRepairs]

@mowtoegee7049 awesome! Pleased to hear :)

[@SeriousSchitt]

The thing is, how do we know our compression tester is good? With a torque wrench, for example, we can periodically send them away to be recalibrated but, with a compression tester who’s ‘yard stick’ are we measuring it by? For example, mine might say 130psi, the next tester might call it 170psi. Which one is correct?

[@VintageEngineRepairs]

Use your air compressor and shoot a set pressure into the gauge and check it matches up.

[@tinkerscorner54]

You wouldn't happen to have links to where we can find the "Small Engine" specific compression testers, would you? All I've come up with so far is ones for "Vehicles" and most aren't as nice as the one I already have, which does have a Schrader valve and adapters to fit different plug sizes. Thanks! And have a great weekend!

[@VintageEngineRepairs]

Hey! I’m afraid I don’t have any specific links, I’d search the 3 suggested brands in the video and go from there :) Amazon or google will come up with them! Thanks for watching!

[@tinkerscorner54]

@@VintageEngineRepairs OTC 5604 Motorcycle Compression Tester. That one is a bit pricey, though.

[@tinkeringtaylor3053]

Your a very knowledgeable guy Tom, well done on putting out these information videos 👌👍

[@VintageEngineRepairs]

Thank you Nev!

[@tinkeringtaylor3053]

@@VintageEngineRepairs Hi Tom hope your doing ok, watching this has helped me out, got a husqvarna chainsaw in for repair at moment will not start for love nor money, followed your steps with the compression test and it will not go passed 75 psi so i think its a new piston and ring, i can see light scoring on the piston through the exhaust hole, so going to strip it down and also check the boar, thank you for sharing your experience with us 👌👍

[@VintageEngineRepairs]

@@tinkeringtaylor3053 awesome Nev! Great to hear mate :)

[@Big_Johns]

Nice video Tom, thanks. 👍

[@VintageEngineRepairs]

Thanks John :)

[@niconine268]

Another great one Thankyou. With all your vids I'm becoming a pro

[@VintageEngineRepairs]

You’re welcome :) glad you enjoy them!

[@haneyoakie14]

Would that be the MV5530 Professional Compression Test Kit? I cannot tell which one has the Schrader valve at the end for the small engine use. Great video. I have learned lots of two stoke stuff watching your content. Your passion shows! Thanks

[@VintageEngineRepairs]

They only sell one kit that is analogue :) go with that one 👍

[@Trolldaddy5]

I learned this the hard way. I bought an automotive one from the auto part store, and it read way low, and i just never used it, figuring it was chinas fault or defective, lol. then i bought a snap on one for 225 dollars, and it was also reading way low. Luckily, he took it back, and i just ordered a mityvac, which says it works with small engines, so fingers crossed.

[@VintageEngineRepairs]

Dang! Glad you could take it back :) glad you got the mityvac, it works well on small engines 👍🏻👍🏻

[@budgillett9627]

As always: Excellent!

[@VintageEngineRepairs]

Thanks Bud!

[@JohnHenderson-x8w]

When you do the test must the throttle trigger be pulled in while making the test?

[@VintageEngineRepairs]

That’s correct, yes :)

[@fast2valve559]

Guessing this is what is wrong with my 281xp. Im getting fuel and spark and flywheel key is good but it won't start for anything. Got some nasty blisters on my fingers from pulling the rope so much. What you think?

[@VintageEngineRepairs]

What is the compression reading?

[@SkypowerwithKarl]

It’s a good idea to ground out the plug lead or keeping the kit lol switch off. Some engines have high energy ignitions. If spark can’t get to discharge, it it’s going to try somewhere else like inside the ignition system itself. This can be permanently damaged.

[@VintageEngineRepairs]

Yep! Spot on 👍👍

[@jasonsmith3573]

good info and presentation..subscribed.

[@VintageEngineRepairs]

Thank you :)

[@victorsimone5445]

Another great video mate. Keep them coming! Is your channel on Facebook as well?

[@VintageEngineRepairs]

Thanks! Na just KZbin :)

[@AReynolds-c1e]

Hi, great video. How are you defining a small engine? does a 1 litre 4 cylinder bike engine fall into this category? Is this why I get low but consistent readings across all four? Thanks

[@VintageEngineRepairs]

Yep a bike engine, same :)

[@justinf1343]

Many thanks for sharing. I have taken a punt on a really cheap Husqvarna stone saw from eBay, and I expecting it might need some TLC.

[@VintageEngineRepairs]

Gotcha :) Husky are awesome, best of luck with it!

[@justinf1343]

@@VintageEngineRepairs your videos have been super helpful in explaining the tests that I need to perform once it arrives.

[@VintageEngineRepairs]

Glad you’ve enjoyed them! You’ll get it up running before you know it. Remind yourself to try and enjoy the process!

[@matthewdonoghue321]

Sorry I am new to small engines and one part confused me... the values for 4 stroke given at 1 min 40 seconds (70 to 80 PSI good). Those values are for an engine with an ACR... or without? Thanks, Matt.

[@VintageEngineRepairs]

They are with an ACR. With that said, even old engines like Briggs flatheads have an additional bump on the intake (some think it’s the exhaust, it’s not) which will reduce compression too. Therefore even on machines that don’t have an acr, still have a means to reduce compression :)

[@TheLawnmowerLady]

Well done Tom!

[@VintageEngineRepairs]

Thank YOU Stella!

[@mrtennessee6862]

👍💯, if you can send me a Amazon link of your recommendation that would be great. Thanks So many choices

[@VintageEngineRepairs]

Thanks buddy :)

[@VintageEngineRepairs]

I’d just google “mityvac compression tester” and opt for their analogue version :)

[@iotioimping]

Hi Tom I have a tester with Schrader valve at the spark plug end just like yours, but I have 200PSI . Isn't that too much ? I looked on Google and said on a forum that 200PSI could indicate a scored piston. Could that be true ?

[@VintageEngineRepairs]

Na that’s not true, 200 psi isn’t common, its very good though :)

[@barryewalt3250]

Great info Tom

[@VintageEngineRepairs]

Thanks Barry!!

[@patrickcreath217]

Very informative, Thanks.

[@VintageEngineRepairs]

Pleasure! Thanks for watching :)

[@MASI_forging]

Another great video.

[@VintageEngineRepairs]

Thank you!

[@topconker2909]

Great vid mate

[@VintageEngineRepairs]

Thanks Conk!!

[@LewisMowersandBoats]

Very cool brother 😎

[@VintageEngineRepairs]

Thank you :)

[@petefroud5308]

Good stuff Tom . How is the bread .

[@VintageEngineRepairs]

Thanks Pete! Good :)

[@GuysPlayingWithTools]

Yeah... if 80psi and the engine is running great... that just means they are testing wrong Lol

[@VintageEngineRepairs]

Spot on mate!

[@timlong1462]

This whole video has me second-guessing my gauge. Currently traveling for work but when I get home I am going to see if I have the Schrader valve in my tester. I suspect I don't as my Johnson 2 cylinder shows right around 100 psi but runs spectacular. my worry is I have given other people advice wrong based off of my gauge.

[@GuysPlayingWithTools]

@@timlong1462 100 psi is probably the minimum you could get away with, I have seen a few motors along the way that run perfectly nice at 100. If it doesn't have a valve and you are reading 100psi, you likely have a good bit more than that.

[@louietownsend2457]

*Promo sm*

[@VintageEngineRepairs]

Don’t understand I’m afraid?

[@Mr.SuperDuper-idk]

Fkn hell 2cycle tester Of course

[@VintageEngineRepairs]

👍🏻👍🏻

[@Mr.SuperDuper-idk]

@@VintageEngineRepairs thanks 🙏

[@Mr.SuperDuper-idk]

@@VintageEngineRepairs I was wondering about compression @100 on small tiller Carb swap and she’s screaming again.