How To Pressure & Vacuum Test (Under 4  minutes!) - SAVE YOUR 2 STROKE ENGINES!

A pressure and vacuum test is the most important test on a 2 stroke engine. It can save a seized top end and diagnose running issues you’ll have when there is an air leak. It doesn’t matter what engine you’re working on from stihl to husqvarna, echo, Kawasaki and Honda. Chainsaws to motocross bikes and even outboard motors, if they have a 2 stroke engine you need to pressure and vacuum test them. This diy tutorial will help you at home complete this process!
TOOLS I USE:
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Mityvac Pressure & Vacuum Tester - amzn.to/3vysI3V
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Mityvac Compression Tester - amzn.to/4aimaFS
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Any links to products are likely to affiliate links and I may earn a small commission from qualifying purchases with no additional costs to you. Thank you!
#pressuretest #chainsaw #vacuumtest #2stroke #engineeepair #yamaha #hondaengine

[@savage22bolt32]

I've watched a few of these press/vac test vids. This is the first one ive seen that knows that vacuum is NOT PSI, but in/hg (or mm/hg). Also: Thanks for the wonderful video, and a huge thanks for not ruining it with crappy background music, and getting right to the point, skipping a lengthy, repetitive intro/outro! ❤❤❤❤

[@VintageEngineRepairs]

Hey :) thanks for the kind words! I really appreciate it!

[@niconine268]

Yes. Can't fault this channel at all.

[@TheGreasyShopRag]

At least a couple major engine manufacturers teach techs that up to 1 pound pressure loss in the first minute is ok. I monitor that when making warranty claims but for other repairs I figure its either tight or it gets fixed. Good video!

[@VintageEngineRepairs]

Thanks for sharing Scott! I’m like you, it’s either tight or it’s not, if it’s not, I’ll find it lol. Thanks for watching! My SparkCheck’r should arrive in a few days, I look forward to trying it out after seeing it on your channel.

[@RC-Heli835]

Heck yea! Love the tapered rubber. No hole drilling!

[@VintageEngineRepairs]

Glad it helped :)

[@donmayberryjrsOPE]

Awesome!!! THIS is what we all need to do more often! So many times I've spent many hours repairing a 2-cycle engine and thinking all is ok only to find out....oops, should've done that vacuum and pressure test!! I'M STILL KICKING MYSELF!!!

[@VintageEngineRepairs]

Quite right Don! 2 main things I always check on a 2 stroke, first the exhaust port for piston skirt scoring and the other is a P&V test :) thanks for watching!

[@donmayberryjrsOPE]

@@VintageEngineRepairs excellent video! Well done!!

[@b.c.goldprospecting1724]

Quick and simple. I do the exact same procedure on all 2 strokes that come into our shop. Good video

[@VintageEngineRepairs]

Good job B.C, it can save so much time and tail chasing can’t it! Thanks for watching :)

[@niconine268]

So cool. Somewhat of a game changer for me

[@niconine268]

​@@VintageEngineRepairsYes exactly

[@justinanderson9280]

That’s awesome Tom, the tapered tube rubber is a simple solution to seal everything. I was dreading making all different sized rubbers to seal my different chainsaws. I won’t have to now and I can try out my new vacuum tester 👌🏻

[@VintageEngineRepairs]

Glad it helps Justin!

[@kevinjohansen8149]

Good summary. I do vacuum test first, because sometimes when you’re pressurize first it’ll force the lips against and pass the vacuum later but if you do the vacuum first, sometimes it will leak

[@VintageEngineRepairs]

Thanks for the heads up, I have heard that but never experienced it myself! I do pressure first just to avoid, in the very unlikely event of accidentally sucking up of fluids that may be in there lol

[@eduardo_k]

It doesn’t get any easier than this, great video! Oh and the tapered pieces of inner tube - brilliant idea! Thanks for posting.

[@VintageEngineRepairs]

My pleasure :) glad it helped

[@radekp.562]

Great, I was looking for exactly this procedure to test my engine.

[@VintageEngineRepairs]

Great :) hope it helps!

[@Big_Johns]

Thanks for the demonstration Tom, I use the cut up inner tube as well. 👍

[@VintageEngineRepairs]

Good job mate, makes it super speedy doesn’t it!

[@andriyshulga2944]

Thank you very much for your concise and informative videos!

[@VintageEngineRepairs]

My pleasure :)

[@Non-Stick_Pan]

Great to find more uses for my Mityvac now! I bought mine a few years ago and only used it once to preload a new turbo actuator for my car, it's been gathering dust since. I've already made one of your adapters from an old spark plug :)

[@VintageEngineRepairs]

Great stuff! Glad you’re enjoying my content!

[@GuysPlayingWithTools]

That's a good test for case leaks. Sometimes looking at the cylinder walls won't tell the whole story.

[@VintageEngineRepairs]

Spot on bill!

[@niconine268]

Im impressed once again. This is a top method for closing up intake & exhaust without getting freeze plugs & plates drilled to manifold spec

[@VintageEngineRepairs]

Thank you :)

[@stevo3644]

A smoke test I find very helpful as well as you can identify where the leak is coming from.

[@VintageEngineRepairs]

Interesting, I use it for a leak down test but not a pressure and vac test!

[@user-ub6zl8qy7l]

Thank you for such a clear and concise production! One question ... during the vacuum test there's a settling-down period at the beginning: the gauge keeps dropping toward zero and it looks like the vacuum isn't holding. You keep pumping and wait a while, and eventually get a stable vacuum to begin the test. What's going on during that settling down period? How can you tell you're not seeing an actual leak? Thank you again. Absolutely excellent video!

[@VintageEngineRepairs]

Thank you! That’s the air bleeding past the piston rings as well as the rubber inner tube stretching and seals too! Keep pumping until you no longer see it drop :)

[@rolfgrosseholz1311]

That sort of test will only show you if its bad. In college we tested them under water to find all the leaks. That is the short engine. That will pick up the small leaks.

[@VintageEngineRepairs]

Pressure tests will often hide an oil seal leak in 2 strokes as the sealing lip gets pushed down and onto the crankshaft. The vacuum test is the correct test to do for an oil seal. That’s certainly not something you want to do under water - or with any water for that matter.

[@rolfgrosseholz1311]

@@VintageEngineRepairs I was trying to cover all leaks. The one under water i was talking about in college picked up a defect in the cylinder casting. Little bubbles coming out at 5 psi. Others had leaks at crankcase bolts on Victa engines etc.

[@williamemerson1799]

Excellent as always.👍🍻 Still have an old plastic MV from the early 80's used to check vacuum advance, but it's vac only. Me thinks there's an 8500 in my future. Thanks for spending $75-$80 for me.🤣

[@VintageEngineRepairs]

That’s awesome :) thanks for sharing!

[@BrucesShop]

Thanks Tom. I missed the vacume test on my old saw. I did do a pressure test .

[@VintageEngineRepairs]

You’re welcome Bruce! Yeah that vacuum test is certainly important :)

[@spelunkerd]

What an excellent channel, we think alike.

[@VintageEngineRepairs]

Thank you! How did you find me?

[@battlehrfred]

excellent sir 100-100 lot s of info in 5 minutes!! ty so much

[@VintageEngineRepairs]

You’re very welcome!

[@user-nw9so4vk8f]

Nice job man. Practical thinking

[@VintageEngineRepairs]

Thanks! Glad you enjoyed it!

[@robcole332]

What a great video

[@VintageEngineRepairs]

Thanks!

[@356Rover]

id be interested in seeing you do this on an old outboard 2 stroke!

[@VintageEngineRepairs]

If one comes along, absolutely!

[@356Rover]

​@@VintageEngineRepairs hopefully a nice 6 cylinder tower of power

[@KensSmallEngineRepair]

I like the timer feature, good Vid Mate!

[@VintageEngineRepairs]

Thanks Kenny!

[@RobsChannel-dc1nn]

Very informative, thanks for sharing.

[@VintageEngineRepairs]

You’re welcome :)

[@tinkeringtaylor3053]

Great tip Tom thank you 👍

[@victoryfirst2878]

Could you please tell me what tapered rubber seal size you made Sir ?? This will help me out so well. Thanks fella too. vf

[@VintageEngineRepairs]

Honestly I just eyeball it to fit, then taper it

[@01bonny790]

I understand the soapy water to check for leaks under pressure, but how do you determine the source of vacuum leak? You mentioned light oil, do you start dripping oil around possible leak points and watch for when the vacuum gauge stops dropping? Loved the video, it took a lot of the mystery out of performing the tests!

[@VintageEngineRepairs]

Thanks for the kind words, the only place that will leak under vacuum and not always under pressure are the seals. Therefore, yes very thin oil, or better yet 2 stroke fuel and oil mix. :)

[@01bonny790]

Thank you so much, that's very helpful. I've been around engines for decades, but I'm new to 2 strokes and channels like yours make it fun to learn, cheers

[@pauliekruger7639]

Great. But how do you build that spark plug air adaptor? JB Weld?

[@VintageEngineRepairs]

Yes - I made a video on how to make one :) kzbin.info/www/bejne/jabOgGyXmdtjmdU

[@pauliekruger7639]

@@VintageEngineRepairs thank you

[@Tyrant2PointO]

@@VintageEngineRepairs I was just going to comment on how you would go about making one of these as I'm currently doing a second re-build on my MS360 Pro after loaning my saw out to someone that had one of his buddies mess with the carb to "get it running better" and I need to figure out how to best ensure I'm doing this right. I really don't want to do this a third time if I don't really have to so THANK YOU for having a simple and to the point video and ensuring every step of the process is fully visible and thoroughly explained!

[@justinf1343]

Thanks for sharing. Will this be the same for a 2 stroke stone saw, that I don't think has oil inside the crankcase. Well, at least I have not seen anyone mention draining oil when replacing crank bearings.

[@VintageEngineRepairs]

As far as I am aware, concrete saws are 2 strokes, same principles, yes! :)

[@barryewalt3250]

Great video again Tom..

[@VintageEngineRepairs]

Thanks Barry

[@RayofallTrades]

Very well done video my friend

[@VintageEngineRepairs]

Thank you!

[@almclean4835]

Great video Tom,

[@VintageEngineRepairs]

Thanks Al!

[@BSSMALLENGINES]

Great video Tom

[@VintageEngineRepairs]

Thanks Brandon!

[@ricks5984]

In addition, maybe a smoke test to seek out any leaks??

[@VintageEngineRepairs]

That is more for a leak down test, the pressures are way too low to show any smoke dissipation. Unless you some how pumped smoke in to the engine maybe!!! As a point of reference, a leak down test (with smoke) is normally done at around 100 psi, a pressure and vac test around 5psi.

[@dousuke1979]

whats the thing that you screw in the cylinder instead of a spark plug called?

[@VintageEngineRepairs]

I made it :) kzbin.info/www/bejne/jabOgGyXmdtjmdUsi=twwu8TiJfI3Wn0ih

[@wow344wow]

Hi V E R, thank you for this very informative video. Can you please advise on a good budget vacuum/pressure with dial unit that is suitable to read small 2/4 stroke engine's. I have 4 small engines but cannot afford the 8500 unfortunately.

[@VintageEngineRepairs]

Hey, glad you enjoyed it! Look on eBay :) one that does pressure and vac is important! Hope it helps :)

[@mattheww7671]

Great video thank you

[@VintageEngineRepairs]

You’re welcome :)

[@ODWALLA123]

I Appreciate You !

[@VintageEngineRepairs]

I appreciate you haha thanks for watching and commenting :)

[@tobesmith7632]

I don't know about going through the spark plug hole to check. the pressure And vacuum. That cylinder he's going to hold 150 PSI..

[@VintageEngineRepairs]

You’re confusing compression and pressure there. Yep I like to test through the spark plug hole if possible.

[@xx3868]

Worse if your engine sort of runs ok but shuts down after 10-20 mins hot and fuel system is ok?? Drove me crazy till i realized the coil was de- laminating and shorting when HOT! I guess to test you could put a hair dryer on the coil and watch the resistance go down a bit? and then suddenly short out!!

[@VintageEngineRepairs]

Thanks for sharing :) yes a classic coil issue! Or a failing condenser in the old machines

[@sypher0101]

I'm a little confused about the vacuum test. You did a pressure test first which passed, meaning there's no leaks, including past the piston rings, correct? If so, how does a vacuum test via the spark plug test the oil seals, if the rings tested ok? Why wouldn't the vacuum remain in the cylinder and not suck from the area around the crankshaft?

[@VintageEngineRepairs]

Because it passes through the transfers :) also past the rings too! Thanks for commenting 👍👍

[@bullitanaconda]

Im curious to know how did you do the spark plug connection

[@VintageEngineRepairs]

Hey, i did a video on it :) kzbin.info/www/bejne/jabOgGyXmdtjmdUsi=QkFspQVWau82cYl8

[@vinopan5374]

Excellent video, at 3:53 min you say 15psi I believe you mean 15 in Hg, correct?

[@VintageEngineRepairs]

Spot on, my apologies - thanks for the correction!

[@Gssmallenginerepair]

Hello sir, could you do a video with the engine on the machine. Like how would you block off the exhaust port of the shroud is still on the engine? Let’s say a stihl weedeater? Thx

[@VintageEngineRepairs]

You can’t you need to take the cowling off to get to the muffler :) thanks for watching!

[@Gssmallenginerepair]

@@VintageEngineRepairs ty sir.

[@jeannettehyppolite9912]

Good!

[@facundopereyra8455]

Can i use this to see if there is a air leak around crank seals?

[@VintageEngineRepairs]

That’s correct yes.

[@bretthaas4606]

Can you seal it off from the other side of the carburetor? I did on a weed eater and found that the shaft for the butterfly valve was leaking air. The weed eater runs okay but I’ve had issues keeping the air/fuel adjustment consistent.

[@VintageEngineRepairs]

There will be a very slight leak even from a good throttle shaft, but it should be minimal. That can mess up the reading, pressure test that separately :)

[@Gssmallenginerepair]

Great video. Do you have to remove the engine like you have it there?

[@VintageEngineRepairs]

Thanks! You don’t have to, you can just block the ports, if it holds then great. If you find it’s leaking, then stripping parts off to get access to the leak is necessary.

[@Gssmallenginerepair]

@@VintageEngineRepairs thx for the reply. Could you tell me what size barb and thread size is the fitting. Like 1/4 x 1/4? Thx

[@gabrielx2389]

hi, I'd like to know how you make the adapter, will you make a video for it ?

[@VintageEngineRepairs]

I have already :) have a look through my videos 👍

[@gabrielx2389]

@@VintageEngineRepairs thank you my friend

[@baileybattistuzzi5651]

Hey tom, How did you make the spark plug for pressure testing ?

[@VintageEngineRepairs]

Just cut the crimp off the metal spark plug, remove it from the porcelain and then add a barb, glued in place wjth epoxy and add an o-ring

[@rockyholt4060]

Where can I get one of those spark plug adapters?

[@VintageEngineRepairs]

You just make them :) I’ll do a video!

[@kwinngeer9070]

what tool did you use?

[@VintageEngineRepairs]

Here you go :) Mityvac Pressure & Vacuum Tester - amzn.to/3vysI3V

[@kwinngeer9070]

@@VintageEngineRepairs Thank you!

[@DicksSmallEngines]

Marvellous explanation & demonstration mate ! 👏🏻👍🏻🔧

[@VintageEngineRepairs]

Thank you Dick!