How To Test Your Motorcycle Engine Compression

[@HeAdChEeSe1983]

Great video! No stupid fluff introductions, advertising, or talking about things that do not matter. I am going to check my valve clearance this winter for the first time by myself and because of this video I can check to see if the rings are not tight too. I would like to do a before and after if I have to shim them. The piece on the oil was pure gold. I appreciate your videos and have had good luck with Tusk products in the past. I think I will buy that kit. Once again thank you. I would not attempt the valve job without KZbin guys like you.

[@anthonybanks45]

2:00 😮😅

[@chandlersuddarth639]

Let’s be honest we’re all here because we either have a pos or bought a pos

[@lolyouwontfindme6070]

I traded one 😂, I got a 1981 Kawasaki kz440 ltd

[@chandlersuddarth639]

@@lolyouwontfindme6070 lmao

[@krishanmendez9119]

Lmao

[@brent3970]

Facts

[@graym5140]

I need it for my neos

[@deliverance3767]

Check valve clearance before test

[@rcktgirl05]

Thanks for this video! I'm taking an online course for motorcycle repair and although it's thorough in procedure, it's not hands on so I'm always looking for videos to see what the text is talking about. You've got a new subscriber now :)

[@thatsallfolks3115]

What’s the online course you take??

[@rcktgirl05]

@@thatsallfolks3115 It's through Penn Foster. I replied a few days ago with the link but I guess that's not allowed!

[@thatsallfolks3115]

@@rcktgirl05thanks I will definitely look into it.

[@1000draggsxr]

Can you tell me if the shraider valve is tight in the end piece. Most of these kits can’t do 50 or 65 cc engines. They don’t move enough air to seat the shrader valve.

[@jamiediseker9232]

I bought a wonderful machine for $100 and she's been nothing but amazing for me since she is a 2021 Blaze wolf moped Blaze 2 150cc absolutely amazing and inspiring on one side of the spark plug because there's some kind of a compression issue what's a cylinder that is the only huge issue I've ever had with her up-to-date right now which that is an issue at all God bless let's make the world a better place and not have poses in it anymore all it would take is some peace of mind

[@s.k7547]

What about bikes who has automatic decompression? Isn't those readings are false if test it with auto decompression?

[@stefanhansen5882]

Awesome! So NO reason at all to inspect valves if the compression is in spec (even if the manual says valve inspection every x hours)?

[@jamesgeorgevellavella1961]

When I screw in adapter I get 75psi? When I use the rubber I get 135-140psi. Do I have a defective tool? I’m thinking yes

[@WOLFEY0812]

I have a Honda Xr80R 2000 my compression is 90 PSI and I was just wondering what you think it is I really appreciate it thank you oh and I started my bike cold when I did the compression test cuz it hasn't started since I bought it. Its a 4 stroke

[@evemizerrago7287]

How to buy this tester? How much equavalent in peso?

[@bobwa399]

My bike is 70cc. How to know the maximum compression for my motorcycle? How much should be the minimum compression in terms of percentage.

[@danilomartinezgonzalez6223]

Hello how are you Could you help me with the proper value (psi) for the Honda CRF250R - 2014? Thank you

[@Duke_803]

What should compression be on a 2021 kx250? Similar to the intervals of this 450?

[@ducaduke]

What if you have a manual decompression lever do you hold it done while your doing the test ?

[@rmatvmc]

It depends if you can kick it over without using it haha. Ideally you wouldn't use it, if I remember right, I think some of the old service manuals would give a spec both ways. If your manual doesn't specify, I'll look into it more. Let me know! -Charles

[@ducaduke]

Lol 😂 it’s a 06 ktm 625 smc. It’s burning oil I believe. Due to the spark plugs being covered in it. And I don’t think it says

[@dallinjensen3456]

What should the compression specs be at normally for a 4 stroke

[@rmatvmc]

Between 120 and 190 usually but you'll want to check the service manual for your exact bike.

[@dylantendoornkaat6155]

I did a rebuild because i had oil from the exhaust. Heads are redone, new piston rings without re-honing the cylinders because they still had a nice crosshatch and no visible damage. New seals and gaskets and exactly done as the manual says. Put back together and she runs fine only problem, still oil in the combustion chambers. As you can imagine this is frustrating me. Anyone any ideas on what this could be? I oiled the valve seals a bit to prevent cracking of the rubber but I'm thinking it could be the valve guides. Any help is welcome, thanks!

[@daytonasayswhat9333]

Great vid. Thanks for

[@rmatvmc]

No problem 👍Thanks for watching.

[@connersnow298]

Awesome vid and edits and filming and tools and shop and bikes

[@brody_schutt]

I have a 2018 crf250R I’m getting 75 psi compression I was wondering if that was good or bad thanks

[@GNX157]

If your bike had a built in compression release on the valve train, 75psi might be fine. Your service manual will give you the spec.

[@Arielna13]

Thanks bro, very helpful!

[@rmatvmc]

Glad it helped!

Best Compression test video I have seen! Regards from South America and please excuse my wrong english. May I ask to your knoweledge? Should a compression test to show an increase of the psi sample on a brand new engine after 1.30 hours of engine break-in to make comparison? Topic apart, Can you give me some lights about main Jetting and spark plug reading? Here, local tech service has not O² sensor and empirical knoweledge seems to be not good at all. I have seen plug chop test here on KZbin and I made my own test two times, two news spark plugs used without carbon deposits as results after test was made. I understand that high rpm and temperature makes a spark plug cleaning, so plug shop makes sense looking for carbon deposits at bottom of insulator. Is that right? I'm a Honda XR150L brand new owner and 5000 miles today, basic motorcycle but I notice that it comes so lean AFR. white spark plug readings and over heat... I just want to be stoichiometric in low jet and slightly rich on main jet. I know about jetting, elevation and temperature range rules... I know about upper side of spark plug reading for low and middle throttle opening range but main jetting seems to have a special method like a plug chop test has. All my setting is stock setting except the main jet. from #102 to #112 tested now. 150cc³. 20mm throttle bore. stock jets #35 *#102* -> #112* +/- 1500 ft asl and +/- 86°F. Jet #112 tested does not shows any carbon deposit at bottom of insulator after cut it's body thread, nothing! Plug chop was much more than 5 minutes at WOT, 6 runs avoiding low jetting and spark plug reading shows just a little brown mark deposits at top of insulator and oriented to the exhaust valve. NOTHING MORE! What is the range of main jets number to test on this kind of engine and environment? Is there a well known range number of main jet to emulate a 13.5:1 or 14.0:1 AFR values for example?. What am I doing wrong?. What information I need to know?. Plug chop method is not known here in spanish tech community. Thanks to you a lot!

[@orgillmathew]

Your English is better than mine lmao

Hi@@orgillmathew oh man I am looking for this tech data but it is not easy... Did you read about "plug chop" method before? That method is not known by local spanish language techman. Cheers man!

[@orgillmathew]

@ Im sure Spanish Techs have there own terminology, but is this what you mean? When it's dirty and black, it's got the shits, You have too much gas you are running rich. When its hot and white, but looks pretty clean, You're 'bout to blow your shit up; you're running lean.

[@1000draggsxr]

Plug chop is the least effective solution to your problem. If you wanna do it right buy a wide band o2. Install it. And make test runs. Real world load test. Shoot for 13:1 wide open. 14:1 cruise. And idle in the 12’s. This will change with temp and altitude. So you will need to find baseline settings for all conditions and jet to suit

Thanks a lot @@1000draggsxr! Unfortnately it's expensive to import a O² wide band.... Local service has not O² Sensor for tunning so old school spark plug readings, throttle response and sensations about engine performance is the way here to do that! I understand the correction factor when jetting but my bike comes very lean from factory so testing main jets until sputtering gives me that info to find that 1.0 factor correction value as start point. I had to step up main jet until wide open sputtering indicating over rich but so far to get numbers and a new question here: *¿how many time of combustion need a spark plug to get enough or insufficient carbon deposits to be readed? Thanks a lot!

[@MeowZaK]

Do I have to take both spark plugs out? Mines a 2 cylinder. 4 stroke.

[@rmatvmc]

Yes, you will want to check the compression in each cylinder.

[@AndrushaNZ]

@@rmatvmc do I need to take them out at the same time or one cylinder first , then sparkplug back and other ?

[@a_drewski]

@@AndrushaNZ the cylinders can be tested Individually, does not matter if the other spark plug is in or not.

[@ItsCheechFool]

2013 kx450 supposed to have how much compression closed throttle closed?

[@rmatvmc]

The throttle needs to be wide open for the test.

[@ItsCheechFool]

@@rmatvmc thanks. I did it closed and got super low numbers 48-55 psi I’ll try it open throttle next.

[@matt2437]

Honestly if you have a four stroke with auto decompression don’t waste your time with this tool. Use the leak down tester instead for an accurate. Wait till you get an adapter stuck in the plug hole too (good time there). Just buy a quality tester with multiple hoses.

[@levisc22]

Simply put loctite on the hose and screw it back into the adapter and it’ll get it out with ease

[@angelg.564]

Hi I'm trying to do a compression test on an 01 Yamaha yz426f. Are able to help me out. I got 88 PSI on the gauge. I'm at 6035 ft. What would it come out to?

[@joeydirt420]

Sounded like my air box was farting/popping when i had throttle wide open and didnt do it with throttle closed. Any ideas? Ktm300xc 2022

[@127Connor_]

What if it’s a carbuerated engine and you still open the throttle all the way

[@orgillmathew]

Yes because you wont be trapping any pressure if you have a valve issue.

[@abelinoaragon9276]

What should the compression be on a 1977 Hodaka Wombat 125cc that won’t start

[@rmatvmc]

Somewhere around 140-150 psi. A service manual is your best friend!

[@rmatvmc]

100psi is probably the minimum the bike would start with, but again, see if you can track down a manual. Don't forget to check for fuel on the spark plug, as well as checking spark. -Charles

[@abelinoaragon9276]

@@rmatvmc Thank you so much!

[@dustinrichards8401]

How much should a 2018 yz250f have

[@juliusnattestad1970]

When you put oil in the spark plug hoke to see if a top end rebuild is neccessary. Do you just use regular engine oil on it?

[@rmatvmc]

Yes, you can use whichever kind of engine oil your bike calls for.

[@CarlosGarcia-ls4hn]

Will the compression test also determine the compression ratio?

[@rmatvmc]

No, a compression test will not tell you the compression ratio of your engine. You can find the formula to calculate your compression ratio online or you should be able to search your bikes make and model and find the compression ratio.

[@ninociancio]

What should the compression values be in a YZ450F 2019 and a CRF 250R 2020?

[@rmatvmc]

Normal compression can range anywhere from about 120 to 200+ psi depending on the specific engine. It's best to check your owner or service manual to get an exact compression spec for your bike as well as any additional instructions for performing this test. Also, because compression can vary so much from bike to bike, checking it when a bike is new or has a fresh piston and then periodically after is the best way to establish a normal range for your bike.

[@jackrayner6715]

i just rebuilt a 93cr125, i have not run the bike yet so its not broken in, but im getting only 100psi compression. i had the cylinder honed and measured with the cylinder its in spec ring is gapped and oriented correctly. bad gauge or just not a full seated ring? having trouble getting bike to start

[@jamesgeorgevellavella1961]

Bro I got very low reading plugging into spark plug hole. Use the rubber end things I got an extra 64psi and now 140 from 75. I think I have defective item like you

[@1176hambone]

Drain Carb and fuel line, turn off petcock?

[@corysargent5234]

Been reading that using the Estart to check compression is really hard on the starter. Is this true? If yes, how can I check my compression with a bike without a kick start and a rekluse?

[@rmatvmc]

What bike? You should be fine. The main thing to remember is you don't want to run the starter motor for too long because it can get hot. I wouldn't hit it for more than 8-10 seconds at a time. That should be plenty of time for your test, but if you need to hit the starter button again, just let it rest for a minute first. -Charles

[@corysargent5234]

@@rmatvmc bike is a 2020 KTM 300 XC-W TPI

[@emilysrosenburg9077]

How much psi should a rm 250 two stroke have

[@rmatvmc]

You'll want to check the manual for your specific bike but it should be around 170 psi or more.

[@joem8986]

If my r6 compression is 35/40/180/180 can it still be saved? Or does this mean i need a new engine?? I hope you see this and reply! thanks!

[@Kevin.OBrien44]

New pistons probably

[@tyschroeder3419]

When you have the tester compressed and start the motor, how does the air stay in the cylinder. Won't the air escape out either the exhaust or fuel valves while rotateing the motor?

[@danjim7056]

There is a one way valve on the tester itself.

[@vijayam1]

Brilliant!

[@motorcyclebettereveryday2373]

amazing video thank you💪💪💪💪

[@reggiexp69]

i think my compression tester is broken.. it gave me 70psi on a running 125cc 4 stroke dirt bike, and 60psi on a 150cc gy6 quad... and 50psi on a banshee (that does have a problem i think it wont move onder its own power) but it starts and idles.. but yeah i think my meter is broken... eveyr thing is between 50 a 75psi...

[@rmatvmc]

Hmm...is there a good seal with the o-ring where it screws in? If so, it could be a faulty gauge. If you bought the gauge from us, then reach out to our warranty department. [e-mail] -Charles

[@reggiexp69]

@@rmatvmc no got one cheap of amazon lost my other one. Came across this video cause i got confused what psi now was good or bad. Thank for the reply, i will just send it back to amazon and buy a new one

[@andybrooks4070]

Man im gonna say my IT250 with 100 psi is no good, runs great once you getter goin but you gotta take a nap after kickin so many times

[@matthewbeaver5026]

Why the need to hold throttle open and ground out the plugs?

[@rmatvmc]

Holding the throttle wide open allows as much air as possible to enter the engine and gets you the most accurate compression reading. Grounding out the spark plug avoids electrical problems because the current needs somewhere to go and can cause damage if not grounded.

[@matthewbeaver5026]

@@rmatvmc the throttle makes sense. Wouldn't flipping the kill switch or leaving the ignition off be equivalent to grounding?

[@gsxrunit]

I’m only at 130ft elevation should that affect my psi ? Your chart starts at 500

[@rmatvmc]

You won't notice a difference. -Charles

[@jamesjanzen9806]

Does everyone no how much psi of compression a 2008 Crf150rb is supposed to have

[@rmatvmc]

It looks like the manual calls for 73 psi of compression. This number seems really low but these bikes have an decompressor which that throws off this number.

[@jamesjanzen9806]

@@rmatvmc oh ok thanks mine says 90 psi so mine is good than but I guess I am used to two strokes thats y it seems low to me

[@johanordonez6998]

I should have done this before buying my 3 dirt bikes lol

[@kolo1367]

hey the test was carried out on a cold engine or a warm one??

[@rmatvmc]

There are a lot of mixed thoughts on this subject. Both numbers should be pretty close but it's best to check with your bikes service manual to see if they give your compression spec on a cold or warm engine.

[@kolo1367]

@@rmatvmc Thanks for the answer, tell me if Nikasil can be sanded with stone??

[@rmatvmc]

We have a great video covering everything you need to know about Nikasil cylinders that you can check out here: kzbin.info/www/bejne/f5_JgaFmgtmChrs

[@rmatvmc]

If the bike runs, you'll want to do the test with it warm since the piston takes shape and slightly expands when warmed up. You'll want to do it the same way every time for consistency and same gauge. If the engine doesn't start, this will be a good indicator of whether or not you have a problem in the engine. -Charles

[@ColKurtz-pi1ku]

It's better test engine compression with hot engine, rings and cylinder hot

[@622wesc]

I agree. But you need to make sure it's the exact same temperature every time. So what's the best for me is always cold.

[@orgillmathew]

@@622wesc Good question. i recon you would want to test operation temperature.

[@Tommy81.519]

How do I do this and NOT have my bike start... cause that happened lol

[@rmatvmc]

Your compression tester should go in the spark plug hole so there should be no way your bike will start with no spark plug.

[@Tommy81.519]

@rmatvmc My bike has 2 spark plugs per cylinder so it does.

[@rmatvmc]

You can remove the spark plug boot from the other spark plug.

[@Tommy81.519]

@@rmatvmc okay

[@davidb9323]

It looks so easy skipping how to take out the spark plug!

[@ACDC77887]

As I can see, you're using in this video cheap, Chinese no name tester for 20$. That's why you got low compression results.