HOW THE COMPRESSION RELEASE WORKS ON MOST SMALL ENGINES 

Dozens of yt videos with small engine compression release explanations - this one is BY FAR the best. Thank you!

I'm 55 and I have wondered for years how the decompression mechanism works - you would not believe how happy I am to finally understand how it works! - Huge thanks for the video

I'm taking an internal combustion engine class in college for an ME degree (senior year). Your explanation cleared up more in 5 minutes than an hours worth of textbook digging and google searching could. appreciate ya!

Concise explanation without all the blah blah blah. Thank you!

Good video Jeremy. This should help people that don't understand how it works!

now I finally understand what this decompression valve is on my 84 Suzuki LT185. I've looked all over the net and this is the most detailed easily understood explanation of this topic. Thanks!

Thanks so much. 2:33 was the hit me over the head ah ha moment for me. I heard it explained many time but, your visual brought it to light for me. Thanks again.

Excellent Jeremy! I understood the concept, but, had never seen the exact detail in which the ACR worked before! Thanks again!

WOW!!! Finally someone, you, explain how these things work. I never knew .. Thank you

Allways wondered what that feeling of release was when I put my small engines at TDC for storage! Awesome vid!

I have a Kawasaki Fc420v, trying to start it, I would have my arm ripped out of its socket. I then realized that the valves needed adjustment. It was that mechanism that was giving me the problem! Thank You for the great video!

I've just started watching you in the last few months. Awesome. Thanks

Been a machine for 35 years that is a verry good explication of how compression release works and i did know B/S had that in the small engines. thank you J C

Your videos are awesome as always !! Been watching you for years

Great explanation MM1, and perfect timing have one in the shop now that I suspect has a bad compression release im going to show this video to my customer to help explain whats going on.

I have the same Intek 18.5 HP engine that is in the video. Adjusted the valves at top dead center, and the engine was hard to start. Had to rotate engine by hand just past the compression stroke, and then it would start, and it ran good. Adjusted the valves again at 1/4 inch past TDC, and bam it cranked right up every time. That 1/4 inch was the difference between hard to start, and cranking right up like it's supposed to do. I reckon the 1/4 inch past TDC has something to do with the compression release.

Thanks for this video. A Gorilla couldn't pull the start cord on my new Honda engine. The service manager had me draining oil and pully the sparkplug before I came across your video. One hit with my rubber mallet apparently dislodged a stuck relief and the engine started with one pull. The engine was shipped to me and I suspect the relief moved. The engine has been starting easily since. Thank you very much!

Awesome, informative, no BS video! I’m definitely going to start using “Like Yay…” in daily life!

I knew the exhaust was opening early but did not know why, you told me and it was so simple once you explained, many thanks now subscribed. PS I'm was a body panel man, not a mechanic until retirement.

Good job my man,got the message across clear and concise!

Thanks I wondered for years you cleared it up for me in a few minutes

I thought for sure there was something off about my cam. This explained it. Thanks a bunch!

Good video now I understand a little bit more about how compression release works, I've been having the worst time with too much compression and in my riding mowers for the last couple of seasons. I keep readjusting the valves and they will run normal for a while but it doesn't last and I'm thinking it's got to be something else...

Great explanation and demo. I have a vanguard 18hp that runs perfectly and strong, but if it doesn't start on the first pull, then the second stroke you feel on the second pull can break the cord. Then it starts every time at least on that third pull if it didn't on the first. Hoping it's this, and I can live with it. Nice to know how they work now though.

Thanks for the short & sweet show & tell. Really helps me understand.

I am working for the first time on a Briggstratton CR 950 and was confused with the exhaust valve because it opens a little bit and it sucked a little air and then opens all the way and discharge. Thanks for this video I learned way.thanks

Thank you. Great explanation. Now I know how it works and finally can fix my little 15 hp Honda. 👍👍👍

Well damn, I knew how the decompression worked on a big chainsaw but could not figure out how it worked on a larger mower engine... now I understand what people meant by "the bump". Thank you!

Thank you for your timer brother, My mower and i watched a lot of compression videos trying to fix it but this was the first showing what the hell makes it not work in the first place. Hopefully i can get it to run now that I know how it works

Perfect! Thank you. Great explanation with visual aids!

okay, thanks. I have a Coleman Powermate 6875 that takes about 35 pulls to start. Once it's starts it runs great. But I noticed it gets easy to pull just before it's going to start. So this sounds like the compression release to me. Thanks!

Great explanation mate 👍

Thanks, when I putting my Honda GXV140 crank shaft/timing gear back together I couldn't figure out the temporary hang up as I was turning the crank. Now I know.

I love it. Short, straight to the point explained simply. Why some cams have no compression release? Is it for racing? Just got in to small engines not too long ago.

Awesome!! I'm gonna tell my customers to watch this so I don't have to explain it to them Lol Great video thank you

I only had a basic understanding of compression releases on small four stroke engines. Thanks for explaining that.

Great explanation 👍

Really useful and concise explanation, thank you!

This was happening to me, it turned out to be a weak battery. It wasn't amping the starter enough to turn it over. I jumped it from the car battery, and it ran just fine. Just in case someone is checking off the easier fixes first before pulling the engine apart 👍

Clearer than mud. THX SIR!!! 🤟🤟🤟👍👍👍

Great video, and very clear explanation as to how that slinger lifts the valve....Thanks! May I ask - in you experience, how far out of adjustment would the valves have to be, to make it hard to start? If they were out 0.001-0.002" would that make it hard to start?

You are the man ! Good explanation sir. Thank You.

Great. I have an old sears mower, probably 20 years old. 5.5 tecumseth i belive. It does appear to have that compression release. I had it appart to fix a broken camshaft. ( yes i tig brazed it back together. ) i thought it might be something else. But when you described how it stops, it makes sence. Ill look into to it. Thank you

Jeremy very good demonstration. Big 👍 # 159 Stay safe, Joe Z

Great demo :) thanks!

Thanks for teaching. You are helpful.

Awesome! This is the best explanation, and demonstration, of how compression release works that I've seen. Thanks TMM1!

Thanks Jeremy

Awesome video as usual Jeremy! There's your dinner!!!!

Great video Jeremy

Great job !!

Great explanation Thank you.

GREAT VIDEO , THANKS FOR SHARING ,

Thanks for the explination

Brilliant. Thank you

thank you excellent explanation

Very helpful, thank you Sir

Thank you. This is the only explanation I've seen of how compression release actually works. Very clear and concise.

Nice. Thank you! Question resolved!

An older woman asked me to help her get her lawn mowers running since her husband passed away. I don't have a lot of expertise but can clean a carburetor, replace the spark plug and put the correct gap in it, etc. With that I got her first mower (push) running. The second is a Cub Cadet xt1 riding lawn mower with Kohler SV541 engine 18hp (I think). There was no oil in it at all and the oil filter was extremely difficult to remove, I had to puncture it with a heavy duty screwdriver to turn off. The little oil in it was really dark. I replaced the fuel filter, spark plug, and cleaned the carb, no start. The carb is spitting gas away from the engine and I can hear a hammering sound when starting. I stuck a pencil in the spark plug hole and the piston seems to move up/down when I twist the flywheel. I did a dry compression test and it is only getting 30psi. Any thoughts? I feel I'm going to have to tell her that this is beyond my expertise.

Good video thank you

👍 I understand how it works now. , always wondered

Thanks for the explanation! I've been trying to get my virtually new generator to run and I think the compression release is staying on. The unit is 2 years old and has less than 5 hours on it. I have only run avgas in it, no ethanol. I tried ethanol mogas because I thought the vapor pressure on the avgas might be too low, but that didn't help. It has spark, but I changed plugs anyway. Disassembled the carb, sparkling clean, but it feels like it's spitting air back out the air intake when cranking. After cranking 10-15 seconds, it drips fuel out the air intake. Manufacturer recommended complete new carb. Same result, so they sent another complete new carb. Same thing. Fuel shutoff on carbs work, oil pressure sensor has been plugged and unplugged. Crankcase vent has been disconnected from carb as it may have been the source for air spitting back through carb, but that didn't help, either. Checked valve clearance and one intake was tight. Set it to factory spec of .006" and no change. It will sputter a little if you pour gas or starting fluid directly into the intake manifold with the carb removed. I'm thinking either a sheared flywheel key or compression release not releasing. I hate to tear into the crankcase on an engine with only 5 hours. Do you know of a way to test the compression release without disassembly? This is a Champion 12000 KW generator, #100111. Thanks!

Thanks, I get it now.

Thanks!

Thanks friend,

Thanks yes

Thanks

I've replaced a broken one and one that was worn just enough to not provide enough of a release or bump to get it to start. I believe they had quality issues with who or how they were built. Both of these were near the 500hr mark.

Thank you sir

Excellent! clearly explained how an automatic compression release works. I have a newbie question, why is there a need to release compression at that very moment and for a given angle? If someone posts an answer I will greatly appreciate it.

thanks. my brand new honda hrx is having issues with the compression release, ugh!

Thx.

This is Sergey I like your videos how many compression releases have failed in your time of them have failed

Yep, I learned something again.

On my 212 engine I put a starter could I take this out thank you the video was great

Great video, dealing with 2nd broken compression release on 19HP 33R877 motor, any chance that the slightly earlier 31P777 cam (697762) will work in our motor ? It is all metal no plastic at the CR weight similar to the design you just showed. I would have to machine the groove for the oil pump drive bit have a milling machine. It seems on the late cams I am wondering if the weigh does not walk down the CR D shaped pin and get into contact with the tappet etc. that tiny open snap ring looks like its intended to keep that from happening but seems if it gets rotated the open end could allow the weight to get by it considering the CR weight is just hanging from the bottom side of the cam gear. If i need to replace that cam with the one with plastic I may tack weld a fork to make sure that weight cannot walk away from the lower face of the cam, any thoughts on making these failures not happen, This last fail bent the cam and broke the cam locating boss in the cylinder housing ? Thanks Ken

Thanks bud

It` a nice tutorial! Can you tell whether smaller Briggs engines have the same system, please? We have 7.25HP on our mower. According to its parts list, camshaft5 is made of green in color plastic (excluding its axle only :) Thank you

Lololo that cam is much better than the new ones 😅

Huh, i have yet to pull apart any of my briggs 190cc motors and all 3 run a compression release. Now i know what it is and how it works. So there is no sacrifice at all, its soley to start the engine. Really cool. But i was looking to see if i can rig a compression relief for the 66cc chinese motorized bike engine on my bike. Around 600 to 800km it gets extremely hard to turn the engine over due to higher compression from the rings seating in tye cylinder. Once started it runs fine.

Honda has the best compression release setup

accuracy is everything & he didn't make anything up. good info !

I have a 04 Titan Sidewinder with a compression release valve the one on rear cylinder is stuck in there a quick fix to unstick it without taking off cylinder head?

Just subbed! If a two stroke chainsaw doesn’t have a compression release button then how does it work?

really help video do some lawn mowers dont have compression realese? how can you tell?

Question sir, my 18 horse briggs,, my compression release is not broken, will worn lobes on cam cause me to have to adjust the valves every time I mow?

Is it on the intake valve ?

Yeassssss this is this video I need why dont Yu have millions of views

What if theres a centrifugal compression . I have honda clone 196 on mini bike and after governor was taken out after plastic plug fell out. Its been hard to pull

Do they ever fail to where it’s stuck decompressing? Got a 18 hp won’t start just bangs and blows air/fuel mixture out carb constantly

I have a Subaru EX-40 engine. Had slight knock, I disassembled the engine and found the decompression release lever broken. Would it cause a knock?

can you tell me if the 708cc toro Japanese engine has similar releases? can't find answers anywhere.

How can I perform a leak down test on an engine that has a compression release mechanism? Any ideas?

Can a broken cam release make a clattering noise? Thanks

I think my 1977 Sears lawn mower with the 12 HP Tecumseh engine has compression release but I'm not sure. Does it have it??

I have a 16 ph Briggs engine, and unless it spins really fast the engine back fires through the intake and exhaust and will only start on a battery with a full charge. Could this be a bad camshaft pressure release causing this issue?

Can you buy just the decompression parts without buy camshaft?

I got a question sir :) On a CG200 motorcycle engine will an aftermarket cam gear with decomp help relieve a kickback problem on my kick starter ? I gotta say my right leg sometimes hurt when my damn motorcycle kick starter kick's back 😵‍💫

I usually file down the end of the valve stem to make the valve close for higher compression. I never trusted the compression release. All you do is hand turn the engine and watch the valves cycle through the 4 stroke process. Between bottom dead center on the intake to top dead center compression, you'll notice how the valve remains slightly open to allow the easier pull starts. It wastes a bit of gas plus emissions that are being banned in future, and at normal operating speeds it still runs underpowered. Once you max the compression 60psi-80psi, you might blow the muffler apart.