Small Engine compression test gauge vs no gauge drop test comparison with chainsaws
Vložit
- čas přidán 16. 02. 2023
- I'm giving away a chainsaw to one of my first 1000 subscribers. • Video
I recently acquired a few chainsaws from a local guy and decided to do a few different types of compression tests on them. In this video I'll do the drop test and an actual compression test on 4 chainsaws and compare the results. Then we will pull the mufflers off and check the piston condition to further evaluate the accuracy of these methods. Stay tuned, its going to surprise you!
Heres a link to the video I did when I got these chainsaws:
• Broken chainsaw haul, ...
Dielectric grease: amzn.to/3YE4PBh
Compression test kit: amzn.to/3KhiAl6
Here's an explanation about what compression is and why its important:
Gasoline engines require compression to operate. The process of compression confines and presses a mixture of air and fuel (mixed in the carburetor) into a small volume within the area of the engine's cylinder. This process presses together all the molecules under very high pressure. Since the gasoline engine has a spark plug, only moderate compression is enough, requiring about 140-160 pounds per square inch (PSI). Depending on their size and application, some engines may require a higher compression such as 220 PSI. The manufacturer gives the exact compression factor. The compression process of the air-fuel mixture and its ignition is what produces the necessary power to operate a vehicle.
As an amazon associate I earn from qualifying purchases at no additional cost to you. Thank you
I have a tip for you. The way you pull on the cord makes a big difference to the wear of the starter. It is better to pull up any slack so the starter is engaged and even till you feel the compression, before yanking hard to start. When you just grab and pull without taking up the slack, those tiny parts that grab the shaft to spin it, get slammed very hard.
Simple and informative. Well done! Two thumbs up
Thanks!
Great job man! Keep up the great work.
Thanks! Will do and I appreciate you watching and giving feedback!
You ah really put some work in on this video 💪
I was going to get a compression tester but a couple decent mechanics showed as you did, testing by feel, AND they pointed out that pistons and rings can be bad and you still get good compression. They also pointed out that some saws showing low compression had clean piston and rings and ran well. I think examining the piston and rings visible condition is more useful. A pressure and vacuum test is more important, I think.
Thanks for the helpful info.
You’re welcome!
Best Test, is the "Spark Test" but you have to grab your best friend and pull as you hold on to him or she, ha ha ha!!! Liked#1
HAHA that's a good one! Thanks as always for the like!!!
Well done. Some hard pulling in the heat.
Lol for sure. Thanks for watching
Always preferred the gauge test
No doubt that test should be the clear winner, but I'm really surprised that the compression tested out so high on that scored one! My new method will be BOTH lol.
As one, or two commented. Leak down test with compressed air is the gold standard. Should be less than 5% on a engine in good health. If you have more than 10% you got problems.
Thanks for watching and for the info!
thanks for all the hard work on this, what I found is you can have ok compression on an engine that you believe is bad, but the leak down test will show rings losing compression to soon thanks!
You're very welcome! Thank you for watching, subscribing, and leaving this comment! That's very interesting indeed. So I would be lying if I said I knew how to perform such a test. I do have a pressure test gauge but that is checking for leaks on the seals and boots and things like that. I'm I will definitely look it up for my own reference. Luckily with a small engine like this its easy to just pull the muffler and get a good view of what's happening. I'm sure that becomes much more complex with large items!
@@mainelysmallengineDIY oil mix 33:1 is ok ? 372 xp 357xp 351
@@Sensei948I run 36:1/ 7ounces -2 gallons.
@@alanmeyers3957 Friend, can 33:1 with Jaso FD oil damage the engine through carbon deposits?
@@mainelysmallengineDIY Friend, can 33:1 with Jaso FD oil damage the engine through carbon deposits?
If you are dry pulling with no fuel mix you can cause a little damage.
I've seen saws with 140 psi with badly scored pistons.
That's why I prefer to do a cylinder pressure, not to confuse with an engine leak-down test.
Good info!
A Pro is running a chrome piston, and the the chrome peeled. They also come in aluminum and aluminum for a 50 hour saw, the Professional saws are chome cylinder aluminum piston and usually double ring, and some single rings too. Poulans also love to just drop a different bore head on the same motor. So yeah, a 42cc head will drop on a 36cc saw as long as they are a Strato motor. Strato Poulans have the choke and run switches on top of another. The older Duralife motors have a kill switch on one side and a choke on the other side of the handle. Duralife motors can be made into a serous motor, the Stratos transfers are just to wacked out to really get serious HP numbers with porting. I don't mind a Strato motor, they are dependable and never really have many problems. The Duralife can usually hit you for a ignition system, and break crankshafts now and then, because they have a lighter crank and more power. I personally love the Pro 4620's and even own two...lol. They sell cheap with a AVX adjustment, but a old school side cover adjuster makes a real great saw. Especially at only 11lbs.
Lot's of good information here that I had no idea about! Thanks for sharing all of this. I'll keep an eye out for a 4620 in that case! What do you make of the compression on the 4218 Pro with the torched piston? How can it be getting 150 PSI in that condition?
@@mainelysmallengineDIY I think your gauge is a little off. I have seen some like that, and usually 115 to 120 at best. Don't worry if the ring is free it will run on for a while, I have a Craftsman 42cc that is a Poulan Pro setup, and after 18 years it shows 100 psi and runs great. It doesn't have as much power as it did, but don't smoke or act up at all. But again I run Husqvarna oil, and.I clean out my cover and filter after every job too. Piston scoring, and sandblasted dome comes from Fines getting passed the air cleaner. Fines is usually what destroys along with crap oil. Treat them well, and they will do you the same
@@SuperMag357 That's exactly what I was thinking as well so I actually borrowed a high end Matco gauge from a mechanic friend and have done a test on it. I'll be putting that video together over the next week or two and posting. Good advice there about the maintenance for sure. Thanks again and make sure you check out that video when I test that gauge out!!
@@mainelysmallengineDIY Just remember to always pull the choke out to help seal up the motor for a accurate reading. Then just deduct the difference off of your gauge. Chances are it will come in the same from saw to saw. My Chinese torque wrench reads 5lb light, compared to a SnapOn. I paid $20 and Al paid $200...lol. Nothing wrong with it as long as you know exactly how far it's off. Keep up the good work, I'll support your channel. Your doing better then most.
So much to learn always! I didn't even think about having the choke open! Now I'm gonna have to go back and test that! lol Thanks for the support and kind words. Its appreciated for sure and I'll keep doing my best to create good content!
Probably heavy Carbon buildup in that Poulan 4218. I'd say Piston/Ring/Jug to get it going good again. If the saw wasn't leaned out way to far, it is likely the owner had a habit of Firing up the saw and after a quick Rev. up or two, immediately Going into the wood. Excessive rapid piston expansion near the exhaust and eventual Scoring.
I am surprised the Gauge showed 135lbs with that light drop test. I think it was being generous, lol.
Thanks for the into. Sounds likely.
Poulan pro is just a name to fool those who don’t know saws. It’s a cheap throw away saw. The craftsman is made by poulan also. The wild thing is a 50 hour saw, after 50:hrs it will be nearly worn out!
Got a 2008 pp, a2010 crafstman. So umm 10 to 15 years?😂😂 let me guess, you own a apple phone😂😂😂😂😂😂😂😂😂😂
@@kraftzion I repair saws, own many, 5 Stihl, 3 homelite, 2 macs, 1 Husqvarna, 3 craftsman made by poulan and wow 6 poulans. Have used them all and preferr the Stihl
@@magicone9327 so what do you think wears out on a poulan after 50 hours? And how long do you think the same part lasts on a stihl?
@@kraftzion rings wear down, not so much in the older ones when poulan made a good production saw. When they switched to selling to residential everything went downhill. I have had older poulans that would have been used felling or on the landing. Newer saw made with Plastics make them so much lighter but the plastics warp over time. I have a poulan 4218 that the clutch had become hot because the owner/user did not understand that when running, the brake must be released or the clutch will continue to spin and the drum won’t, it got hot. Apparently the chain wouldn’t stop so he tripped the brake when it sat idling. That practice was probably what took the temper out of the clutch springs and made it continue turning the chain. Anyway the plastic around the clutch and crankshaft melted enough that the oil pump drive moved away from the driven oil gear and would not oil. No repair for that one. Still have it as the engine is ok just the plastic is ruined. The old metal ones would have survived. Stihl uses chrome plate cylinders with higher quality ring material. On the cheaper home owner saws the rings wear rapidly and then the combustion gases start leaking by and it’s not long that the saw either seizes or loses so much compression that it just won’t fire.
120 for that saw with the scored piston may not be high it may be low for that
You are right what you say 2 stroke engines need at least 125 to run most of the time but each type and size of saw has different specifications on compression. Before doing a test you normally would look up the saws spec for that and then you know for sure . I was actually thinking it could have been an easy start system on the recoil as they don't do too well on the drop down check or pulling the recoil check . As for rebuilding that one i think that will be a clamshell so it may be more than the saw is worth for a cylinder and piston and a lot of hassle for nothing . But i would be good content for you
Thanks for the info. Yeah I’m not sure if I’ll ever rebuild it but if I do it’s for a learning experience only and not because it’s worth it! Lol.
I don’t think there is an easy start there either but that and the manufacturers specs are definitely good tips to look at!
Thanks
I’ve seen a lot of crap but this crook put like stp in cly to increase compression
My friend bought a used saw with trashed cylinder and paid top price for it because he did the pull rope test
Oh wow that’s not cool at all. All tests aside the best thing to do in any situation if possible is to get a look at that piston.
I have a Poulan pro that was scored that bad and would not start at all . I replaced the cylinder and piston and it fired right up .
Awesome!
P.S. The Wild Thing is the same Strato motor as the AVX and all parts are interchangeable. The AVX has better air filter, better cylinder depending on what model WT it is. Poulans come in 50 hour, 125 hour and 300 hour saws. Have fun my friend, I am enjoying the channel, keep it going.
Oh cool I didn't know that! And that's hilarious 50 hour, 125 hours, and 300 hour saws!!! I did pick up a Beaird Poulan (vintage) the other day also but I think that one was built a little better. I'll post a video on it one of these days. It's not in the greatest shape but I got it for cheap and It'll make for a fun project. Thanks for comments and I'm glad you are enjoying! I'll stick with it!
Friend, can 33:1 with Jaso FD oil damage the engine through carbon deposits?
@@Sensei948I don't see how it can be any worse then any other oil. Usually they are very small amounts as most are Synthetic. About the only one that I have seen that bleeds a black carbon oil residue is the Husqvarna XP+ and one Echo oil I tried. The LS Husqvarna oil leaves a dry carbon residue that is brown in color. I have pulled a few apart that run a few tanks of the XP+ and the motor was washed clean of any carbon buildup. The downside was the exhaust was bleeding the black wet carbon. The last two I brought home, actually got the XP+ until it finally stopped bleeding carbon, when I pulled the muffer it looked brand new, it also showed some damage to the top of the piston from Fines getting passed the air cleaner. Normally I have to drop a scope down the sparkplug hole to see that. I don't know about 32:1 ratio, but my old Poulan CV3400 shows 20:1 in the manual with Dinosaur oil, but everyone and myself run Synthetic at 40:1 with no trouble. You might wanna look at a higher end oil that covers from 16:1 to 100:1 that way you know your covered. You can look around on the net at your saw, weedeater or whatever you're running, chances are someone is running it on modern oil with a good working ratio. Don't get too worried if you just go Husqvarna or Echo at 40:1, cause I have 3 saws that smoke when starting and warming up, just like it was running the Dinosaur oil...lol. The Poulan Pro 330 can kill mosquitoes in the first minutes of running...lol.
@@SuperMag357 I just use Husqvarna LS+ oil ?
@@Sensei948 XP+ if you want to clean the motor, LS if you want traditional type oil that has Ash in it like conventional oil.
Would pushing the decomp on the 460 cause a different reading on the gauge?
The answer to that is self explanatory bud you know decompression valve
Yes. Don’t test with it pushed in.
Air in from muffler? I don’t think so!
All the saws, with exception of the Stihl, are Poulans with bare aluminum cylinders.
Thanks for the info!
This method doesnt work as good on a lot of newer stuff because they have built in compression release to make it easier to start. The drop and hold the string method that is.
Should test with WOT on four stroke engines
Yes, wide open throttle on both 2 stroke @ 4 stroke
Thanks for the info!
question: ? i have basically the same test kit. Mine is a craftsman but probably the same .... made in china. It works great on standard spark plugs 12mm and 14mm. but i just tested 3 stihl HT 131 and HT101 trimmers that take the cmr6h small ngk plug and i had to use the small adapter for the spark plug hole. the reading is 50-to 70 on all the trimmers , after adding a bit of oil into the cylinder. the trimmers all work great , no loss of power. my question is ( and i'll do some more investigating on the instructions of the compression tester ) does changing to the smaller adapter change the reading of the compression ? I will try and do a drop test but these are long pole pruners and a bit hard to do a drop test with. Thanks for the great video .. Mahalo
Hi,
I wouldn’t have any reason to believe that a smaller adapter would change the readings at all.
I’ve not worked on either of these or any Stihl 4 mix engines for that matter (although I do have one that I bought broken down and I may get to one day). I believe these are both 4 mix engines, so in a nutshell a 4 stroke that takes a pre mixed gas like a 2 stroke would. I think the 4 strokes in general compression test much lower than a 2 stroke. Also there is probably some kind of compression release built into it to make it easier to start which would also effect the readings. Sounds like if they are all running good then the readings are accurate. Hope this helps!
@@mainelysmallengineDIY you are correct. I was unaware that these new stihl engines on their pole priluners and trimmers are 4 cycle engines. That changes the compression ratio , from every engine I've tested that is a 4 stroke. 4 stroke engines like Briggs and Stratton, Tecumseh, Honda, etc all test around 40 to 60 psi and run great. I will have to do some further research as to why 2 strokes seem to have higher compression that 4 strokes. I'm sure it must have something to do with the valves.
should do it a wide open throttle
14:04 thanks for watching!
Prob dumb question. Are you in Maine?
Haha yeah I’m in Maine now. The videos that are up there are from FL and I moved to Maine within the last year and got sidetracked with the channel. That said hopefully starting up again soon!
I named the channel when I decided to move to Maine. I was pretty excited! Lol
Nice. Love to collab im in Windham.
Yeah we can do that in the future probably!
you know why its higher 3 th time? CHINESE METER, when you dropp it it messure WRONG...
Not sure what you mean but thanks for watching. It’s the same with USA gauges.
Anyone who "really understands" how all this works. SAVE UR TIME, this guy knows nothing of 2 stroke chainsaws
And tell me something did you know everything about two-stroke engines when you were first starting out, think about your comment!!!!!!!
So where are your videos, mister expert?
What did he do wrong and didn’t like?
Wrong. He knows the basics. He's the same place you were at some time. Don't like his content? Don't come back......
I genuinely want to know what is wrong with people like you. You are miserable and want others to be like you. Either that or you are jealous of this guy out here making videos. You will probably have some snappy comeback to my reply but deep down you know I'm right.
Gday brother , could you try the same compression test on the engines after they are warm / mabe idling for 🤷 30 seconds or so . 👣🦘👍
Hi, I can probably try that in the future.