I find your videos very simple and explained well. You can always prove your point by showing it in action; not many people do these days; they just run their mouths. Keep posting, I enjoy learning from you and expanding my knowledge on dirt bikes.
That is freakin' amazing. If you would have pulled me off the street and asked me what a hole in the piston would do to compression, I'd say it would drop to near zero. But I guess it makes sense on a 2-stoke with the crank being pressurized. Thank you sir!
If you had a hole in your piston that occurred while riding and not via a tiny drill bit, then you would have had near zero compression. The size of the hole that was drilled in the piston in this video was approximately the same size as the hole that could come in a compression release valve… and when a compression release valve is depressed there is still compression albeit less.
Great advice. Thanks!! My 2020 TM 300 EN has almost 100hrs on it but it still makes tons of power. I should probably look in the exhaust port and do the other things you mentioned.
Compression test is just one diagnostic. A leak down test would have been the next step and would clearly have let you know that there was a major loss of actual compression via Rings, Valves or Piston wear, cracking etc.
I never check ring gap because if I have it apart I'm putting new in. Also I changed my top end on my 250 2t approximately 40 to 50 hours regardless if it needs it or not.
If you don’t check, you don’t know how much wear you have. Like I said, if you don’t care you can certainly change it much more often than necessary. It’s also very important to check end gap on new rings. Just did one today that was too tight. Very likely would have seized.
I've always considered a leak-down compression test to be a much better diagnostic procedure as it shows a more complete picture of the cylinder's ability to seal. Are you familiar with a leak-down test? And is it something you ever perform in lieu of a standard compression test?
I rarely use a leakdown test either. It’s better than compression, but still subject to more variables than most people think about. I use leakdown for very specific checks. Top end wear is too generic.
as a young tech i dont rely on compression i rarely even do it. i wanna see with my eyes the condition of the engine. i scope it. if its a 4 stroke leak down has done me just fine but i still scope everything i touch that has a running issue.
Leakdowns are better because they can sometimes pinpoint where the problem is, but they can be deceiving too. I just recently had a 4 stroke with less than 2% leakdown and burning oil badly past the rings. I did a leakdown on only the ports to verify and then replaced the piston which solved the issue. I always try to stack tests logically to get an idea of what’s happening.
It can be, but they can be deceiving too. It’s important to remember that whatever test you’re doing, it’s a piece of evidence that needs to be viewed in context of the whole situation.
![How To Perform a Compression Test - [EASY]](http://i.ytimg.com/vi/3VmmL0YAO14/mqdefault.jpg)
I find your videos very simple and explained well. You can always prove your point by showing it in action; not many people do these days; they just run their mouths. Keep posting, I enjoy learning from you and expanding my knowledge on dirt bikes.
That is freakin' amazing. If you would have pulled me off the street and asked me what a hole in the piston would do to compression, I'd say it would drop to near zero. But I guess it makes sense on a 2-stoke with the crank being pressurized. Thank you sir!
If you had a hole in your piston that occurred while riding and not via a tiny drill bit, then you would have had near zero compression. The size of the hole that was drilled in the piston in this video was approximately the same size as the hole that could come in a compression release valve… and when a compression release valve is depressed there is still compression albeit less.
💯
It's just one part of a diagnostic challenge
I've been working on engines for+30 years and rarely do you see identical failure modes.
These videos are great, keep ‘em coming
Didn’t expect that to have 130psi with a hole. Wild
What Is the purpose of these pair of holes in the pistón?
Just for learning.
Hehe no sorry, i mean the two holes both sides piston, i just see this in KTM, maybe lube holes?
Thanks for taking the time to publish this!
Great advice. Thanks!!
My 2020 TM 300 EN has almost 100hrs on it but it still makes tons of power. I should probably look in the exhaust port and do the other things you mentioned.
Compression test is just one diagnostic. A leak down test would have been the next step and would clearly have let you know that there was a major loss of actual compression via Rings, Valves or Piston wear, cracking etc.
Ah the good ol YZ piston canyon effect. Great testing!
I never check ring gap because if I have it apart I'm putting new in. Also I changed my top end on my 250 2t approximately 40 to 50 hours regardless if it needs it or not.
If you don’t check, you don’t know how much wear you have. Like I said, if you don’t care you can certainly change it much more often than necessary.
It’s also very important to check end gap on new rings. Just did one today that was too tight. Very likely would have seized.
@@ChuckfromTrueTech I check the piston to cylinder wall for clearance.
I've always considered a leak-down compression test to be a much better diagnostic procedure as it shows a more complete picture of the cylinder's ability to seal. Are you familiar with a leak-down test? And is it something you ever perform in lieu of a standard compression test?
I rarely use a leakdown test either. It’s better than compression, but still subject to more variables than most people think about. I use leakdown for very specific checks. Top end wear is too generic.
Helpful video, thank you!
as a young tech i dont rely on compression i rarely even do it. i wanna see with my eyes the condition of the engine. i scope it. if its a 4 stroke leak down has done me just fine but i still scope everything i touch that has a running issue.
I’ve had the odd leakdown throw me for a loop, but it certainly sounds like you’ve got a critical & deductive approach.
Interesting! Thanks for this. Would a leak down test be any more informative?
Leakdowns are better because they can sometimes pinpoint where the problem is, but they can be deceiving too. I just recently had a 4 stroke with less than 2% leakdown and burning oil badly past the rings. I did a leakdown on only the ports to verify and then replaced the piston which solved the issue. I always try to stack tests logically to get an idea of what’s happening.
This is an excellent video. Time to get me a boroscope 😅😂😂
Would a leak down test be better?
It can be, but they can be deceiving too. It’s important to remember that whatever test you’re doing, it’s a piece of evidence that needs to be viewed in context of the whole situation.