had a bunch of comments on the last video about my compression test not being good because I did it with the throttle stuck half way open. l said it would only make a minimal difference at half or full throttle. so lets see what the actual difference is at closed ,half, and full throttle,
Nice
I understand what your doing but don't see the point. Seeing how I don't start a bike with the throttle wide open. I want to know what the condition of the engine is in
and how it's configured under normal circumstances. In addition , I've never done this with a car while performing a compression test.
If you want to see higher compression numbers that are totally inaccurate. Take a hair dryer and hook it up to the intake and force more air into the cylinder. That should also
improve your numbers. It won't change anything or make the engine run better. But you will satisfy your need to see higher numbers.
By changing the throttle , you corrupt your baseline and no longer have a point of reference and you end up masking your real numbers or a potential problem.
I can see why you might do this test with the throttle wide open, if you race. Racing bikes spend a great deal of time at full throttle, but are often hard to start due to higher
compression ratios and advanced timing. Street bikes and recreational bikes spend most of their time under 25% throttle input.
Thanks mate. Top vid.
MUSTIE 1/////ROCK'S
Hmmm, I think I screwed up my last compression test…
Good show.,educational as always!
Been doing a Mustie thon. Learning so much from your videos. Who needs cable TV. Love your channel.
No idea why but the results were opposite to what I expected! Very interesting keep it up.
So if no diffrence does that mean bad valves?
The engine should also be warm
Had a guy come with his "certified mechanic" to buy a Honda 300 4X4 from me. Hie wanted to do a compression test, which I had no problem with. He even brought his own gauge, hehehe. He spun her up and tried to knock 1000 bucks off the 4500 price because the compression was low. He asked what I though of that. I said the price is now 5500 bucks. He said that I can't do that because I listed it for 4500. I said once you deviate from listed price, the listed price no longer applies. He argued that it wasn't fair and he was going to call the cops. I said go ahead, but don't forget to tell them that you tried to cheat me by bringing a fake mechanic and doing a compression test with the throttle closed. I then turned to the "mechanic" and asked to see his trade card (most mechanics have their journeyman's card in their wallet)so I can report him to the board. They got in their truck and drove away. Same truck came back next day with different guys in it and paid me $4500 without looking at the bike very hard at all, hehehe.
Restricted exhaust would make a difference, however quite small. The difference is in atmospheric pressure VS pressurized air being forced out by the piston. (Also the reason why intake valves are larger than exhaust) Now, a RUNNING engine is a whole 'nuther matter because the gasses have now expanded. Then restricted exhaust makes a huge difference!
Many thanks !
Great info.
You are one of my favorite YouTube channel's
Mustie1.
I don't care what anyone says, I'm sure you know what you're doing. All the Safety Sams and the nit pickers annoy me too.
From across the pond. One other check is to add a small amount of engine oil in the plug hole, then redo the test. This determines whether any escaping gases are going past the piston rings or the valves. Any change in the reading would indicate the rings are broken or worn. It also seems to pick up scored cylinder walls quite well. Obviously if the damage is serious this extra test does not work.
I am a youtube commentor. I don't have a channel or any videos, nor do I contribute in any way, but somehow I still know more than most content creators. I don't have many talents or skills, but why bother working when all I have to do is find people that ARE talented and skillful, and leave a comment stating they are wrong and that I am better than them.