Question about 2004 Yamaha YZ 450 F

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I need to know what psi the compression on my 450f is supposed to be at is it 60~90psi dry and 110~120psi wet or what?

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Should be at least 100 psi

Posted on Jun 24, 2009

  • thomas foster
    thomas foster Jun 24, 2009

    what you need to understand is that bike has a compression release in it for easy starting what is your problem why u need to know what the compresson is maybe i can help



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Getz 2009 model Compression test dry 1-0, 2-120, 3-170, 4-180 Wet 1-0, 2-240, 3-250, 4-250

not happy with the compression readings
adding a squirt of oil to seal off the rings will not increase the compression by 70 psi so too much oil was used for the wet test even the dry at 180 psi may not be correct as the compression of most cars is 165 max
no 1 with nothing is a valve problem because even with ring failure you will get a reading of some sort especially in the wet test
regardless if the readings can be believed , a variation of 10% is allowed so 3 & 4 would be acceptable but 2 is low against no 3
The head will have to come off and be machined flat and damage to the bores can be inspected while the head is off

Jun 01, 2017 | Cars & Trucks

1 Answer

Compresssion 2000 4.3 gm motor

Compression depends on many factors and it is most important that all cylinders test within 10% same as the others. Generally, tests are affected by being done with throttle wide open, weather conditions, engine wear, whether you test "wet" or "dry", battery condition, etc. Compression above 120 psi and same on all cylinders is pretty good, while 150 + is very good for most engines.

Jul 28, 2016 | GMC Cars & Trucks

1 Answer

What should idle psi and 2500-3000 rpm psi with a warm engine be.

compression pressure is read at cranking speed with throttle wide open. For petrol engine it is 155-165 psi hot dry with an allowed variation of no more than 10% between adjacent cylinders and around 175 psi hot wet (OIl injected to seal rings)
For a diesel engine it can be 550 psi -650 psi hot dry at cranking speed with the only engine being test while running being a detroit diesel 2 stroke
There is no compression reading done at rpms as it is meaningless

May 07, 2016 | Cars & Trucks

1 Answer

, about 1 litter per 1000 km.No smoke, no leaks, no loss of power. I fill oil in ( about 200ml) then oil level show correct. after driving a distance then oil level is low again.What can the cause be

have a wet and dry compression test done on the engine
compression pressure should be around 150-165 psi with a variation between adjacent cylinders or not more than 10%
If the compression is down to say 120 psi wet then the problem will be a worn engine
the smoke is there but the cat converter is doing its job and burning it off

Jan 18, 2016 | Cars & Trucks

1 Answer

Renault Scenic 2001 - burning oil, good compressions

That shoul be enough compression and if same that is a good sign check for bad Breather or PCV valve, engine has to breath or pressure will force oil. also HOW MUCH OIL DO YOU HAVE / What does the dip stick read. Could be bad intake valve seals / Valve guides.

Dec 12, 2013 | Cars & Trucks

1 Answer

Rough idle multipule misfire

Hi. The most common cause that I have found for an " only idle misfire" is low compression. The engine needs at least 100 psi of "dry " compression to idle smoothly in most cases and if any cylinders are higher or lower by more than 20 percent of any other cylinder, you will also have an idle misfire condition felt. Should you perform a compression test, make sure to disable the igntion system completely, not just move the ignition wires out of the way as you will still have spark and the fuel injectors will still inject fuel in nearby proximity to possible ignition source. Always perform two tests, "dry" and "wet" compression. "Dry" is warm engine with spark plugs removed. "Wet" is after performing "dry" test add a few drops of light oil into cylinders and perform compression test again to see if the number rise. If they rise, you have worn piston rings or cylinder walls. If they do not rise, you likely have worn valve seats, misadjusted valves, or head gasket issues, possibly cracks in the cylinder head. If you need to know how to compression test with a tester in detail, message me back and I can help. I'm assuming you may already know due to the fact you state you replaced all the parts likely by yourself so you probably have strong technical merit.

Aug 09, 2012 | 1999 Honda Civic

1 Answer

Low compression on #2,4,6,8,eng has been siting for 2 years

When the compression goes up wet then your solution is the rings,The best conclusion is to remove the cylinder head.

Apr 02, 2012 | Cars & Trucks

1 Answer

1995 toyota will die and will not start until engine is cold

Your problem sounds like either your fuel pump is cutting out when hot,,or the condencer or coil or you are losing compression due to piston rings worn or broken.
So first get a compression test if all cylinders are around 110 cold then check again when hot they should be up by 20 psi even if 1 or 2 cylinders are down to 80 it could be valve problem so get a WET and DRY test done, but once you have ruled out the compression and its ok then you need to look further.

Let me know how you go. RON

Jan 09, 2011 | 1995 Toyota Camry

2 Answers

Was just wondering when doing a compression test on motor..what the numbers should read....and also what should they read when testing a new motor?

The standard compression for your honda would be around 175 psi the minimum would be around 135 psi. they should be the same new or old engine. and there not the same for all engines

Sep 30, 2009 | 1989 Honda Prelude

1 Answer

1999 Daewoo Lanos SX is not idling properly even after I canges the MAP and the Throttle position sensors, what could be wrong?

go back to basics
do cylinder compression test, dry and wet
if compressions 25 psi lower than another one this can cause rough idle(valves leaking)
should be 150-180 psi any lower engine wear.
check pcv hose from rocker cover to throttle body especially port in throttle body for blockage.
are any codes being set?

Apr 16, 2009 | 1999 Daewoo Lanos

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