checking compression

[joho5]

Unplug the and ground the wires...Take 1 plug out at a time and replace with compression checker, then do I pull it untill the meter wont go up any more? Or do I just pull it a certain amount of times?

thanks

 

[sb220]

Re: checking compression

Take all your plugs out( no spark plugs in the engine ), ground wires and/or flip your safety cutoff switch, install gauge into a cylinder and turn over (try to count to 5 or so with the rhythm of the motor turning over.

And you should get higher readings if the engine is warmed up before hand

 

[Chris1956]

Re: checking compression

I leave the ignition off and jumper the starter solenoid to spin the motor, all plugs out. Let the gauge top out and note the reading. Remember pressure gauges are likely to be reliable, but not accurate. Therefore if all cylinders are close in compression, the motor is probably good, reguardless of pressure. Of course this doesn't apply to a single cylinder or two cylinder motor with a blown head gasket

 

[joho5]

Re: checking compression

why pull all the plugs?

thanks

 

[tashasdaddy]

Re: checking compression

because, that's the way you do it.

 

[LubeDude]

Re: checking compression

why pull all the plugs?

thanks

Yea, that's the way you do it!! But the reason is that the engine will turn over faster and give you a more accurate reading!

You should start with a fully charged battery also!

And, just in case someone tells you to crack the throttle open when you do the comp check, you do not have to do this with a 2 stroke!!

 

[samm835]

Re: checking compression

I don't want to hijack.... when I bought my last motor I was able to take it to a marina to have it inspected. My brother is looking at buying a boat so I want to test the one he looks at prior to buying. So you 1) take all plugs out 2) install gauge in first plug 3) turn motor over for roughly five seconds 4) do to all cylinders 5) make sure strong battery. I have heard all cylinders should be within about 5 difference..is this true? Also shouldn't you be looking for at least 110 reading? Thanks and again sorry for the hi-jack

 

[joho5]

Re: checking compression

because, that's the way you do it.

I am in no way trying to be tacky, but when I ask why, its because I want to learn. I am the type that doesnt just do things because "thats how you do it" I am OCD about understanding why I am doing what I am doing.

I wouldnt have asked the question otherwise.

 

[Bigprairie1]

Re: checking compression

TD is right, its just the way you do it.
Why, because:
1) You want to check for the best/maximum compression....make sense?
2) The way you get that accomplished is by having the motor and pistons operate as quickly and freely as possible to create maximum pressure in the cylinder being tested with a gauge....make sense?
3) The way you get that accomplished is by removing the all the spark plugs so their is no resisting back pressure in the other cylinders which would slow the cranking down somewhat. Having them out gets the motor spinning as quickly as possible....make sense?
Ba-da-bing.
BP

 

[joho5]

Re: checking compression

got it...makes sense, yes.

appreciated.

 

[marquette]

Re: checking compression

why do you have to crack the throttle open on a 4 stroke?