What should my Compression be?

[BL4ST3R AL3X]

Hello,
I done a compression test today as I had the tank off and thought I'd see what it is at and only got 105psi on a stone cold motor? It rides great but wasn't sure if this is low?

Thanks in advance

 

[joeak47]

Make sure you are holding the throttle WIDE OPEN while doing the test. Its easy to forget this.
Be sure to kick the engine over until the gauge stops reading.
You can also try another (know to be accurate) gauge. I highly recommend you do this.
Please report back with your findings.

 

[joeak47]

Testing at a higher altitude will also give slightly lower readings than when testing the same engine at a lower altitude

 

[BL4ST3R AL3X]

I held the throttle wide open and kicked it until it stopped rising.
I am about 480-500foot elevation, I am using a brand new gauge so can't guarantee it is accurate or not but as it is brand new I'd hope so.

 

[jus_me]

The brand and or the hose length can also affect the readings also.

Post a pic of the tester along with the fittings. This way we know what your working with..

 

[JoeJoeSX]

No one has answered the original question. What is a good compression spec?

 

[Larry's Shee]

The brand and or the hose length can also affect the readings also.

Post a pic of the tester along with the fittings. This way we know what your working with..

This /\/\ where Schrader valve matters too. Anything cheaper than a Craftsman probably isn't worth buying.

 

[jus_me]

No one has answered the originaStockSto,k Sl question. What is a good compression spec?

Good point... Stock should be around 120ish. There's a few variables but anywhere around 120 is ideal for a stock blaster. 100psi is about the bottom of the threshold to redo a top end.

 

[joeak47]

This /\/\ where Schrader valve matters too. Anything cheaper than a Craftsman probably isn't worth buying.

Larry is CORRECT! /\ /\ /\

Don't use a piece of crap tester that may have been dropped, or has known issues.

Your doing the test correctly. We just want you to be sure of the results.
It isn't a harbor freight compression tester is it?

 

[BL4ST3R AL3X]

It was an eBay buy I think, my girlfriend bought me it as I didn't have one and I mentioned I needed one. I think it was a cheap one if I'm honest, I think I will go ahead and buy a decent more expensive one and retry the test before i do anything else. I will post a picture up soon and will give as much info as I can about it. but like I said I think it was just a cheap one off eBay :/

 

[joeak47]

There is nothing wrong with an "inexpensive" gauge as long as you know its accurate. Accuracy is the key here.
If you can, just borrow a gauge from a buddy and re-test. If its showing the same, then you know your gauge is good to go.
As far as I'm concerned, your ahead of the game, because your blaster is in running condition to start with.
Kudos to you for compression testing! Its important and tells you a lot about cylinder condition.
I wish more folks would do that. It would save them a bunch of headaches.

Be sure to clean your air filter too, and a fresh plug.

 

[Larry's Shee]

Most may be hard to start at 105#. If you don't get ahold of another tester right away don't sweat it, if it still starts good, IMO.

 

[BL4ST3R AL3X]

Starts 2nd mostly 3rd kick On first start up and runs fine will see if I can borrow a mates gauge to double check compression again, just got a brand new air filter and a new spark plug, Put in when I done the compression test