Compression tester

[md86]

I think I'm gonna pick me up one of these things , butI have some questions .
1: I don't have a compressor . Gonna be a problem ?
2: I THINK I remember seeing gauges that don't need a compressor , you just kick the engine ove until the gauge stops rising or something ?
I found one from JCW that says "fits all motorcycles" , and basically looks like just a gauge with a hose and coupler . That sound like what I want ?

[trinc]

get a regular compression guage and screw it into your spark plug hole - unplug the coil ( so the bike won't start ) and crank it over.

to charge the cylinder with air is a 'better' test but for the home mechanic
that just wants a general condition ....


tim

[Black_peter]

+1 trinc
I can't seem to find my compression tester..
I have managed to move the damnedest things from New England to Arizona to Texas without loosing them but my compression tester??
Gone..

Basic compression testers have a tire type valve in them and you either hold a rubber cone into the spark plug hole or screw it in. when you turn the engine over it holds (via the valve) the highest pressure each cylinder can create.


The second kind is to test "leak down"
You pressureize the cylinder and record the pressure drop over time. This is expressed as
Psi per minute (or hour). This is the rate the cylinder leaks by the rings and valves.
Leak by is always there..

[arsenic]

yeah, any compression tester will work. I just picked up a spare tester at harbor frieght for like 15.00 bucks. I know harbor freight isn't great tools by any means, but 15 bucks, how do you pass that up.

[Black_peter]

Right!!!
Really compression testers do two things..
(sorry this didn't get mentioned before)
Firstly basic pressure built by the cylinder.
Second making sure all cylinders are close in pressure
This is a little more important and where the price point of the gauge is not as important.

[trinc]

Right!!!
Really compression testers do two things..
(sorry this didn't get mentioned before)
Firstly basic pressure built by the cylinder.
Second making sure all cylinders are close in pressure
This is a little more important and where the price point of the gauge is not as important.

i did have a guy that wanted to buy my truck bring his guage over and found a pretty wide spread between the 4 cylinders ( toyota - they did have a head gasket problem ) he was bumed because he loved the truck & it ran great - i told him he had a POS guage - he finally came back the next day with a new 'good' guage and all cyliders were in the upper spec range - just like i knew they where.

some tools you want to spend the extra dollars & care for them a little better.

tim

[arsenic]

oh for sure. My Matco gauge is the one I use all the time. I just needed a spare to have around in case soething happends to the other one. I'm certainly not saying that the compression tester from harbor freight should be your #1 compression gauge, I just that that 15 dollars for a tester was unreal, even if I only works once.

[The CyberPoet]

two bits to add here:

You don't need a compressor if you can get a compressed air source. Various firms sell just air tanks that you can fill up at a standard pump or compressor and take with you -- those will hold enough air to do a leak-down test, and save you buying a full compressor.

The second bit is the valves -- you need to do a valve adjustment (or know they are in adjustment) before undertaking the test, because a valve out of adjustment will leakdown just like a set of bad rings would -- letting the air escape via the valves.

Cheers
=-= The Cyberpoet

[md86]

Okay , I just bought one from JCW for about $30 . I actually bought it to test an old CB I'm tinkering with , but I'll probably use it on every bike in the area before too long ! Thanks guys .