How do I do a compression test? Is there a cheap tester that I can buy?

I have tried a number of local garages around here and none of them want to know. The car garages because it is bike engined and the bike garages beacuse it is a car. I'll di it myself if I can.

[Edited on 12-11-2005 by smart51]

I bought one off this ebay seller a couple of weeks back -- great quality & price and the quickest delivery ever, he also sells some other nice tols.

http://cgi.ebay.co.uk/BRAND-NEW-COMPRESSION-TESTER_W0QQitemZ8013463510QQcategoryZ30921QQtcZphotoQQcmdZViewItem

if its only a compression test, why dont any garages want to know??

An engine is an engine after all! Same test whatever the engine! Remove spark plug and screw in compression tester!

All cylinders should more or less be the same compression

Thinking about it many car style testers don't fittings for 10 and 12 mm plug threads.

One with a rubber cone push/hold on fitting like this one might be best

http://cgi.ebay.co.uk/PRO-TUNE-COMPRESSION-TESTER-KIT_W0QQitemZ8013747854QQcategoryZ30921QQrdZ1QQcmdZViewItem

[Edited on 11/11/05 by britishtrident]

I'm currently in the process of doing the head gasket in my civic. One of the goals in doing this, was to improve or even out compression on all pistons, so obviously I needed to go buy a compression tester.

I went to Sears and bought a $25 tester and did the standard once-without-oil, once-with-oil test (oil improved compression on all pistons by 15psi)

Question though... One of the pistons was down by 15 psi from all the others (all were 195 except piston 3 was at 180) The oil test raised ALL pistons by 15psi, so they were still off (210, 210, 195, 210).

Does this point to a valve problem, since the rings seem to have improved an identical amount when given oil?

I'm going to clearance the rockers and examine the valves anyway, so I may just answer my own question but... Anybody have thoughts on this?

Very slight variation probably one valve not seating quite as well as the others all in all very good compression for a high mileage engine -- best left untouched just check the valve clearnces.

Could indicate worn cam lobes, sometimes you can see the compression going up on some cylinders !

I've done a compression test and the results are not too good.

1 - 110 psi
2 - 98 psi
3 - 129 psi
4 - 103 psi

each of these readings goes up by 1 psi after a few drops of oil have been dripped in through the spark plug hole.


Mr. Haynes suggests that the minimum pressure should be 192 psi with 206 psi nominal and 213 max, and with no more than 14.5 between max and min.

my lowest cylinder is half of the nominal and there is 26 psi max difference.

I did the test with the engine warm rather than really hot. Would this make much difference?

What could be wrong other than valve seating and head gasket? How do I check and how do I fix it?


[Edited on 12-11-2005 by smart51]

Did you have the throttle wide open?

Oops! I realised, just as I was leaving the house earlier, that I hadn't opened the throttle during the test. Something for me to try tomorrow.

This thread looks interesting, I haven't tried it but this technique looks more helpful than a straight compression test:
http://www.locostbuilders.co.uk/viewthread.php?tid=34279

Caber

Repeated the compression test this morning with the throttle wide open and all the spark plugs removed. These are the results in psi without / with oil

1) 155 - 155
2) 95 - 99
3) 151 - 156
4) 153 - 155

the manual states 192 psi min, 206 nominal and 213 max. 155 is 75% or nominal, 95 is just rubish.

What can the problem be?

[Edited on 13-11-2005 by smart51]

try a little oil in the low cylinder to see if the rings are knackered,( this should seal some of the affected area and will give an increased figure ) as by the sounds of it there is a problem with either piston rings or valve seats / valves

hope this helps

marc

another thought
are all the butterflys openening ok

[Edited on 13/11/05 by mnr laptop]

Valve seats burnt perhaps as R1's get proper caned and why not if the motor begs to be thrashed
Is there any info anywhere on whether the valves shrink into the head like the 400cc screamers do?

I tried it with a bit of oil. That's what gives the two figures for each cylinder. The difference with oil isn't very big so the problem is likely to be in the head, isn't it?

The butterflies are all opening nicely.