SuzukiSavage.com - Cylinder compression

Thomas Högberg Junior Member Offline SuzukiSavage.com Rocks! Posts: 61 Vårgårda, Sweden Gender:	Cylinder compression 07/16/14 at 02:38:53 Hi everyone What should be a normal compression reading in kg´s? My local repairshop got 6 kg... He also said that it leaks through the exhaust valves. /Thomas
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Gowor

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Re: Cylinder compression
Reply #1 - 07/16/14 at 03:25:17

Kgs are a unit of weight, not pressure. If it was 6 kg/square centimeter, then you get about 85 psi, but I'm guessing here.
I think a normal value is about 145-200 psi.

Check if they disconnected the decompression electromagnet at the shop when testing. If not they'll get a very low compression and leak at the exhaust valve, because basically that's what the decompressor is for

One mechanic checked my engine without disconnecting it - he got a very low compression, and couldn't figure out how the engine works at all.

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Thomas Högberg

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Re: Cylinder compression
Reply #2 - 07/16/14 at 05:29:31

Gowor wrote on 07/16/14 at 03:25:17:

Kgs are a unit of weight, not pressure. If it was 6 kg/square centimeter, then you get about 85 psi, but I'm guessing here.
I think a normal value is about 145-200 psi.

Check if they disconnected the decompression electromagnet at the shop when testing. If not they'll get a very low compression and leak at the exhaust valve, because basically that's what the decompressor is for

One mechanic checked my engine without disconnecting it - he got a very low compression, and couldn't figure out how the engine works at all.

You are probably right about the unit

let´s see... for how long is the decomp active?
until the engine runs?

in that case I understand that there will be a low comp value if you check it without having the solenoid disconnected.

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Gowor

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Re: Cylinder compression
Reply #3 - 07/16/14 at 05:59:27

From what I checked, it disengages half a second after the starter begins turning.

From what I remember, the guy who checked it got a very low compression on my engine ("too low for the engine to work"), and a normal reading after I told him to deactivate it. I'm not sure how he checked it though.

EDIT: It's possible that in my case it wasn't engaged when he tested it, but adjusted incorrectly, so the exhaust valves weren't completely closed, even after it switched off.
Anyway, since you have an exhaust valves leak, and the decompressor opens them, that would be the first thing I would check.

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thumperclone Serious Thumper Alliance Member Offline PGR rider riding with respect Posts: 6067 Grand Junction Colorado Gender:	Re: Cylinder compression Reply #4 - 07/16/14 at 07:33:34 ssm standard: 1000-1400 kPa 10-14 kg/cm2 142-200 psi limit: 800 kPa 8 kg/cm2 114 psi
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Thomas Högberg

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Re: Cylinder compression
Reply #5 - 07/16/14 at 10:40:50

Gowor wrote on 07/16/14 at 05:59:27:

From what I checked, it disengages half a second after the starter begins turning.

From what I remember, the guy who checked it got a very low compression on my engine ("too low for the engine to work"), and a normal reading after I told him to deactivate it. I'm not sure how he checked it though.

EDIT: It's possible that in my case it wasn't engaged when he tested it, but adjusted incorrectly, so the exhaust valves weren't completely closed, even after it switched off.
Anyway, since you have an exhaust valves leak, and the decompressor opens them, that would be the first thing I would check.

Thanks you all for your help

I will check if the wire is adjusted right.
I do have a play at the rocker arms, both on exhaust and inlet side at TDC, so that leads me to believe that the decomp lever in the head can´t be that much wrong...

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Thomas Högberg

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Re: Cylinder compression
Reply #6 - 09/16/14 at 10:01:03

An update:
after redone my valves and seats due to low compresson, 6-6,5 kg/cm2 (85 psi)

I took the bike for a run and it´s still without any power....

it runs fine at idle and up to 50-55 mph if I am gentle but it would not accelerate good if I force it and it has no power actually.

the bike has had this problem since I bought it this spring.

Checked the compression today and it was 13 kg/cm2 (185psi) so the valve job worked out just fine

K&N freeflow in airbox
half spacer
47,5 jet if I remember correct, need to verify that.
152,5 main, a bit uncertain there as well, have been changing a few times...
Dyna muffler, probably the california (cat) model, cause it has blued a lot at 5 inches from the downpipe.

the bike is a -97 and has 33000 km (20500 miles)

what would you guy´s do next??

/Thomas

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Ed L. Serious Thumper Alliance Member Offline "We All go a Little Crazy Sometimes" Norman Bates Posts: 2808 Sunny Florida Gender:	Re: Cylinder compression Reply #7 - 09/16/14 at 15:40:53 Check the cam chain adjuster and see how far it has moved out. At 20K miles it is time for a look.
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Thomas Högberg Junior Member Offline SuzukiSavage.com Rocks! Posts: 61 Vårgårda, Sweden Gender:	Re: Cylinder compression Reply #8 - 09/16/14 at 22:22:12 Ed L. wrote on 09/16/14 at 15:40:53: Check the cam chain adjuster and see how far it has moved out. At 20K miles it is time for a look. Thanks, I have modified it similar to a verslavy. /Thomas
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HondaLavis Senior Member Offline It's nothing personal; the other one came first. Posts: 451 Plano, TX	Re: Cylinder compression Reply #9 - 09/17/14 at 20:56:37 Were the valve gaps set correctly after the seat job? Maybe your valves aren't opening all the way?
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Thomas Högberg Junior Member Offline SuzukiSavage.com Rocks! Posts: 61 Vårgårda, Sweden Gender:	Re: Cylinder compression Reply #10 - 09/17/14 at 22:58:06 HondaLavis wrote on 09/17/14 at 20:56:37: Were the valve gaps set correctly after the seat job? Maybe your valves aren't opening all the way? I adjusted all four valves to 0,1 mm.
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Cylinder compression Reply #11 - 09/18/14 at 00:05:22 What's that in thousandths?
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jcstokes Serious Thumper Offline SuzukiSavage.com is very useful Posts: 2119 Mauku New Zealand Gender:	Re: Cylinder compression Reply #12 - 09/18/14 at 03:34:21 Just under 4 thou, I think.
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Thomas Högberg Junior Member Offline SuzukiSavage.com Rocks! Posts: 61 Vårgårda, Sweden Gender:	Re: Cylinder compression Reply #13 - 09/18/14 at 08:33:24 jcstokes wrote on 09/18/14 at 03:34:21: Just under 4 thou, I think. Thats correct, sorry I´m not that familiar with inches...
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Cylinder compression Reply #14 - 09/18/14 at 12:56:27 I should have just found a conversion table.. I'm not familiar enough with YOUR system. I apologize for that. I have spent some time today on various conversion tables. Fahrenheit to Celsius,MPH to knots and MPH, BUT I totally forgot to look at that one..
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