how do you do a compression test??

**Tue Nov 15, 2005 8:51 pm » Post: #1 » Download Post**

Can anyone tell me how to do a compression test please?

Should the piston be in a specific position in the cylinder?
Any special tools needed?

Cheers
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After years of moaning about immigrants now i am one...

**Wed Nov 16, 2005 2:34 am » Post: #2 » Download Post**

When I did mine, I simply removed the spark plug, and screwed in the tester.

Open the throttle and kick it over.

Should get readings above 115psi for a good engine, but it's also important to have similar readings between the two cylinders - no more than 10psi.
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**Wed Nov 16, 2005 1:17 pm » Post: #3 » Download Post**

You should warmup your engine 1st to get a proper reading.

1. Warm up engine.
2. Switch off bike
3. Remove spark plug
4. Screw in compression tester
5. kick the kick starter a few times
6. Read compression guage

Repeat for other cylinder
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Jerry Lai
NSR250 [MC21SP]

**Wed Nov 16, 2005 5:01 pm » Post: #4 » Download Post**

"Off Topic: Australia has qualified for the 2006 FIFA World Cup in Germany!!"

Is that football?

Yawn... Rolling Eyes

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**Wed Nov 16, 2005 11:59 pm » Post: #5 » Download Post**

I can feel a Forum Administrator Moderation coming on for Jezza's signature! Laughing

We'll have no discussions about the sport of poofs on this Forum, and anyone that offends can f**k off now... and don't let the door hit you on the ass on the way out!!! Smile

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Andy.
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**Thu Nov 17, 2005 12:04 am » Post: #6 » Download Post**

Sorry, I just love sports of all form... ok, except golf Confused

It's only taken 32years for us to reach the World Cup Shocked

We've lost the Ashes and we've lost in Rugby... this is all we have left Very Happy

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Jerry Lai
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**Thu Nov 17, 2005 12:07 am » Post: #7 » Download Post**

No excuse! And that wasn't an excuse to talk about it!! Consider your wrists slapped!!!

No sport is sport unless it has an engine involved!!!!
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Andy.
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**Thu Nov 17, 2005 12:17 am » Post: #8 » Download Post**

What about mud wrestling?
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**Thu Nov 17, 2005 12:34 am » Post: #9 » Download Post**

I have a couple of trademark sayings, that seem to get me through life OK...

"You don't know its' limits 'till you've crashed it!"

and

"I'm not really interested unless it's got an engine or a bikini!"

I guess mud wrestling comes under the second saying, although I'd prefer baby oil wrestling! Laughing

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**Thu Nov 17, 2005 12:51 am » Post: #10 » Download Post**

when i did my compression test i got these readings

lower-140
top-120

Are those good numbers?

**Thu Nov 17, 2005 5:08 am » Post: #11 » Download Post**

140? Bloody hell, that's amazing. Strangly high to be honest. I also don't like the 20psi split between them, ideally they should be closer numbers.

Did you do several checks and take an average?
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**Thu Nov 17, 2005 6:49 am » Post: #12 » Download Post**

Why does the difference in compression need to be closer together? Will it cause issues having a big difference between the two cylinders?
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Jerry Lai
NSR250 [MC21SP]

**Thu Nov 17, 2005 2:50 pm » Post: #13 » Download Post**

It can yeah. One cylinder is likely to be making more power than the other, it'll tend to vibrate more.

It's more to do with why is one down? What's the problem, since they're both built the same. Is one un-naturally high, which may cause too high a compression, for instance mixing SP and R barrels and heads. Or is one low through an air leak or other damage?
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