My compression test results school me please

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My compression test results school me please

Postby kpla51 » 08:50 pm Jun 21 2013

So I did a compression test first kick the gauge read 90 after four to five kicks it read 150-160 how do I go about these readings should it hit 150 with a certain amount of kicks?
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Re: My compression test results school me please

Postby Jason » 09:00 pm Jun 21 2013

throttle fully open, kick several times to get it at its high reading
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Re: My compression test results school me please

Postby diymirage » 09:10 pm Jun 21 2013

so in short getting up to 160 with 5 kicks is well within the usable range...right?
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My compression test results school me please

Postby kpla51 » 09:22 pm Jun 21 2013

That's what confuses me should it reach a certain number with a certain number of kicks or just until the needle stops climbing. The manual said between 90 and 152 so is 60-65 to high? I just need some insight on how it works
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Re: My compression test results school me please

Postby Julien D » 10:50 pm Jun 21 2013

Kick till it stops going up. 60 - 65 would be wicked low. 160 or 165 would be on the high side, but that's fine as long as it's not pinging.
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My compression test results school me please

Postby kpla51 » 12:03 am Jun 22 2013

ok i checked again and its around 170 is this alright? and what is pinging
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Re: My compression test results school me please

Postby bufftester » 04:08 pm Jun 24 2013

170 is way up the high side, has the engine been apart and had any work on it? Pinging (or detonation) can be caused by high compression ratios which cause combustion to occur early (among many other things), and is a distinct metallic pinging sound.

From the manual:
Kick the kick starter until the needle on the gauge stops rising and compare your reading with specification.
(Specification for compression pressure check is 90 to 151 psi)
A low reading is a possible indication of a damaged piston and/or piston rings, leaking base or head gasket or a worn-out cylinder.
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My compression test results school me please

Postby kpla51 » 07:09 pm Jun 24 2013

what could cause such high compression?
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Re: My compression test results school me please

Postby Postigo » 07:28 pm Jun 24 2013

Carbon buildup in the cylinder and piston or maybe some modification to the cylinder head like an RB mod for race gas.
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Re: My compression test results school me please

Postby KarlP » 08:11 pm Jun 24 2013

How does it run? The other day you were all set to take it apart. I wouldn't, it sounds fine. Most gauges can be 3-5% of full scale off when brand new, so a 200 psi gauge may be +/- 10 psi. That is extreme, but it could easily be off 5 psi and the KDX motor is kind of low compression anyway. The worst that can happen is pinging at high RPM, if you hear funny stuff at WOT, back off.
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Re: My compression test results school me please

Postby kpla51 » 08:25 pm Jun 24 2013

she runs fine and dont hear any strange sounds if it could be 5 psi off i think the reading would be closer to 60
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Re: My compression test results school me please

Postby Thrahl » 09:22 pm Jun 24 2013

In my E series manual it says the usable compression range is 119-185 psi so I would say 160-170 isn't too high, it sounds just about right.
After the break in on my full rebuild I was getting 180-190 psi with no pinging on 93 octane.
Just run premium and don't worry about it.
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My compression test results school me please

Postby rbates9 » 09:48 pm Jun 24 2013

If your that worried about it you could leave the air filter out for a few rides. That will get the compression back down. :lol:
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Re: My compression test results school me please

Postby Jason » 11:03 pm Jun 24 2013

LOL! :partyman:
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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