Compression test advice

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bultaco4ever
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Compression test advice

Post by bultaco4ever »

So, I'm having some difficulty kick starting my '93 200. But, I can bump start it easily. A good friend suggested that I perform a compression test for a stuck or worn rings. I bought a guage but didnt warm up the engine at all. How much will that affect the results? It was really low. Bike runs really well after it lights up.
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Julien D
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Re: Compression test advice

Post by Julien D »

When you are using the compression tester, how many times did you kick it over? You should kick repeatedly until the gauge stops rising. What was your reading?
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bultaco4ever
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Re: Compression test advice

Post by bultaco4ever »

About 5 - 6 times by hand. It stopped rising at 50
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Re: Compression test advice

Post by ohgood »

bultaco4ever wrote:About 5 - 6 times by hand. It stopped rising at 50
it needs piston speed (kick it!) and a wide open throttle to be accurate.
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Re: Compression test advice

Post by bultaco4ever »

Oh yeah....wide open throttle...I forgot that part. When I said "by hand", I didn't baby it. I forced it quickly but...by hand. So, I'm thinking that warming it up first and remembering to wide open throttle it....then I'll get a better reading. I'll report again after that happens.
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Julien D
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Re: Compression test advice

Post by Julien D »

Hold the throttle open and kick that sucker with your foot repeatedly. Warming up is not necessary.
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Corey
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Re: Compression test advice

Post by Corey »

Also, press and hold the kill switch while you are kicking it over to prevent possible electrical system damage.
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Re: Compression test advice

Post by bultaco4ever »

Good tip...thanks...
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Re: Compression test advice

Post by bultaco4ever »

OK...I warmed up the engine, used a wide open throttle, pushed the kill button and kicked the start lever like Landon Donovan. I got the compression guage up to 70. ......guess I need rings at a minimum.
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Re: Compression test advice

Post by bultaco4ever »

So, after I identify the piston...where should I get the rings?
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Re: Compression test advice

Post by ohgood »

bultaco4ever wrote:So, after I identify the piston...where should I get the rings?

I usually buy stuff as a kit from ebay or amazon (amazon prime ROCKS)

if someone has a better source, or one that benefits kdxrider, holler, cause i'll use them instead :D
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fuzzy
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Re: Compression test advice

Post by fuzzy »

Put a piston AND rings in it. All you need to identify is that the plating on the cylinder still looks good.
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bultaco4ever
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Re: Compression test advice

Post by bultaco4ever »

That's probably great advice.
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Julien D
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Re: Compression test advice

Post by Julien D »

Definitely.
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bultaco4ever
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Re: Compression test advice

Post by bultaco4ever »

If the left side Kips valve was broken...would that be a cause of a low compression reading? Mine is sheared off and not moving at all. Mine broke off just below the splines for the operating rod.
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Re: Compression test advice

Post by Julien D »

Common issue, unfortunately. But no, no effect on compression there.
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Re: Compression test advice

Post by bultaco4ever »

With 'one' operating Kips valve (the right one) and low compression (had to bump start it)...this bike still ran great! How does it do that?
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Re: Compression test advice

Post by bultaco4ever »

Well...I must be measuring compression wrong or I had a bad head gasket. My piston, cyl, and rings all look like new. And they measure out at standard specs. My head gasket was a black paper or plastic feeling material. I thought they were copper.
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Re: Compression test advice

Post by Julien D »

The head gaskets on these guys are thin metal plate with coating of some sort on them. Not the old copper gaskets like you used to see. When I first got my 89, I rode it for an entire season with compression at about 60 psi. They just keep on running. Heck, I thought it ran great. After a full rebuild of top and bottom end, it was not recognizable as the same engine. HUGE difference.
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Re: Compression test advice

Post by bultaco4ever »

Maybe head is warped.
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