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Compression test advice

Posted: 07:38 am Nov 13 2015
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.

Re: Compression test advice

Posted: 09:43 am Nov 13 2015
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?

Re: Compression test advice

Posted: 09:53 am Nov 13 2015
by bultaco4ever
About 5 - 6 times by hand. It stopped rising at 50

Re: Compression test advice

Posted: 11:29 am Nov 13 2015
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.

Re: Compression test advice

Posted: 12:13 pm Nov 13 2015
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.

Re: Compression test advice

Posted: 02:13 pm Nov 13 2015
by Julien D
Hold the throttle open and kick that sucker with your foot repeatedly. Warming up is not necessary.

Re: Compression test advice

Posted: 12:56 am Nov 14 2015
by Corey
Also, press and hold the kill switch while you are kicking it over to prevent possible electrical system damage.

Re: Compression test advice

Posted: 10:45 am Nov 14 2015
by bultaco4ever
Good tip...thanks...

Re: Compression test advice

Posted: 09:33 pm Nov 14 2015
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.

Re: Compression test advice

Posted: 09:40 pm Nov 14 2015
by bultaco4ever
So, after I identify the piston...where should I get the rings?

Re: Compression test advice

Posted: 06:32 am Nov 16 2015
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

Re: Compression test advice

Posted: 10:29 am Nov 17 2015
by fuzzy
Put a piston AND rings in it. All you need to identify is that the plating on the cylinder still looks good.

Re: Compression test advice

Posted: 06:38 am Nov 18 2015
by bultaco4ever
That's probably great advice.

Re: Compression test advice

Posted: 07:18 am Nov 18 2015
by Julien D
Definitely.

Re: Compression test advice

Posted: 02:48 pm Nov 23 2015
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.

Re: Compression test advice

Posted: 04:03 pm Nov 23 2015
by Julien D
Common issue, unfortunately. But no, no effect on compression there.

Re: Compression test advice

Posted: 07:17 pm Nov 23 2015
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?

Re: Compression test advice

Posted: 07:52 am Nov 24 2015
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.

Re: Compression test advice

Posted: 08:56 am Nov 24 2015
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.

Re: Compression test advice

Posted: 10:44 am Nov 24 2015
by bultaco4ever
Maybe head is warped.