Compression test advice

Got questions? We got answers....

Compression test advice

Postby bultaco4ever » 07:38 am Nov 13 2015

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.
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby Julien D » 09:43 am Nov 13 2015

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?
Image
User avatar
Julien D
KDXRider.net
KDXRider.net
 
Posts: 5672
Images: 7
Joined: 07:53 pm Nov 07 2008
Has thanked: 47 times
Been thanked: 126 times

Re: Compression test advice

Postby bultaco4ever » 09:53 am Nov 13 2015

About 5 - 6 times by hand. It stopped rising at 50
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby ohgood » 11:29 am Nov 13 2015

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.
ohgood
Supporting Member II
Supporting Member II
 
Posts: 912
Images: 3
Joined: 10:00 am Jan 04 2014
Has thanked: 149 times
Been thanked: 66 times

Re: Compression test advice

Postby bultaco4ever » 12:13 pm Nov 13 2015

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.
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby Julien D » 02:13 pm Nov 13 2015

Hold the throttle open and kick that sucker with your foot repeatedly. Warming up is not necessary.
Image
User avatar
Julien D
KDXRider.net
KDXRider.net
 
Posts: 5672
Images: 7
Joined: 07:53 pm Nov 07 2008
Has thanked: 47 times
Been thanked: 126 times

Re: Compression test advice

Postby Corey » 12:56 am Nov 14 2015

Also, press and hold the kill switch while you are kicking it over to prevent possible electrical system damage.
Corey
Member
 
Posts: 97
Joined: 11:48 am Feb 11 2014
Has thanked: 7 times
Been thanked: 1 time

Re: Compression test advice

Postby bultaco4ever » 10:45 am Nov 14 2015

Good tip...thanks...
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby bultaco4ever » 09:33 pm Nov 14 2015

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.
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby bultaco4ever » 09:40 pm Nov 14 2015

So, after I identify the piston...where should I get the rings?
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby ohgood » 06:32 am Nov 16 2015

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
ohgood
Supporting Member II
Supporting Member II
 
Posts: 912
Images: 3
Joined: 10:00 am Jan 04 2014
Has thanked: 149 times
Been thanked: 66 times

Re: Compression test advice

Postby fuzzy » 10:29 am Nov 17 2015

Put a piston AND rings in it. All you need to identify is that the plating on the cylinder still looks good.
'91 KDX 200 Project $300 KDX
'95 KDX 200 Project $600 KDX
'94 WR 250 Always a project
User avatar
fuzzy
KDXRider.net
KDXRider.net
 
Posts: 3437
Joined: 01:29 pm Jun 18 2003
Location: Fredneck, MD
Has thanked: 0 time
Been thanked: 9 times

Re: Compression test advice

Postby bultaco4ever » 06:38 am Nov 18 2015

That's probably great advice.
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby Julien D » 07:18 am Nov 18 2015

Definitely.
Image
User avatar
Julien D
KDXRider.net
KDXRider.net
 
Posts: 5672
Images: 7
Joined: 07:53 pm Nov 07 2008
Has thanked: 47 times
Been thanked: 126 times

Re: Compression test advice

Postby bultaco4ever » 02:48 pm Nov 23 2015

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.
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby Julien D » 04:03 pm Nov 23 2015

Common issue, unfortunately. But no, no effect on compression there.
Image
User avatar
Julien D
KDXRider.net
KDXRider.net
 
Posts: 5672
Images: 7
Joined: 07:53 pm Nov 07 2008
Has thanked: 47 times
Been thanked: 126 times

Re: Compression test advice

Postby bultaco4ever » 07:17 pm Nov 23 2015

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?
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby bultaco4ever » 07:52 am Nov 24 2015

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.
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Re: Compression test advice

Postby Julien D » 08:56 am Nov 24 2015

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.
Image
User avatar
Julien D
KDXRider.net
KDXRider.net
 
Posts: 5672
Images: 7
Joined: 07:53 pm Nov 07 2008
Has thanked: 47 times
Been thanked: 126 times

Re: Compression test advice

Postby bultaco4ever » 10:44 am Nov 24 2015

Maybe head is warped.
bultaco4ever
Supporting Member I
Supporting Member I
 
Posts: 267
Images: 21
Joined: 04:37 pm Sep 24 2015
Has thanked: 0 time
Been thanked: 7 times

Next

Return to KDX General Q&A

Who is online

Users browsing this forum: Majestic-12 [Bot] and 8 guests

cron