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good old 4 strokes

Posted: 10:36 am Aug 30 2011
by brayden55
srry i dont post more about my kdx on here it jsut never breaks down ;)

i have a 1986 klr 250 in the shop at the moment and it seems to be burning oil. a couple months ago it got sand in the cylinder and siezed all the rings so i cleanded them all up and reused them. it worked fine lots of compression and not burnt oil. anyway latly iv noticed that it would always burn a little oil but not much so i though it might be the valve seals. any idea how to check them without taking the whole valve assembly apart? the head and cylinder are off now. so recently i had the bike at the track and dirt got into the carb so i cleaned it and ran the thing and it filled the backyard with smoke! wayyy to much to be valve seals (from what iv read) so i looked at the rings on the piston and the oil scrapper has a lot less of a diameter than the compression rings. is taht normal?

any help? it ran great for a month or 2 after the sand got in and i jsut cleaned all the rings and valves

Re: good old 4 strokes

Posted: 10:56 am Aug 30 2011
by scheckaet
>|<>QBB<
brayden55 wrote: i have a 1986 klr 250 in the shop at the moment and it seems to be burning oil. a couple months ago it got sand in the cylinder and siezed all the rings so i cleanded them all up and reused them.
Are you for real??? :shock:

>|<>QBB<
brayden55 wrote:so recently i had the bike at the track and dirt got into the carb so i cleaned it and ran the thing and it filled the backyard with smoke!
what did you expect?

your valves seats are probably fubar along with your rings, and cylinder wall is probably messed up from eating all that sand...

Posted: 11:04 am Aug 30 2011
by Julien D
U can check the valve seats by removing the head, turning it upside down, and pouring fuel on the valves. The fuel should sit on top of the valve without running through.

Posted: 09:09 pm Aug 30 2011
by gsa102
I do not know of any way to check valve seals, except by visual inspection. You can borrow a valve spring compressor from autozone or advance auto, use it to pull the valves and replace the seals. Pretty easy with the right tool. Your bike is old enough to need them. The seals should be fairly cheap, or even come with the gasket set you will need to reassemble the engine. Ask to make sure.

And the oil rings are probably shot. If you have a manual, it will give you an end clearance for them if you would take them off of the piston and just put the ring in the bore. You measure the gap between the ends with a feeler guage, too much end gap and they say replace it. I say don't bother, buy a new piston and rings since you have it apart. Check the cylinder closely for damage.

And put in a new cam chain...

It should run another 25 years if you keep the dirt out of it.

Posted: 06:42 am Aug 31 2011
by KarlP
If you have a compression tester you can usually tell if rings are going or valve seats are leaking.

Check compression on a warm engine, throttle wide open.
Add a teaspoon of oil to the cylinder and check again.

Improved compression indicates a ring problem - oil in the cylinder will help the rings seal but not the valve guides

I had an XR200 we did some horrible things to. It just kept on running.

Posted: 07:21 am Aug 31 2011
by gregp
IMO - By the sound of things, you need to disassemble the top end and rebuilt it - new piston/rings, and valve guides and seals at a minimum.
I had an older KLR250 as well (it seems that I have owned pretty much everything). Mine ate the cam journals, and started making horrible noises. I found a used head (no small feat in the days before CL and E-Bay) and just replaced the whole thing.
Again, parts prices could quite possibly make repairing this machine impractical. Many bikes meet their fate this way. Then they like to end up in my garage. But I am trying to quit. Really, I am. :wink: