KX Riders

Maintenance & Technical => KX500 Original => Topic started by: Michael janowicz on December 21, 2014, 07:24:43 AM

Title: Very low compression K5
Post by: Michael janowicz on December 21, 2014, 07:24:43 AM
Hello everyone, I was wandering if the Kips valve has any thing to do with loss of compression if installed incorrectly?? Thanks in advance, Mike

I think I may have slid the right side out, not sure if I put it back in correctly
Title: Re: Very low compression K5
Post by: sandblaster on December 21, 2014, 09:20:16 AM
Rings, cylinder wall, piston, head gasket, head volume, head, plug threads, and distance from the exhaust port closing to TDC effect your compression.
There is some bleed from the kips reliefs in the cylinder wall to help with starting but that won't for the most part give you a low compression reading.
What compression are you reading and when was the last time a complete top end was done?
Title: Re: Very low compression K5
Post by: Michael janowicz on December 22, 2014, 07:05:30 AM
I'm pretty sure the top end is original, really low hour bike, I can crank it by hand!! Single ring piston!! Maybe a broken ring??
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 22, 2014, 07:32:42 AM
Single ring piston!!

no kiddin...what year is it?....'87 was the last year for the single ring...or is it a newer bike that someone installed a single ring piston into?
Title: Re: Very low compression K5
Post by: sandblaster on December 22, 2014, 12:52:35 PM
If you pull the head off and rotate the engine I think you will see the issue...
Look for any color differences in the cylinder wall especially by the ports..
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 02:09:55 AM
The bike is a 86' single ring piston, I had the cylinder off and it all looked good, I may have slid the Kips valve out on the right side?? Not sure if it went in right?? Could this cause low compression???
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 27, 2014, 02:26:05 AM
Could this cause low compression???


not that dramatically.
just because everything "looked good" when you had the jug off, don't assume that it is.
I would go back to sandblasters 1st post, and make sure all your clearances are within spec.

what brand of head gasket did you use when you put it back together?...and did you lap the head and jug mating surfaces to be sure they were flat when you had it apart?   

post some pics too if you have a chance.
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 02:44:31 AM
The bike was running mint and stalled out at an idle, found the problem to be the nut in end of crankshaft- water pump side backed off rubbing against water pump! The flat washer that locks nut wasn't folded down far enough from the factory. I put the bike back together as it came apart, loss of compression now???
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 02:45:52 AM
I used Cometic gaskets!!!
Title: Re: Very low compression K5
Post by: sandblaster on December 27, 2014, 03:51:05 AM
Trapped compression is the amount of compression that your engine makes once the piston covers the exhaust and kips ports.
So, once your piston is on it's way up and closes off those kips ports they no longer play a roll in compression.
Ok, what makes the compression after those ports are closed?
Piston, ring, cylinder wall, gasket, head to cylinder mating surface, spark plug threads, spark plug, and the cylinder to head alignment pins.
It's gotta be there somewhere.
Remember, you can remove your kips valves completely and all you will loose is your bottom end to mid range power.
The top end power will come on like a scalded monkey butt.
Start with the cheapest and easiest thing first.
Replace the plug and make sure it torques to specs.
Then I would pull the head and make sure that the alignment pins are not too long and the mating pin holes are clean and free of debris.
I would mic the cylinder wall and have someone who knows what to look for inspect your cylinder.
If the cylinder mics correctly and there are no flaws in the plating, and if the piston walls are cherry, I would as a minimum replace the ring, lap all the mating surfaces, inspect and replace any kips parts not in spec, and clean it all up to look better then new.
Then use new gaskets to assemble.
Of course with the cylinder off I would check the crank to connecting rod clearance with a feeler gauge and compare to the factory specs.
If it is out of new spec, I would plan on a complete rebuild.
Upon finding anything not in spec with the cylinder or piston I would pull the cylinder and clean up the transfers, bridges, ports and boost ports, studs would be removed, the cylinder would go to the plater,  head would be re-chambered and compression release installed, lapping of mating surfaces would be done, new Wossner piston kit installed with oiling holes, new cylinder studs installed being careful to chamfer the stud holes, using only Cometic gaskets, everything cleaned to look better then new, and everything torqued to spec.
Probably missing a step or two in there but you get the idea.
Then again if it was my bike and it was a 86, I'd clean the air filter filter and just rebuild the whole motor  :lol:
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 27, 2014, 04:04:15 AM
still post some pics of this thing when you get it squared away...if it's got that little time on it, it would be cool to see an old '86 in good shape.   
Title: Re: Very low compression K5
Post by: sandblaster on December 27, 2014, 04:07:27 AM
still post some pics of this thing when you get it squared away...if it's got that little time on it, it would be cool to see an old '86 in good shape.   

+1  8-)
Title: Re: Very low compression K5
Post by: Brute on December 27, 2014, 04:24:53 AM
Wow Sandblaster. Nice explanation! You must have an unusual amount of extra time this morning.  :-D
Title: Re: Very low compression K5
Post by: sandblaster on December 27, 2014, 06:50:06 AM
I'm the fastest two finger typist I know of   :-o
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 10:19:33 AM
I appreciate the time of you all explaining this to me, I never pulled the head off of the cylinder I just pulled the cylinder off whole. I got to year it apart Againsnd look at all the things Sandblaster mentioned. I just didn't want to go through those motions if it was the kips valve!!

Thanks guys and Sandblaster!!!

I'd post pics, but not sure how to!!
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 27, 2014, 10:21:36 AM
here's a "how to" on pics...

http://www.kxriders.com/forums/index.php/topic,10040.0.html
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 12:41:27 PM
(http://)(http://)
Title: Re: Very low compression K5
Post by: sandblaster on December 27, 2014, 12:43:34 PM
I see your having problems posting pics.
Do you have them at photobucket or some other picture hosting service?
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 12:47:54 PM
I just set up an account at photo bucket, using my mobile phone, not sure what to do!!
Title: Re: Very low compression K5
Post by: sandblaster on December 27, 2014, 12:53:46 PM
When you have a pic uploaded to photobucket you need to copy the location or address of the picture, then come to this site and click on the "Insert Image" button.
Then,  paste that address and click the "Post" button.
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 01:00:18 PM
(http://)<iframe width="480" height="360" src="http://s166.photobucket.com/user/jano37a/embed/slideshow/Mobile%20Uploads"></iframe>
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 01:02:29 PM
Thanks Sandblaster for your help, I'm still a little new on all this stuff!!!lol
Title: Re: Very low compression K5
Post by: sandblaster on December 27, 2014, 01:04:14 PM
Your close...

(http://i166.photobucket.com/albums/u112/jano37a/Mobile%20Uploads/image_zps1776e665.jpg?924)

(http://i166.photobucket.com/albums/u112/jano37a/Mobile%20Uploads/image_zps2e819d56.jpg?568)

(http://i166.photobucket.com/albums/u112/jano37a/Mobile%20Uploads/image_zpsd99f625a.jpg?519)
Title: Re: Very low compression K5
Post by: sandblaster on December 27, 2014, 01:07:58 PM
Take a look at this:

(http://www.oem-cycle.com/forum/download/file.php?id=2859)

These are the addresses of each individual pic
When you post it should look like this but with each unique addresses.

And no problem on the help, we all had to start somewhere..
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 01:15:05 PM
Appreciated!!!
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 27, 2014, 01:36:44 PM
nice original condition...where'd ya find it?...
brings back some childhood memories.
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 09:41:42 PM
I got it from a guy in Gardner, Ma. Traded him a four wheeler for it!!
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 27, 2014, 09:43:23 PM
no kiddin...you live in Mass?
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 10:00:02 PM
Yup, Foxx4Beaver I live in Sterling, between Worcester and Leominster!! Are you also from Ma???
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 27, 2014, 10:02:41 PM
yeah, I'm in Plymouth...we'll have to meet up sometime and go riding.
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 10:08:40 PM
That's pretty cool, small world!! Right now I'm Actually working in Middleboro!!! Right in your neck of the woods!!! I run heavy equipment, building a new cell for a landfill there!! Is there a lot of trails down that way??
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 27, 2014, 10:29:54 PM
That's pretty cool, small world!! Right now I'm Actually working in Middleboro!!! Right in your neck of the woods!!! I run heavy equipment, building a new cell for a landfill there!! Is there a lot of trails down that way??

sent you a PM.
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 11:19:30 PM
Did my PM get back to you?? Still figuring out this site!!! Lol
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 27, 2014, 11:22:23 PM
Did my PM get back to you?? Still figuring out this site!!! Lol

yup, I've gotten them.
Title: Re: Very low compression K5
Post by: Michael janowicz on December 27, 2014, 11:29:08 PM
Sorry so many wasn't sure it was working!!! Lol
Title: Re: Very low compression K5
Post by: Foxx4Beaver on December 28, 2014, 04:04:06 AM
Sorry so many wasn't sure it was working!!! Lol

eh...no worries....I'm usually juggling 4 or 5 windows on my computer, bouncing back and forth...so some times it takes me a few minutes to get back to people.