Maintenance & Technical > KX500 Original

normal tolerences

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orderofsion:
hi guys , ive got an old '86 k5 . can anyone out there help me with this one. having read the excellent rebuild guide i was inspired to check out my squish and compresion . i've never previously done this to this or any other engine . first i tried the 2mm solder and at TDC no pinch ! so with the exhaust off i placed a pea sized lump of warm wax onto the top of the piston just by the port and and turned the engine through TDC . when i took it out i got a squish reading of 4mm !
 when i took the head off i discovered that there were 2 thick head gaskets fitted and as best as i can tell they are 1.25mm each , they look factory made also the (new wiseco) piston stops about 0.8mm short of the top of the cylinder , at BDC the bottom of the exhaust port is 2mm higher than the top of the piston and the bottom of the inlet transfers are 1mm lower than the piston . the top of the exhaust port is level with the top of the kips but if the duration is measured around the BDC cycle then it is about 190' . is any of this normal ? my budget is tight , where do i start ? please help.

mun:
Your values are ok for stock bike!

There are my old std values:
http://img88.imageshack.us/img88/6012/1986kx500b2tiedoteng26lv.jpg

doordie:
Mun,your are nice to cheer your data to him! :-D
But 4 mm in squish is far to much don?t you think Mun? :-o
I will suggest to take away one of these headgasket. :wink:
What is thickness of basegasket?
I think someone have raised the barrel to get higher porttimes and
even raised head  with 2 gaskets and that because of low oktan of gas. :?
You can measure volume of head and see what numbers you get
orderofsion. :|

//doordie

mun:
Sorry Doordie. I must always correct my writing and always you are right. :-D

If "orderofsion" take second head gasket off, so squish height is something like me std and it is badly too big. Best value to squish height is about 1,6-1,3mm and as Doordie says, not below 1,3mm (http://www.kxriders.com/forums/index.php/topic,1406.0.html).

I have newer buy original base gasket, so don't know its thickness. I have make base gaskets of different thickness paper, mostly 0,6mm. Your 0,8mm piston top to cylinder top is little big, so there can be base gasket about 0,8mm? Sometimes thicker base gasket is better. You get more degrees to exhaust, but some more degrees to transfers than exhaust > little easier to ride.
Then you must change head gasket too for squish height. You can make own head gasket of different thickness copper. Copper gasket works fine if you soften it sometime with torch.
Some tuners raise cylinder quite lot so that get degrees what he want. Then he shaving top of cylinder to get squish height back to correct.

Don't bother bottom of ports. You get not more power even you lower them to BDC, especially exhaust port.

orderofsion:
Thanks for all your help guys . Looks like I've got some measuring to do but hopefully I'll soon be out of this 40hp hole my bike is stuck in . One more question though , from Muns data I wondered if all k5 pistons have a flat top like mine ?
  Thanks.

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