Rebuilt Top End. Has To Much Compression

S

SamRyan

Alright guys. I have a 05 Kx250f. Bike ran pretty good, but smoked and ticked just a tad. So decided to put in a new piston and gaskets and adjust the valves. So after putting everything back together I realized that it was super hard to kick over, It has wayyyy to much compression. You can kick it over but not fast enough to start it, Ive started cr500's and its way more than those have. When I had it tore down the crank was good with no play. So since I couldn't start it by kicking it, I tried to roll it off and eventually it did start but it sounded like crap and it was either ticking or knocking pretty bad. But it ran fine before. And now also the oil mixes with antifreeze instantly and looks like eggnog. Im thinking either wrong gaskets or something like that. Possibly wrong piston. Any help would be great. (Also I checked valve clearances and there good)
 
Trfsrfr

Trfsrfr

Welcome to the forum Sam.
I have an 04 KX250F that I just got and it needs to be reassembled so I am sure I will be running across the same things you did real soon.
First off, do you have a factory service manual?

While I wont be much help right now, it's probably safe to say that somewhere along the line something got messed up.
Oil in water sounds like maybe a seal was missed. I've done this.

As far as the rest, some numbers are probably gonna be in order.
Like what is the compression, etc?
Are you sure the cam chain is on right and you're not standing on the kickstarter with the piston slammed into a valve? We gotta ask...

I am sure some of the forum big boys will be along soon to ask other important questions to help you figure this out, so dont worry. They live for this stuff.
Some pics are always helpful as well.
 
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Mihylo33

Mihylo33

Trfsrfr:
Ooh I didn't think of that...good call.
But lets hope not.
Whats the plug look like?
Click to expand...

They have head warping issues hence the water pump and engine ice I mentioned. That's one of those bikes where everything needs to be oem except the water pump.
 
Mihylo33

Mihylo33

SamRyan:
So waterpump needs to be replaced? Ive got another gasket set, should I put a new head gasket on and see if thats issue
Click to expand...

Only if it's OEM.
We don't have all the answers and I'm only speculating what it could be. You will have to do the troubleshooting and the work. I would pull the plug and see if it's covered in antifreeze and see if your radiator is low. While the plug is out see if it turns over easier.
 
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2Wheels

2Wheels

All kidding aside .. WHAT?!
Possibly wrong piston? Dude you are in way over your head.
I don't think I can even begin to help you. So all I have to say is good luck.
 
M

MikeinFresno

or the cam chain is off by a few teeth causing the valves to open at wrong time in relation to the piston which causes much compression...also does the bike have an auto decompressor mechanism? If so that may not be assembled right. Does sound like bad head gasket tho for the oil water mix.
 
SRAD97750

SRAD97750

Moderator
Staff member
When assembling an engine, after each new component is installed, the assembly should be spun 360* to ensure no binding. This way, when you encounter something like this, you only have one step to backtrack in fixing the issue.
It is 100% not a compression issue, more like a friction issue.

I would tear down slowly until you find what was binding.
The water turning to milkshake is the water pump seal on the oil side. I would replace the water pump impeller as a kit.
-BIG DAN:thumb:
 
O

ossagp

I am dying to hear how the plug looks. Sounds like a crowded combustion chamber is a pretty real possibility, but to me very doubtful that you could do a normal cylinder installation with clearances that were too tight, but it isn't specified to what means the OP went to to get the cylinder on.
 
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