Maintenance & Technical > KX250 / KX125

Coolant leak at cylinder head on rebuild....torque spec's for nuts

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dinkyguitar:
Hi all,

On my 87 KX250 rebuild, I've assembled most of the parts and today as I'm pouring the coolant I noticed a leak at the cylinder head.

The manual said to torque the bolts to 25ft lbs. but I'm thinking it still needed more.

The gasket I have is one of those metal style sandwiched between paper so maybe I just needed to tighten it down. There's also those 3 m6 bolts in the front. Should these be tightened last?

I checked both mating surfaces and I don't see any gaps.

I also removed the head to see inside and the coolant just came out the side and not in the cylinder.

Should I just reassemble everything and tighten it a little more? I'll be reusing the same head gasket since everything is new.

dinky,

Foxx4Beaver:
bummer....did you by any chance lapp the head and cylinder mating surfaces whilst it was apart?...taking a shot in the dark here, but I'm thinkin you didn't.
since you've already got the head off, might as well pull the cylinder and pull the studs out of it too.
get either some #400 grit sandpaper, or more preferably, a can of TimeSaver lapping compound...


and read here...
http://www.kxriders.com/forums/index.php/topic,11552.0.html

another good trick is to countersink the stud holes slightly.

you could try your way 1st...who knows, you might get lucky and it'll seal up.
if you can, get a Cometic base and head gasket....much better.

dinkyguitar:
Nope...didn't lap it....

I visually inspected it and used a precision straight edge....

I remember when I rebuilt a chevy 350 they recommended sealer around he water jackets...

Does anyone use a sealer or anything?

dinky,

Foxx4Beaver:
you could use yamabond4 or threebond...just a SKIM coat though, that stuff can, and will ooze out as you tighten things down and get in the way of the water passages and into the cylinder if you use too much...it's best not to go this route at all...but I know, you wanna ride.

I would rather see you go the extra mile and lapp the head/jug, get Cometic gaskets, and be done with it now.

dinkyguitar:
Thanks...

I'm exploring my options....

dinky,

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