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

[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,

[dinkyguitar]

So I tried dryed the gasket overnight, spraying brake cleaner.

This morning it looked dry, and I sprayed 2 coats of permatex copper head gasket on both sides.

Bolted it up and still the coolant was seeping from the head gasket. It's seeping in the middle on both the left and right sides at the head gasket. I even tightened the bolts down but no go.

After filling with coolant, I waited 5-10 mins. and I could see a water droplet forming at the cylinder head gasket on both sides. This is where they form on both sides.



I took everything apart and to me it looks like the gasket is wicking up the coolant and dripping it out the sides. I could see on the gasket that everything was making contact, and the spray on gasket had a ridge outlining all the holes in the head.

To test for warpage, I took the studs out, laid the head on top and uses those 3 m6 screws the hold the head in place not tightening them.

I then took a .0015" feeling gauge slipped it between and pulled the gauge out. I went all around the head. Each time the head would move as I pulled out feeler gauge, and I couldn't find any spots where the gauge just slipped in.

I'm thinking it a crappy head gasket....and since I need a new head gasket, I found this.

http://www.ebay.com/itm/Cometic-GASKET-KIT-KX250-87-88-/360973810522?pt=Motorcycles_Parts_Accessories&fits=Year%3A1987%7CModel%3AKX250&hash=item540bb73b5a&vxp=mtr

dinky,

[Motorrad]

Cosmetic.     

[reklessj]

Cosmetic.     

No no no Dont go raid the old ladies make up bag just yet!!¡!! 
Buy Cometic

[sandblaster]

Cosmetic.     

No no no Dont go raid the old ladies make up bag just yet!!¡!! 
Buy Cometic

+1 

[Foxx4Beaver]

I even tightened the bolts down but no go.

whatever you do...don't KEEP tightening down on the head nuts!...you'll start pulling the studs up through the cylinder, then you'll have a whole 'nother can of worms to deal with.
18ft lbs is the max.

[dinkyguitar]

I even tightened the bolts down but no go.

whatever you do...don't KEEP tightening down on the head nuts!...you'll start pulling the studs up through the cylinder, then you'll have a whole 'nother can of worms to deal with.
18ft lbs is the max.

Yeah, I was careful....only used a 3/8" drive and figured if it was still leaking then something is wrong...

I do have a hard time believing the head will seal at 18ft lbs. though....

dinky,

[Foxx4Beaver]

I do have a hard time believing the head will seal at 18ft lbs. though....

that's straight outa the Kawie manual...the 500's are 18 lbs too and don't leak,(providing everything's "true" with a good gasket).

[Motorrad]

Cometic Cometic Cometic

[dinkyguitar]

I do have a hard time believing the head will seal at 18ft lbs. though....

that's straight outa the Kawie manual...the 500's are 18 lbs too and don't leak,(providing everything's "true" with a good gasket).

Yup...I have the Clymer manual that I've been using for this whole rebuild, and I've been using the torque spec's....well with the exception of the head.

I've ordered the cometic top end gasket set which should come in next week. I'm keeping my fingers crossed that I just had a crappy gasket.

dinky,

[Motorrad]

If you have taken the head stud's past 18.  You might add well order those too.   You have stretched them past t-y