Tecate 3 Leaking coolant out of the head after rebuild

[niftylittleguy]

So i just rebuilt the head with a new jug and cap. I torqued everything to spec. When i started the bike it started to rain coolant out of the head gasket. I torqued the head to 18ft/lbs. I noticed that 3 of the nuts on the stud only had the stud about halfway or so through the nut while the others had the stud all the way through the nut. Also when the bike was running it was blowing a lot of white smoke. I can use a suggestions or something i may have done wrong. The gasket is new btw.

[fabiodriven]

Disassemble and inspect. It will be obvious.

[RubberSalt]

New head gasket?

[yaegerb]

Smoke is white because your head gasket is leaking coolant into the cylinder.

Some questions:
1. What do the mating surfaces look like on the head and top deck of cylinder? Marred from a screwdriver?
2. Have you put a square across the mating surface of the head to see if it's true?
3. Are the cylinder studs all at the same height? Concerns me that some of the nuts aren't flush.

Pics always help.

[niftylittleguy]

Yea new head gasket. Could it be possible that the studs are no good?(streched out)

[niftylittleguy]

The cylinder surface was clean. The cylinder cap was a little sticky almost like there was some sort of glue on it. There were no scratches that i could remember. Also ill check the height of the studs. That was the first thing i noticed when i put the head back on and the studs were all at different positions on the nut.

[yaegerb]

You need to check surfaces for square as well to ensure he head isn't warped.

Did it leak before you took it apart?

[niftylittleguy]

The head i had previous did leak. I bought a head off of ebay that was just replated. So im guessing that it shouldnt be warped. Also how do i check that it isnt warped?

[yaegerb]

So the previous head leaked and now this one leaks? I would say something is up.

Check true by putting a carpenters square across the surface of the cylinder. And measure it in different spots around the cylinder. I prefer to do it bolt to bolt. Look at the bottom of the square. Is there a gap anywhere on the cylinder? Do the same to the head and check for gaps. Are you positive you don't have any gouges on the deck of the cylinder?

[El Camexican]

So i just rebuilt the head with a new jug and cap.

What exactly did you do to the head that constitutes a rebuild?

[niftylittleguy]

New base gasket, head gasket, piston and rings

[niftylittleguy]

Ill take it apart tomorrow and see if i missed something

[RubberSalt]

To che for flatness, use a straight edge and lay it across the head. It should have even contact with the head or jug.

If the jug has been tapped or over torqued, it can warp the mating surfaces. If things are warped, take some glass or granite, tape some sand paper(wet dry) to it. Grab some dish soap with water and squirt it on the paper. Begin working the head or jug in a figure 8 motion to smooth down any high spots.

Depending on condition.

I'd stsrt at 320 grit and work my way to atleast 800.

The dish soap let's you rinse the paper clean and reuse it again and again and again. It also controls the dust from sanding.

This will take off a very small amount of metal, not enough to be concerned about.

[nd4speed]

You could also not add coolant and heat the motor up enough to get the head gasket to melt and mate the surfaces. Also, some of your studs may be loose and turning.

[niftylittleguy]

I took the head off and found that the studs are all at different heights. Im going to order new ones and replace them,

[yaegerb]

Did you check for true on the cylinder and head surfaces? Did you find any gouges on the cylinder surface?

[loganm]

You replaced the head or the jug? Did you use the same head or a new one? Take the damn thing head and cylinder to a machine shop and have them check all surfaces and machine if necessary.

[Twittle]

The studs being a different lengths shouldn't really matter unles you are using acorn nuts and they are bottoming out or you are running out of thread before it is tightened all the way. Like multiple people have said you need to check both the cylinder and head for flatness.

[niftylittleguy]

I checked the cylinder and the head and they are completely flat. There is no scratches or anything in the head.

[RubberSalt]

If all is true, then this was a bad or damaged head gasket or the bolts not torqued properly, one or the other.

These are a dry fit. Everything must be 100% clean. I use brake clean on the metal prior to installing.

[oscarmayer]

as Yaegarb says you need to check for flat straight surfaces. if your not comfortable, take the cylinder and head off and take them to a machine shop to get decked flat for sealing. then use new gaskets to re-assembly them. I have not done a tri-z if us uses O-rings like the YZ motors, then measure the stock o-ring thickness then measure the inside edge where the oring sits in the cylinder and do a google search for silocone orings in that size. you will probably be able to find higher quality ones at a good price shipped. I imagine if O-rings you have 2. 1 inner for sealing off combustion chamber from water and then water from outside of cylinder. so you would need 2 orings.

good luck! but either way get them decked flat. do not use a sander..

[86T3]

I'd check to see if your studs are pulling out of the head, I dont see why there would be different length studs.

[fabiodriven]

What exactly did you do to the head that constitutes a rebuild?

He means the cylinder. TecateDan does that all the time as well, referring to the cylinder as the head. I think it's nautical guys who do that mostly because of the term "power head" for outboards or something, I don't know. Just a theory.

Guys rocket science this is not. A first-gen Tecate top end is as easy as it gets. Make sure all mating surfaces are true, look for cracks or any other issues, and use good gaskets.

[nd4speed]

Is this cylinder sleeved?

I have had a similar problem with head nuts torqued to spec with coolant in it right away. Had to start over with new head gasket and melt it with no coolant in it. Also tightened nuts real snug then checked after heat cycles.

Had lots of blown head gaskets and pulled studs on the 86/87. And Bad sleeve deck heights on 84/85.

[niftylittleguy]

The cylinder is sleeved. So should I buy new studs or keep the old ones?

[yaegerb]

if the studs are all at different heights I would buy new ones.