Head Gasket Will Not Seal! HELP!!!!!

[97cr250]

I have a 84 CR250 that keeps leaking @ the head gasket. I tried two different head gaskets, had the head and cylinder milled and still no luck.

The gasket leaks internaly instantly. There is so much blow by that the radiator cap cant prevent the coolant from blowing out the overflow hose. When I remove the cap and rev the motor, collant shoots out like a garden hose. I tried the same test on my 97 CR250 and didnt have that problem.

Any ideas! I have tried everything but shooting the bike!

Please Help!

 

[buffmaster]

Have you checked the head and cylinder for flatness? Throw the head on a plate of glass and see if there's any high spots. Try the same w/the cylinder but use something w/a straight edge, like a framing square or something like it. Having it milled should've taken care of it, but you never know. If the head has some high spots, put some fine grit wet/dry sandpaper on the same piece of glass and take it down some. Use some WD40 on the sandpaper before you start and it'll help if you use a marker to color up the part of the head you'll be trying to sand down. If it works, send a thank you to Rich R. ;) Past all of that, someone else will have to help.

 

[97cr250]

Thanks for the tips...I already tried all the steps you just mentioned. :bang:

I have been calling repair shops and trying to get some input. Some have said that there is something wrong other than the sealing surface between the head and cylinder...but have no input as to what.

I have heard that if the head is over torqued, it will cause this type of leak. I ordered a new gasket and will be trying to torque the head to spec (17 - 21 ftlb) I know that I torqued the bolts by hand more than spec calls out for, trying to stop the leak.

 

[fatty_k]

Might be a stupid question, but are you cross tightening the head bolts? I usually snug all bolts just so they are touching the head, then set my tourque wrench in inrements, and work my way up to the spec. Always tightening in a criss cross pattern. ie, set my wrench to say 9ft/lbs, and tighten all bolts to 9. Then set it to 12, and tighten them all to 12, etc. might be overkill, but might as well spend a little more time doing it just for extra insurnace. Im at loss for any other ideas, other then having it milled again, but this time just skim it, maybe take off .002-.003" only.

 

[uts]

Are you absolutely sure there are no cracks in the cylinder or head.

 

[97cr250]

Yes, the bolts have been cross tightened in a star pattern. The head and cylinder have been to two different shops for machining / inspection, including Pro Circuit.

The only thing remaining is the torque of the bolts being incorrect when tighted by hand. I estimate that I tightened to about 40 ftlb...maybe that distorted the head gasket too much.

I later found out that the head bolts should be tourqued to 17 -21ftlb. I have ordered my final head gasket; I will actualy torque with a torque wrench and hope for the best. If I still experience the blown head gasket symptoms, I will shoot the bike cause it's driving me :eek:

 

[fatty_k]

40ft lbs! That could be enough to deform the complete head. Hopfully you wont need to buy a new head completely, unless you can mill more off of it, and get a thicker head gasket.

 

[97cr250]

I rechecked the flatness of the head and cylinder again by doing the old light coat of paint on each surface and sanding on a flat surface. Both are still flat.

My new head gasket comes in today, I will put it on and torque it to spec and see if that was the problem all along.

Thanks for all the tips! I'll report back after the new gasket is installed and torqued and let you guys know the outcome.

I will kick myself if this bike went through 3 head gaskets because of the torque of the bolts.

Thanks again!

 

[reelrazor]

"I will kick myself if this bike went through 3 head gaskets because of the torque of the bolts."


I am betting that it did. 40ft.lbs. is halfway to tight enough for truck lug nuts. Like fatty K said up there, the head was likely being distorted by that kind of torque.

 

[mliebal]

Is it possible that your cylinder to engine gasket is leaking? You can build some pressure there also.
Good luck.
Mike

 

[97cr250]

I installed the new head gasket last night @ 9pm and drive the bike around the block (I'm sure my nieghbors love me now :aj: ) But the bike didnt leak! :yeehaw:

I guess the only problem was the incorrect torque on the head gasket.

You learn something new everyday :cool:

Time to ride :ride:

Thanks for the help!

 

[reelrazor]

So, where did you kick yourself, and how hard?

 

[Gibby]

hopefully in the nuts haha

 

[SFO]

Studs will go elastic after a certain point, usualy 5~10% of their rated torque.
Replacement is your only avenue to insure proper torquing at this point in time.
OTW, you are just making yellow snow on yourself.