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Coolant leak from head gasket

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Hey guys, recently my old man an I rebuilt the top end on his '06 250X. All went well until we started it up. The bike ran fine but coolant was leaking from the gasket between the head and cylinder. We replaced the gasket thinking there might have been a default but it did it again with the new gasket. We took the head, cylinder and gaskets into our local shop to check for warping or any grooves or knicks in the surfaces. They inspected it and seem to think it is all fine... All nuts and bolts were done up to the right torque settings and we are now lost as to what the problem could be. Does anyone have any other ideas that we could try or anything else we should be looking at? Thanks heaps!!

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what's the part # of the gaskets you used? might make sure your not getting the 04 gaskets or the 2010 r, were the installed up side down? use any sealant? I've seen the front bolts get loose on big bore motors and high comp pistons (should be rechecked during valv insp) but never experienced on a stock bore

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what's the part # of the gaskets you used? might make sure your not getting the 04 gaskets or the 2010 r, were the installed up side down? use any sealant? I've seen the front bolts get loose on big bore motors and high comp pistons (should be rechecked during valv insp) but never experienced on a stock bore

I just grabbed the part numbers from the store on this site, so ill check them when i get home from work. As far as i know, the gasket can only go on one way right? there is a cut out for the camchain and slider? we had literally only just tightened up all the bolts and put the motor back together when we started it up, so im assuming they wouldnt have come loose. If the part numbers are right and it leaks again, i guess we'll just have to take the bike in somewhere and get someone to look at it... thanks for your reply!

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I checked the part number of the gasket and we have the correct one. we will be putting it all back together again on the weekend so ill have to check for the bypass collar then, im kinda hoping its not there and that will fix our problem, but i have a feeling we put it back in last time... thanks for the advice mxscotty!

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Did you lose the water pass collar?

http://www.bikebandit.com/houseofmotorcycles/2005-honda-crf250x/o/m2266#sch410303

Part #25 on the CYLINDER-HEAD schematic

That part is the dowel pin that the head fits on to position it. The water pass collar fits between the right crankcase cover and the right crankcase. It would not cause water to leak at the head gasket. It would leak into the crankcase. You would not have messed with it just doing a top end, only if you take off the right cover.

If you are using quality gaskets and the metal surfaces are both straight, then there is only one thing that could cause a leak. For some reason the two metal surfaces are not being clamped together with sufficient force. Now, the hard part is figuring out why. Two things immediately come to mind.

1. Defective torque wrench or wrong wrench. You are using a foot pound wrench, not an inch pound one right??? Dumb question but gotta ask:smirk:

2. Something not allowing the two surfaces to mate properly. This could be many things. The locating dowels slide into recesses in the head and cylinder. Is there debris in the recesses? Are the dowels bent or corroded? Are the cylinder studs stretched? Stretched studs mean that the head nuts can run out of thread before they clamp the head and cylinder together. My suggestion..... make sure the piston is down in the bore and then slide the head on without a gasket. The two mating surfaces should sit flush against each other. Don't torque it or anything, just hand pressure should be enough to easily get the pieces against each other. I bet when you do this you will feel and/or see where it is binding up.

When doing the top end, the head was not milled down was it?????? Was the top end because of a failure, or just routine maintenance?

Bottom line.... figure out why the two pieces of metal aren't clamping together. Something is in the way.

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