KX head sealing question

[hillclimber147]

Has anyone not used a head gasket and just gone gasket sealer? I'm in need of a quick compression boost and don't have the time to have the cylinder shaved down. How much jump in compression would one expect from not using a head gasket?

[jigggawatt]

I don't think it will seal . At the very least , I would think you would need a copper gasket will the right sealer.

[demographic]

You could get it machined for O rings?

[don46]

how thick is your copper gasket 1mm? you could probably modify a stock thin gasket to fit your 89.5 mm bore. Easier still would be to have the head cut down, what is your compression? How much Squish do you have?

[KXcam22]

I did that exact thing on my last road race bike, a watercooled 2-cyclinder 350.  In that case I milled the head, tossed the head gasket then lapped the head to the cylinder with valve griding compound.  Used some kawasaki bond for a head gasket.  I wasn't expecting it to work but it never leaked in the two years I rode it!!  It's worth a try.  I think the trick is in the lapping. Once the surfaces mate well it doesn't take much gasket material to achieve a good seal. Cam.

[mdw471]

KXcam

was it a rz or an lc....i can also vouch for the fact that it works on an LC

i wonder if the one piece, two barrell head might offer a greater mating surface than the KX?

Mark

[hillclimber147]

Thanks guys for the opinions. I'm building a "KX 560" with a CR500 rod and 91mm piston. I had to move the cylinder up 5.5mm for the piston skirt to close the exhaust port at TDC. The head, combustion area, was milled out to copy a CR500's head, but the volume was only taken out to 52cc not 60cc like the CR500, because the water passages were getting close. So I held off on milling the cylinder in order to verify what the compression would be. And like I said above it only came to 110 lbs. Unfortunately I have finals this week and a hillclimb coming up so I'm scrambling trying to get this done in time! Afterwards I'll tear it down and have the cylinder milled down.

[KXcam22]

MDW,
 That is a good point. It was the RD350LC.  A bit different from the KX in that the 4 cylinder studs go thru the cylinder and head vs the KX which has cylinder mounted studs, although more and radially spaced. Might make a different in the type of clamping effect the head gets. Still though I think it should seal - there is likely more issues with too little squish clearance than with sealing. Cam.

[demographic]

Thanks guys for the opinions. I'm building a "KX 560" with a CR500 rod and 91mm piston. I had to move the cylinder up 5.5mm for the piston skirt to close the exhaust port at TDC. The head, combustion area, was milled out to copy a CR500's head, but the volume was only taken out to 52cc not 60cc like the CR500, because the water passages were getting close. So I held off on milling the cylinder in order to verify what the compression would be. And like I said above it only came to 110 lbs. Unfortunately I have finals this week and a hillclimb coming up so I'm scrambling trying to get this done in time! Afterwards I'll tear it down and have the cylinder milled down.

91mm piston?

Would that be a 2mm oversize CR piston then as I have never seen a KX piston bigger than 88mm?