Tech Forums > SOHC/4 Bikes
brandEn's leak free top end thread = Tips, Tricks and Suggestion encouraged
Dimitri13:
Any chance you'll be doing a leak-free bottom end? That's where most of my oil is coming from :(
jessezm:
--- Quote from: brandEn on May 17, 2012, 01:48:29 PM ---So I need some tips here. What is everyone thoughts on using the Hylomar on the base and head gaskets?
--- End quote ---
I used Hylomar Blue in the aerosol spray on my head and base gaskets after after rebuilding my top-end twice and having a weep. Results are that I have no leaks at the head anymore. I did have a very small one at the base that went away, but I'm pretty sure I know what happened. When you apply the spray, you have to do it very lightly in several coats. With the base gasket, I started praying to close too the gasket and got a drip/high spot, which is where it leaked I believe. But the leak went away after re-torque and a few hundred miles anyway. I was much more careful about spraying the head gasket. 3 light layers on either side and let it cure. I'm very pleased and will use it again.
chewbacca5000:
I am surprised no one has mentioned resurfacing the head or cylinder block and the head is often warped from heat curing. I had this on my 73 CB750 and asked for a minimal resurfacing of .005 per Hondamans instructions and the head was perfectly flat after.
Also, I did not use any goo in my engine except to seal the rubber pucks which shrink in time and end up leaking. I do not like sealant as I can not work fast enough to get everything torqued down fast enough. With heavy duty studs, two flat matting surfaces and O-Rings of the correct thickness for oil passageways there is no reason for a leak to develop at least on the older style heads. Getting the correct orings is a big deal. Do not automatically assume the ones with your kit will work as intended.
brandEn:
--- Quote from: chewbacca5000 on May 18, 2012, 04:54:25 AM ---I am surprised no one has mentioned resurfacing the head or cylinder block and the head is often warped from heat curing. I had this on my 73 CB750 and asked for a minimal resurfacing of .005 per Hondamans instructions and the head was perfectly flat after.
Also, I did not use any goo in my engine except to seal the rubber pucks which shrink in time and end up leaking. I do not like sealant as I can not work fast enough to get everything torqued down fast enough. With heavy duty studs, two flat matting surfaces and O-Rings of the correct thickness for oil passageways there is no reason for a leak to develop at least on the older style heads. Getting the correct orings is a big deal. Do not automatically assume the ones with your kit will work as intended.
--- End quote ---
Good point and your absolutely right! I was getting to that during my next wrench session. My head is still mocked up for the studs to settle in. I was going to cover warpage and how to check for it as well as a few other items that can be a problem.
Jerry E.:
My 1975 CB750F0 also has knock pins that are above the mating surface of the cylinders. I do not know the history of my engine, other than I have a 1973 K3 frame with a 1975 F0 engine in it. I thought I had a stock/original condition motor in need of some work. Does having longer knock pins mean my head was resurfaced at some point? Could this be a stock condition? The head definitely doesn't sit flat on cylanders without a gasket on it.
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