Different head gasket for 1970 cb750

[Goldenoldy63]

I have been redoing the motor on my 1970 Honda CB 750. I’m just noticing the head gasket is a little bit different and not sure if I should be using a different one? There is one hall on the front part of their head gasket but no hole there I think it would be OK but I am not sure. I will send a picture. What are your thoughts

 

[dirtdigger]

As long as the inside part of the head gasket is on the sealing surface of the block it should be fine. You could check to see if you can get a very early honda head gasket but I doubt you will find one. Shortly after the 70 model year honda added the extra bolt there to help stop oil seeps. Aftermarket wont make a gasket for a one model year so they make the later gasket. If you want you could add a dab of hondabond on there for some insurance.

 

[Goldenoldy63]

As long as the inside part of the head gasket is on the sealing surface of the block it should be fine. You could check to see if you can get a very early honda head gasket but I doubt you will find one. Shortly after the 70 model year honda added the extra bolt there to help stop oil seeps. Aftermarket wont make a gasket for a one model year so they make the later gasket. If you want you could add a dab of hondabond on there for some insurance.

Thanks dirtdigger.i will do that, it looks like people have had issues with headgaskets leaking as was this bike as well.Im thinking of torqing bolts down a few extra pounds

 

[dirtdigger]

The biggest reason for head gaskets seeps is actually the stock cylinder studs. I never use stock studs. The stock studs relax tension especially with this type of head gasket. I would at a minimum use heavy duty studs. These head gaskets should be heat cycled then retorqued which is a pain in frame as valve cover has to come off as well as the cam towers. Most people dont do this and which is why the heavy duty studs are even more important.

 

[Goldenoldy63]

The biggest reason for head gaskets seeps is actually the stock cylinder studs. I never use stock studs. The stock studs relax tension especially with this type of head gasket. I would at a minimum use heavy duty studs. These head gaskets should be heat cycled then retorqued which is a pain in frame as valve cover has to come off as well as the cam towers. Most people dont do this and which is why the heavy duty studs are even more important.

Very interesting and makes sense

 

[Old_Crow]

The biggest reason for head gaskets seeps is actually the stock cylinder studs. I never use stock studs. The stock studs relax tension especially with this type of head gasket. I would at a minimum use heavy duty studs. These head gaskets should be heat cycled then retorqued which is a pain in frame as valve cover has to come off as well as the cam towers. Most people dont do this and which is why the heavy duty studs are even more important.

Anybody make an MLS head gasket for these bikes? I switched to an MLS gasket on my old Shovelhead and never had another head gasket problem after that.

 

[dirtdigger]

Yes there are MLS gaskets but that requires machining both surfaces to be compatible. The surface needs to be perfectly flat and a smoother finish.

 

[Old_Crow]

Yes there are MLS gaskets but that requires machining both surfaces to be compatible. The surface needs to be perfectly flat and a smoother finish.

Gotcha, thanks. Hopefully I'll never have to deal with it.

 

[Goldenoldy63]

The biggest reason for head gaskets seeps is actually the stock cylinder studs. I never use stock studs. The stock studs relax tension especially with this type of head gasket. I would at a minimum use heavy duty studs. These head gaskets should be heat cycled then retorqued which is a pain in frame as valve cover has to come off as well as the cam towers. Most people dont do this and which is why the heavy duty studs are even more important.

dirtdigger. I now have 200 miles on my Honda and so far no issues with leaking head gasket. I don’t know if it made a difference, but when I was torquing the heads, I went a few pounds, heavier and retorked three days in a row. Not sure if that made a difference. Anyway, all is well so far and a fun bike to drive. Thanks for your help.

 

[dirtdigger]

yes retorquing is definitely a good practice. Heavy duty head studs are first line of defence against leaking. You can torque a bit more with them safely and they wont relax like the 50 year old stock ones. But yes retorquing can help, you should retorque after heat cycle but requires removing engine and valve cover and camshaft and towers with a stock style gasket. Glad it went well for you.