Topic: is there something better???

[luss71]

I have a cb750 1974,i rebuilt the bike 5 years ago,but now the base gasket is leaking,i know it's not uncommon for these bike,before i install another gasket i would like to know if i can find better gasket than those sold by honda?

any suggestions???

[Lumbee]

...odd that the base gasket is leaking, usually its the head gasket.  I've rebuilt 3 750's, and I've always used the Athena gaskets with good success.  Actually 2 or of 3 didn't leak, still not sure what happended with the F2, it was fine for about 2 months, then back to weeping.     So I sold it.   

...I'm sure your'v heard it before, but I would emphasize technique, especially on the head gasket.  Make sure both sides are nice and smooth, I use a slightly abrasive wire wheel mounted on my drill to clean any gasket gook thats on either side of the mating surfaces.  The other big decision is wether to use gasket sealant or not.  I personall do not.  My logic is I would rather have a slight weep over the possiblity of getting gasket goop in the internals of the motor.  I know others on this board who are master mechanics that do use gasket sealer, so I know it can be done safely...I just don't feel confident that I know how.

[luss71]

I did some research on this site,and athena don't seem to have a good reputation,i'm surprise that you don't seem to have any problem with them!


i was wondering why they don't make this gasket like the head gasket,it would be much more durable

[Lumbee]

...u'r right, I've heard others say they go with another brand...I don't recall it at the moment, but I'm sure someone will chime in.  I was just sharing my experiences, and like I say, I'm only 2/3 on non-leaking heads, so maybe using Athena is the difference.  As I said I've never heard of a base gasket leaking.  Are you sure its not coming from somewhere else?

[ofreen]

At 52,000 miles (1996), both the head and base gaskets began to weep on my '75 750F.  I re-torqued the head, and both quit leaking.  At 82,000 miles (2002), I had to replace the seals under the cam towers, so I took the opportunity to re-torque the head again, though there were no leaks.  The bike is at just under 103,000 miles at this time with no leaks.  The engine has never been apart, the gaskets are original.  If the mating surfaces are sound, a re-torque may do the job for you without disassembling the engine.

[dusterdude]

try to find cometic gaskets,not sure if they make a kit but,they make awesome head gaskets.

[Dennis]

i was wondering why they don't make this gasket like the head gasket,it would be much more durable

Maybe because it is only sealing oil and not compression (much higher pressure) and combustion (much higher pressure and heat level).

[luss71]

...u'r right, I've heard others say they go with another brand...I don't recall it at the moment, but I'm sure someone will chime in.  I was just sharing my experiences, and like I say, I'm only 2/3 on non-leaking heads, so maybe using Athena is the difference.  As I said I've never heard of a base gasket leaking.  Are you sure its not coming from somewhere else?

Yep,i'm sure,that why i really want to do the job for the last time.

[kaysystems]

try to find cometic gaskets,not sure if they make a kit but,they make awesome head gaskets.

http://www.cometic.com/

Also worth checking the flatness of the head and if is warped. I had to have 10 to 12 thou taken off to straighten mine. It sprayed oil until then. I sed the Athena gaskets, but a Honda head gasket. So far after 1000 miles I'm totally leak free and I have a good old K0 that is supposed to leak from the head!

David

[Jonesy]

I did HondaMan's trick of torquing the head to the max. spec, let it sit for 24 hours and then back off each head nut a quarter-turn (one at a time) and retourqe in the original tightening order. I noticed I was able to turn the nuts down farther on the second phase of tightening. I just completed this a few weeks ago and so far no leaks... (OEM gasket set, BTW)

I also tightened the head down in 3 passes, I.E. 1st pass, 5 ft-lbs; 2nd pass, 10 ft-lbs; 3rd pass 15 ft-lbs. This helps to eliminate the possibility of warping the head during assembly (so they say for automotive cylinder heads). I also used a very thin film of Permatex around the oil gallery seals. This way, the rubber seal will keep the gasket sealer out. The main thing is to use gasket sealer sparingly. I've seen some engines simply slathered in the stuff. I've pulled god knows how many RTV "worms" out of my 750 engine...

[Lumbee]

I've pulled god knows how many RTV "worms" out of my 750 engine...

...and thats what scares me about using the stuff...if that clogs a oil jet...  "Dats ya ass Mr. Postman!!!"

[kaysystems]

I did HondaMan's trick of torquing the head to the max. spec, let it sit for 24 hours and then back off each head nut a quarter-turn (one at a time) and retourqe in the original tightening order. I noticed I was able to turn the nuts down farther on the second phase of tightening. I just completed this a few weeks ago and so far no leaks... (OEM gasket set, BTW)

I also tightened the head down in 3 passes, I.E. 1st pass, 5 ft-lbs; 2nd pass, 10 ft-lbs; 3rd pass 15 ft-lbs. This helps to eliminate the possibility of warping the head during assembly (so they say for automotive cylinder heads). I also used a very thin film of Permatex around the oil gallery seals. This way, the rubber seal will keep the gasket sealer out. The main thing is to use gasket sealer sparingly. I've seen some engines simply slathered in the stuff. I've pulled god knows how many RTV "worms" out of my 750 engine...

Tightening is stages certainly seems to help. Last time I used a Honda cylinder head gasket with the sticky stuff already on it. No leaks.

David

[fang]

I am about to use a Cometic head and base gasket on my 900cc engine.  Both gaskets are copper.  I will be sealing them with that "Permatex Copper Spray-A-Gasket Sealant" stuff. 


I am interested in your experience with
1.  copper head gaskets (this will be my first time to use one in a CB750)
2.  the need to re-torque the motor after 500 miles... i.e. remove the motor and retorque it.  I always have done this and have never had any proplems, but is this REALLY necessary?

Peace and grease
-fang