Gasket brands, are they all the same? Recommendations for CB750 DOHC...?

Snickare

Snickare

Active Member
I just had my mechanic rebuild my 1982 CB750 with new valves and all new gaskets. The top end is leaking like you wouldn't believe. SO, it's getting redone again. I bought an Athena gasket set and the mechanic swore you didn't need to use gasket sealer. However it's bad. I've called a few parts places looking for new gaskets for his re-rebuild, but looks like Honda has discontinued the gaskets for their DOHC CB750s... :( Now I'm left with aftermarket gaskets only.

I've tried looking for aftermarket race, no leak, and/or MLS gaskets, but still no avail... I can't even find a simple top end only gasket set.
I've called a custom SOHC shop that has some full sets of DK gaskets, and he says you MUST use gasket sealer on them. That's fine to know now before getting in to replace all the gaskets, but is there anyone out there that knows the difference between all the gasket makers and can recommend one in particular? Athena, DK, NE, Vesrah...? Are there any others? Who makes the most reliable?

Any help would be great. What are your experiences with keeping your oil on the inside of the motor...?

Do you use RTV? Gaskacinch? Copper spray?

Thanks all.
 
I always use a sealer on gaskets unless it's a rubber gasket. Pick up a tube of right stuff and you can actually use it as a gasket maker. I've been doing this for valve covers, oil pans on cars and automatic transmission pans for years and a lot of other techs do as well.

Did you look on vintagecb750.com for a gasket?

Copper spay is not for this application and rtv is evil if it comes in contact with anything not steel or aluminum.
 
They carry the same gaskets that everyone else does. The vintage site you mentioned carries Athena gaskets. That's what I just used, and had issues with the thicknesses. Do you have any experience with the different brands?
 
I like the Vesrah gaskets, have had good results with quality and fitment. I run an oiled finger over the rubber gaskets to aid in release and reuse; you're going to get different answers, no doubt, but I've not had problems with leakage doing it that way.

Head gaskets get a light copper spray.
 
Re: Re: Gasket brands, are they all the same? Recommendations for CB750 DOHC...?

Snickare said:
I just had my mechanic rebuild my 1982 CB750 with new valves and all new gaskets. The top end is leaking like you wouldn't believe. SO, it's getting redone again. I bought an Athena gasket set and the mechanic swore you didn't need to use gasket sealer. However it's bad. I've called a few parts places looking for new gaskets for his re-rebuild, but looks like Honda has discontinued the gaskets for their DOHC CB750s... :( Now I'm left with aftermarket gaskets only.

I've tried looking for aftermarket race, no leak, and/or MLS gaskets, but still no avail... I can't even find a simple top end only gasket set.
I've called a custom SOHC shop that has some full sets of DK gaskets, and he says you MUST use gasket sealer on them. That's fine to know now before getting in to replace all the gaskets, but is there anyone out there that knows the difference between all the gasket makers and can recommend one in particular? Athena, DK, NE, Vesrah...? Are there any others? Who makes the most reliable?

Any help would be great. What are your experiences with keeping your oil on the inside of the motor...?

Do you use RTV? Gaskacinch? Copper spray?

Thanks all.
Click to expand...

Where's the top end leaking from? IIRC the dohc 750 uses an unusual valve cover gasket.
 
Well, the base gasket leaked immediately, then the valve cover gasket leaked profusely, and now the head gasket is blowing oil everywhere... I've been soaked three times now, on my short break in rides...

The mechanic is going to rebuild it with new gaskets and Gaskacinch, as he had some issues when rebuilding it the first time. But I have to get him yet another gasket kit. Honda has stopped making the gaskets for the DOHC... :( So aftermarket is all that I have to choose from.

I've researched all the brands available. Seems like Athena has the fewest bad reviews. But now I've found one called Noboru...? It says they are NOS Honda gaskets. Has anyone heard of them? Are they the original Honda gasket manufacturer?
 
Wow. I think I found the very last OEM Honda Head gasket in existence... And had to pay a premium for it... But it really does look like the highest quality gasket I've seen yet. I can't believe Honda has discontinued making gaskets for these bikes! :-\
 
I would suspect crankcase pressure or an improperly torqued head rather than the gaskets...
 
Rich Ard said:
I would suspect crankcase pressure or an improperly torqued head rather than the gaskets...
Click to expand...
this,dont blame the gaskets
also gaskets on these Hondas none of them should require any sealer at all,they were not designed for it
a cleanly preperated surface void of fourin matter is all you need

side case gaskets i like them to stick to the removable cover/side case so i will dress them on one side
i use Loctite 518 it is all you need the best stuff made,replaces and repairs gaskets as well
also works well for a thread sealer/removable thread locker
 
^ +1. Make sure a breather isn't plugged on your case. I do not have any experience with those gaskets from that site but the guy who ruins it seems very knowledgeable about the old cb750 dohc so I can't imagine he would sell shit.
 
I've taken apart as much as I am going to do on the bike. The motor is coming out to go to my mechanic. he's going to do a leak down test, and check all his build. Then replace the gaskets with stock gaskets. The few things I'm seeing here already are, leaks from the base gasket, head gasket and the valve cover gasket. Once the header came off, I was able to see the number 2 cylinder leak. Looks like the valve seals are leaking. My header was full of oil.... Based on the pics, can anyone determine what else may be the cause of the leak? It seems to be leaking mostly from the left side of the motor, and only the front. The back of the motor is mostly dry. I've found quite a consistent leak from the CAM tensioner, and just under it around the head gasket.

Thanks for your input.

Todd
 

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Here are a few more of how bad it was getting.
 

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I've had good luck with Vesrah. Get the engine up to temp, shut it down, let it cool, and retorque the head. But, I'm old school, just the way I was taught, regardless of the engine involved. Or transmission. Or any other part that heat cycles.
 
Thanks Scruffy. That was one of the first tries I made. I put a couple miles on it, brought it into the shop, removed the Valve Cover, and retorqued the head. It didn't help a bit.
I'm getting the motor out of the bike today and gonna do a rebuild with Stock gaskets. I'm also gonna need to replace the valve seals in at least the #2 cylinder. The OEM VS are really pricey, the VS I have in there right now are Athena, and they have less than 400 miles on them. Something must have been wrong with the ones in #2. I think I may just replace those with new Athena VS.
 
Haven't had an inline 4 Honda in almost 20 years, no idea unless your crankcase isn't venting properly. That's about the only spot on my 250 CL that DOESN'T leak...
 
I'm using UNI crankcase breather filters to vent the crankcase. They seem to work just fine. They certainly aren't blocked, as the filters are laden with oil.... Could they be offer too much resistance, or maybe too little?
 
Snickare said:
Here's what my crankcase breathers look like.
Click to expand...

Are they saturated with oil? They have a tendency to get full of oil and then cease acting as breathers and instead block the relief of pressure.
 
I'd also tend to think that your engine has overheated in the past to the point that the gasketed surfaces are warped. (I think you may have mentioned this in another thread). Your crankcase must have been pressurized to quite some degree for that much oil to have exited - I'm impressed :)
 
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