Topic: CB750, No exhaust gaskets?

[brazwell]

So Ive now entered the darkside and have purchased my first metric. Began tear down on my new 73' 750, upon ripping into the top end Ive found that there are no exhaust gaskets in the heads. The Athena top-end gasket set Ive purchased has what ooks like 4 crush style exhaust gaskets in the kit. Clymer manual has no info regarding this subject. Should this bike have exhaust gaskets? Did a previous owner feel they were not needed?

[TwoTired]

So Ive now entered the darkside and have purchased my first metric.

Sure know how to play an audience.

Or, are you just trying to tell us you're "in the dark"?

[Porscheguy912]

So Ive now entered the darkside and have purchased my first metric.

I believe most of the world uses the metric system and only a handful of stubborn nations still insist on using the "standard" units of measure.

Wouldn't that make metric the "Light side"?

PS: i have no clue about your question.
But welcome to the Forums!

[scondon]

 Stock exhaust gaskets can look amazingly like part of the head.They are flat, wide, and aluminum colored. Clean the carbon and inspect closely. The copper crush gaskets in the Athena kit look much different.

[Hush]

Used gaskets get so pressed into the head that they look like part of the exhaust port.
Scrape away a little inside the port with a blunt screwdriver, if you strike copper (gold) you have old crushed gaskets in there and you need to carefully scratch them out.
I bought new crush gaskets and fitted them but had to remove exhaust and add exhaust cement to complete the seal as sometimes exhausts don't quite pull back especially when new.
Noise will tell you if you got it right, if it sounds too noisey torque the exhaust back but if you feel it wont seal, I'd remove it again and add cement to it.

[MCRider]

So Ive now entered the darkside and have purchased my first metric. Began tear down on my new 73' 750, upon ripping into the top end Ive found that there are no exhaust gaskets in the heads. The Athena top-end gasket set Ive purchased has what ooks like 4 crush style exhaust gaskets in the kit. Clymer manual has no info regarding this subject. Should this bike have exhaust gaskets? Did a previous owner feel they were not needed?

Yes. If it is stock, the gaskets (copper O rings) go behind the spigots which are held on to the head with 2 flat head Phillips screws. The exhaust pipes clamp to the spigots without any further gaskets. If it was running with spigots in and no gaskets, it would leak terribly.

If the spigots have been removed to fit an aftermarket pipe, as most are, then the gasket goes in the same place but it is directly between the head and the exhaust pipe, no spigot. They have to be replaced each time you remove the pipe.

If you have the spigots out, the washers will be crushed flat and if you didn't know they were there might not see them. You'd have to pick them out with a small screwdriver or such.

If the spigots are still in, you do not have to remove them or replace the gaskets in a teardown.

[brazwell]

Ah Yes. Ive seen some things. I have bead blasted the heads and I am certain there are and were no exhaust gaskets on this bike when I DISMANTELED it. The bike is still running the spiggots with a 4-1. So the verdict- use the new exhaust gaskets!

[eurban]

Listen to the advice here and look very very carefully again at your exhaust ports. 

[MCRider]

Ah Yes. Ive seen some things. I have bead blasted the heads and I am certain there are and were no exhaust gaskets on this bike when I DISMANTELED it. The bike is still running the spiggots with a 4-1. So the verdict- use the new exhaust gaskets!

Not sure you are understanding me. Or maybe I'm not understanding you. 

If the spigots are there and relatively undisturbed the gaskets should be there and let a sleeping dog lie.

If you suspect the spigots were re-installed at some point without gaskets, then you'll need to put them in. But that would have been a very sloppy move on PO's part.

I just re-read your post and maybe you are saying you are still running spigots, but they are not installed at the moment? If so, yes you need the gaskets. BTW, the old ones may have been stuck in there and the bead blaster blew them out.

Examine the phillips head screws if they appear mangled, then someone may have been in there.

[goon 1492]

someone needs to add pics to clarify the situation , thanks for the info though because I didn't know about the spigots and i thought that the copper chrushys' had to be replaced when I was to drop the pipes to change out the back tire, now knowing this I can leave the spigots on but drop the pipes, right? That is sweeeet!

[brazwell]

When I originally removed the spiggots, I used my tiny flat head and there were absolutley no crush washers! This bike was in pi$% poor shape when I received it, and who know what some previous owner has done along the way. The wiring is a nightmare( my newly constructed harness is almost complete), both tires are on backwards, and apparently somebody saw fit to run with no exhaust gaskets. I guarantee they werent there, me and my buddy examined said heads and I put off any further work until I got an answer regarding the missing gaskets.

[MCRider]

someone needs to add pics to clarify the situation , thanks for the info though because I didn't know about the spigots and i thought that the copper chrushys' had to be replaced when I was to drop the pipes to change out the back tire, now knowing this I can leave the spigots on but drop the pipes, right? That is sweeeet!

Sorry no pics from my sources but sounds like you're getting the jist of it. If PO ran without the gaskets it would have sounded ... well... terrible. And the spigot screws are often not easy to get out first try. Needs an impact driver or such.

But you say you removed the spigots yourself, so there you go.

Responding to your previous post, yes once everything is assembled properly with gaskets, you can install and remove your exhaust over and over without replacing the gaskets. The spigots stay on the head, the exhaust headers clamp to the spigots.

[MCRider]

here's the schematic, you may have to scroll it some and it may not be your year, but its the same set up. The parts book calls it a "flange" but i was raised calling it the exhaust spigot. http://www.bikebandit.com/houseofmotorcycles/honda-motorcycle-cb750k1-1971-muffler/o/m9142sch394598

#3 is the spigot and #4 your gasket. Put the gasket in the head, screw the spigot into place, clamp the header on.

[brazwell]

Thanks for all your replies. I essentially need to make sure I use exhaust gaskets when reassembling! Its strange, I rode this bike in the parking  of my shop immediately after purchasing it, before ripping it down, and heard no exhaust leak. Sure, the bike ran poorly, been sitting, timing way off, carbs needing soaked, valves adjusted, etc. Thanks for all your help, I also just downloaded the srvc manual made available on this site, looks much more hrlpful then my Clymer!

[MCRider]

Thanks for all your replies. I essentially need to make sure I use exhaust gaskets when reassembling! Its strange, I rode this bike in the parking  of my shop immediately after purchasing it, before ripping it down, and heard no exhaust leak. Sure, the bike ran poorly, been sitting, timing way off, carbs needing soaked, valves adjusted, etc. Thanks for all your help, I also just downloaded the srvc manual made available on this site, looks much more hrlpful then my Clymer!

Yup that's strange, maybe it had sealed itself up with exhaust debris?   

Anyway, sounds like you're on track. Have fun!

[scondon]

If PO ran without the gaskets it would have sounded ... well... terrible.

 and ran like......well...... #$%*

Thanks for all your help, I also just downloaded the srvc manual made available on this site, looks much more hrlpful then my Clymer!

    Should make wrenching a bit easier and tuning to spec more exact. Hope yer back to saving baby turtles soon