New to the CB750 and have header question.

[breakbeatz69]

Yup

Gotcha.

 

[breakbeatz69]

Think I figured out my getting the engine out of the frame problem…(evil laugh)

 

[mrtwowheel]

Never seen someone to use a sawzall to get their engine out before. That's a new one.

 

[Loose Chain]

Wow. Not the best way

 

[breakbeatz69]

When you’re hardtailing it anyways all that frame material has gotta go so I figured let me just rough cut the frame to about where it’s gotta be for the hardtail and now I’m able to work on the engine and use what’s left of the frame as an engine stand. Because I cut all that away, I was able to take everything off the top end. I was even able to get the jugs off to expose the pistons.

 

[81cb750f]

Yeah you've got original parts there. They weren't placed into the collars right, slightly out of whack, that's why they're bent up. I've found that before and straightened them good enough to use. Don't know about yours.

Edit....on second look, those are usable, just straighten them so they fit into the collars.

not sure if you figured everything out so I'll add my comments.
First off, no 81 CB750 came stock with headers. My CB750F (see pic), which I still have came with 4 into 2. The 750C, yours, came stock with 4 into 4, same with the 750K.
I now have a header on my bike and from your pics it looks very similar to yours. Mine is a MAC header.
Those shims are essential to get a proper seal between the end of the pipes and the head with the gaskets in between. If you don't use them and only use the collars, the end of the pipes wont squish the copper gaskets properly and you will have no seal at the head and you will have major exhaust leaks. You have to place them into the collars so that the thick ends push against the flange at the end of the pipe. The skinny end of the shims faces the other way and faces towards the front of the bike when installed. I've attached a pic of mine and you can just see the the skinny end poking out between the top of the collar and the the pipe. Hope this helps.

 

[Trkdrvr1376]

Hey everyone! So I’m new to the forum but not new to bike forums or metric bikes in the least. I’ve been building choppers and bobbers out of sportsters a little but my main bag of tricks comes from building choppers and bobbers out of the Yamaha XS650. I’ve done numerous xs’s with everything being done in-house by myself, I’ve had a couple bikes featured in magazines, and blah blah blah.

But now I’m tackling the one that always seemed to allude me, and that’s….you guessed it…a 1981 CB750c. I’m super stoked to finally do one of these bikes but I’m LOST when it comes to the DOHC style engine. I can tear down Harley Evos and Yamaha parallel twins like nobody’s business but this CB750 is a different monster entirely. I did order a Clymer service manual because, for one, I’m not an idiot that thinks I’m just gonna fly through this bike because I know a thing or two about motorcycles, and two, I know I’ll need it to understand this beast of an engine….so at least I got that going for me.

So to get into my first of many questions to come, I got my donor bike home today and got it in my shop and wanted to put it on my motorcycle jack right away but realized the 4 into 1 exhaust was in the way of the jack being able to sit on the lower frame rails. So I went to take the exhaust and headers off and when I did only 5 of these half moon shim looking things came falling out as I removed the headers. I checked the exhaust ports and there weren’t any stuck in the engine or on the headers themselves. So I have 5.

Now, I’m no mathematician, but with 4 exhaust ports having 5 of these things doesn’t make sense. So I looked online to find new ones to buy and couldn’t find shit in the way of any new ones. I did however find a set of 8 used ones on eBay and promptly ordered them since they were pretty cheap. Now, 8 makes sense to me, 2 for each header, but what in the fuck is the purpose of these things (whatever they’re actually called)??? I know there’s also gaskets that go into the 4 exhaust manifold ports, but what is the purpose of these half moon looking pieces? Are they some sort of weight support due to all the steel from 4 headers hanging off of the engine? Or do they serve another purpose? And are they necessary to have, or are they a part that can be deleted?

If you made it this far thanks a lot for riding with me until the end. My posts from now on won’t be as long winded now that I got my introduction out of the way and everyone has an idea of my experience level. Any and all comments/advice are welcome and thank you all in advance for your help. FTW!

Good luck with your project looking forward to following your progress as I am in the process of an80 750c barn find/rescue myself