Topic: 1974 cb750 k4 exhaust flange question

[Hoffsquig]

Hey all.  I did read some threads about this, but just wanted to make sure im correct.  Im almost done with my build, but cant get the Hooker 4-2 headers/ muffler to line up with the rear peg mounting hole correctly for gym 1/4.  Its just about a quarter inch short.  It appears the 1&4 exhaust flanges are not flush with the head, which could be the extra distance i need. Do I just need to slowly crank on the flange screws until the new gasket crushes?  Cylinders 2&3 flanges mounted flush with very little effort, but 1&4 are already tight with a good deal of flange screw thread still showing.  I did remove old exhaust gaskets and replace with new copper.  Head was from a "spare" engine i had to purchase to get a good case (chain punched a hole in original) so the engine may not be a '74, though all parts lined up with the original engine.  Were flanges/ports all the same if it is a slightly different year?  I can post some pictures when i get home tonight.  Any help appreciated

[Hoffsquig]

I should add the Hooker 4-2 came off this engine b4 the rebuild, so it did fit at one time.

[Bankerdanny]

You need to add a couple more posts so that you can start including photos. Questions like this are much easier to address if we can see what you are seeing.

[robvangulik]

First try, without the flange, if the flange screws will completely screw in, if not use a tap to make the thread free.
If they do, hit the flange itself with a rubber or wooden hammer until it sits flush with the head as it should be....

[Hoffsquig]

Rob - I'll give it a whack with the mallet tonight.  Just wanted to make sure they were definitely supposed to be flush since 1 and 4 were almost the exact same "unflushness"? Lol

[bryanj]

Are you 110% certain that there are not two gaskets in there?

[Hoffsquig]

Are you 110% certain that there are not two gaskets in there?

I'll call it 90% certain, but I'm going to go look again.  I pulled 4 gaskets out that weren't carboned up too bad, but never really went digging with a pick to verify that was all of them.  However, now that I look more closely, 2 and 3 aren't seating either.  I hit 4 pretty solid with a rubber mallet about 10-15 times, and the gasket will not compress at all.  Looks like these might have been the Athena gaskets that came with the entire engine rebuild kit from cb750supply

screws go all the way in, so not a problem with the threads


#4 cylinder


#1 cylinder

[Hoffsquig]

Just to clear this thread up.  I switched to some cheap copper exhaust gaskets from 4into1, and everything fit perfectly.  The silver Athena gaskets just wouldn't compress.  no leaks, mufflers and everything lined up.