Topic: Dunstall cb500/550 pipes

[big bad bob dog]

Hey guys,
has anyone ever had any experience with the dunstall cb500/550 exhaust? I'm going insane. Each pipe is of different length, two have (1) stamped on them the other have (2). Nothing is seeming to fit. Arg



Cheers guys

[srook]

No experience with the 500/550 exhaust but plenty with the 750 exhaust.  The numbers on the Dunstall pipes should read from right to left.  They do not correspond to the cylinder # that Honda assigned which is left to right.  The numbers should read 1, 2, 3, 4 so you may be missing pipes 3 & 4.  In any event pipe # 1 fits on cylinder # 4 and pipe # 2 fits on cylinder # 3.  Once you have those in place see if you can fit the other 2 pipes.  Dunstall stuff never just bolts right on.  It always takes a little work to get the stuff to fit but you shouldn't need to do any major reworking.  Remember the outside pipes cross over the frame down tubes and run inside of them. 



Scott

[haill]

have at higher res if you can't see it...

[big bad bob dog]

all four pipes are of different angles and shape, yet two are marked (1) and the other are marked (2). It was brought to my attention that the inlet rubbers are not numbered one to four, but rather (1) four cylinders 1 and 4 and (2) for cylinders 2 and 3. As soon as I get these bastards on i'll update this for future reference.

Thanks for that guys

[haill]

from the picture it looks like there are two pipes that have a slight bend, like a women's hips,  allowing them to move around the oil filter. these go to the middle sections or cylinders 2and3

[big bad bob dog]

have the same photos on my packaging, that photo is of the 750 dunstall kit, not the smaller honda 4. those bends are different to the photos in the actual manual. They must have printed all kits with the same photos. Frustratingly, the are close to the same shape, but they are not.

i'll let you guys know how it goes.

[bryanj]

Even on the 500/550 the centre two pipes bend around the filter just not as prominently as the 750

[Kframe]

I have these on my 550K, got them from Ontario cycle Supply.  They will fit but were a pain to get on.
I will take some pictures tomorrow that may help you.
-K

[bryanj]

All of Paul Dunstalls stuff was a pain to fit!!! even when you could get him on the phone for advice

[Kemp]

I had the same problem fitting a NOS Dunstall system on my 550K. It took me 3 days to get it on!! I had to cut off the sidestand and re-weld the mount closer to the front of the frame and spaced out on a 1" extension. The system would not mount otherwise. If you look at the picture Dunstall supplies, you"ll see the system was designed for the early CB500/550 up to 74 and fit better on these bikes that have the sidestand at the front. Even with all the fiddling, it was not possible to completely clear the oil filter housing, the #2 cylinder head pipe needs to be removed for filter change. Performance was great and the sound is sooooo mellow! Interestingly, the header pipes are tiny in ID but that was the design (Dr Gordon Blair and Paul Dunstall) devised back in the day, possibly to get a higher gas velocity?? Anyway, they work.

[big bad bob dog]

Hey K frame, is it possible to get some snaps of your exhaust? This is the 6th time I've tried fitting the pipes and I have a terrible feeling by the angles (could be wrong) that this might be for a 750. Would the exhaust ports match up for a 500 and a 750? The box says 500. The manual says 500. My mind says murder. arg.

[srook]

I am assuming the picture from the first post is the exhaust you have.  If so it is definately not for a CB750.

Here is a pic of the CB750 Dunstall Exhaust:


Compare how the head pipes from that picture are longer as they come out of the head.  This was becuase the 500/550 cylinders/head were straight.  Compare the cross pieces.  The CB750 item has more curves than the 500/550 one.  That doesn't mean the exhaust in the picture is for the 500/550 but it is not for the CB750.  This may sound funny but the outside head pipes cross over the frame downtubes and if you are trying to install them like the Honda exhaust (outside of the framerails) they just won't fit.  My advice would be to mock up the entire thing right next to the bike.  #1 pipes on the outside #2 pipes on the inside then compare it to your motor and frame.  You still may be missing pipes 3 & 4 in which case it will never work.  Do the mock up and see what isn't right.  Take pictures and post them.  We can help.  As for the poor fitment of Dunstall stuff I think this post has overstated it.  Dunstall stuff didn't fit like Honda stuff but it shouldn't take major reworking of stands or any other parts of the bike.  Kemp's exhaust was not for his bike but an earlier version of it.
Scott

[srook]

This may help.  Again this is for the 750 but you can see how the exhaust should look when mocked up.



See how the outside pipes curve out towards the top while the inner pipes bow out around the oil filter.  Your exhaust should have the same look when mocked up.  Once you start putting the pieces together off the bike you will see what isn't right.
Scott

[Kframe]

I hope these help.
It was very frustrating for me, too.  Was a few day project, even had a buddy come over and help hold pieces up while I crawled around looking at clearances. 
What finally worked was figuring out which headers were #2 and #3, connected them loosely at the head, and loosely to the collector.  Then I played around with the two remaining pipes, getting #1 situated around the kickstand and finally putting on #4. 
It was a total #$%* to do, and I had to persuade #1 and #4 to line up with the openings on the collector. 
Then I tightened the headers at the head, then at the collector. 
As you can see, it looks like I have a bit of an exhaust leak on #3 and #4 at the collector, but not too big of a deal. 

The pipes I used were Dunstall-replica Emgo's that I got from Dennis Kirk for $50 each.

Oh, you can see from the rear view that the right pipe is further from the midline than the left, as you look at the collector you can see that it is not symmetrical (a mirror image of itself).  I think this is to accommodate the kickstand and possibly the right side of the swingarm.



Let me know if you need any different picture angles.
Good luck!

-K

[big bad bob dog]

your all a bunch of legends. I was ready to kill everything.

Srook, i panicked until I realized they were 750 pipes. Thanks for that.

K frame. Funny. The pictures show pipe 1# goes behind the frame rail. They layout in real life would suggest otherwise, i'll take some photos when I attempt it again and then post my mortal frustration. Also, the angle of the headers, following underneath the frame rails were meant (at least in the photo) to run parallel. Mine, like yours have an angle to them.

Cheers again fellas,

i'll let you know...

[big bad bob dog]

Well well lads,

These pipes are for sure not the same pipes that are in the photo srook posted. I've tried mounting these 24 different ways, and as kframe could attest, it's a massive pain in the deck. Allegedly these are parts bin specials, made with the intention of cutting and heating the headers for a correct fit. Which would most certainly foul my rearsets. Bugger. Thanks for all the help lads. I've ordered a nice yoshi replica marving 4 into 1 instead.