four into four exhaust system 1981 DOHC custom special!

[Gearbox]

I have looked at a number of downpipes for the CB750 on the internet and none seem to have the pressure balancing pipe (as I might refer to it) that my custom special has. Mine has a balance tube connecting the two inner pipes in a position just where the down pipes start to dissapear under the engine. It isn't just a structural solid pipe but allows gases to join between the two pipes. It has developed a few holes at the junction where the connecting pipe joins to the downpipe in a very awkward position to mend.

Do I need to have these middle two connected together by a through pipe or could I replace the centre two downpipes with unconnected ones?

If it's not clear what I mean please say!

Any advice very welcome.

[unclehowlie]

I don't have balance tubes on my 81 750c, but if you have them I would try to keep them. I am new to the motorcycle world but I found some basic info on "H pipes" on the flowmaster website,

"Flowmaster strongly recommends using an "H" pipe, commonly known as a "balance tube" on all "true dual" exhaust systems. An "H" pipe equalizes the pressures between both banks of the engine giving a broader and flatter torque curve throughout the rpm range. It also eliminates "back-rap" common on deceleration, and creates a deeper mellower tone both inside and outside of the vehicle."

hope this helped