Topic: will a 1978 cb750 supersport 4 into 1 exhaust fit a 1973 cb750k

[Nealeigh]

I have a stock 78 cb750 supersport exhaust. Will it fit my 1973 cb750k without any mods?

[moham]

No, to my knowledge, 77/78 are distinct from 69-76.

[Jerry Rxman Griffin aka MuthaF'er]

The exhaust port spacing is the same so yes in that respect. You will need studs and nuts for the head to bolt the header on so yes in that respect. Your rear mount will be different but that can be easily made as witnessed with the numerous Kerker 4 into 1's we use so yes in that respect. 

Yes, but it will require minor mods.

[Nealeigh]

Thanks. That's the exact set up I have. 78 supersport 4 into 1 with the a Kerker. Does it improve performance?

[Jerry Rxman Griffin aka MuthaF'er]

No easy answers but, yes, it can but may not. Any time you do a mod such as this it MAY require you to do something else. Such as rejetting the carbs which can be a daunting pain in the ass. This can be dependent on what baffling you have in the muffler as well as what air filter you are using. It's all about air flow. Better/more air flow needs more fuel = rejetting with larger jets and possibly resetting the needle jets to gain more fuel flow at midrange. You have to have the air/fuel ratio correct to make them run right. Be prepared to open a can of #$%* here and learn how to jet if it is necessary.   

[Nealeigh]

It has K&N airpods too.It's going to my mechanic to be rejetted when he installs the exhaust and tunes it up. That way its all set up correctly.

[scondon]

Just to add, you will also need the later model finned collars as well as split flanges( 2 per pipe ) to mount the header to engine. If you do not have these you will need to source them.

[moham]

No, to my knowledge, 77/78 are distinct from 69-76.

Shows what I know. Sorry for the misinformation...