Topic: cb750 exhaust option and a center stand.

[ntm1974]

I've read about 20 threads on this and am still a little confused.

1. Does a 4 into 1 exhaust increase horsepower with larger jets?  If so, how much hp can you gain?  Does this hurt gas mileage?


What exhaust has the best combination of hp gain, ground clearance and can still maintain the ability to use the center stand?

[ntm1974]

Bike is a 76 cb750K

Ok, broke down and got a 4-1 MAC exhaust.  Anyone else running this pipe?  If so: What size jet do I need to get to make it work best with a 4-1 pipe?

Where do you buy jets? (I tried to regular suspects with no luck: partsnmore, bikebandit, oldbikebarn with no luck)

[Duke McDukiedook]

I don't think center stands and 4-1's are compatable.
No HP increase usually just weight decrease.

[Radam]

I have that exhaust on my 78 750F (no center stand), but it was already on when I got it so I don't know what the jets are? You can get jets here http://cb750supply.com/

[Steve_K]

 I have a Mac 4 into 1 on both my 73 750K and my 76 550K and the centerstands work and function like stock.  You may have to make a stop so the centerstand does not hit the chain.  I am sure the 559 has a Mac, but the 750 exhaust looks like the 550's.
Hope that helps.
Steve

[Retro Rocket]

I don't think center stands and 4-1's are compatable.
No HP increase usually just weight decrease.

If you are going to use a good performance pipe then you will need to rejet and there WILL be a small gain in HP as exhaust gas flow has been increased....

[GammaFlat]

My K6 had Mac 4-1.  The center stand needed an "L" bracket off of the footpeg to stop the center stand from reaching the chain.  If you don't have one, they're easy to fabricate. 

In terms of horsepower and jetting... I don't think there's much difference between the Mac's and stock.  I believe I ended up with stock jetting working fine (after I 86'd the pods and went back to a factory air box). 

I've since picked up a new set of HM341's and I'll be running the MAC pipes on my K7. 

[Retro Rocket]

I wouldn't consider a Mac a performance pipe, from what i have seen they offer 2 types of baffle, one for the street, {stock jetting} and a less restrictive baffle that would require some small jetting changes. Some performance pipe manufacturers offer dyno charts to show HP gains.....All the performance 4 into 1 pipes i have used have required jetting changes or they ran lean.....

[ntm1974]

Thanks for the advice.  My thinking on getting a 4-1 is to increase ground clearance and to allow me to use a center stand.  If I got a performance increase, it would just be an added bonus.  I figured that I should change the jets if needed considering that I have to take the carbs off to clean them anyway.

Thanks again

[Retro Rocket]

Just to let you know, most of the pipes i have used did not allow the use of a centre stand, i always take them off anyway because they are bloody heavy and scrape on the road.....