Topic: '73 CB500K - making 4 into 1 pipes work

[tennesseebreeze]

I've got questions about putting 4-1 pipes on my '73 500 build. As of now I've got 4-4 megaphone pipes from a 750. I'd guess a late 70's model. Not the cool sandcast types. I want to up the performance of the bike and give it a racer look. I'm wondering if the 4-1 pipes would give more compression and horsepower. And what, if anything, would I have to do to the rest of the fuel/airflow to get it to run right. Here's what I've got so far with the build:

Rebuilt carbs with stock jets - 100's and 35's?
Honed but not rebored cylinders with standard rings (new).
Recut valve seats and valves (which pushed the valves up in the combustion chamber by a smidge)
Stock airbox
4 into 4 pipes from a cb750 - late 70's I think.

And if anyone has some 4 into 1 pipes for sale that won't break the bank, let me know. Thanks forum!

[zenocchio]

my '72 '500 has a 4 into 1 and velocity stacks. jets are 40 and 120

[calj737]

T-Breeze - pipes won't increase your HP nor will they increase your compression. They can create more back pressure in the flow of air, which is not remotely close to compression. Rejetting is quite common when changing from 4:4 pipes to 4-:1 systems for the back pressure adjustments necessary.

[Retro Rocket]

T-Breeze - pipes won't increase your HP nor will they increase your compression. They can create more back pressure in the flow of air, which is not remotely close to compression. Rejetting is quite common when changing from 4:4 pipes to 4-:1 systems for the back pressure adjustments necessary.

Sorry Cal, slight adjustment, good pipes can definitely increase HP when set up correctly, most stock pipes are set up for noise regs and or pollution regs so putting a better flowing pipe and the appropriate jetting can increase HP, they can also create more or less back pressure depending on the baffling....

[calj737]

Thank you, I stand corrected. And I agree, pipes can produce a modest HP gain.

[Killer Canary]

Generally speaking, more power near the top of the powerband, with a sacrifice in the mid-range. Generally speaking. Usually a weight saving over other configurations also.

[eideteker]

And if anyone has some 4 into 1 pipes for sale that won't break the bank, let me know. Thanks forum!

I put the 4-1 header from a CB550F Super Sport on my CB500K, I don't remember how much I paid for it but I know it was less than a MAC system.

[tennesseebreeze]

Thanks for the input. I'll probably put it together as is for now, but I definitely want to reduce weight and gain some power when I have the dough to do so. I just spent a bit on getting some replacement wheels and triple tree. I'm deep in an engine rebuild right now. I'll see if it runs at all.