Topic: Mac 4-1 re-jet cb550

[le_sterls]

Hey guys it's been a while. But I've got a question or two about a Mac 4-1 for my 1977 CB550k. I have the original pipes on (4-4) but I've been looking to change up to a 4-1 for more noise, performance, etc. I know I'll have to fiddle with the carburetors to get in running how it is, which is phenomenal right now. My main question is, could I just use cb550f jets to  get it running more properly? I live in SE Michigan, not sure what the altitude is. If your running a 4-1, what Jets are you using? Where would be the best place to buy them? Any feedback is greatly appreciated.

[nsargeant]

you can buy the jets at z1 enterprises.  My guess is that you won't have to rejet though.   i didn't when I went to a 4-1



nathan

[shizzomynizzo]

I'm in livonia, mi...not that location matters for this... and i had a mac on my bike last year...no need to rejet.

If you plan to remove the baffle and run it like that, you will need to. Otherwise you're fine.

[TwoTired]

The 77-78 Cb550 K 4 into 4 mufflers create more back pressure than the prior years 4 into 4.  The exit diameters are smaller for the 77-78 models.

The Mac 4 into 1 is NOT a performance muffler.  It was made to be a cheap replacement for the earlier 4 into 4 style.  So, you wouldn't need to re-jet an earlier 550 after installing the MAC, but almost certainly do for the 77-78 K model, unless you don't care about lean overheating of the engine.

The 77 CB550K also used PD style carbs, whereas the F models used an earlier style.  I know of no parts that interchange between these two carb styles, and certainly not jets.

Cheers,

[le_sterls]

I figured I would need to rejet, considering I'm already running a touch lean. Now I just need to figure out sizes. Which is tricky for me for whatever reason. Wish I didn't care about breakin' the bank right now, because a Kerker would be great! Thanks for the input fellas!

[xsmooth69x]

i have a 1975 cb550k1 (i think its a k1) and i thought the 550 runs rich.....

do the 77 run more lean?

(not trying to thread jack) but i thought the cb550 are notoriously rich......

[spammasher]

Iv'e got a 77 CB550K with a mac 4-1. These mufflers look pretty good and are cheap but deffinately not for performance and the sound is pretty average after saying all that i like mine it suits the style of my bike. My bike has always ran too lean probably because of the pod filters, iv'e just put in 115 main jets and it runs a bit better but still not 100% so be prepared to tinker a bit with the carbies. Good Luck.

[TwoTired]

i have a 1975 cb550k1 (i think its a k1) and i thought the 550 runs rich.....

do the 77 run more lean?

Yes, if it has PD carbs.  And, all the F models came with #98 mains and leaner throttle valve setting.

but i thought the cb550 are notoriously rich......

There are certainly differences among models and years. And by 77 the EPA was making import restrictions on exhaust emissions.

Cheers,

[shizzomynizzo]

The 77-78 Cb550 K 4 into 4 mufflers create more back pressure than the prior years 4 into 4.  The exit diameters are smaller for the 77-78 models.

The Mac 4 into 1 is NOT a performance muffler.  It was made to be a cheap replacement for the earlier 4 into 4 style.  So, you wouldn't need to re-jet an earlier 550 after installing the MAC, but almost certainly do for the 77-78 K model, unless you don't care about lean overheating of the engine.

The 77 CB550K also used PD style carbs, whereas the F models used an earlier style.  I know of no parts that interchange between these two carb styles, and certainly not jets.

Cheers,

That's good to know TT. I knew they had different carbs, but I did not know they were that different as far as rich/lean.

Learn something new everyday!