4 to 1 exhaust...Rejet?

[Curt750F]

I've got a 1980 CB750F Super Sport, I just bought a Mac 4 to 1 exhaust, with a removable baffle.  The disclaimer when I bought the system said that a rejet is not necessary, and I have heard a few reliable sources say the same.  I have also heard some other reliable sources say that I will need a rejet.  What do you all have to say?

[blackhawkrider]

Might seem cliche but sometimes you do sometimes you don't. Although most of the time the motorcycle will benefit from a rejet especially after a new better flowing exhaust is added. My recomendation is to try without any jet work with you new exhaust. If it runs poorly or if it runs poorly in spots you should rejet. Also since most motorcycles a set too lean from the factory an exhaust usually tips the scales, but you might get lucky.

[heteroclite]

on most any thing if you change the exhaust you must also change the intake in order to keep the backpressure balanced properly with the smoother running 4/1 no baffle you will have significantly less back pressure.

[sbc1320]

Should be pretty close with the baffle in it. If you pull the baffle out then go up 1-2 sizes.

[Kng_Cafe750F]

i am also ordering the same exhaust for my 80 cb750 f ss... i took it to a local shop that is known very well arounf my parts that has a moto dyno and they told me they recommend getting the exhaust and getting it retuned, not rejeted. most factory jets are capable you just need to adjust the settings... according to my source... this guy has ages of history on his belt and he went through every detail with me and with my average knowledge it made perfect sense. maybe try that? Good luck bud

[Piute]

Kng_Cafe750F wrote

i am also ordering the same exhaust for my 80 cb750 f ss... i took it to a local shop that is known very well arounf my parts that has a moto dyno and they told me they recommend getting the exhaust and getting it retuned, not rejeted. most factory jets are capable you just need to adjust the settings... according to my source... this guy has ages of history on his belt and he went through every detail with me and with my average knowledge it made perfect sense. maybe try that? Good luck bud

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  My "77" F2 with stk."key-tops"and header pipe,custom tractor muff ,simple tuning was only needed,running great,stk air box N filter type

[seestheday]

I recently rejetted my 81 cb750K and the bike is running much better.

I have a 4-1 with a generic clip on muffler.  When trying to tune just using the air/fuel mix screws I was up to 4.5(!) turns out and it was still running lean.  I moved up my primary jet from a 68 to a 75 and now have the air/fuel screw out 1.5 turns.  The bike idles much better, isn't excessively popping on decel anymore, and my spark plugs are good.