Open Pipes on a 1977 CB750F

[mluk1]

Right now I am running a stock 4-1 exhaust on my 1977 Cb750F, I want to find another stock set and make them open pipes and/or drag pipes, and heat wrap them. I'm planning on putting baffles on them as well (there are motorcycle noise violations here starting yesterday). I'm running a stock airbox and the carbs were just synced on a Dyno Jet Tester. I was reading on a similar post that 77/78 models don't have to be rejetted and maybe the carbs will just have to be tuned a little bit again?

Will this be a risky thing to do to my bike? What are some of the things I have to keep in mind if I were to do this?

[Re-run]

In most cases all you need to do on a 77/78 is tune the idle mix screw. Since it is a fuel screw and not an air screw, it has a wide range of adjustment. Remember, OUT is richer and IN is leaner.

[mluk1]

Re-run wrote

In most cases all you need to do on a 77/78 is tune the idle mix screw. Since it is a fuel screw and not an air screw, it has a wide range of adjustment. Remember, OUT is richer and IN is leaner.

Re-run wrote

In most cases all you need to do on a 77/78 is tune the idle mix screw. Since it is a fuel screw and not an air screw, it has a wide range of adjustment. Remember, OUT is richer and IN is leaner.

So running an open exhaust will result in a leaner fuel mixture? How much of a rotation would I have to turn each screw in order to have a correct fuel/air mixture? 1/4 turn? 1/2 turn?

I found 4" long baffles and am thinking of putting them in aswell, will this be a disadvantage or advantage to the fuel/air mixture?

[Re-run]

Well any baffling will reduce scavenging in the cylinders thus lessening the leaning of the mix. Now this can go the other way too and make things richer but that is a very restrictive exhaust.
Since you already have a 4-1, you may not need to change anything. Reading your plugs will tell you for sure though but if you do have to adjust, I would do it in 1/8th turns unless you have REALLY white plugs, then make the first a 1/4th turn.

I know the old thinking is that plugs should be a caramel brown or so but in the 77/78, I feel that is too rich. I shoot for a very light tan at the darkest.
So when you make a change, get the bike warmed up and idle for a few minutes with no idle. Pull the plugs out and see what the insulator looks like and go from there. Once the idle mix is set, do a wide open chop.
Get on an open stretch of road and gun the throttle and go through the gears keeping the gas wide open.
Once you hit 5th, pull clutch and hit kill switch right away and then brake to a stop without letting go of the clutch. Now the engine will be HOT so be careful. Pull the plugs out and see what the plugs look like.