Exhaust and jets

[woozybigfoot]

I have an 82 CB750F Super Sport and it has the original 4-2 exhaust on it. I do much prefer the sound of a nice 4-1 exhaust system. Will I have to adjust/change out jets in the carbs for the 4-1 exhaust or would I be okay with just plug and play with it?



If not how would I be able to find out the proper jets needed for specific exhaust systems

 

[brettp]

I did plug and play; 1981 cb750.
Use new plugs after installation and run the bike for a few miles, then check them.

 

[woozybigfoot]

Okay okay sweet just check the plugs to see if any of the cylinders are running lean after the exhaust swap then?

 

[brettp]

Lean or rich, yes.

 

[woozybigfoot]

Lean or rich, yes.

Does anyone make a tool to reach the adjustment knobs under the carbs to adjust that? Because it's a pain using a flat bit I'm my hand all tight like that

 

[brettp]

Adjust what?

 

[woozybigfoot]

Adjust what?

The carbs fuel / air mix. The little brass nobs on the bottom of the carbs

 

[woozybigfoot]

The carbs fuel / air mix. The little brass nobs on the bottom of the carbs

These little guys here

 

[Loose Chain]

There are many tools on the market. This is just one of them.
https://www.amazon.ca/Motorcycle-Carburetor-Adjustment-Replacement-Snowmobile/dp/B0C9F71ZDY/ref=sr_1_74?crid=17DBAGOT5AD25&keywords=carburetor+adjustment+tool&qid=1699078875&sprefix=carburetor+adjustment+tool+kit,aps,224&sr=8-74

 

[woozybigfoot]

There are many tools on the market. This is just one of them.
https://www.amazon.ca/Motorcycle-Carburetor-Adjustment-Replacement-Snowmobile/dp/B0C9F71ZDY/ref=sr_1_74?crid=17DBAGOT5AD25&keywords=carburetor+adjustment+tool&qid=1699078875&sprefix=carburetor+adjustment+tool+kit,aps,224&sr=8-74

That's perfect!!!!

 

[brettp]

If your plugs are telling you the engine is too lean or rich, you're changing jets not adjusting the fuel mixture screw.

 

[woozybigfoot]

If your plugs are telling you the engine is too lean or rich, you're changing jets not adjusting the fuel mixture screw.

I'm trying to avoid pulling the carbs and these screws should help me adjust them before taking that route

 

[Loose Chain]

I'm trying to avoid pulling the carbs and these screws should help me adjust them before taking that route

Actually it won't. If the engine is running too lean or too rich you will need a change in jet size.

 

[brettp]

Loose Chain is 100% right. And usually is! If you have to rejet, you're not getting out of it. The fuel mixture only adjusts the mixture at idle. Your jets play the larger roles after that.

 

[woozybigfoot]

So what is the purpose and or course of action on setting those 4 knobs to idle perfectly?
I started with this bike not idling at all and now it's okay as far as I can tell. How do I tell if the idle is off on each individual cylinder?

 

[Loose Chain]

You need a starting point. Take each adjuster and screw it in all the way, just till it stops. Now turn them all out the same amount, say 2 1/2 turns to start with. Start the bike up and let it warm up. See how it idles. If it is too slow or too fast then just adjust the main idle screw (the big black knob) on the number 2 carb. You can reach it from the left side of the bike. Let us know how it runs then. This is only an idle adjustment.

 

[woozybigfoot]

You need a starting point. Take each adjuster and screw it in all the way, just till it stops. Now turn them all out the same amount, say 2 1/2 turns to start with. Start the bike up and let it warm up. See how it idles. If it is too slow or too fast then just adjust the main idle screw on the number 2 carb. You can reach it from the left side of the bike. Let us know how it runs then. This is only an idle adjustment.

So I did that I backed them all out 2 turns not 2.5 turns. And I adjusted the idle knob on cyl 2 and it's idling decent seems like it wants to sit around 1100 rpm to idle. What next? Thank youf or the help I'm very new to this

 

[Loose Chain]

If it is idling smooth at 1100 rpm then you are good as far as idle goes. How does it run on the road under power?

 

[woozybigfoot]

If it is idling smooth at 1100 rpm then you are good as far as idle goes. How does it run on the road under power?

So it doesn't seem super responsive I have to kinda baby the throttle till it gets up into gear then it runs on the road fine as I can tell. If I go to "snap" the throttle it dies tho

 

[woozybigfoot]

So it doesn't seem super responsive I have to kinda baby the throttle till it gets up into gear then it runs on the road fine as I can tell. If I go to "snap" the throttle it dies tho

I have a video it's not letting me upload an I able to send them