Topic: First ride - running rich/ high idle?

[The other Derek]

Finally got a chance to take my CB750 K6 out today and had a really nice ride.  I picked the bike up a couple of weeks ago and yesterday finally got the hinges I needed to mount the new seat.   Didn't put but 20 miles on but realized that it was idling kinda fast (~2700 rpm) once it warmed up.  I also noticed that the exhaust smelled pretty gassy at least before it was warmed up.  I didn't really notice once I got out on the road- was having too much fun.

I'd like to put a new exhaust on the bike (either 4-2 or 4-4) as it's currently got a rusty 4-1 header.  Was planning on waiting until next year to do that, but if I am going to spend time tuning the carbs and then have to do it all over again next year with the new exhaust I'm thinking it might be better to try to do it all at once.

[ekpent]

Have you cleaned or checked the carbs yet just as a maintenance issue on a new to you bike. I always check them and make sure the fuel tank is clean for starters on any new ride as I give it a full tune up. Doing so will also let you know what size main and slow jet etc. is currently installed so you can ponder with more info what your situation is. Stock jets on a 76 would be a #40 slow jet and a #105 main to give you a baseline. See if they upped the main with the 4-1 pipe.
  As for the idling issue there is an adjustment knob on the rack under the gas tank that you can simply adjust even while sitting on the bike if needed.

[flybox1]

+1
Find your idle adjustment screw, and complete a 3000 mi service on your bike. This will take care of most of the issues youll find in a New bike.

[lucky]

I doubt if you will have to rejet for a different aftermarket exhaust.
Maybe just a mixture adjustment is all.

4 into 2 .
4 into 1.
4 into 2 into 1.
Drag pipes 4 into 4

Jetting would be about the same.

[The other Derek]

I'll try to take a peek at the carbs this week.  I'm a little nervous about cracking them open.

[Johnie]

If you do take the carbs off be sure to take pics as you dismantle the stuff. Makes it a lot easier when you put it back together. Do not let the carbs scare you. Not a big deal especially with the guys here.

[ekpent]

Hey Krinky. One good feature about are carbs is the fact that they have a float bowl clip and not any screws. If your apprehensive about removing the carbs for now at the very least  remove maybe the outside bowls just to take a peek to see what kind of crud may be in the bottoms and what the condition of the carbs look like. You will be able to remove the main pretty easy to see what size it is also. If they are really dirty or negleted that may inspire you more. Ask questions before taking them off and remember a heat gun will be your friend on those rubbers.
  Next time you run it after she warms up touch a wet rag to all 4 headpipes on the exhaust and compare the sizzle sound of the water to see if your hitting good on all 4. Very cheap and easy test to keep you going.

[Johnie]

Great point ekpent...especially if you are a bit apprehensive take the bowls off for a look. You can get at the main and slow jets out from there. The main is I believe a 9mm wrench and the slow jet you will see is a small flathead screwdriver to remove. When you get them off look to see if you can see light through all the holes. When you put them back in just snug them up...they are brass and I have seen the slow jet twist off if you give it to much english there. Lastly, be sure to put them back in the carb they came from. I use 4 labeled containers to keep it straight. The pic will give you an idea of what you will see. The middle brass is the main and the one to the right is the slow jet. Hope yours look this clean, but I bet they need attention. Let us know how you come out. Click the pic to enlarge it.

[dhall57]

Krinky, I've had a K6 since 2009 and there great bikes. I know you're going to love it. Post some pics when you can

[The other Derek]

Thanks for the replies.  I'm going to try to tackle this on Saturday or Sunday.  I'm registered for a MSF class on Sunday and may postpone the tinkering until after the class.  I'd hate to miss the class and coaching (need to bring your own bike for this one).