Topic: Sometimes it revs out. Sometimes it doesn’t.

[Coredozer19]

1973 cb350f. Sometimes it revs out last 6k no gurgling or struggling and full of power.

Other times it gurgles and the further you gas it the worse it gets. Am I missing something here?

Seems to run better when it’s cold then when it’s warm.

[Coredozer19]

But I feel like it’s running better and better the more I run it and let it cool off

[piefairy]

Make sure you are not just twisting the throttle to max, but working into it. If you just crank on it, it will bog down a bit.

[Coredozer19]

I’m not just smacking it. I’m rolling into it. When I get so far in rpms it just gurgles and stumbles.

[camshaft1991]

Are you running on all 4 at idle? You can tell by putting a few drops of water on each exhaust pipe upon start up. If the water beads off then it’s firing. If it doesn’t even boil, try revving it up and see if the water boils. I used to spit on my exhaust pipe to demonstrate that cylinder #4  on my 350f was not firing at idle and it was even cool enough to grab but I would advise against grabbing exhaust pipes

[jgger]

Sounds like a fuel supply issue from what you describe. Maybe check:
   1. Inline filter if you have one.
   2. Proper routing of the fuel line.
   3. Sediment bowl at the petcock.
   4. In tank screen (filter).
   5. If it has a screen inside the petcock (above the sediment bowl).
   6. Pull the fuel line and check for sufficient fuel flow.
   7. Floating crap in the carb bowls.
After you check all of that then you can start screwing with the carbs IF YOUR TIMING AND ADVANCE ARE WORKING AND SET CORRECTLY. Do not turn any adjustments at the carbs until you verify ALL of the above.

The first thing to do with the carbs is a clear tube test to verify the fuel level is correct. 

Now get to work! Dadgummit!!!!

[Coredozer19]

Update. It runs so #$%*ing good when it’s cold (right after startup) for a good 15-20 minutes. Oh and I forgot to mention I have fiberglass heat wrap on the whole 2-1 exhaust pipe.

I set static timing and checked with a timing light. Spot on.

I just don’t get why it runs good cold but when it heats up it runs like #$%*.

[jgger]

When it starts to run like crap, take off the gas cap and then replace it. Flog it to see if there is any difference. If it runs Good again then your tank is not venting.

[TwoTired]

The spark plug deposits are your information source regarding combustion conditions.  If the center electrode insulator is covered with conductive carbon, there goes your spark energy dumped straight to ground.

Cold engines need an over rich mixture because atomization is poor when cold.  When hot, atomization is good and the mixture can be leaned.  That's why choke is employed when cold.

Cheers,

[Coredozer19]

I will try the vent thing. And get back to you. Today I lost the nut for the drum hold bar. I hit the rear brake and all hell broke loose. So now I have to order a new rear drum assembly and a pull rod aswell.... I feel so stupid for not putting a cotter pin in it.

[jgger]

Done there, been that!