Topic: cb500, diagnosing a rich condition.

[lucky]

I think you are quite rich for so few mods to intake and exhaust. I think a 105 main, needle at 2nd clip from the top, 38 pilot and air screw at 1.5 turns out. Because you are running the original airbox you really just need a bit more fuel. A 105 will give you more fuel not just at wide open throttle but everywhere.

The main jet mostly controls WOT and some cross over from 3/4 throttle.
You are right about that original air box. I agree.
This bike should only need a adjustment to the mixture screw.

The slightly larger main jet is good insurance though .

[TwoTired]

TwoTired im pretty sure every question you raised in your last reply has simply already been answered in this thread...

You mean, the internal difference between the 649a and the 627b, 022A, 087a, etc?
Where was that?  Please point it out.   There is more to re-jetting than just the fuel jets.  Air jets, for example?  Anyone measured those?

Personally, I think the OP is doomed to endless recursive experimentation with the 649a, strung along by the forum members here.  The only example of a success story is Delta's WITH the air restrictor and it still runs too rich, by his own admission.  But, it is the OP's time to do with what he wants.

Have fun!

[paul_D]

GREAT NEWS everybody, the bike started up today!
Though, the new plugs are pretty black already and my exhaust at 0 to 1/8th is pretty black and sooty.

I think you are quite rich for so few mods to intake and exhaust. I think a 105 main, needle at 2nd clip from the top, 38 pilot and air screw at 1.5 turns out. Because you are running the original airbox you really just need a bit more fuel. A 105 will give you more fuel not just at wide open throttle but everywhere.

The main jet mostly controls WOT and some cross over from 3/4 throttle.
You are right about that original air box. I agree.
This bike should only need a adjustment to the mixture screw.

The slightly larger main jet is good insurance though .

I am leaning towards Lucky's suggestion of just the air screw. 1.5 turns out.
How do I perform a plug chop properly at this setting ?

I will check 1/2 throttle to see if 3rd is currently ok and then I will decided to leave it or move it to 2nd.

[Deltarider]

I can certainly recommend a long ride (for at least 45 min) at rpm above 5000, preferable @ around 7000 where your motor is most happy. You'll get lost of carbon buildup. Then you may inspect the plugs noses again.
Anyway, don't be tempted to adjust your idle as clean as possible. You need a certain overrichness at idle to get a nice acceleration.
Gasoline has changed over the years.

[paul_D]

Good point delta.  I just need to get my safety inspection and put it on the road.  But my left fork tube won't pass I don't think until I get it to stop leaking past the new fork seal.

I can't legally take it for such a long ride right now.

Yesterday evening it was running good but like I said exhaust was black. Not white anymore. Below 2-2.5k rpm it sputtered. Over that it pulled nice and strong (lower gears in neighbourhood mind you, that whole not legal on the road yet thing. )  I'm going to resync the carbs today with my new manometer that doesnt leak air into the oil. And see how that affects things and then try to get a safety next week during first week of school.