probably need to clean my carbs, right?

A

andrew embassy

Been Around the Block
So under normal riding conditions my bike runs awesome, but when I start my bike it usually it takes about 5-7 kicks or so and and then I have to let it idle for a while before I give it gas, otherwise it'll die.

When it does settle into an idle it seems to idle fine at about 1200rpm, which seems about right, correct?

Then often when I arrive at a stop, especially after going fast like getting off a freeway or something, if I don't give it any gas it'll die. Also I seem to need to be giving it gas when I kick start it again - it'll start no problems, but not without a little twist.

Thoughts? I just went through the whole carb syncing process, but maybe I didn't do it right? I sure as hell didn't feel like I knew what I was doing... Especially the fuel / air mixture part, I was like "uhh, that seems to have killed it, I guess I'll twist this out this way... okay it's running now..."
 
I have similar problems with my 450, although probably not quite as bad as yours. Smae symptoms only not quite as often. I actually thinking about taking it to a mechanic *GASP* that actually knows what they are doing. Now, if I could only find one of those in ATL.

Did you check to make sure the floats aren't too high?
 
Flugtechnik said:
I have similar problems with my 450, although probably not quite as bad as yours. Smae symptoms only not quite as often. I actually thinking about taking it to a mechanic *GASP* that actually knows what they are doing. Now, if I could only find one of those in ATL.

Did you check to make sure the floats aren't too high?
Click to expand...

Nope : )

I think what I'm going to do is take the bike to this dude Jeremiah at North City Vintage Honda and have he and I go through the carbs together - that way I'll see how he does it and I can do it myself next time...
 
One other thing I've noticed - when I pull my plugs they're definitely sooty - not so bad that they don't spark or anything, but they're definitely not clean - this means I'm running rich, right?

The engine / carbs / exhaust are all bone stock...
 
yes. What year is yours? A 73? '72 and on had the larger 145 main jets which tended towards the rich side. If the floats are too high, it will run rich as well.
 
Flugtechnik said:
yes. What year is yours? A 73? '72 and on had the larger 145 main jets which tended towards the rich side. If the floats are too high, it will run rich as well.
Click to expand...

'74 - I've heard things about them running rich as it is - so when it runs rich is it just just that you get deposits on the plugs?
 
Deposits, boggy performance and I think the stalling as well. Like when you try running it with the choke on. Doesn't get enough air so it dies. Not sure that is your problem, but may be.
 
Flugtechnik said:
Deposits, boggy performance and I think the stalling as well. Like when you try running it with the choke on. Doesn't get enough air so it dies. Not sure that is your problem, but may be.
Click to expand...

hmm, "boggy" is a good descriptor of the low end performance...
 
Are your plugs sooty when you just start it and idle (not riding)? Or is the sootiness caused when riding and accelerating. There are different "circuits" in the carbs that perform at different rpms. With the idle issues there may be something wrong with the pilot circuit. Have you cleaned this circuit and checked the pilot jets? The mains don't have any affect on the idle performance, as they only kick in under higher acceleration.

If they are sooty at idle, the float levels could be causing this. Check them out like Flug said. Do you have any intake or exhaust mods? As this will probably necessitate larger jets (pilot and main).
 
At least in the Keihin carbs on the 450s, the slow jet feeds from the main jet.  I figured the size of the main jet would influence the slow jet as well.  However, high floats would effect everything.

See attached carb schematic
 
I had exactly the same issue on my CL450... same symptoms, but I tried syncing the carbs and it turns out that it runs pretty good now... I (shamefully) haven't checked my plugs yet, for fear that there's more wrong with it :)
 
How does the fuel / air screw adjustment work actually? I mean - aside from it killing the bike at one extreme, I have no idea what all the way in vs. all the way out means. If I'm running rich does this have anything to do with it?
 
Your bike requires a certain air and fuel mixture as it goes into the chamber to fire...

The air adjustment screw is turned, you're adjusting the amount of air that gets mixed in with the fuel.

The more air, the more lean... the less air, the more rich...

Think of it as a gate, when you're pulling the screw out, you're removing the gate and allowing more air to flow through...

(Disclaimer: I'm incredibly new to motorcycles and this forum, but drawing from basic information on carbs and how engines work, I feel I'm right)

I used this to help with mine: http://www.hondtwins.net/forum/viewtopic.php?f=29&t=537
 
If you look at the schematic I posted, the fuel/air screw actually controls fuel flow, and not air, but the idea is the same, just backwards. When you back it out, you are adding more fuel, richer.
 
I'm experiencing some of the same issues with my CB200! If one of us figures something out before the other we should swap ideas! HAHA
 
Flugtechnik said:
If you look at the schematic I posted, the fuel/air screw actually controls fuel flow, and not air, but the idea is the same, just backwards. When you back it out, you are adding more fuel, richer.
Click to expand...

Whoops! I tried to disclaim that I may be wrong :)
 
I have a 74 cb450 as well and I have similar problems. I can get it to idle as long as I hold the throttle a bit. It won't even start without twisting the throttle either. Really try cleaning your carbs out. Boil them and the jets in lemon juice if you have to and check out the float level (I'm confused on this though lol).

Have you checked the points and timing? Maybe it isn't firing right.
 
goodfornothing said:
I have a 74 cb450 as well and I have similar problems. I can get it to idle as long as I hold the throttle a bit. It won't even start without twisting the throttle either. Really try cleaning your carbs out. Boil them and the jets in lemon juice if you have to and check out the float level (I'm confused on this though lol).

Have you checked the points and timing? Maybe it isn't firing right.
Click to expand...

do you still have this issue even after cleaning and boiling out your carbs?
 
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