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Okay so rebuilt the cb350.
Carbs are clean
Spark is good
Compression is good
Static Timing is perfect
Point gap is good
Valves are adjusted
So my problem is this:
The damn thing won't run.
If I let it sit for a while it starts right up and runs okay for about 30 seconds. Then it goes to the point where I have to run it at full throttle to keep It running and it only runs on one cylinder until
It won't run anymore. If I let it sit for 15 minutes or so this will start all over.
I cannot figure out the problem.
The only other thing I can think of is float height, but I've adjusted it several times and when I pull the carbs there seems to be a good bit of fuel in there.
I have square floats from Sirius consolidated and am unsure what point to use as reference for measuring.
I painted my carbs recently with por15. I scraped it off of the vents to no avail.
So someone please give me some insight into what may be going on!
What is the actual compression?
What jets are you running?
Square floats? Thought the OEM was round brass, why change them to a non OEM?
Have you checked that the vents are actually venting?
cracks in the diaphragms?
Sounds like the float hight is wrong.
You have factory manual?
check that the petcock is flowing as it should too
i would suggest that the answer lies in the carbs....float would be good to re-check there are several methods depending on the carbs, but always a pain in the ass
why did you paint your carbs? that sounds like a bad idea...
Check that you are actually getting fuel into your carbs. Cleaning them and adjusting the float levels when they are off the bike is fine, but don't assume there's fuel in the bowls just because you cleaned them.
Are the floats the exact same size?
What are you using to measure the float height?
Are you doing it the way it shows in factory manual?
Just because it ran before does not rule anything out. My uncle was alive, right before he died....
Things break or fail or go wrong.
Need to start at the beginning.
Is the fuel in the good? Do you know how to check?
You said fuel is flowing to the carbs so that's good.
Next is float height. Have to know what that is and get it exactly right now
Hmm, weird intermittent problems like you described always tend to lead me to electrical/ignition problems. Are your coils, wires, and condensors all functioning properly?
Check the plug to see if it is ignition or carb related. Wet = ignition, dry = carb.
Some stuff that I experienced for non-starting bikes:
1. bad ground to coil.
2. semi-clogged slow jet. Just because you can see light thru it doesn't mean it's good. Clean it with a jet cleaning wire.
3. float too low. I made a U-shaped jig out of wood to measure float height. Make sure the gasket isn't deformed and blocking the float from moving. Check fuel in bowl by draining the fuel. You can get an idea of the float height by relating it to the amount of fuel drained. Someone with the correct float bowl can drain their carb. Measure it in ounces as a reference. Then you can get an idea if yours is too low or high. Another way to check proper float function/height is by blowing into the fuel line (make sure it's dry and clean -- duh!). Then, push up the float with the afore mentioned measuring jig. Once, the bowl is at the correct height, the fuel line will be blocked. If your blowing stops before the correct height, it is too low. If it doesn't stop, it is too high.
To check the venting, spray carb cleaner in each orifice and force it thru with a compressed air gun. You'll see where it vents from the carb cleaner spraying out. This helps you to know where all the venting leads.
I just re-read the original post. It sounds like you have vapor lock. Open the gas cap. Or open the petcock to a fuel can. See if it stops flowing after some time. If so, your gas cap vent is blocked.
Sounds almost like a clogged vent in the fuel tank filler cap. Runs fine for a few minutes and then dies. Fills bowls if you wait for a few minutes, etc
Try it with teh filler cap open and if that's not the issue, remove the float bowl drains and arrange to catch the fuel then turn of the fuel and watch it for 1 minute or more to see if the flow changes
That it would, but I have a generic cb350 manual and the floats are round so the float heights are incorrect for my square floats. Which is why I phrased it so specifically
It's not vapor lock. The tank can be wide open and it still happens. I'm thinking it's got to be floats. Tonight I'll take them apart again and do some more testing.
Floats adjusted to about 19 mm (stock setting for a 1968 cb350).
She runs enough to take her around the block then starts running on left cylinder only. So I'm going to drop both to 18 mm and see how that works for me.
getting close!
Really appreciate all the help guys.
Also since you're here anyway
Valves adjusted to spec, and I get a whole lot of chatter. I can hear them knocking around pretty badly.
I set it up by hand an just got them to a barely audible click but then my compression dropped telling me they were too tight.
My question is is it acceptable to adjust them by ear or do I need to stick to stock specs?
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