Freshly Built CB450 engine.

Well After putting 175 miles on a Freshly Rebuild CB450 Engine bored out to 483CC. I've noticed no matter how much I adjust my Carburetors I have to readjust after about 10 miles. I'll get it adjusted to where it Idles properly and runs well for a couple miles pull the plugs and they will look tan then about 10 miles later it will start cutting out and The Spark plugs foul pretty badly. They appear Damp and Black after I pull them out. It almost looks like oil but I'm not sure. They smell kinda gassy sometimes but not very strong. Could this just be because the engine is still breaking in and the characteristics such as compression and oil consumption are still changing? I've changed the oil 3 times already just because its a fresh engine. The oil smells a little gassy as well.

Any motor after a rebuild will pass oil until the rings bed in.

As for the constant carb adjustments, how much slop is there around the carb throttle and choke shafts? Air drawn in here [or at the boots] will make tuning difficult.
An ignition fault causing the ignition to falter will also give you dark, wet looking plugs as combustion will have been hit and miss. Are you still running points? Try new plugs just to rule them out, they're cheap.
Does it completely cut out or go onto one cylinder or what?
Love the 450s, have 3.

Have you checked the float heights and ensured the float valve is seating correctly and not leaking? I had a similar issue with one of my carbs (i.e. constant readjustment), turned out float valve had a groove worn in it preventing it from sealing correctly.

it cuts out and goes to one cylinder usually goes to just the left but i've had it go to just the right as well just not as often. I'm thinking maybe my battery was just a little too flat. I've got it on the charger right now. The bike would run great as long as I wasn't on a winding road with slow corners or town driving. I'm thinking the low RPM's combined with low battery and headlight on was causing a weak spark. I'll update on this later after putting the fully charged battery back in.

Also yes I am still running points but the points are brand new and recently adjusted the timing/gap etc... I've gone through about 4 sets of sparkplugs. New plugs don't help they foul out just as fast as old ones that have been cleaned.

Have you replaced the points condenser/capacitor? Also the points and capacitors available now are generally not as good quality as these items were 30 - 40 years ago.
Hopefully the problem is just a lack of battery power, the 450s charging systems were a bit marginal when the bikes were new and 40 years won't have done it any favors. Also the regulators were marginal Many of these bikes are running with the yellow regulator wire disconnected and running with the headlight on instead. New modern type rectifiers are available for these bikes fairly cheaply.
I'd put a multimeter across the battery terminals and run the engine between idle and 5 grand and observe your voltages, at 5 grand you should be seeing a peak in the low 14 volts. If low, try it again with the yellow reg. wire disconnected and the headlight on. If still low you probably have a week stator.
It is worth cleaning all electrical connectors on a 'just in case' basis.
I have a sneaking idea from your description that your problem may be engine temperature related, are the coils getting hot? The engine [having just been rebuilt may also be making more than it's fair share of friction/heat] if this is the cause it should subside in the next several hundred miles, though I would still be a bit sus on the capacitors.

No i just put in a new points plate assembly. It was a NOS item. I might give the yellow wire thing a try and let you know what I find out Its not fouling as bad now that I've charged the battery and I just leaned my Mixture screws out 1/8 turn and it seems to be running ok for now but we'll see what happens over the next 100 miles. What would happen if i forgot to have the headlight on though with the yellow wire off?

You might boil your battery.

I'm getting 13.4 volts with the engine wound to 6,000 RPM its 12.4 at idle and with the engine off. It seems to cut out and go to one cylinder only when the engine is hot and only when i'm below 3,000 rpm. If i keep the RPM's up I can go for miles. If i come to a stop sign the right cylinder will die but if i put it in neutral or clutch it and rev it up it will come back and run on both again. Bike runs fine when the engine is cold.

Might be worth swapping your coils from side to side in case this is an engine temperature induced coil problem..

Some dud coils wait until they're warm before misbehaving.

You have the points and the timing correct on both cylinders?
They can be a real bitch.
Those charging figures are a little low, but only a little.
These weren't a great charging system.

Yeah the timing appears to be correct on both cylinders. The timing light comes on on the dash that says LF which is just a tad before TDC same thing for the right cylinder the RF mark. Its not running quite as poorly now after lubing up the spark advance system and resetting the timing. but I got on the bike really hard today and it cuts out around 8,000 rpm and the right cylinder just seems to die below 3,000 rpm. It runs fine at idle and revs up fine its only when riding at a slow constant speed it dies out unless I roll on the throttle harder. I'm trying to rule out posibilities. I've determined that its not getting the fuel it needs at those rpms or its not getting the spark. however I tore the carbs apart and thoroughly cleaned them so I don't think its the fuel. How would I do the coil swap to check if the problem moves to the other side?

Sorry It kinda just sounded like I was repeating myself and it didn't get any better but what i meant to say is it doesn't kill the engine when i come up to a stop sign anymore. It will idle perfectly its only when I ease on the throttle at low rpm or try to putter around town that the right cylinder dies.

I think you may have to get into that right carb again. Sounds like it could be a dirty low speed circuit.

These things often dictate the points gaps because of the way the right cylinder has to be timed but the smaller end of the specs is best as this allows the max dwell for the charge to build up for a little more spark at high RPM.

By swap the coils I meam remove them and physically swap them from side to side, then you can see if any problems follow the coils from one cylinder to the other.

http://globalcxglvtw...c.php?f=19&t=32
These CX 500 carbs are not the same but they're close so this may be some help'
Several days soaking in white vinegar works well.

That was a very interesting and eye opening read cxphreak thank you very much. That article hit the nail on the head for me. My carbs were calcified very badly. I will tear back into them and try the vinegar thing. I was sure I had gotten them clean but after reading that I'm not so sure. My right carb idle screw is screwed in 1 full turn more than the left carb even though the float levels are pretty much dead on the same. so it very well could be junk in the carbs. I'll let you guys know what I find out in a couple days. Any more tips would be appreciated.

PS one more question I noticed the exhaust sounds different on the right side. Much louder rougher sounding exhaust than the left side. The left side has a nice smooth deep sound. The right is louder and poppier. Could that be valve adjustment?

http://www.ebay.com.au/itm/ws/eBayISAPI.dll?ViewItem&item=130490961005&ssPageName=ADME:L:OC:AU:1123
These are cheap and good, they'd rule out any possible issues with your coils.
It says for CDI but they work with point systems.
It wouldn't hurt to recheck the valve clearances, they're very narrow on these so there's not a lot of difference between spot on and no clearance but it's probably a carb issue anyway. Whatever it is, - there's the reason for the change in exhaust note.

Well I soaked the carbs in vinegar and cleaned them very well and it seems to be to no avail. The passageways seem to be clear but after syncing the carbs back up the right exhaust note is still different. I've found that now if I'm running 60 mph and ease on the throttle I can get up to around 85 or 90 mph if I got a tail wind but If I just crank on the throttle It will pull hard for just a second then the right cylinder just cuts out completely untill i let completely off the throttle. Then it pops and backfires about 3 times and comes back to life.

It's not a low float level?

That sounds like float to me as well, or complete loss of spark? OR maybe flooding the right because of the popping and sputtering after? Is there anything sticking in the right carb to cause too much fuel when you whack open the slide/buterfly? I wonder if you tried a plug chop right after you have whacked open the throttle and the cylinder dies to see if it is all fouled with gas, cause if fuel is not atomised and in the cylinder as a liquid you don't get combustion even with good spark. This is just a theory of course but with the popping as the throttle is let off makes me think there is unburnt fuel in the exaust and it is igniting as it gets pumped out from the heat.

well i flipped the coils around today problem stayed on the right side. I tore back into the right carb and found a float that was much heavier than normal. Gave it a shake and guess what full of gas. could it be that since I've tweeked the float to where it won't overfill the bowl its not functioning properly at all. Maybe because the float is floating lower than the other it can't open up enough to give it enough gas at WOT. I've got a new float ordered it will be here in a few days.