1981 kz305 intermittent white smoke from one exhau

Hello all,

I have a new-to-me kz305 that has a weird problem with puffs of whitish smoke coming from one cylinder, and some rough running and vibration. Let me run down a couple of things I've noticed/done:

1. I changed the spark plugs- the old ones came out looking blacker than night- before I did this, I would have to hold the throttle slightly on to keep the bike idling correctly, and now it idles on its own (sort of)

2. The PO lost the air box and replaced it with a pair of pod filters, and I don't know if this is contributing to the rough running or not

3. The PO also said that he thought the bike was running a bit rich because it wasn't idling and it smelled of mostly unburned gas from the exhaust- after I changed the spark plugs though, the bike runs and rides much better and only smells somewhat like unburned gas- it kinda smells like a lawnmower if you leave the choke on too long

4. I noticed that the oil level is way too high (it's higher than the top of the sight glass) and it has the murky brown color suggesting it has water mixed in with it- could this be causing the white smoke?

5. There doesn't appear to be any loss of compression, as the bike still starts up and rides perfectly, and there's no discernible exhaust or fuel smell coming from the crankcase. FYI I have not done a compression test yet

6. My main suspect is that one cylinder is running richer than the other and they just need a balance, however there is a small amount of rust sitting in the bottom of an in line filter under the tank, and this worries me- do the carbs need to be cleaned?

7. The last thing I noticed is some slight hesitation on acceleration accompanied by some popping from somewhere in the engine- this only happens when the one cylinder is smoking, when it doesn't it rides perfectly with no noise or hesitation.

Besides these things, it runs and rides and stops perfectly for a 32 year old bike- I'm just hoping nothing major is wrong with it besides the things i can do myself- a carb cleaning, balance or a valve adjust, etc.

Thanks,
Geoff

First, do not ride the bike. You have serious carb issues.
White smoke means fuel, running rich. Murky oil means fuel in the crankcase.
Pull the carbs and fix the fuel leak, and check the petcock for leaks. Replace the filter and oil and you will be ready for step two.
Come back at that time.

I haven't been doing any serious riding, just to the end of the street and back to test the new plugs and see if there are any other problems, which is how I found out about the popping- there aren't currently any leaks that I can see coming from around the carburetors or the petcock- could it be that the float bowl on one carb is stuck open? I did notice that there was some rust in the fuel lines, could that have gotten into the carbs and caused a leak somewhere?

Ill go see if i can get a filter and a couple gaskets, and I'll report back after giving the bike a proper tune-up

It is usually a stuck float. You have gasoline in your crankcase. That is very dangerous on several levels.
Do you know how to fix/test for stuck floats? If not, I can walk you through it.
The very last thing you do is change out the filter and oil.
LMK.

You also need to fix the rust in the fuel lines. If it got into the carbs it is probably keeping the needle and seat from closing, which would make the carbs overflow.

As a temporary fix for the rust, you need a fuel filter. One designed for a gravity flow system. You can find them at a hardware store in the lawnmower section. Splice it into your fuel line. Preferably a clear one so you can see the fuel flowing.

Please acknowledge, then go get the filter while I write up what you need to do to the carbs.

How to clean contaminated carbs:

Remove the carbs

One carb at a time
remove the fuel bowl
remove the float by gently tapping out the small shaft
remove the needle
Spray everything with carb cleaner
install the needle
install the float by lining up the float with the holes in the towers and gently tapping in the small shaft
take your time with this step, be gentle as those towers can break if you hit them too hard
install the fuel bowl
repeat for each carb

Now they should be ready to test while off the bike.

put the carb bank in a pan, orient them so they are parallel to the ground
connect a fuel source. your gas tank on PRI will do in a pinch
let stand for at least 10-15 minutes
check for leaks
if any leak, repeat cleaning process for that carb(s)
repeat test until none leak

now re-install on bike, connect fuel and vacuum lines

For your bike, be sure that fuel filter is inline.
Change your oil and filter
See if it still smokes when it runs.

I'm currently on my way to pick up everything I need- the bike currently has a small inline fuel filter Between the petcock and the carbs, but it looks like some very fine particles got past it- I'll also have a look through the carbs at some point this weekend

Also, is it too late to run seafoam through the carbs to clean them?

Change the filter. Try to get one that is microfine.
Don't bother with seafoam unti the leak is resolved.;
Do not run the engine until you change the oil and filter. I cannot stress this enough. You are down until you get this fixed.
Do everything I said, in the order I said.

Will do- will spend the weekend changing the oil and testing/rebuilding the carbs, then I'll do a valve check and timing check to make sure everything is absolutely right- this will give me the opportunity to de-rust and reseal the gas tank too