'82 KZ305 CSR - Running problems

Hello,

I'm looking for help troubleshooting my 1982 KZ305 CSR. Bought it a week ago with 4000 miles on the odo from a popular vintage import bike shop in my area (Rice Paddy, Columbus OH). They told me they rebuilt the carbs after finding the bike in an estate sale. The previous owners of the bike said it had sat for many years under a roof but outside. It ran pretty good for a few days, now startup is inconsistent. I'm having trouble getting it to fire up reliably.

After a few days of riding it, the in-line filter that came on the bike from Rice Paddy had a fair bit of brown within. I'm thinking that's rust.. I've opened up the carb float bowls and had a look, they seem pretty clean. When the bike does start, it doesn't need any of the choke. I neglected to open the top of the carbs to check the diaphragms (rookie mistake) and I will be doing that today when I get home from work. I know the battery is brand new and in great working order. Not sure about the coils or how to check them, I've seen a lot of suggestions around the internet to look at that. The bike does seem to be using a little bit of oil. I had to top off the level the other day, and noticed a small amount of smoke coming from around the carbs before this running issue began.

I've attached a few pictures I'd like some commentary on - The first one is a mysterious hole under the carbs/on top of the crank case. I have no idea what it's for. It never had a hose or fitting of any kind when I bought the bike. It was left completely open, is this okay? The second picture is of my fuel line/filter, I'm wondering if having the in-line filter could possibly be restricting flow from the gas tank? I've checked the fuel flow straight out of the petcock (no fuel line) and it's flowing a steady stream just fine. For some reason, when I hook everything up 100% from petcock to carburetor, it seems like very little fuel is moving. I can't seem to get the in-line fuel filter to fill all the way up. It's very strange.. Any ideas?

I also have a '94 Harley 1200XL sportster that I'm far more familiar with. I appreciate any wisdom you guys are able to provide. Thanks for reading.

- Luke

Try riding the bike with a new fuel filter or no fuel filter at all (just as a test).
The tank may have rust & the petcock screen could be clogged.
I would remove & clean the fuel tank & petcock and install a new fuel filter.

The unknown port is the crankcase breather. There should be a 90^o rubber fitting connecting it to the airbox.
See the engine covers & airbox diagrams at Kawasaki.com.

martin_csr wrote: Try riding the bike with a new fuel filter or no fuel filter at all (just as a test).
The problem seems to be fuel starvation from tank rust; the petcock screen may be clogged.
I would remove & clean the fuel tank & petcock and install a new fuel filter.

If the petcock/tank is clogged, would it still flow freely when completely removed/detached from the fuel lines? I have tested this and I get a reliable/steady stream from the petcock. No shaking or jossling of the tank required..

martin_csr wrote: The unknown port is the crankcase breather. There should be a 90^o tube connecting it to the airbox. See the engine covers & airbox diagrams at Kawasaki.com.

Am I going to blow the engine up without this 90 degree hose? I just looked around the internet and saw what you're talking about. Will try to source one of these hoses ASAP.

Thanks for the tips, man.

Try riding the bike or check the fuel flow with the fuel cap open.
I would still check the tank & petcock screen. If the fuel filter has gotten brown already, there's probably a good amount of rust in the tank. Anyway, I prefer to verify stuff; check something, double check my work, then move on to the next thing.

The open breather isn't going to blow up anything, but it could let water into the crankcase.
Is the breather port at the airbox capped or open? Without the rubber elbow, the airbox hole should be plugged.
In the mean time you might be able to find a suitable piece of breather tubing from the auto parts store & either connect it to the airbox or route it behind the engine.

Thanks again, Martin. Gave the gas tank and carburetors another look last night. Fixed the fuel delivery problem and threw on a new line/filter. I think it was having trouble passing gas because the line had not been properly burped.. So now the bike starts up and runs without stalling. It does seem to be running lean though.

At wide open throttle the bike has some pretty bad hesitation. It pulls pretty hard but has these jarring "spurts" that push me forward when I'm riding. I'm wondering if maybe an upjet would fix that? I think it's just lean. Could be wrong..

Your bike has CV carburetors which are sensitive to vacuum leaks.
Is the airbox breather hole plugged? If not, that would be a big vacuum leak.

Make sure the air filter & airbox cap are properly installed. The 305 airbox appears to be kinda similar to the 440. On the 440 a test is to gently pull up on the back of the cap --- if it moves, the cap is installed wrong. The cap can break, so don't pull too hard.

Also, check to make sure the airbox ducts & carb holders have a good tight fit --- you can use carb claner spray or wd40 to check: spray the stuff & check/listen for an rpm change. All easy stuff to check.

Thanks again, Martin. The fuel delivery problems have been sorted. We also found that the on/off switch was loose enough on the handlebars to cause a "stuttering" effect when the bike goes over bumps. Very strange..

Next problem to tackle is oil related. The bike seems to be using or leaking oil somewhere.. After a week or so of pretty regular riding, the oil becomes dark black and the level drops dramatically. To the point where smoke comes up from the crank case.. I don't see any obvious leaks, and I'm also assuming some of the smoke is being produced by oil dripping out of the bottom of the carbs (normal?). I have even observed a bit of smoke coming out of the oil fill hole when the cap is removed and the bike is hot. Any suggestions??

Luke