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First Bike -- 1982 KZ250

8K views 14 replies 4 participants last post by  grendel 
#1 · (Edited)
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First of all, I'm completely new to maintenance and troubleshooting on motorcycles. I've replaced the spark plug with the recommended one (previous owner was using the wrong plug).

It'll start and idle, but after a couple minutes, starts to slow down and dies. At that point, it won't easily restart again - I have to open the throttle to get it to start back up (which means I'm introducing more air, I think), but it won't stay running at that point. I have to actually let the bike cool down before trying again. Obviously, the bike is unrideable at this point (well, I assume it is... I don't want to risk getting stranded somewhere LOL).

I've checked the air filter, and while it's an old filter, it's clean. I used some compressed air on it, and there was no sign of any dirtiness at all.

At first, I suspected bad gas, since the bike had apparently been sitting for a while under the previous owner. I don't have an inline fuel filter on the bike. I removed the fuel line from the carb and drained a bit of gas out from the tank - I expect that it would have come out pretty quickly (with a stream matching the diameter of the hose), but it was coming out at about half the rate I expected. This was with the tank's fuel cap still on, though - not sure if it would make any difference... might try that tomorrow.

:71baldboy:
 
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#3 ·
Try removing the gas cap and restarting after it dies to see if that is the issue. It's easy to check for a bad vent and will eliminate that as a problem.

If there is still old fuel in the tank, drain it out and get rid of it. Again, it's something to eliminate as a problem.

Make sure there is plenty of fuel in the tank and mix in some Seafoam. The Seafoam can help clean any lighter deposits that may be built up in the fuel system.

Check that the fuel petcock is in the correct position.

These are all easy things to do before tackling more complicated or expensive ones.
 
#4 · (Edited)
Try removing the gas cap and restarting after it dies to see if that is the issue. It's easy to check for a bad vent and will eliminate that as a problem.

If there is still old fuel in the tank, drain it out and get rid of it. Again, it's something to eliminate as a problem.

Make sure there is plenty of fuel in the tank and mix in some Seafoam. The Seafoam can help clean any lighter deposits that may be built up in the fuel system.

Check that the fuel petcock is in the correct position.
Thanks for the tips!

I did as you said re: the gas cap. Once the bike died, I opened the cap, and tried to start again. It still struggled and wouldn't fire up. I guess since it's the same with the cap sealed/open, that means there's no problem with the venting?

Gas is new, and Seafoam was added.

Petcock is set correctly. As an experiment this last time, I set it to 'RES', started the bike, and then immediately moved it to 'RUN'. There was no change in idle speed or anything when I did that (and the bike will start with it set to 'RUN', I was just curious if it would show anything).

Funny thing, though. Apparently, someone previously installed a secondary cutoff switch for the fuel, after the petcock. It goes like this:
Tank -> Petcock -> secondary cutoff -> carb
I couldn't understand why until I started playing around with these things. Apparently, the petcock's OFF position doesn't actually stop the gas flow... gas will still trickle through. The secondary valve stops it (so you have to open that valve in order to ride). Is this relevant to the problem of the bike slowly dying, or is this just something else that I'll change out and make proper anyway?

For the record, I've got the 2 fuel switches thing figured out, and I'm running them wide-open, so that can't (in and of itself) be the cause of the slow death.. LOL

check the fule mix screws on the carb (pilot screws) they are usaully nearesr the engine on the bottom. turn them 1/4 turn out at a time till you get your desired effects. use a fan when you start the engine! you don't want it to overheat.
I'll have to check those tomorrow (ran out of time today).
 
#5 ·
It sounds like the original petcock is leaking so someone added a stop-gap measure rather than replacing it.

Without actually looking to be sure, there may be a restriction in the old petcock or the new valve that was added later. The fuel should flow freely when the petcock is open, not slowly.

My guess is a restricted fuel supply may be your problem, because after sitting for a while it starts right up then dies after running a while.

I would replace the original petcock and get rid of the secondary valve.
 
#7 ·
So, surprise surprise: the petcock/tap for this bike is discontinued. I know... shocking, right?? The guy at the local Kawi shop helped me piece together the internals that I could replace, but I'm thinking that's only worthwhile if this is the OEM petcock - since so many other things on this bike have been changed up, I'm not sure it would be. So, I'm just going to replace the thing entirely (once I find a suitable or OEM one).

In the meantime, I drained the tank down to where nothing was coming out on the 'reserve' setting... removed the seat... removed the tank, and with the tank angled so no fuel could pour out, I took the petcock/tap off of the tank. I figured I'd at least operate on it and see if there was anything I could clean out. All the gaskets/o-rings looked to be in good shape. There was a small piece of black plastic inside of it, and I got all excited when I saw that, thinking this was gonna be easier than I expected.

So, I finished cleaning everything up with a rag and compressed air, and then replaced the petcock back into the tank... replaced the tank onto the bike... replaced the seat... and noticed that it was leaking a bit, right from where it attaches to the tank! It's not actually dripping, more like.. seeping.

Soooo... do I just need to replace the petcock entirely (I'm leaning to YES)? As well, is there anything I can do to stop the leakage? I should have just left the damn thing alone LOL!
 
#8 ·
Did you apply any type of thread sealer to the petcock threads when re-installing it? You need to. Make sure it's fuel-resistant sealer.

You should be able to replace the gaskets inside the petcock to make it shut off properly. Unless it's damaged, that's all you will need. You can take the petcock to the dealership to make sure the rebuild kit fits.
 
#11 ·
I picked up that stuff (the Permatex Aviation Form-A-Gasket No. 3 Sealant), and pulled the tank off the bike again, removed the petcock and applied. I've left the tank off the bike, propped up, so it can cure overnight. I figure I'll check it in the morning by just holding the tank horizontal - if nothing seeps out, then I'll be good to go for reassembly onto the bike.

Thanks for the assistance, Dodsfall... I'm a n00b at this stuff, so you've been super helpful!
 
#12 ·
For the record, those Kawasakis had a vacuum operated fuel valve. It sounds to me like the vacuum components are buggered. I'm wondering if the slow leak fills the carb bowls enough that it will run for a few minutes until it runs out and you have to let it sit for a while (i.e. until the bowls slowly fill back up again).

Pingel makes nice aftermarket fuel valves. They aren't vacuum operated, so you'd have to make sure you turned it off after each ride.

Check out Z1Enterprises.com. I've bought from him before and had an excellent experience. He's the go-to for KZ parts.

http://www.z1enterprises.com/catalog.aspx?pid=KZ250-L1-1982-CF0
 
#13 · (Edited)
So, on the list for today was checking/adjusting valves! FUN, or at least I THOUGHT it would be...

Alternator cover off:


Engine rotated to where it's supposed to be ...

Valve adjusting caps removed ...


Valves adjusted to specs ...

Caps replaced, and then it all goes to hell. Two of the 4 bolts required to hold the valve caps on feel like they're stripping. I step backward on one of 'em to check, and this is what I get:



So, be honest... how fu#*%d am I?

EDIT: 2 of the bolts torqued down properly, 1 on the intake, 1 on the exhaust.
 
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