Throttle too stiff, busted return spring, leaks

'79 KZ650 B3

OK, so first:

Throttle too stiff: Maybe I have unreasonable expectations. I'm used to a super-light throttle. My DR350 has a 2-cable, push/pull setup just like my KZ650, but the throttle is effortless. On my KZ 650, it takes quite a bit of effort. On the other hand, when you release the throttle, it's slow to come back to idle. I've lubed the cables, but saw little improvement. How stiff should the throttle be?

Second:

Busted return spring: So, I decided to stretch the return spring a bit to see if that made any difference. I took the tank off and after a surprising amount of grief and cussing and trying different screwdrivers and pliers, I finally managed get the throttle return spring loose at the top.

So, of course, I stretched it too much. Wayyyy too much. I'm now going to need a replacement, and I just don't see how I'm going to get it hooked back in, especially at the bottom, with the carbs on the bike.

a) what do I do for a replacement?

b) do I need to pull the carbs off the bike to simply install a return spring? If not, what's the trick? I can't even see where it hooks in at the bottom, or feel it with my finger.

Additional info:

With the return spring off, I worked the throttle a bit, and it seems to have resistance at the throttle, rather than at the carbs.

Third:

If I leave the bike sitting with the petcock open overnight, it leaks a pretty good bit of fuel. I've been unable to isolate which carb is leaking. How do I do that, and what is the likely fix once I isolate it?

Thanks

You may need to remove the twist grip and clean/lubricate where it turns on the handlebar. I had similar symptoms, and discovered a rusty bar end under the grip. Once I cleaned and greased her, all is well. In order to remove the grip, you will need to undo the two screws that hold the right side switch pod together. They are the two phillips head screws under the switch pod. Once the pod is seperated, the twist grip should slide out.

As for the broken return spring, I'm not sure if Z1enterprises stocks them, but I bet if you called, then they could at least advise you where to get one. Then there are the obvious possibilities of ebay, or possibly another member has a spare. Sadly, I do not or I would send it your way. You will probably need to remove your carbs to get the replacement on. Sorry, I know you didn't want to hear that.

As for the fuel leak. You could place the ends of the rubber overflow tubes in individual jars overnight to see which one is leaking. However, it is not recommended to leave your petcock in the on position. You run the risk of hydro-locking your engine, should you fill a cylinder overnight and then attempt a start in the morning. I would suspect a bad needle and seat if a carb is leaking. The fix is to rebuild the carb or at least replace the leaking needle and seat from a rebuild kit.

Good luck.

Thank you for the detailed information. That gives me a lot to work with.

It also appears the "Phantom oil leak" thread I started may be related: kzrider.com/index.php?option=com_kunena&...d=2&id=411790#411790

I went out and smelled inside the crankcase. I didn't smell gas, but I'm still suspicious. I stuck a finger down in the crankcase and got some oil on it. It feels viscious, and does not smell of gas.

When looking down into the crankcase, should I be able to see standing oil?

Concerning hydro-locking, and possibly having gotten fuel in the crankcase:

The day I went out and found all the oil under the bike, I got some of it on my fingers and rubbed them together; it felt viscious. I smelled the oil on my fingers; it didn't smell like gas at all. However, I realized that most of that big puddle had evaporated by the time I got home that night. There's a stain on the floor, and still a bit of oil, but nowhere near as much as there was when I went out there that day. I'm wondering if that puddle was a mixture of gas and oil?

Also, after putting oil in until I could see it in the window, I went to start the bike. The starter wouldn't turn it over. Now, my battery is in the process of going south, so I didn't think much about that.

When I went to kickstart it, though, it would barely budge. I tried again, pushing harder. It barely budged.

The third time, I kicked like hell, and it turned over, but wouldn't start. It kicked fine after that, and started on the third try. Ran rough for a bit, but eventually smoothed out.

Now, I know at least some of that big mess on the floor was oil. Shortly after I started it, smoke began coming off the pipes under the engine. Clearly oil spilled on them was burnin off.

Does it sound like I hydro-locked it, too?

Yes the two threads are related.

I don't think that you should be able to see standing oil, the fill line is well down in the crankcase, and you shouldn't be able to reach it with a finger.

Regarding the leak evaporating, oil won't evaporate on it's own. It could seep into the concrete of the floor, but if it actually evaporated, I would suspect gas.

Sure sounds to me like it was hydro-locked when you attempted to start it.

Now you are left with what should you do. I would change the oil, pull the spark plugs, and make sure that the fuel supply is completely cut off from the carbs. Then crank it over to remove any excess fuel. Then it's time to get hold of a compression tester, and see if the condition did any damage. Run a compression test and see if any cylinders are low. If they are, then I would suspect a bent connecting rod as a result of the trying to start a cylinder full of fuel.

If there was no damage done, then proceed by rebuilding the carbs and possibly the petcock. You need to remedy the fuel leaks.

Sadly, if you did bend a connecting rod, then you are in for a rebuild or replacement of that motor.

Sorry for all the bad news, but I am just working off my experience. Run the compression test, it will tell you alot.

Well, if it was indeed hydro-locked (as I think it was), I don't think the hydro-lock did any damage. Once I got it started that day, I rode it to and from work; about 35 miles. It made no noise, as I'd think it would if it had bent a rod. It also kickes over quite easily now, and has ever since.

I'll definitely change the oil, and go ahead and replace the pan and side cover gaskets while I'm at it. I think I'll do the compression test first though. Don't want to put oil, filter and gaskets in when I may be rebuilding or replacing the engine.

Those darn carbs had full kits put in them less than 2000 miles ago. I guess it would have to be the needle and seat, though. If it was a stuck or misadjusted float, the cylinder wouldn't have filled with gas, would it?

Are you running a fuel filter between the tank and the carbs? I guess that it is possible for a small piece of debris from the tank to get lodged in between the needle and seat and cause it to hang open. I would think this to be a temporary condition however.

If the float had somehow stuck, leaving the needle and seat open, then it would cause the same condition. If the float were mis-adjusted, and the needle was sealing, then I would just suspect an overflow thru the overflow tubes to the outside.

If it ran that far, then it is at least hopeful that the damage was not bad. I would suspect that if it was in fact hydro-locked, and it didn't bend a rod, that you are loosing some compression. Either the rings or the vavles are leaking. That hydraulic pressure had to escape somewhere.

I am running a fuel filter.

If the cylinder had filled with fuel, when I kicked on the kickstarter the first time and it barely moved, but did in fact move, and got the same result on the second kick, and on the third kick it turned over, but did not start, I'd think the bulk of the fuel would have evacuated out the exhaust valve.

When it did fire, it started for a second, then died. Then, it began running, but poorly. I'm wondering if all that fuel didn't foul the plug for a short time, causing it not to fire, but eventually drying off and doing so, as evidenced when the engine cleared up?

Ok, good that you're using a filter.

Yes, the plug was fouled because of the excess fuel, and likely burned off the junk as it ran.

Yes, the excess fuel did escape throught the exaust once the vavle did open.

The problem is the compression stroke. When the engine wouldn't turn over was when the full cylinder was on the compression stroke. Both valves are closed effectively sealing the cylinder. When under compression, if the cylinder is full of fluid (gasolene) and not a proper air fuel mixture it acts as a hydraulic cylinder. The fuel is not capable of compressing. In order to get past the compression stroke on a hydro-locked cylinder one of four things needs to happen. 1) Remove the spark plug so that the fuel can escape (recommended.) 2) Fuel escapes past leaking compression rings. 3)Fuel escapes past leaking valves 4)Connecting rod bends under the strain. You have to make it through the compression stroke and the power stroke before you get to the exhaust stroke when the exhaust valve opens.

That makes sense.

So, approaching it with hindsight, I think we can rule out bending the rod. If it had, I'd think there would've been some pretty serious noisein the 35 miles, or so that I rode it afterwards. A compression check will tell me more.

I think we can rule out it going past the rings, as well. If it had, I'd think there would be a fuel smell in the oil, and there is none at all.

That leaves the valves, which is possible. The simplest check would be to put air pressure in the cylinders and see if it hisses at the carbs (leaking intake valve), hisses at the tailpipe (leaking exhaust valve), or hisses at the crankcase (leaking rings).

When I last ran a compression check, it was low on #3. We'll just have to see how it does.

Also, just checked z1enterprises.com. No return spring listed.

Heck, if it runs, and makes enough power for you, then don't worry about it. Fix the fuel/oil leaks and go down the road. Compression test will tell the real story, but as long as the bike starts every time, and you are happy with the performance, then don't stay awake at night worrying about how soon it needs a rebuild. Just make sure that the fuel isn't leaking. There will be no good coming from fuel leaks. Outside fuel leaks lead to fires. Inside fuel leaks lead to poor performance, fouled plugs, poor mileage, washed out rings, premature wear, and cam bearings not properly lubricated. All of these will cause premature engine failure eventually.

I'm a pragmatist when it comes to engines. Keep them running right so they will last as long as possible. Does it run and make you happy? If so, then cool, who cares if its a little worn? If you are racing, then you worry about compression. Sounds like you have a decent plan.

So, I just talked to my friend Reagan (Mechanic #3). He's the guy who finally solved the electrical problems on that beautiful, red, classic @#$%^&!!! KZ650, so I put a lot of weight to what he says.

He thinks the gas leaked past the rings, mixed with the oil, and all that mess leaked onto the floor. Since the gas thinned the oil out, it made the leak much worse, hence the huge leak. He told me he had a generator do that once.

We'll see when I get it out to him.