TOPIC:

Hey hey everybody. It's been a while since I've had any issues, but now I'm back. Not sure if it's an engine or carb issue, or what.

Started maybe a month ago when after a decent ride I started to feel a loss of power and the idle got pretty rough, like not all cylinders were firing. Then I noticed fuel leaking from the pods. Maybe somehow the fuel level rose and was flooding the cylinders causing some not to fire? I lowered it, and no more leakage, but 3, 4 and sometimes 2 still won't fire right. Sometimes I can hear them trying to get going, and things smooth up once I go above 1500 rpm, or when I squeeze the clutch. All plugs have a spark. There is also some popping on deceleration and some surging after running for a bit. Any pointers?

Valve adjustment and sync.
Steve

Do you have a good fuel filter in the fuel line? Some tiny bits of dirt or rust could prevent the float valves from closing, causing what you describe.

Just did the valve clearance. Only three were slightly out of spec, but I did adjust them and not much improvement if any.

I've never successfully done a vacuum sync since the tops need to be off and I've always ended up making things worse that way. Any way I had them gone over by Wired George last year and they were fine until now. Could they have gone out by now?

As for the fuel line, I do have a good filter in there and it is pretty clean, as well as the float valves.

I checked ignition timing and it's right where its been since converting to electronic, though I will say since those instructions tell you to set timing at the advance, the idle marks have been slightly off.

Replace the spark plugs.

daless wrote: . . . fuel leaking from the pods. . . .

'77 KZ1000A1 - Mikuni VM29s, Kerker 4-1, K&N pods . . .

Smoothbores don't have overflow circuits. Fuel rising for whatever reason into a carb body flows not only rearward toward the pod but also flows forward through the intake port into the combustion chamber and down around the piston into the crankcase thereby diluting the oil. And this can happen while the petcock is allowing fuel flow regardless of whether the engine is running or not running.

Would sniff-test the crankcase oil and examine its physical condition. Sometimes the oil window appears deceptively full or even over-filled due to fuel having entered the crankcase which raises the level of fluid.

If the crankcase oil is diluted with gasoline, do NOT run the engine.

Lack of an overflow circuit means that constant vigilance is imperative with smoothbores to assure that each and every float valve is functioning as it's supposed to. And all the more reason to assure that no gasoline ever enters the carbs without having first passed through an aftermarket in-line fuel filter.

Good Fortune!

Replace the spark plugs.

First thing I tried. In the past, when cylinders would fail to fire, that would always get me going again. Not this time.

Fuel rising for whatever reason into a carb body flows not only rearward toward the pod but also flows forward through the intake port into the combustion chamber and down around the piston into the crankcase thereby diluting the oil.

Now we're making sense. Would a simple oil change solve this, or is there more involved?

Popping on decel indicates a lean condition. Random surging indicates a lean condition caused by an airleak in the intakes. Random cylinder misfires could indicate too lean of a mixture to fire. All symptoms are consistent with an air leak in the intake. Loosen all the clamps and make sure the carbs are fully seated. If you can remove the carbs easily, put some armor-all on the inside of the mounts as a lubricant. This will make them easier to seat. Because the misfire is on 3 &4 and sometimes 2, pay extra attention to the right side of the carb bank. Compare both sides and you may notice that your carb bank is at a slight angle when viewed from the top. If you still have the original intake mounts, it may be time to invest in a new set. They become hard and stiff over the years.

daless wrote:

Fuel rising for whatever reason into a carb body flows not only rearward toward the pod but also flows forward through the intake port into the combustion chamber and down around the piston into the crankcase thereby diluting the oil.

Now we're making sense. Would a simple oil change solve this, or is there more involved?

After first correcting whatever is causing the float valve malfunction (such as a dirty float valve or leaking float or sticking float, etc.), changing the oil and installing a brand new oil filter is sufficient to restore the crankcase oil supply to the desired condition free of contamination. Do not run the engine to "heat the oil" before draining it. Just remove the oil drain plug and drain the cold oil for a few minutes. Then also remove the oil filter and allow the crankcase to further drain for a few more minutes.

Before refilling the crankcase with fresh oil, be positive that the correct fuel level is holding stable in each carb -- clear tube testing each should indicate whether or not the carb's fuel level is holding stable.

To help avoid crud and grit from reaching and overwhelming the inline fuel filter, would also consider removing and cleaning the petcock, and also removing and flushing the fuel tank via the slosh and upside down fast dump through the open cap (several times). Which is sometimes sufficient, depending on just how crappy the tank interior happens to be.

More aggressive means of interior fuel tank cleaning are also available. No-nonsense favorites include: muratic acid; padded and spinning in clothes dryer while partially filled with sheet metal screws or what-have-you, with no heat; etc. Each of the numerous methods deserves a separate full explanation.

Good Fortune!

It's possible and usually feasible to restore the fuel tank interior to like-new condition.

It might be possible to flush a bit of crud or piece of grit from the interface of the float needle's pointed tip with the needle seat orifice by allowing fresh clean gasoline to drain through the carb for a few moments with the carb drain screw open.
But it may be necessary to remove and clean the float valve needle and seat.
Remember that the needle and seat are married to one another, and should not be mixed and matched during reassembly of the carbs.



Good Fortune!

daless wrote: Just did the valve clearance. Only three were slightly out of spec, but I did adjust them and not much improvement if any.

I've never successfully done a vacuum sync since the tops need to be off and I've always ended up making things worse that way. Any way I had them gone over by Wired George last year and they were fine until now. Could they have gone out by now?

As for the fuel line, I do have a good filter in there and it is pretty clean, as well as the float valves.

I checked ignition timing and it's right where its been since converting to electronic, though I will say since those instructions tell you to set timing at the advance, the idle marks have been slightly off.

I agree with the above suggestions. The carbs have to be synced on the bike no matter who did them on the bench. Now that it's been run, the engine will need different settings. After everything has been done a sync will get it to idle and run smoother.
Steve