TOPIC:

Hello,

New member here… recently purchased a 1980 KZ440 and I’ve been trying to get it running, without success. The bike currently runs on one cylinder (left side); right side is getting fuel and has spark. Below is all I’ve done so far - looking for some assistance/guidance.

Carbs were cleaned (soak, hot water wash, compressed air) and float levels were set per the service manual. Rubber parts were removed/left out for the soak. Added non-drying liquid seal to the intake boots and changed the bolts to allen head. No air leaks @ the carb boot clamps (both sides); I still have a small leak through the air box duct/boot at the box interface.

Valve clearance was adjusted and timing was checked. Coil was tested as well with a multimeter and is ok per the manual. Getting good spark on both cylinders. Running a stock intake (air box) and exhaust; carb jets are all stock as well. Changed the oil and filter when I got it about a month ago.

Tried doing a compression test but I’m not sure I can trust the results. Both cylinders showed 80 psi when tested with a HF gauge and another gauge rented from O’Reillys. However, the bike starts easily and idles on the one cylinder. The HF one does not have the schraeder valve on the quick connect hose; the O’Reilly one does. I read on another thread that this could cause issues with the readings.

Also tried doing a leakdown test (@TDC). Both cylinders showed about 25-30% leakage (still in the low range of the gauge). I could hear the hiss noise stop as the intake valve closed while rotating the engine by hand. Leak was through the intake and the crankcase ventilation on the valve cover.

I’m new to motorcycles and am learning as I go. If I left anything out that might be relevant please let me know.

An engine requires air, fuel, compression, and spark; I think you are going about this the right way.

Two things come to mind:

- Even with the cleaning of the carb, it is important to verify visually and mechanically that absolutely all of the passages are clear.

- Are you performing the compression tests with the throttle held wide open? You got consistent results with two different gauges, so I think the results may be attributable to technique.

Side question: what happens when you try to start the engine with the choke on?

For the carbs, I used a rubber tip nozzle on all the holes I could find. I did verify all the needles under a light to make sure all the holes were clean.

Compression test was done with the throttle open all the way. I also tested while the boot liquid seal was drying (no carbs), so at that point throttle did not matter (engine was cold though). Still, I could be doing something wrong. My other bike also showed low compression with the rented tester, but it starts and runs without issues. Not sure what's going on; might be good to check it with the HF one to see if I get anything different. On the KZ, I've tested the left (working side) side cold and hot but the results is the same.

I start the bike with the choke and it revs up to about 3k RPM. I then play with the choke to get it around 1.5-2k. After it warms up it idles relatively normal on the one cylinder without the choke.

It would be interesting to see if the HF gauge and the rental gauge give the same results on your other bike.

When the engine starts on choke, is it still just the one cylinder that runs?

So I rode the other bike for a while and came back to test the compression with the engine warmed up. Both gauges gave me the same result... 70psi. Only tested two of the four cylinders to avoid draining the battery. Tested both at WOT. Spec says it should be between 128-171psi. Not sure if this tells me both gauges suck, or if there is some other issue.

When the KZ starts on choke, it is still the one cylinder that runs. I can start the bike with the other plug removed and grounded.

Hmmm. I'm also starting to wonder if both gauges suck. I have trouble believing the other bike would be running and rideable with only 70psi.

So back to the 440. When the plug is out and grounded, it does have spark; I believe you said that earlier. You cleaned the carbs the same way on each side.

You mentioned that the valves were adjusted. and the two cylinders have the same compression, so that is probably not the issue.

That brings us back to fuel delivery. At this point I think the next step is to revisit the carb on that cylinder. it could be something as simple as a disconnected throttle cable or choke linkage.

Does the spark plug on the non-working cylinder smell like fuel or does it look wet/damp with fuel? It may sound silly, but you could try to start the bike and then smell the tailpipe on that side. Yes, I'm serious. If the air-fuel mixture is passing through the cylinder and not burning, it will be pumped out of the exhaust.

Yes, there is spark on the right cylinder. The plug looked wet to me, but I'll double check tomorrow (along with the smell test). I'll revisit the carb too just in case. I know for sure the throttle cable and choke linkages are ok. Ask me how I know already had issues with both springs not being in the right place after I took out the carbs for a quick check on something else.

If I spray some starting fluid on the dead cylinder and start the bike, it revs up right away which tells me that the plug is igniting the fuel at that point. Starting fluid burns easier though; just wanted to share the info in case it helps.

[EDIT] I actually put 90 psi to the HF gauge with my compressor and it read correctly. That was with the quick connect hose attached. I noticed that the o-ring at the plug opening is deforming (a lot) while the hose is screwed in. I suspect it does not allow the pressure to build up past a certain point... say 60-70 psi.

Thanks.

I could not smell fuel on the exhaust. Put a new plug on the right side. I did notice that if I rev the engine the exhaust tends to get hotter on the dead side as if the cylinder had started to work. On idle, the temp. rarely goes above 150F on the exhaust. Took the bike for a quick ride up and down the street and the temp went up above 200F (still not as hot as the left cylinder).

Could not pull the carbs off today, but will try tomorrow.

If the bike runs for a little while on the left cylinder, eventually heat will leach/soak through the head via conduction and will start to warm up the right side. I don't know how fast or how thoroughly that will happen, though.

One thing about the 400s/440s: they are quite sensitive to battery condition. If the battery is marginal, starting can be a real bear. Ask me how I know that. :-D

With no fuel smell in the exhaust I think there are two options: either the fuel isn't getting into the engine or it is being burned before it heads out the exhaust. When the throttle is opened, that moves the carb flow off the idle jet to the pilot or the main (depending on throttle opening). It's possible your idle jet is blocked, which would make sense as it has (IIRC) the smallest openings.

How did it pull when you went for the ride? Did it feel like the right cylinder was running properly?

The heat transfer makes sense. I'm just using the temperature as a guide to know if the right cylinder is firing at idle. Looking more at how fast it goes up in temp and the differential between the two pipes, than the actual temp number.

It was not running good when I took it out. I'm glad I did not go far as it did not want to start at the end of the street. Had to use the choke and it would just rev up like crazy. Need to find and fix the vacuum leak(s). Pilot screws on either side are doing nothing to the RPM when turned in/out. It was bogging a little... in the garage, I could hear popping from the right exhaust as the cylinder started to fire.

Last time I took the carbs out, the right side boot was wet. I'll check again once I remove the carbs to confirm it is fuel.

As a side note, I bought another 440 ('81) as a parts bike. Came with carbs... will open them up and see how they look.

The pilot jets are very small. Use a guitar string or wire brush strand to be sure they're clear.
Steve

I checked the carbs but I could not see anything out of place or suspect. Checked the pilot jet on the dead (right) side and it seems to be clean (pic attached).


I put a piece a shop towel on each exhaust and that way I was able to smell fuel on the right side exhaust. I have spark but the mix is still passing through.