both cylinders running in rythym up down up

My rpms are unsteady, carbs checked and rechecked, no vacuum leaks... The strange thing is it seems to be both sides. i felt the exhaust and both sides are running in rythym. Fast Normal Fast Normal. Air comes out Fast Slow Fast slow. on both cylinders. What could cause this??

Sounds like a missfire or poor compression.

Using a spray bottle with som water in it. Fire up the bike and after a minute of idling the header pipes at the engine should all be hot enough to vaporize (steam) the water sprayed off of them instantly.
If any drops of water stay present on a pipe at the header, that cylinder is not firing properly.
If it is both inside cylinders/outside cylinders - most likely spark/ignition problem.
If jsut a random cylinder - most likely fueling issue/poor carb balance.

Have the valves been properly maintained? Good compression numbers?
These two things are considered the most important part of necessary maintenence.

WOOPS - KZ440, guess I should have paid more attention! meh, still good info...
With te exhuast fluctuating like you say, that can just be attributed to the difference in engine speed with the rpms bouncing up and down.
Good luck!



POOR carb balance...? were slides matched up to correct height after cleaning.inspection?

Some engines on the twins had 360 degree cranks(both pistons go up and down at the same time), others had 180 degree cranks(alternating movement).

Check the advancer too. That's an easy check. Look for one spring broken or both stretched out and weak. A better check is to check the timing with a strobe while running. At idle, it should not advance at all.

MFolks wrote: Some engines on the twins had 360 degree cranks(both pistons go up and down at the same time), others had 180 degree cranks(alternating movement).

I don't know of any KZ twins with a 180 crank, maybe something had that config and I just haven't run across them, but the KZ440 has a normal 360* crank.

loudhvx wrote: Check the advancer too. That's an easy check. Look for one spring broken or both stretched out and weak. A better check is to check the timing with a strobe while running. At idle, it should not advance at all.

Good info Lou...

Make sure with the timing light that it is firing at the same position at idle everytime (F MARK), else this will make rpms jumpy. Usually due to weak advancer springs. If it is missfiring even just once in a while, that means ignition problem - not carbs/engine/anything else, cause the plugs should fire every revolution no matter what else happens.

Changing idle up/down slightly can help with weak springs sometimes - make sure to start with idle correctly set @ factory specs with a known good tach -NOT your bike tach, as it notoriously unreliable at low rpm.

Good luck!

The kz twins with 180 cranks are rare (in the U.S., at least) and small. In the U.S., probably the only one you'll see is the KZ305. But I think other parts of the world got a 250 twin that the 305 was based on.

There was also a 250 single in the U.S., based on the KZ200 single.

loudhvx wrote: The kz twins with 180 cranks are rare (in the U.S., at least) and small. In the U.S., probably the only one you'll see is the KZ305. But I think other parts of the world got a 250 twin that the 305 was based on.

There was also a 250 single in the U.S., based on the KZ200 single.

Thanks for the info; I learn something everyday on this site! Here's a diagram showing the KZ305 180* crank for anyone interested:

You guys are all a bunch of perverts! :laugh: :laugh: :laugh: :laugh: :laugh:

Crossover pipe? Just thinking. :whistle: