2020-12-08 Kz1300 A1 Test Ride - Overheating cause Identified?

stocktoy wrote: Just a thought is the ign timing correct if its off I've seen it on other engines that the engine will run hot and nothing will bring the temp down until the timing is corrected.

Kawboy wrote:

stocktoy wrote: Just a thought is the ign timing correct if its off I've seen it on other engines that the engine will run hot and nothing will bring the temp down until the timing is corrected.

+2 on this one. The science behind this is if the spark is advanced too much, the flame front of combustion will be heating up more of the cylinder wall than the coolant system can handle. Usually takes about 10 degrees or more too far advanced to accomplish this. If the timing is too far advanced by more than 15 degrees, starting issues and piston ping would also be indicated.
We did find the timing to be retarded by ~10 degrees. It was reset to correct, although we did have to slightly elongate the holes in the pick up plate. After this, the majority of the heating issue went away AND the motor is much crisper, easier starting, and pulls strong, STRONG to redline.

Lean fuel mixtures can also run hot but this is more of a worry for 2 strokes (burning holes in pistons) although I have seen evidence of near failure in 4 stroke pistons where the aluminum on the head of the piston boiled and nearly blew through.
Last but not least, some people insist on running premium fuel in engines not designed for using premium. What happen here is the fuel takes too long to burn exposing more cylinder wall to excess heat and also exposing the exhaust valve seat faces to the flame front when the combustion process is still in effect.
Ok.. I'm naive and will check FSM for recommendations, but I have been running premium fuel.

Bottm line for me and where I cast my vote is the burping issue of the coolant system. This topic keeps coming up over and over and in the end the answer has always been the coolant system burping. If Kawasaki had been smart, they would have moved the rad cap to the right side of the rad so that coolant checks, top ups and rad burping could have been accomplished with the bike on the side stand thus having the rad cap at near the top of the coolant system.
My bud Greg runs KTM's. Per KTM, burping has to be done with front end way higher than the rear to move the bubble. I might try putting the KZ on center stand, lifting the front end with jack as high as possible. Another bud, retired MC tech, also. suggested squeezing the hoses when attempting a burp. At this point I'll try anything..

Post note- I just took the time to look at both videos (thanks for posting !!) I've never seen coolant flowing that ferociously past the rad cap hole and it leads me to think that the rad is partially blocked causing the coolant to flow more rapidly through a reduced number of rad tubes. Maybe take some Fluke readings across the rad and look for cold spots on the rad.
I suppose anything is possible, but that radiator is a custom built 3 row from Randy's Cycle . I like the idea of checking across radiator for hot/cool spots.

Neville wrote: I'm with Kawboy on this. There seem to be two issues here: 1) the expansion tank should be receiving "hot" coolant as it expands in the engine cooling circuit and 2) the coolant pump inlet should be way cooler than you are measuring with the IR gun. This suggests 1) the connection to the expansion tank is blocked somewhere
As soon as I'm done posting I'll get to wrenching.. Remove tank, check hose routing and blow through it to be sure no internal blockage.
and 2) you are getting very little flow through the radiator.
Hmmmm. I just happen to have 2 or so Yamaha FJR1300 radiators with *minor* leaks. I just might plumb one of them up and test again. Just a bench test.
In my experience, the variations in temperature around the block are not significant.
I tend to agree. A 10 degree differential across banks as compared to 250F base temp is very small percentage.
Clearing the potential blockage to the expansion tank will be straightforward but finding a blockage in the radiator can be challenging as there is no easy access to all of the downtubes in the matrix.