[sailor]

On the first failure the temperature was high for two reasons: the original radiators were opaque to light when compared to the ones I replaced them with and I had left the left hand radiator fan unplugged on my spring maintenance routine. I did not realize that until I dismantled it later, and decided to replace them with some clean ones. When I replaced the motor, I ran it until both fans kicked in and the temperature never went above middle until it conked again 2500km later.
Bad cooling was certainly a contributor on the first failure but not so much on the second. I too wonder if there is something in the #2 cricuit that might be another source of the problem, hence my question to the group above: air leaks, partially plugged exhaust, bad injectors, blocked catalitic converter, other?

Since you gave me more info during your visits here (and a few emails exchange) , I taught I would post this addition... please comment if my understanding is incorrect.

Besides the radiators, I think you need to specify a few other jobs / repair that have been done just before (or at same time) as you installed this new engine.
By a process of elimination, I believe these items are important to help pinpoint WHY this 2nd engine would fail again:
1) Your 4 injectors have been checked and cleaned by a reputable local injector shop a bit before this used engine was installed
2) I think you had replaced the Oxygen sensor - but I cannot recall when this was done timewise


IMPORTANT QUESTIONS... some I may have asked in our previous exchange, but I cannot recall all the details:
A) Do you have the Motronic version of your ECU ? This can be read using a GS911 -or- by removing the ECU to read the label on opposite face.

B Do you have a GS911 to check if the air-box temp sensor is working properly ? This is is important as you said you have removed the "cheater" device that was connected to it. You can make a rough check using a Multimeter OHMS function on the 2 male pins with connector removed:
- at 8 celcius (46 F): should read 3800 Ohms
- at 20 celcius (68 F): should read 2500 Ohms
- at 40 celcius (104 F): should read 1000 Ohms (you may use a hair dryer at "low heat" to warm up the tip)

C) have you ever tested the fuel-pump running pressure ? I have the needed gauge and adapters here but you need to have the right side fairing removed to connect "inline" between fuel tank quick connectors. On the K1200RS forum (and probably here too) we had at least 1 case where a pin hole / crack on the short hose connected to fuel-filter (inside tank) would cause a lean mixture. Total running pressure was not proper as per specs at 51 PSI.

 

[sailor]

1) Yes the four injectors were refurbished before the first failure.
2) Oxygen sensor was replaced in december, after fall rides and before Florida trip.
A) No Gs911 and don't have info on chip but believe it is original 1999 fabrication date.
B) Will try to check temp sensor but it may be when I get back in two weeks
C) never tested pressure but I do hear the pump start/stop when turning the key. Changed gas filter and hoses last April in the catch up maintenance before first failure

Thank you for added info / confirmation.

About the Motronic ECU , I think I have mentioned this in our private emails (just after you bought this replacement engine):

• UNLESS you bought the bike new , I would suggest to open the ECU to check for presence of a so-called performance chip. In particular the older "Rhinewest" chip have caused similar issues (damaged cylinder / piston caused by detonation)
• John Zeigler has reported here two separate K1200LT similar engine failure - both had a Rhinewest performance chip addition,

You will need a set of tamperproof TORX bits to remove the 4 screws holding the ECU unit cover.

 

[sailor]

Are you lugging the engine with the side car ?. The more weight you have the more you would like to keep the engine rpm's higher. Your final drive gear ratio in the 1999 K1200LT is 2.75. I just sold a 2.91 gear ratio final drive to a member hear in Florida with a K1200LT side car and he likes it much better. If I had a side car I would use a 3.09 ratio.

Dave , thank you for bringing this up. It may not be a factor in this specific case, but it worth repeating as we have seen many members here saying that they change gear below 4000 RPM all the time (even when accelerating hard). Some think they will damage this engine by revving it - when in fact the opposite is true - this is NOT a large twin cylinders engine with a low Tach red line.

When he showed me the compression result and the engine internal damage (for the 1st original engine) I didn't dare insist too much about lugging the engine and the RPM he uses for various gear / conditions. It certainly crossed my mind, but I have found that some riders will take this as questioning the quality of their motorcycling knowledge.