Often these engines were run on cheap regular fuel and, since there is no knock detector on the LT, they suffer damage to the piston ring lands from detonation. This leads to broken rings and scored cylinder walls. I have changed out three engines with damage like this (none were my bike) from other riders. Most were in the 40-80,000 mile range. Since on a used engine you have no way of knowing how it was run I would at least get one of the cheap bore scopes out there to look in each cylinder to look for scoring. Always run premium fuel in the LT.
Woe is me (twice)!
I retired last spring and spent the first months doing all sorts of catch up maintenance on the LT with plans to drive around the country for the coming years. I had hauled the bike to Florida in February and caught a snowstorm on the way back that had me have to clean up the bike and replace several corroded bolts along the way. The to doo list was 25 items long and I did most of it except replace the clutch and oxygen sensor which I postponed till the following season.
When I took the bike out for my first long ride in late May the bike was behaving like it wanted to ride and gobble up the miles. I had the sidecar rig attached and drove around 300 km when the bubble burst on the way back home: the motor started to lose power and the exhaust was making a distinct popping sound. No white or blue smoke, but definitely a motor problem at 235000 km (145 k miles). Fortunately, my problem occurred within a few kms of Sailor’s home so I went there, and he graciously agreed to plug his computer on it and we could not find any listed problems. I limped back home and tried to diagnose the problem (changed spark plugs, spark wires, switched injectors but cylinder #2 exhaust never heated up on short start). Finally bought a compression tester, mine was on the island with my older bikes, and found I had lost compression on cylinder #2! Woe is me!
I had planned a road trip on the north shore of the St-Lawrence for June and ended up doing it in the PHEV SUV which was a blessing in disguise as the windshield washers were running for most of the trip. When I got back home, I bought a used 1999 motor in NH with 60k miles and drove down to pick it up before I left to spend the summer in the Maritimes as I now do every year.
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When I came back in September, I took the damaged motor out and replaced it with the salvaged unit. I took the motor apart and found an exhaust valve on #2 cylinder had broken.
Every cylinder also had damaged sections on the inner linings, the largest being on cylinder #2. Broken valve and cylinder damage seem to point to detonation problems. The motor was burning a bit of oil (1 liter/qt per 4000 km/2500 miles) but I thought that was normal for the mileage.
![Automotive lighting Hood Automotive tire Vehicle Grille]()
When the motor failed it was relatively hot (30 deg C, 86 deg F) for our neck of the woods and the temperature gauge was sitting very high but no warning lights. I also had a booster module on the airbox temperature sensor that I removed after the failure thinking it might have had an impact. While changing the motor I replaced both radiators with refurbished units that Sailor had available to avoid any further overheating. While discussing potential detonation issues with Sailor he mentioned possible air intake from the lower seals on the throttle body that would create lean burn/detonation conditions. I did not change any as they looked good on inspection.
The new motor was installed and ran well when I rode it for over 2000 km before winter set in. It was quoted as having 60k miles and there was no sign of oil around the clutch so I left it there and it worked fine. No smoke except for the initial start-up and no oil consumption. Temperature was at the middle mark and gas consumption was good. Compression test showed all cylinders in the 210 psi range. I changed the oxygen sensor before the end of the season.
I hauled the bike down to Florida again this winter, this time timing my travel to avoid any snowstorm issues. Filled it up with high octane gas in Florida as I always do, took it out for a few short rides and all was fine. I then took it out for a longer ride around lake Okeechobee in 75 deg weather. Halfway around the lake I feel some hesitation on the motor and potential knocking symptoms. I limp back home having done 450 km (265 miles) on the gas tank which is right on average for me without the sidecar and check it the next day: good spark on all cylinders but cylinder #2 exhaust hardly heats up on short start. I bought another cheap compression tester and #2 has 2/3 the pressure of the others. Woe is me again!
The bike is on the trailer waiting for me to return up north at the end of the month as planned. I found a used motor with transmission, injectors and starter in Melbourne on sale and drove up to pick it up. It is also on the trailer, and I will make the switch when I get back.
What else should I be looking out for? Air leaks, plugged exhaust, bad injectors, other?
When I took the bike out for my first long ride in late May the bike was behaving like it wanted to ride and gobble up the miles. I had the sidecar rig attached and drove around 300 km when the bubble burst on the way back home: the motor started to lose power and the exhaust was making a distinct popping sound. No white or blue smoke, but definitely a motor problem at 235000 km (145 k miles). Fortunately, my problem occurred within a few kms of Sailor’s home so I went there, and he graciously agreed to plug his computer on it and we could not find any listed problems. I limped back home and tried to diagnose the problem (changed spark plugs, spark wires, switched injectors but cylinder #2 exhaust never heated up on short start). Finally bought a compression tester, mine was on the island with my older bikes, and found I had lost compression on cylinder #2! Woe is me!
I had planned a road trip on the north shore of the St-Lawrence for June and ended up doing it in the PHEV SUV which was a blessing in disguise as the windshield washers were running for most of the trip. When I got back home, I bought a used 1999 motor in NH with 60k miles and drove down to pick it up before I left to spend the summer in the Maritimes as I now do every year.
When I came back in September, I took the damaged motor out and replaced it with the salvaged unit. I took the motor apart and found an exhaust valve on #2 cylinder had broken.
Every cylinder also had damaged sections on the inner linings, the largest being on cylinder #2. Broken valve and cylinder damage seem to point to detonation problems. The motor was burning a bit of oil (1 liter/qt per 4000 km/2500 miles) but I thought that was normal for the mileage.
When the motor failed it was relatively hot (30 deg C, 86 deg F) for our neck of the woods and the temperature gauge was sitting very high but no warning lights. I also had a booster module on the airbox temperature sensor that I removed after the failure thinking it might have had an impact. While changing the motor I replaced both radiators with refurbished units that Sailor had available to avoid any further overheating. While discussing potential detonation issues with Sailor he mentioned possible air intake from the lower seals on the throttle body that would create lean burn/detonation conditions. I did not change any as they looked good on inspection.
The new motor was installed and ran well when I rode it for over 2000 km before winter set in. It was quoted as having 60k miles and there was no sign of oil around the clutch so I left it there and it worked fine. No smoke except for the initial start-up and no oil consumption. Temperature was at the middle mark and gas consumption was good. Compression test showed all cylinders in the 210 psi range. I changed the oxygen sensor before the end of the season.
I hauled the bike down to Florida again this winter, this time timing my travel to avoid any snowstorm issues. Filled it up with high octane gas in Florida as I always do, took it out for a few short rides and all was fine. I then took it out for a longer ride around lake Okeechobee in 75 deg weather. Halfway around the lake I feel some hesitation on the motor and potential knocking symptoms. I limp back home having done 450 km (265 miles) on the gas tank which is right on average for me without the sidecar and check it the next day: good spark on all cylinders but cylinder #2 exhaust hardly heats up on short start. I bought another cheap compression tester and #2 has 2/3 the pressure of the others. Woe is me again!
The bike is on the trailer waiting for me to return up north at the end of the month as planned. I found a used motor with transmission, injectors and starter in Melbourne on sale and drove up to pick it up. It is also on the trailer, and I will make the switch when I get back.
What else should I be looking out for? Air leaks, plugged exhaust, bad injectors, other?
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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.
I Always used premium gas.
I also always used Castrol Edge synthethic oil either 10W40 or 10W50. Pistons showed no damage of the rings but did have some scuff marks on the skirt below the rings..
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