[Ferax]

So I was out on a ride on one of my days off as per usual, nothing too crazy. I do ride fairly hard and wringing the bike out but That's generally how I ride anyways and haven't had an issue up until now. Usually my temp gauge stays around 4 bars at operation temps (I use water wetter being in southern california). Once I got onto one of the roads I usually ride which is about 20 miles in I noticed I was losing power.

Looked at my temp gauge and it was still at 4 bars. I rode until I could get to a safe spot (another couple hundred yards maybe) because I was losing power more and more fairly gradually. When I stopped and turned off the bike, I turned the key off and on and the temp gauge read that it was at the maximum. Threw me for a loop for sure. I waited for the engine to cool and tried to start the bike and no dice. Didn't want to turn on at all. I also heard gurgling right by the thermostat as the engine was cooling down.

What I'd like to know is why this issue was caused and what might be the solution to it. The cooling itself could be the thermostat but that wouldn't explain why the bike isn't starting. I also didn't notice my fan come on at all when I was riding and it was a fairly hot day but maybe that was me not paying attention. I also didn't look back so I have no idea whether I was getting smoke or not from a possible blown head gasket. Either way I'm going to be tearing the bike apart to see what I can do to get it back up and running.

Any and all advice would be greatly greatly appreciated!

 

[KTMasean]

Strange, Water Wetter is a non water based coolant and doesn't expand as water does is my understanding. I would first check if your fan runs on a direct 12V supply. No clue, really, why she won't start after cooling down. On my 390 first series, the fan only comes on when urban riding or stop @ a traffic light, never during outside rides moving >50 km/h

 

[fabbrisd]

Overheating can be a "biggie" - either from coolant loss, fan malfunction, engine malfunction etc - high internal engine temps can temps cause water coolant to "vapor lock" in the coolant passages.

When I read your comment "doesn't turn on" - if that means your instruments/indicators don't come on when you turn the key - then 1st things 1st - pull your battery and have it checked.

"Water Wetter since I am in Cali" sounds so '90's, really !

Bike Enthusiasts and Semi-Pro/Pro biker's use Evans Powersports "Waterless Coolant" for increased cooling efficiency - "waterless" won't vapor lock - and "waterless" won't cause internal filming/Slurpee-coolant-separation either - and can be "forever" coolant if you don't ever add water down the road. That said - "waterless" does run 3-5 degrees "hotter" but the advantages outweigh the minor temp change for a bike.

Evans Coolant Prep (1st) and Evans Powersports Coolant are both pricey - but enthusiasts/pro's - especially that own multiple bikes - find it a more-than-worthwhile to changeover for "waterless" advantages.

 

[KTMasean]

Reading your post again, and the follow ups, vapor lock might well be the answer.
A gurgling sound at the thermostat and the indicator still at 4 bars but when stopping jump to full bars surely does sound like vapor lock.
Did the bike turn over when trying to start after letting it cool, and didn't want to start or did it not turn at all?

 

[Ferax]

Reading your post again, and the follow ups, vapor lock might well be the answer.
A gurgling sound at the thermostat and the indicator still at 4 bars but when stopping jump to full bars surely does sound like vapor lock.
Did the bike turn over when trying to start after letting it cool, and didn't want to start or did it not turn at all?

Instrument cluster turns on, starter motor goes but the engine doesn't turn over.

What I'm mainly trying to find out is why the bike will not start back up. Before I have to tear it apart and check the head/ head gasket. There could be a number of possibilities when it comes to the overheating part, vapor lock could be the issue or a faulty thermostat perhaps but then again I went on numerous rides before hand after working with the coolant and absolutely no issues.

My current plan of action is to check compression, check the spark plug, potentially check the relays and see if those are faulty in any way? The battery was charged back up so it's a possibility that could've been the issue in regards to my fan but I never noticed it so I cannot confirm whether it actually turned on or not. But the battery was charged from around 10.4v the other day back up to normal but when the break down happened it was sitting at 12.2v.

 

[washoe4]

Is it posslble that the starter isn't engaging the "flywheel(?)" if the starter "goes" but "the engine doesn't turn over" ?

 

[Ede]

I suggest also check the battery. I had never problems with my battery until one day when I used the starter the engine turned over (a little) but didn't start. I was thinking about lots of possible problems. The KTM dealer told me likely the battery is the problem. They replaced it and all is fine now. Maybe just try with a good battery.

 

[Ferax]

So as an update I found a very large issue with the bike. The spark plug had the tip blown off/melted off, therefore not being able to make a spark. This would be a big answer as to why the bike wasn't starting. I checked inside the cylinder and there was no scoring on the cylinder so I think I got insanely lucky for the circumstances. As to why the tip was gone I think the bike is running hot and will get an opinion as to whether I need a new tune for the parts I have on it. I will keep this thread updated though for anyone potentially going through an issue as weird as mine.

 

[Syer Shulver]

So as an update I found a very large issue with the bike. The spark plug had the tip blown off/melted off, therefore not being able to make a spark. This would be a big answer as to why the bike wasn't starting. I checked inside the cylinder and there was no scoring on the cylinder so I think I got insanely lucky for the circumstances. As to why the tip was gone I think the bike is running hot and will get an opinion as to whether I need a new tune for the parts I have on it. I will keep this thread updated though for anyone potentially going through an issue as weird as mine.

Dodged a Bullet right there !

Glad you found the issue: and amazing you hopefully ‘got away with it’. Did you find / remove the end of the plug ?

With a bit of luck a simple ‘tune’ and new plug sorts you out….

 

[KTMasean]

Indeed very lucky as the plug's tip must have exited through the ex-valves directly BUT, it doesn't make sense to me why the bike would 'lose' power, then upon stopping go from normal temp reading (on the dash) to over temp and after this not being able to start? Have you drained the coolant? If so how much came out? If the tip fell off at the moment you pulled over, the engine would have shut off by itself, if it came off after turning off the engine, the combustion chaimber temp was WAY too high and most likely the piston is now stuck inside the bore.

 

[fabbrisd]

Spark plug electrode can appear "melted" from Cylinder Detonation... too-rich/ignition timing off... with a missing spark plug tip.. need to check with lighted borescope.. and then decide if head needs to come off or not..

 

[Mirius]

Spark plug electrode can appear "melted" from Cylinder Detonation... too-rich/ignition timing off... with a missing spark plug tip.. need to check with lighted borescope.. and then decide if head needs to come off or not..

Too lean not too rich.

 

[390 Pain]

I am going through something very similar to OP with my 2020 duke 390 less than 1700 miles, Coober ECU, high flow air filter, and full moshitmoto exhaust w/ cat delete. Was riding down the highway then noticed I was losing power, I looked down at the instrument cluster and saw my temp gauge was flashing at me full bars, 30 seconds - 1 minute prior to losing power it was normal. I immediately shut the bike off and coasted to the shoulder. Waited 20-30 minutes checking the instrument cluster by just turning on the ignition every 10 minutes or so for the bike to cool down. Tried to restart and cranked but didn’t start. Tried popstarting by coasting down an exit twice and still nothing. Had the bike towed home and there she has sat since this happened in Nov 2022. I had a melted spark plug tip/end as well. Replaced spark plug with dialectric grease on boot and top of plug, got no spark. Tested wiring harness connector for coil and had power but no power out of the coil. Replaced coil and now had spark confirmed visually and through the left side of my body as I wasn’t careful. Bike still wouldn’t start. Checked all fuses and relays, bike still wouldn’t start. Took injector apart and cleaned by connecting a 9v battery to a series of rubber hoses gradually going up in size from straw that comes out of Carb Clean to a hose that fit over the end of the injector. Sprayed for about 10 seconds with it squirting and cleaned out. Reinstalled with dialectric grease on connectors and still won’t start. Had the battery load tested it works just fine and the bike is connected to a 12V Trickle charger continuously but bike still just cranks and won’t start. I’ve tried disconnecting the battery and unplugging the ECU as well and still does the same thing just crank and won’t start. I’ve tried spraying brake clean in the intake to help ignition and still does the same with a occasional pop. The intake is sucking the spark plug is sparking and the exhaust is pushing exhaust gas/light smoke upon the bike cranking. What am I missing? Please help!