Engine blew up during race

matheusoleiro

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Hello everyone,

Something unacceptable happened to me last weekend. I was racing with my 2017 KTM RC390 and my engine just blew up during the last lap of a 12 lap race. It happened in Homestead, FL, during the FMRRA 3rd round.
My bike is almost stock. I just did minor mods like exhaust, clip-ons, rear set and bodywork. My engine is stock, the bike has 1500 miles. No flash tune, fuel commander or anything like that.
For whom knows Homestead, it happened between turn 1 and 2. Turn 1 is a full gas turn and turn 2 it's a slow corner. So, I was in 6th gear and downshifted to 3rd. When I got the 3rd the engine just blew up and spill oil in the hot line. Someone behind me slipped in the oil and crashed so hard. In other words, she crashed after braking in the oil that my bike spilled. She went to the hospital and I got some updates that she is fine. I felt bad once it was my bike that spilled the oil. Everyone that race knows that shit can happen anytime for any reason. However, it's totally unacceptable a bike that says "ready to race" make almost a disaster.

I am so upset with this situation and I am considering to go to Kawi 400 to keep playing on the same bike class.

KTM-engine.jpeg
 

ReidMcT

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Wow, the balancer flew out along with the front of both crankcase halves! I'd guess the root cause was a casting flaw in the crankcase. It looks repairable if you find a crankcase and do your own work. Paying someone to do it would cost more than just buying a used engine. And, as you probably know, there is probably no warranty coverage since it was racing.

Sorry for your loss. That's racing. Good luck.
 

Formula390

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My guess is your downshift didn't go as you planned. You may have gotten down into 1st or 2nd, dropped the clutch, the motor spun to 50,00,000 RPM, and kableewie! Paxton has some experience with this... where he dropped too many gears and motor tried to put him into low earth orbit.

"That's racing." is how it goes. If you aren't prepared to set your racebike on fire just to watch the pretty colors, then well, you might need to consider another sport. It sucks, and I'm sorry, but well, sometimes racebikes, regardless of manufacturer, well... explode. :(
 

Frisco Fred

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Could the balancer gears failed and allowed the balancer to hit the crank?

FWIW; Engines in GP Bikes during the 1970's were only good for one race.
 

Bikingbagga

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Well what's clear 6th to 3rd the weak link is the cases just cannot handle that kind of sudden loading. Don't give up I think its lesson learned. I did the same type of thing on my RGV250 one miss shift ceased the engine cases survived.
 

kostean

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My guess is your downshift didn't go as you planned. You may have gotten down into 1st or 2nd, dropped the clutch, the motor spun to 50,00,000 RPM, and kableewie! Paxton has some experience with this... where he dropped too many gears and motor tried to put him into low earth orbit.

"That's racing." is how it goes. If you aren't prepared to set your racebike on fire just to watch the pretty colors, then well, you might need to consider another sport. It sucks, and I'm sorry, but well, sometimes racebikes, regardless of manufacturer, well... explode. :(

For avoiding overrevving the engine on downshift at the race track, an aftermarket slipper clutch is really reccommended.. Experience with KTM slipper were that it did improve the situation with wheel hop but still caused the engine to rev pretty high at engine braking. Now later with TSS slipper, the engine pretty much runs idle at the engine brake so aside on improving the lap times, the aftermarket slipper certainly has a positive effect from the engine reliability side as well.
 

Formula390

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For avoiding overrevving the engine on downshift at the race track, an aftermarket slipper clutch is really reccommended.. Experience with KTM slipper were that it did improve the situation with wheel hop but still caused the engine to rev pretty high at engine braking. Now later with TSS slipper, the engine pretty much runs idle at the engine brake so aside on improving the lap times, the aftermarket slipper certainly has a positive effect from the engine reliability side as well.
A slipper clutch can only do so much. Drop from 6th to 1st, and drop the clutch at speed, and I bet the TSS would also still spin the motor to the moon and over rev... But yeah, the stock KTM slipper is nothing more than a marketing bullet point and it's garbage.
 

Frisco Fred

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50 or 50,000 RPM still doesn't answer the question, what was the weak link / what part failed first? That's the main question and it remains unanswered.

Without ever seeing the inside of one of these engines, I'll guess that the balancer drive broke, allowing the balancer to hit the crank. Outside of running 90% nitro methane, I can't imagine any other circumstance that could break and totally separate top from the bottom end.
 
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Formula390

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50 or 50,000 RPM still doesn't answer the question, what was the weak link / what part failed first? That's the main question and it remains unanswered.

Without ever seeing the inside of one of these engines, I'll guess that the balancer drive broke, allowing the balancer to hit the crank. Outside of running 90% nitro methane, I can't imagine any other circumstance that could break and totally separate top from the bottom end.
Usually the piston snaps in half or the valve retainer breaks and sends the valve into the piston. Once either happens, if you are lucky, you just end up with shrapnel that stays in the case. If the piston wedges and the rod comes down too far, then it will thrust fore or aft and push/smack the front or rear of the case. If it goes forward I can see it blowing out the front of the case and ejecting the balancer with it.

The phrase "that's racing" exists for a REASON. Racing motors rarely self destruct nicely. Blown head gaskets, while annoying, aren't THAT bad. I've had motors come COMPLETELY apart. I had a Hawk GT650 eject a piston straight up THROUGH the tank when the conrod upper cap let go. Big singles spinning fast have unbelievable g-forces at the piston edges when it snaps down from TDC.
 

Frisco Fred

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Usually the piston snaps in half or the valve retainer breaks and sends the valve into the piston. Once either happens, if you are lucky, you just end up with shrapnel that stays in the case. If the piston wedges and the rod comes down too far, then it will thrust fore or aft and push/smack the front or rear of the case. If it goes forward I can see it blowing out the front of the case and ejecting the balancer with it.

The phrase "that's racing" exists for a REASON. Racing motors rarely self destruct nicely. Blown head gaskets, while annoying, aren't THAT bad. I've had motors come COMPLETELY apart. I had a Hawk GT650 eject a piston straight up THROUGH the tank when the conrod upper cap let go. Big singles spinning fast have unbelievable g-forces at the piston edges when it snaps down from TDC.
Those are very plausible sets of circumstances. Particularly the one about a dropped valve getting trapped between the piston and head. I guess that there's no possible way the balancer could hit or interfere with the crank. My condolences to matheusoleiro.

Thanks for the follow up.
 

Topaz

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I'm in South Florida and I ride Homestead too. Everybody goes down from 6th to 3rd in turns 1-2 and nobody blows the engine. I really doubt he went into 2nd or 1st gear. It should have been something else.
 

1JZSupra

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I'm in South Florida and I ride Homestead too. Everybody goes down from 6th to 3rd in turns 1-2 and nobody blows the engine. I really doubt he went into 2nd or 1st gear. It should have been something else.
based on experience the rear tire would have been skating around a lot dropping down that many gears.
 

Topaz

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"That's racing." is how it goes. If you aren't prepared to set your racebike on fire just to watch the pretty colors, then well, you might need to consider another sport. It sucks, and I'm sorry, but well, sometimes racebikes, regardless of manufacturer, well... explode. :(

Well, it depends... FMRRA is club racing. Many of us are in tight budgets and have to go to work next Monday. We don't go 'kill or die'. We just try to have fun.
 

Formula390

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Club racing is where I always raced. I was never fast enough to get to the national level much less more than that. Too big. Too heavy. Too slow. WMRRA, OMRRA, AFM, Willow Springs. You don't have to race "kill or die" to blow up motors. At the end of the day, a DNF is still a DNF. You drop one too many gears, hit a false neutral, bounce of the limiter (on purpose or otherwise) with the throttle pinned to the stop... well, something dramatic can happen. "That's Racing" is how it goes. I stand by my statement that if you aren't prepared to just watch the pretty colors when your racebike explodes into flames, well, maybe consider doing trackdays instead. I'm all for just trying to have fun, I am, but, well, racebikes live to tear themselves to bits. Especially "cheap Indian made ones with a KTM badge on it instead of Bajaj." At the end of the day, it may have a KTM logo, but it's a Bajaj bike. I say this as a guy who puts groceries on the table because of this outrageously fun bike! The bike can't be beat, when it's working right.
 
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