Engine blown up
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There's a few possible causes:
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Your spark plug is too hot, but since you said it was too cold I don't think this is the case
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Your jetting is off and your bike runs way too lean.
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Your ignition timing is too advanced. This propably isn't the case if you haven't modified your ignition.
I'd say your bike was running way too lean.
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@Thomas_Chr said in Engine blown up:
@DTR-NSR Its a BR9ES plug i got on it now
What did you have in it before? There's no normal detonation marks round the edge of the head. Looks like the hot spot was concentrated at the plug tip and piston directly below. What grade of fuel are you running 95 ron?
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To me it looks like it could be down to running a plug with a too hot heat range. Causing pre ignition at the plug tip, melting it away and the spot on piston. Not sure what you mean by 100% fuel? Fuel with a lower ron rating will be more likely to pre ignite. You problems could be down to several contributing factors.
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Was it a 10 heat range plug then? 9 is stock. Seen 6's fitted before : 0 the fuel might not have any ethanol in but what octane rating is it? Lower octane fuel is more prone to detonation.
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On the older dt125r's BR9ES is the stock plug, often upgraded to a 10 range plug for tuned/continued high speed use. Over here have we have 95 ron unleaded and 97 ron super unleaded. Both with ethanol : (. Did you ever measure the compression of the athena kit? It may raise the compression ratio too high.
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@DTR-NSR On the workshop manual for my machine BR8ES is stock. I never measured the compression since i only got to drive with the kit for 1200km. From the graphs ive seen it does make more power than stock. So it might have a higher compression compared to stock. Will a diffrent plug make a big diffrence if the compression is higher?
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Ash deposits leading to misfire caused by excessive oil in combustion chamber or poor quality oil/fuel
Quote from Haynes manualI’ve never had that happen to me but my mate did. Ate a hole through a piston. He had put a ‘new’ plug in it and ridden a hundred miles to a rally. I’d look at air fuel mix as well. You got a standard filter setup? I’m guessing not...
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A colder plug will likely foul in a stock engine a hotter plug will probably cause pre ignition I doubt a plug would cause your piston to get so hot that it burns that just sounds lean to me as in an air leak
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It’s possible that a wrong octane fuel can cause detonation. It’s also possible that ash deposited on a plug That’s too cold or too much oil can cause hot spots, which can cause detonation...
I’d look into the octane rating of this 100% fuel...
The only other thing I could find was ignition timing. Which doesn’t come up with a standard dt stator...
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The hole isn’t caused by heat ‘as such’
, it’s caused by ‘knocking’ or pre-detonation. It can be caused by over advancing the ignition or having a hot spot that glows hot enough to pre ignite the fuel/air mix.
I’m your case (IMO) it was caused by a cold plug that carried too much heat away from the spark plug element, causing it to foul with ash. The ash led to a glowing hot spot which caused knocking, which caused pressure waves and ate a hole in your piston. I’d rebuild and fit a standard plug. Check it very often during running in and alter as needed.Do some googling on plug temps and ‘plug ate hole in piston’. There’s some really interesting stuff out there that I never knew about...
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The engine could well still be running lean aswell. But if lean was the only cause you'd normally get a 4 point heat seizure of the piston before it melted the piston in a 2 stroke atleast. Like what's been said
High compression
Lean mixture
Low ron fuel
Wrong heat rating plug
Carbon build up
Too advanced ignition timing
can all cause detonation.
Your engine failure could be down to any number of the above causes. -
Yeah, I did think it could be lean as well. One things usually exasperated by another. I just thought it best to start with a known ‘symptom’ and taking it from there. All you can really do is rebuild and keep a good eye on the plug for other symptoms. The only way I know to check for air leaks needs the engine to be running. Carefully spray suspect areas with carb cleaner and see if the revs settle down/alter...
