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Discussion Starter #1
Hi I'm from India. I have rc390. Recently I checked and found airfilter box has crack and my bike is giving smoke. Can anybody help me what the problem is this? And how to resolve?
 

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So if you have a gen 1 duke, I believe this is a manufactures defect. This is one of the main reasons I feel that the intake box was completely changed with the gen 2 setup. I am on my second airbox and I have seen a bunch of people that have experienced this issue as well. There is something about the design of the airbox that is causing pressure and flex to have happened enough to crack it over time. After my second airbox cracking, I applied a shitload of JB weld to the airbox, which seems to have fixed my issue. As for the smoke, you could be sucking up oil into the engine. Normally, crankcase ventilation happens via the airbox, and oil is then redirected back into the engine.
 

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Didn’t he mention that he rides an rc390?
 

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So if you have a gen 1 duke, I believe this is a manufactures defect. This is one of the main reasons I feel that the intake box was completely changed with the gen 2 setup. I am on my second airbox and I have seen a bunch of people that have experienced this issue as well. There is something about the design of the airbox that is causing pressure and flex to have happened enough to crack it over time. After my second airbox cracking, I applied a shitload of JB weld to the airbox, which seems to have fixed my issue. As for the smoke, you could be sucking up oil into the engine. Normally, crankcase ventilation happens via the airbox, and oil is then redirected back into the engine.
Thank you for your reply. I have 2016 model. You said somehow oil is going through airfilter box then what should I do now? And are my rings and pistons okay?
 

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Didn’t he mention that he rides an rc390?
Yes I ride rc. But I needed help so I thought you guys can help me because I asked to service center guys, they said It's happening because cylinder kit is gone and have to replace complete kit. They didn't check engine, they are just assuming.
 

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You could conduct a leak down test or compression test. How many miles are on it? The 2016 Duke and RC390 have the exact same air boxes,
 

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ravidagar,
After just over 15,000 km, if the engine has been treaded as should (oil/filter changes in time, valve checks/adjustments etc), there would be no problem with it.
Air boxes crack mainly at the top where the air filter cover screws on (first Gen)
Smoke can be caused by many things and will be very, very difficult to determine over the forum.
Does it smoke all the time, only when starting, or only when hot etc?
Best is to take your RC to a good KTM dealer to figure out what is the reason for the smoke.
You can search for compression tests and or leak tests on the Internet.
If your airbox is cracked along its body you may try to close this again with liquid plastic or the likes.
Good luck with fixing your problem with this RC.
 

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Both of my airboxes have both cracked at the exact same areas, along the bottom where the PCV hoses attach to the airbox. To date that is the only location, I have seen them on other first-gen dukes / RC390s. An engine can smoke for a number of reasons, even at 15,000 km. It really just depends on how it was treated and if something has happened to force it to smoke. I've seen cars and motorcycles alike blow engines with less than 1,000 miles on them... some times **** happens.
 

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Discussion Starter #10
ravidagar,
After just over 15,000 km, if the engine has been treaded as should (oil/filter changes in time, valve checks/adjustments etc), there would be no problem with it.
Air boxes crack mainly at the top where the air filter cover screws on (first Gen)
Smoke can be caused by many things and will be very, very difficult to determine over the forum.
Does it smoke all the time, only when starting, or only when hot etc?
Best is to take your RC to a good KTM dealer to figure out what is the reason for the smoke.
You can search for compression tests and or leak tests on the Internet.
If your airbox is cracked along its body you may try to close this again with liquid plastic or the likes.
Good luck with fixing your problem with this RC.
Ok thanks I'll search for good ktm service guy.
 

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Discussion Starter #11
Both of my airboxes have both cracked at the exact same areas, along the bottom where the PCV hoses attach to the airbox. To date that is the only location, I have seen them on other first-gen dukes / RC390s. An engine can smoke for a number of reasons, even at 15,000 km. It really just depends on how it was treated and if something has happened to force it to smoke. I've seen cars and motorcycles alike blow engines with less than 1,000 miles on them... some times **** happens.
I never treated my bike badly. The service guy at ktm center told me that my bike is giving smoke because of airfilter box crack. My cylinder kit has gone and need to be replaced completely.
 
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