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**TheDukester** · 01-10-2023, 01:05 AM

Hi All,

I own a 2018 Duke 390 and I'm running into a problem. I've seen white smoke coming out of the exhaust for the past few days.

Took it to the service centre today and they mentioned that the bore is weak and the entire kit has to be changed along with valves, etc.

The bike has run for only 29K Kms and the service has been done fairly on time. The only two times where there was a delay was during Covid where it went upto 8 mths.

I did not notice this a few weeks back.

Either way I got it serviced and came back.

Is there any hope other than changing the entire Bore Kit? Would changing the piston rings work?

Thanks!

The DukeSter

**B7ACKTHORN** · 01-11-2023, 12:23 AM

Smoke can mean a variety of things, not isolated to bore alone. It can mean weak piston rings alone, or leaky valve stem oil seals alone or a combination of both, all these can and will cause white smoke when revved hard and sometimes during early morning starts depending on the severity. Usually, what SVC does is they replace the entire valve train and bore kit to eliminate the possibility of a recurrence, it's easier for them in that way. Another way is to do a through compression check which can perhaps yield an even better picture, if it's the rings or the valvetrain.

I would recommend you carry out a thorough compression check/test and then proceed with the rings replacement.

Good luck. Keep us updated.

Cheers!
VJ

**TheDukester** · 01-11-2023, 08:12 AM

Hey VJ,

Thanks!

This is what I was thinking as well. However there is one more problem that I forgot to mention. The engine had died during running (maybe three times in 1 month) and it took me a long time to get it running again.

Would this be due to the faulty ring or faulty valvetrain?

In the meantime I'm trying to find out places in Chennai that do a compression test for bikes.

Regards,
The Dukester

**ksuresh92** · 01-28-2023, 08:45 PM

Not a tech post - felt this today

Went for a 1000kms ride inclusive of ghats , highways and city.

such a powerfull machine it is. I was revving hard just to outgrow the 390 and make my mind to get a more powerfull one. But oh man ! Every time i push it harder there is so much adrenaline pump and i never feel i will out grow this machine ❤❤

i have tried twin cylinders in this price range 650's , ninja 300, R3 , benelli 300 .. all these machines felt like a gentleman and was easily outgrown with few 100 of kms.

But the 390 has such a character that it is brutal hooligan. Dropped the plan for upgrade

**Ajay Vishwanath** · 02-15-2023, 10:21 AM

Originally posted by ksuresh92 View Post

Not a tech post - felt this today

Went for a 1000kms ride inclusive of ghats , highways and city.

such a powerfull machine it is. I was revving hard just to outgrow the 390 and make my mind to get a more powerfull one. But oh man ! Every time i push it harder there is so much adrenaline pump and i never feel i will out grow this machine ❤❤

i have tried twin cylinders in this price range 650's , ninja 300, R3 , benelli 300 .. all these machines felt like a gentleman and was easily outgrown with few 100 of kms.

But the 390 has such a character that it is brutal hooligan. Dropped the plan for upgrade

Totally agree, even after using since 5 years, I feel there's no need for an upgrade no matter what. Probably is giving me ideas to pick up a xpulse or MT15 for kicks in the city and for fun and mainly mileage. Other than that, I see absolutely no reason to upgrade from the D390. Perfect in city and powerful enough in highways, It's got everything that latest and greatest bikes right now do!!

**ksuresh92** · 03-04-2023, 09:38 AM

Hi all,

What is the best engine oil that this bike can get?

I am using motul 7100 and planning to try castrol power1 ultimate superbike oil or amsoil . The bike is already smooth with 7100 10w50 with mos2 and xp95 fuel

Just planning to give a try of other oils to see if any other oil is better than motul. Please provide your suggestions.

and xp95 makes night and day difference in smoothness and power delivery

**abhishek7706** · 07-20-2023, 01:54 AM

Hi Friends,
On my DUKE 390, 2017 NEW model, 23k on the ODO,
I am getting "thak thak" sound from rear suspension while going over even small potholes or small undulations on the road
Authorized SVC suggesting complete replacement
Any suggestions ?

**B7ACKTHORN** · 07-25-2023, 06:09 PM

Start off by inspecting wheel bearings, first, usually a sharp tak followed by grinding noise usually indicates a bearing failure. If the sound comes on any undulations, check your rear swingarm bearings, a faulty or a worn out swing arm bearings would usually mean even a small bump or undulation would produce thud, tak and khatak sounds. Ask your SVC to check the swingarm bearings, wheel bearings followed by shocker.

Good luck.

Cheers!
VJ

**ksuresh92** · 09-16-2023, 03:24 PM

Ripped the threads for this bolt. Now it's is hanging in last few threads but not tightend fully.
what can be done and can i ride with this situation?

Screw is 1st from top on the inner sprocket cover.

**B7ACKTHORN** · 09-16-2023, 10:13 PM

Originally posted by ksuresh92 View Post

Ripped the threads for this bolt. Now it's is hanging in last few threads but not tightend fully.
what can be done and can i ride with this situation?
Screw is 1st from top on the inner sprocket cover.

You've ripped the threads of the wrong bolts at the wrong location. These bolts thread carcasses behind carry oil galleries. If this bolt is either loose or a thread is stripped, oil shall, can and will leak and that's a bad thing from the stripped thread location. Your only bet, either re-thread them using a tap, an oversize bolt which is cheaper. Or replace the left center casing, which in any case is what I'd suggest.

Good luck.

Cheers!
VJ

**ksuresh92** · 09-17-2023, 08:40 AM

Originally posted by B7ACKTHORN View Post

You've ripped the threads of the wrong bolts at the wrong location. These bolts thread carcasses behind carry oil galleries. If this bolt is either loose or a thread is stripped, oil shall, can and will leak and that's a bad thing from the stripped thread location. Your only bet, either re-thread them using a tap, an oversize bolt which is cheaper. Or replace the left center casing, which in any case is what I'd suggest.

Good luck.

Cheers!
VJ

Thanks VJ ,

I have upcomming ride to ooty and currently there are few threads which holds the bolt. But still can't tight it to full torque spec.

Will do a stress test run to see if there are any oil leaks. If it doesn't can I ride some 1000 kms ? Will engine vibrations loosen it ?

Thinking of using red loctite and a 6 mm stud with a bolt and fix it permanently. So that even in case of left engine case removal stud will help.

Any idea on the cost of the left center case ? I talked to asc and he is quoting atlesst 20k for this job.

Thanks for the response!

**ksuresh92** · 09-17-2023, 01:53 PM

Originally posted by ksuresh92 View Post

Ripped the threads for this bolt. Now it's is hanging in last few threads but not tightend fully.
what can be done and can i ride with this situation?

Screw is 1st from top on the inner sprocket cover.

Update :

Applied little anabond acrylic glue and tightened the bolt to until I cannot rotate by hands. It is holding onto few threads inside !

took the bike for a ride for 200kms non stop for stress test to see if there are leaks from this bolt. Did some extensive speeds and checked the bolt for leaks post that.

The insides and the bolt seems to be dry and very normal and there are no traces of oil at all in the edges , inside the inner sprocet and also the inner areas below it ! Seeems this tightness is holding 😊

Hopefully it stays as it is 😊 .

Changing the tyres to Apollo Tramplr 140/70 , will update post changing

Hapy motoring 😊

**B7ACKTHORN** · 09-17-2023, 09:33 PM

Originally posted by ksuresh92 View Post

Thanks VJ ,

I have upcomming ride to ooty and currently there are few threads which holds the bolt. But still can't tight it to full torque spec.

Will do a stress test run to see if there are any oil leaks. If it doesn't can I ride some 1000 kms ? Will engine vibrations loosen it ?

Thinking of using red loctite and a 6 mm stud with a bolt and fix it permanently. So that even in case of left engine case removal stud will help.

Any idea on the cost of the left center case ? I talked to asc and he is quoting atlesst 20k for this job.

Thanks for the response!

Vibrations can and will loosen a bolt overtime owning to the skimpy thread it's hanging onto. The glue might work as a temporary solution, but the temperature of the engine can eventually cake-off the glue and and the bolt can undo itself over time. Now, talking about price, the case perhaps can cost around 6k to 7k and the associated labor can turn out to 3k (ballpark). If you can get a used case, well and better. If it's holding up, let it hold, once it gives up, there's no looking back.

So, you have a Ooty ride. Let me know, I reside in Ooty, maybe we can catch up for a cuppa if time permits. Please DM so that we can be in loop.

Cheers!
VJ

**ksuresh92** · 09-18-2023, 07:56 PM

Originally posted by B7ACKTHORN View Post

Vibrations can and will loosen a bolt overtime owning to the skimpy thread it's hanging onto. The glue might work as a temporary solution, but the temperature of the engine can eventually cake-off the glue and and the bolt can undo itself over time. Now, talking about price, the case perhaps can cost around 6k to 7k and the associated labor can turn out to 3k (ballpark). If you can get a used case, well and better. If it's holding up, let it hold, once it gives up, there's no looking back.

So, you have a Ooty ride. Let me know, I reside in Ooty, maybe we can catch up for a cuppa if time permits. Please DM so that we can be in loop.

Cheers!
VJ

Thanks VJ

DM'd you about the ride. Also I have checked with the SVC , technician confirmed that only middle bolt will leak and first bolt is just to hold the sprocket cover.

He confirmed by opening all the bolts and starting the engine and oil came only in middle bolt , and said these changes are for 2nd generation 250 and 390 only. I think i have been just saved by an inch !!!

Just applied locktite and pushed the bolts to the threads present .

**B7ACKTHORN** · 09-18-2023, 11:33 PM

Originally posted by ksuresh92 View Post

Thanks VJ

DM'd you about the ride. Also I have checked with the SVC , technician confirmed that only middle bolt will leak and first bolt is just to hold the sprocket cover.

He confirmed by opening all the bolts and starting the engine and oil came only in middle bolt , and said these changes are for 2nd generation 250 and 390 only. I think i have been just saved by an inch !!!

Just applied locktite and pushed the bolts to the threads present .

It's not the middle bolt? Oh my! Maybe I couldn't infer clearly from your post which bolt, because of the oil stains. Yes, it's the center bolt that is crucial and if it's stripped, there's no looking back. The first and third bolts are comparatively smaller shanked bolts than the center one and that explains why it held in the first place, because no amount of Loctite or superglue would hold the hot oil bathing the bolt which would eventually give loosen up the agent. If it bothers you, you can take it to a local lathe shop or who does re-threading and they can tap a bigger thread and use a bigger bolt since this particular bolt is out of harm's way.

Cheers!
VJ

2007 - 2010	Kinetic Nova
2010 - 2015	Honda Unicorn
2014 - 2019	KTM RC 200
2017 - Today	KTM Duke 390

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