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Discussion Starter #1 (Edited)
Hi guys,

Just bought a used 2018 Duke 390. Got a pretty good deal for a 5000KM unit.

Previous owner installed the crash bars and radiator covers.

Looking forward to learn more from here!

Some quick questions first.

Sprocket sizing - Is it ok to upsize the rear sprocket by 1-3 teeth for more top speed?

tire sizing - read a few articles here about downsizing from stock 150 width tyres to 140 width, also any issues with those?




53008
 

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Welcome,

If looking for more top speed you will need to down-size the rear or up-size the front sprocket.
In theory 1 tooth in the front equals 3 teeth on the rear.
So either try to go to 15T in the front or to 42T on the rear.

On the tyres, the optimal size for the rear rim is 140.
Factory comes with 150 but as you may find in various articles, in order to fully use your tyre profile (which only a hand full of people will be able to do) 140 is the best.

Good luck and many kilometres on your Duke.




Hi guys,

Just bought a used 2018 Duke 390. Got a pretty good deal for a 5000KM unit.

Previous owner installed the crash bars and radiator covers.

Looking forward to learn more from here!

Some quick questions first.

Sprocket sizing - Is it ok to upsize the rear sprocket by 1-3 teeth for more top speed?

tire sizing - read a few articles here about downsizing from stock 150 width tyres to 140 width, also any issues with those?




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Discussion Starter #3
Just collected the bike.

First thing I noticed was... My god, the fan sounds as loud as my mother in law when I piss her off. Unbelievable. Those Spal fans are much needed.

Second thing was... How light the bike was. Nimble, agile.

Third thing was the hot air on the left side of the engine. Cons of a single cylinder.
 

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First thing I noticed was... My god, the fan sounds as loud as my mother in law when I piss her off. Unbelievable. Those Spal fans are much needed.
I don't think SPAL fans are much quieter. They're just more robust.

Third thing was the hot air on the left side of the engine. Cons of a single cylinder.
How is it a single cylinder thing? Any motorcycle larger than like 200cc will be hot, it's a lot of energy in a super small package. Duke 390 is also high compression, so that drives up the heat, as well.
 

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Discussion Starter #5
I don't think SPAL fans are much quieter. They're just more robust.


How is it a single cylinder thing? Any motorcycle larger than like 200cc will be hot, it's a lot of energy in a super small package. Duke 390 is also high compression, so that drives up the heat, as well.
Sorry, I've must have left out the lumpy engine on low rev which I meant as a con of the thumper. not the heat but i think the heat i felt was from the lack of the heat cover seen on 18 and older dukes, mine doesn't have it. I'll probably fabricate one from some old heatshield i have lying somewhere.

The SPAL fans are not quieter are they? hmm....

Don't be mistaken though, I love the bike for what it is, especially the acceleration. Letting it rip from stop is an absolute adrenaline rush. The bike really wants you to be a hooligan on it and the super light and agile chassis is just beautiful.
 

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You can add a booster plug to mitigate the low speed choppiness. Real easy install, takes less than 10 mins. Mine is noticeably smoother since installing. Which part of MY are you? I visit Penang quite often (or used to before covid!!)
 

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Discussion Starter #7
Took the bike in for servicing since ownership 2 weeks ago.

The fluids were not changed for the past 2 years so everything was kinda shite.

New Engine Oil - 10w60 Elf.
New Filters
New Coolant
New Brake fluids

Forks were leaking so serviced those and added new seals in. There was also very mild rusting and pitting on one of the forks which the mechanic told me to monitor.

Tyres were from 2015 and hard as rocks so I swapped them out for Pirelli Diablo Rossos Sport in the CORRECT width of 140 rear and 110 front.

Have to say the bikes ran much better with everything replaced, especially the brakes. As suspected there was air and water in the brake fluid which led to spongy brakes with no feedback. Still running stock pads though so might consider upgrading those if I still feel unsatisfied with them.

The tyres was the best part. 140 INDEED is the right size for the bike. Much thanks to the folks here who contributed to the tyre size thread. Bike is more nimble and turns well. Had to ride through a heavy rainstorm on the way home and the tyres performed exemplary.

Last work was drilling out the stock end can baffle to deepen the exhaust.

Total cost? Ringgit Malaysia 983 for the service work. RM 460 for the tyres.
 

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Great,

Swap your old brake pads for EBC HH Sintered ones.
Did you change the fork oil as well? Hope so!

Took the bike in for servicing since ownership 2 weeks ago.

The fluids were not changed for the past 2 years so everything was kinda shite.

New Engine Oil - 10w60 Elf.
New Filters
New Coolant
New Brake fluids

Forks were leaking so serviced those and added new seals in. There was also very mild rusting and pitting on one of the forks which the mechanic told me to monitor.

Tyres were from 2015 and hard as rocks so I swapped them out for Pirelli Diablo Rossos Sport in the CORRECT width of 140 rear and 110 front.

Have to say the bikes ran much better with everything replaced, especially the brakes. As suspected there was air and water in the brake fluid which led to spongy brakes with no feedback. Still running stock pads though so might consider upgrading those if I still feel unsatisfied with them.

The tyres was the best part. 140 INDEED is the right size for the bike. Much thanks to the folks here who contributed to the tyre size thread. Bike is more nimble and turns well. Had to ride through a heavy rainstorm on the way home and the tyres performed exemplary.

Last work was drilling out the stock end can baffle to deepen the exhaust.

Total cost? Ringgit Malaysia 983 for the service work. RM 460 for the tyres.
 
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