Slippage/jumping in 4th gear?

[StevoKenevo]

Hi,

I did a track day yesterday on my stock rc 390 2015 and during the third session I started having an issue only in 4th gear accelerating hard above 6.5k rpm, where it feels like the gears are jumping or slipping or something. If I accelerate gently I can go right to the limiter in 4th no problem. The gear light constantly says 4th when it's jumping i,e doesn't seem to be selecting a false neutral.

Has anyone had a similar problem? Or have any ideas to a solution?

Any help much appreciated,

Steve

 

[Drstimpy]

No quickshifter or pc installed?
Make sure your foot isn’t accidentally riding the shifter as it may need adjustment. Especially if you have new boots amhik


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[StevoKenevo]

Stock rc no quickshifter or pc.

Foot isn't riding the shifter, only happens in 4th hard acceleration, never in any other gear.

Something I didn't mention is that it doesn't jump for the first 5 minutes of riding, I suppose until the bike is at max running temp.

 

[Andy]

Looks like you might be in the same place as me. I'm currently fitting a Factory shift detent arm but failing that looking at having to check the shift forks!

 

[Formula390]

Sounds like a typical case of the detent arm and shift drum/forks not getting positively engaged enough. As the bike heats up, parts "grow", and tolerances get smaller... making engagement potentially harder to get fully seated. As Any also stated, I would say start with getting the updated shift detent arm and see if that resolves your issue.

 

[StevoKenevo]

Yea I was looking at that, but not cheap for something that may not fix the problem. If it was jumping out of gear completely then I definately go for the Factory detent arm. Is yours jumping out of gear completely or stuttering/slipping?

 

[StevoKenevo]

Factory Pro detent arm installed (195€ with shipping and import taxes, from Rottweiler Performance) nice crisp gear changes, but 4th is still slipping exactly as before, looks like I have a big job ahead of me.Guess I'll need to take the gearbox apart and check shifting forks and gears?

 

[StevoKenevo]

SOLVED

So I split the case and had a look at the gearbox, the dog teeth on 4th looked a bit rounded, also the shift fork for 4th had been hit but wasn't visably bent. I've changed 4th gear and the shift fork and no more slippage!
I also did the overdue valve check that the dealer said wasnt necessary and 3 out of 4 valves were out of spec.

I think the damage to 4th was caused by me often miss shifting and crunching when changing from 3rd to 4th, since installing the Factory Pro Detent Arm I haven't crunched any gears.

 

[John390]

how hard is it to change that Factory Pro detent arm?

its bloody expensive for what it is, but maybe it would be worth it if it saved a headache down the road. as long as its not a big ordeal to change out.

I am an auto tech and have my own tools.

 

[StevoKenevo]

how hard is it to change that Factory Pro detent arm?

its bloody expensive for what it is, but maybe it would be worth it if it saved a headache down the road. as long as its not a big ordeal to change out.

I am an auto tech and have my own tools.

Fairly easy;

Front spoiler off
Right wing off
I then lay the bike on it's left side, so I didn't have to change the oil.
Disconnect clutch cable from engine
Take off engine clutch cover
You can then access the detent arm and unscrew it with an allen key, remove and replace (loctite 243).

 

[Andy]

Did you not take the clutch basket off?

Sent from my HUAWEI M2-801W using Tapatalk

 

[John390]

Fairly easy;

Front spoiler off
Right wing off
I then lay the bike on it's left side, so I didn't have to change the oil.
Disconnect clutch cable from engine
Take off engine clutch cover
You can then access the detent arm and unscrew it with an allen key, remove and replace (loctite 243).

View attachment 5132

thanks, that's not too bad

 

[StevoKenevo]

Did you not take the clutch basket off?

Sent from my HUAWEI M2-801W using Tapatalk

No, you don't need to, but it does make installing the detent arm a bit fiddly if you don't.

 

[MotorcycleReclamation]

Greetings all, I have just got a 21 reg KTM 390 Duke, it's doing the same in 4th gear, not going out of gear but split second loss of drive (not clutch, feels more like injection) on firm accelleration, otherwise great bike. I called Gear4 to see if they have come across it and they have never had it. It does not feel like the arm will do anything more than make the selection feel more positive. The bike has done 5000miles so it could be the gear selectors but surely if it's going to flick out of gear it would not be for a tiny fraction of a second? I don't mind paying out money as I got the bike at a good price but I want to do the job once not change arm and forks then find out it's injection mapping. What's the latest please