RC 390..top end power loss,overheating,running lean? ,low oil pressure.

[shreeshar7]

hello everyone,
this issue has been bugging me since a month.

okey,so my rc390(2015) engine was rebuilt last month since it broke open due to conterbalancer shaft key shearing.(complete engine newly built including case to head)
after the rebuild i rode it easy for 1000 kms run in and then oil change and first service .
when i took it for a spin last week and yesterday,i noticed that the bike was taking longer than usual to hit the rev limiter and isnt pulling as hard as it used to at higher rpm.

i got a straight stretch and with wide open throttle ,the bike started to feel like it didnt have enough juice,its not even able to hit rev limiter in 5th gear,if i shift it to 6th gear,i hardly goes 155-157 and then just hovers there without further acceleration.
the bike feels like it has totally lost top end torque.

after into around 30 kms of riding,low oil pressure light came on and i stopped the bike, once i restart the ignition ,the warning goes away and dosent come for another 10 kms,
->checked all fluid levels and they are normal.

whenever i stop the bike after a spin and then restart the temp usually climbs a bar or two,but now its going to the extent of "high coolant temp" .

bike is performing only 70%
running hotter than usual.

AT COLD: starts up fine and idles,sometimes stalls and if i try to slowly let off the clutch in first gear ,it stalls.
runs fine once its warm,until then..jerky on off throttle transitions and stalling.

WHAT have i tried?

• replaced air filter.
• replaced fuel filter.
• checked spark plug wires and reinstalled spk plug.
• run a tank full of fuel with injector cleaner.
• cleaned throttle body.
• cleaned and reinstalled injector, tmap,tps and IcV sensors.
• refitted intake system.
• no fault codes (mil) in ecu.

still the issue persists

oil: motul 7100t 10w50
coolant: engine ice
fuel:shell vpower petrol

the bike runs fine during short city and highway commutes(<7000rpm)(10-15kms)
although the fan tuns on more often

help me get this sorted,service guys here have no idea what to do.

 

[chevaliernoir]

I would check the camshaft phasing

 

[chevaliernoir]

What do you mean by "IcV sensor"

 

[shreeshar7]

I meant idle control valve icv or idle actuation valve..or whatever they call it.

 

[shreeshar7]

I meant idle control valve icv or idle actuation valve..or whatever they call it.

 

[shreeshar7]

I would check the camshaft phasing

Could you please elaborate?
what is camshaft phasing? how could it cause something like this? im not able find wha is camshaft phasing in context to this.

all i know is the camshaft is retained from the previous engine since they say,it had not suffered any damage.

things changed are:
bore kit.
engine complete casing
valves
head assembly.
counter balance shaft
clutch
crankshaft
gear assembly
magnet

things retained :
cam shafts
cam chain

(the bike was kept at the service place for 2 months without engine in it.)

 

[chevaliernoir]

Thank you for the ICV explanation.

About camshaft timing, this would fit with the description, and the history of your bike.
We have 2 camshafts on the bike : one for the 2 inlet valves and 1 for the 2 exhaust valves.
Here are pictures from Chad about them
View attachment 376View attachment 377View attachment 378
As you can imagine, they are driven by a timing gear connected to the timing chain.
It is very important that the position (angle) of the cams is exactly the good one when the piston is at the upper dead center.
In order to reach this, there are some marks in the camshaft that have to be aligned

If this is not done in the propre way, the intake valves (or the exhaust valves, or both) will open and close too early, or too late.
So the quantity of air that will enter/exit the engine will not be the good one, then the EFI cannot compensate as the difference is too big.

So maybe, if this is your issue, all parts are in good condition, but the camshaft angles should be checked in respect to TDC.

 

[shreeshar7]

I would suspect cams but then engine starts with a single crank and runs butter smooth.. No idle fluctuations.
It heats and flats off after 7000+ rpms.

 

[chevaliernoir]

this behavior could come with intake camshaft too early, or exhaust cams too late.

 

[shreeshar7]

this behavior could come with intake camshaft too early, or exhaust cams too late.

Just got it checked... They say the cams are put in correctly, they're also saying that fuel pressure and compression is all under spec.

 

[shreeshar7]

Ktm service guys are inspecting and changing suspected electronic parts one by one, we noticed that the battery was almost dead,voltage drops under load and not enough amps. Could a bad battery cause something like this?

 

[Diploman]

The service shop should test to ensure that the battery is charging correctly. You could have either a bad battery or a fault in the charging system that will not keep the battery up to proper charge while running. Low voltage from the battery could affect the ignition system and coils or even the ECU. There have been a few known cases of North American 390 which experienced charging problems because of faulty alternator stators.

 

[KTManny]

let us know when you find the culprit!

 

[shreeshar7]

let us know when you find the culprit!

Currently its at ktm wokrshop.
They opened up head cover, inspected cams, said they're fine and replaced shims just in case.
Replaced coolant temperature sensor,throttle body and allnits sensors, injector, oil pressure switch and now putting it together, will get it by tomorrow. Will see if its sorted and keep you updated.

 

[Diploman]

Since we are speculating on possible causes for this loss of performance, I wonder whether the piston rings might have been installed in the wrong sequence or orientation during the engine's re-assembly. This could cause additional friction and heat, especially at high RPM's.

 

[shreeshar7]

Since we are speculating on possible causes for this loss of performance, I wonder whether the piston rings might have been installed in the wrong sequence or orientation during the engine's re-assembly. This could cause additional friction and heat, especially at high RPM's.

Well,that would be highly unlikely because the cylinder bore and piston come as a kit "bore kit
"
You'll just need to lock the con rod pin to the piston that's already inside the bore.

 

[shreeshar7]

Got the bike today, feels much better, haven't taken out for top speed run or anything have to still check that.

One thing I'm noticing is the ticking sound in the engine head, which was almost non existant before.
The sound increases when warm although Not noticeable while riding.
Should I be worried about the shims/tappet noise or just leave the noisy valves be there happy?

 

[shreeshar7]

Got the bike today, feels much better, haven't taken out for top speed run or anything have to still check that.

One thing I'm noticing is the ticking sound in the engine head, which was almost non existant before.
The sound increases when warm although Not noticeable while riding.
Should I be worried about the shims/tappet noise or just leave the noisy valves be there happy?

Rode the bike to Hills today..once I started doing higher rpms..the bike started to slowly loose power..
Its doing 67-70 kmph in 4th gear and sometimes asks for a lower gear,even at wot the bike runs like there is brake applied.

Once I stopped it and turned off the key,after 5mins the bike temp Guage shows max bars and high coolant temperature.

 

[GOJO]

When you say hills does this mean a altitude/elevation change before the performance of the bike is affected?

 

[shreeshar7]

When you say hills does this mean a altitude/elevation change before the performance of the bike is affected?

hills is located just 12kms from my place,elevation of around 1000mts..by riding in hills im telling in the context of loading the engine. even if its not a hill,even on straight roads,this happens after around 30+kms of riding,
also the motul engine oil has a kind of perfume and i can smell it when engine gets hot.(no visible leaks anywhere on the engine.)