Troubleshooting a changed 300RR

[Balkan boy]

Engine on my 2018. 300RR feels noticeably different after 20h/500km from new, and I hope I can get some help diagnosing the issue.

Bike ran very good from the box. There wasn't any noticeable change when riding from 0m altitude (sea level) to 1500m, and in temperatures from 10-25C. I used OI (+1% oil in the gas tank) for about 5h/150km, and then switched to premix with 2% Nils oil.
Right up to 20h of operation the power delivery was crispy and predictable.

On the following ride the bike felt a bit sluggish and slow to rev in the first 10-20% of throttle. It still had a lot of power but the delivery from the bottom changed. This also affected speed and stability through corners, so I was going wide and slow everywhere. This is on a familiar track where my braking points and shifts are consistent, and it's easy to notice a change. In places where I used to carry 2nd gear with decent speed I now have to be in 1st. It's similar to having a very wide gear ratio. Engine starts every time and it doesn't bog down when snapping or closing the throttle.
This is all at ¬50m above sea level. Ambient temperature has risen a bit to 25-30C, humidity is around 50%.

I pulled out the plug and it looked rich (break in was with a slightly richer mix).



After replacing the stock plug with a new one the bike was crispy again, but it lasted only for one ride.
I thought the plug was getting fouled again, but the new one doesn't look bad after 2h/60km:


I adjusted the idle and air screws in small increments, but it doesn't make much difference.
I opened the air screw form 1.25 turns (stock) to 1.75 turns, but it seemes to make the issue worse.

Bike is completely stock with jets like in the highlighted field:



There are some other symptoms that I'm not sure play a part in this:
- Radiators stay pressurized after completely cooling down, and there is a small burp of coolant when taking the radiator cap off. This was happening since new, but after the last ride I also noticed a slight drip of coolant from the thermostat.
- There is a slight gear oil leak (a drop or two) at the countershaft seal.


In summary, only thing that changed is ambient temperature that has risen to 30C, and the bike that was running great isn't anymore.
Surely this small change in temperature doesn't require different jets.

Edit:
The issue is present on both the Sunny and Rain maps.

[aj_mariner]

If your radiators are still pressurized after completely cooling down, you need to switch to the KTM head o-rings. They will even stay pressurized after days of the bike being off.

The plug looks pretty good. Have you cleaned your air filter?

[newbeta]

Can't believe Beta still hasn't changed the o-rings. A common problem for many years.
I suggest before doing anything else: change to the KTM o-rings in the head. I had the same problem before changing these . Perhaps you also loose compression (and therefor grunt) because of this?

[Balkan boy]

The head o-ring issue is supposedly resolved for the '18. models. I've read about it, and I'll be looking into it if the issue persists. There weren't any signs of overheating (or running hot) even in the stop-and-go rock crawling. I'm going to change the coolant to see if it makes a difference. Radiator pressure cap and the spring seem Ok.

I'm not sure this is the cause for loss of grunt. The bike has been very strong for 20h.
Air filter was due for cleaning, but it wasn't terribly dirty. I clean it every 5-7h.

[newbeta]

It sure does seem like you have a head o-ring problem. I had that exact issue with preassure cold and a little colant leak. Changing the o-rings is really cheap and easy.

[Balkan boy]

It sure does seem like you have a head o-ring problem. I had that exact issue with preassure cold and a little colant leak. Changing the o-rings is really cheap and easy.

Yes, the pressure in the radiators is probably connected with the head o-ring.
Did you notice any change in engine performance before you changed the o-ring?

All I can think of for now is that it needs a different pilot jet, but as per Beta chart the size 38 is recommend for a wide range of conditions.

[mtdirtbag]

This may not have anything to do with your problem but I will pass it along. I follow along on dirtbikeworld.net: an Aussie forum (trying to learn an addl language ) and it was brought up by one of the members who is a dealer of European bikes, post copied and pasted.

New bikes blowing coolant...
In the last week I've been involved with 2 bikes (possibly a third) blowing off coolant out from under the radiator cap-valve, even when cold. The event is generally accompanied by a smell of ammonia (NH3)

Nitrogen from the air-gap mixes with hydrogen from the fill water to create ammonia. This pressurises the top tanks and pushes the cap-valve.

The reactant for this process is alloy soldering flux. The radiator makers aren't washing out the rads properly and this is the result.

The fix is easy, flush thoroughly and fill with quality coolant.

The same radiator company supplies most of the Euro brands so if your new bike has pressure building, especially when cold, this is the issue.

Cheers all.

[Balkan boy]

Update:

I've put in new coolant (Motul MotoCool) and it seems it has fixed the issues with power and radiator pressure.
I only did a 30 minutes ride, so I'll need to test it more in hot conditions.

I won't complain if new coolant is all it takes, but I'm surprised at how much the bad coolant influenced the bike.
Factory coolant came out murky.

This may not have anything to do with your problem but I will pass it along. I follow along on dirtbikeworld.net: an Aussie forum (trying to learn an addl language ) and it was brought up by one of the members who is a dealer of European bikes, post copied and pasted.

New bikes blowing coolant...
In the last week I've been involved with 2 bikes (possibly a third) blowing off coolant out from under the radiator cap-valve, even when cold. The event is generally accompanied by a smell of ammonia (NH3)

Nitrogen from the air-gap mixes with hydrogen from the fill water to create ammonia. This pressurises the top tanks and pushes the cap-valve.

The reactant for this process is alloy soldering flux. The radiator makers aren't washing out the rads properly and this is the result.

The fix is easy, flush thoroughly and fill with quality coolant.

The same radiator company supplies most of the Euro brands so if your new bike has pressure building, especially when cold, this is the issue.

Cheers all.

I think this may have been the case with my bike.
After the last hot ride bike was really bad and the smell of burnt coolant hung around the bike for two days even without leaking.


There's still a little weeping of oil around countershaft seal. That needs looking into next.

[motorcycledan]

I make these billet thermostats that fit all the beta 2 and 4 strokes from 2010 to current, its a nice fix to the annoying leaky thermostats. They come as a kit with 4 hose clamps and an o-ring.

therm1.jpg (73.78 KiB) Viewed 10491 times

[moto367]

Before changing the o-rings, drain the coolant and refill and bleed the cooling system. Our bikes had the same symptoms with pressurized radiators. We refilled and bled the coolant and no more pressure in the coolant. Basically had to force fill the coolant and in doing so got a huge burp of air out of the system. Haven't had a problem since.