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.