Hi, martinina... Prior to this problem, I had recently replaced the coil pack. The one I replaced it with was the incorrect coil pack which was causing the loss of power. When I finally got the right coil pack, it solved my power issue. I also learned not to be shy when approaching steep hills or deep mud holes. You basically have to "ride it like you're mad at it" - put it in a low gear and gun it. Others might disagree, but this is what has helped me. Good luck!

 

The bear tracker has been mine for 10 years now, so I know it’s something wrong with the moto. Even on a small hill loses power and won't go up… And sometimes in a mud terrain don’t have strength... I never had a problem with these situations before .... The only difference was that this year (about 6 months ago) I changed the oil (before I always did in a mechanic, but I lost confidence in him). But the oil I used was the specified in the manual "LIQUI MOLY Getriebeöl (GL4) SAE 80W", and I have been riding for the last 6 month with no problem till now

 

If the engine looses revs when faced with a hill, first thing to do is fit a new plug and check the colour of the old one, death white at the nose indicates a weak mixture, black, a rich one, or electrical problem. If the new plug has no effect, give the carb a clean out, do not alter settings, just remove the float bowl and clean it, the jets and the holes they are in with compressed air. If the plug nose was black, check air filter and choke mechanism.