Just how reliable are the 420 conversions? The only conversion example I know about made me very happy not to be the owner of the bike. I was racing in the Toyota Desert 1000(km) race in Botswana in 1999 on my 1998 KTM 300 when I heard a YZ 400 catch me up. This was after about 100km on the second day (500km each day) and I though well the race is on. Unfortunately this was not to be. The first time we hit a flat out 5th gear sandy whooped river bed he came past me like I was looking for parking. Now a KTM 300 is no slow coach but I had absolutely no answer to his attack. I went back to 4th gear to no avail, he just disappeared into his own dust. On a long race like this you've got lots of time to think about things and I started trying to figure out what was wrong with my bike, it couldnt be making maximum power as I had had other races with 400s and the contests had been faily equal. About 100 km's later I came across him again but could see he had a blown motor (oil all over the place)- I had got back my race position. I finished the race late that afternoon and attended the prize giving that evening. Lo and behold this same rider walks in at about 21h00 having been picked up by a sweep vehicle. It turns out he had been riding a YZ420 not 400 and this was obviously why he had so much more power than me but obviously a lot less reliability. Of course, I felt a lot better about my 300, knowing I didnt have to strip the motor down to find my power deficit. Now I have a YZ426. I hope its a lot more reliable than a 420 conversion.