So my 426 is now running great, but of course there has to be another problem. All gears 1-4 work perfectly, but I get into the 5th gear and it doesn't run right. It feels like it bogs down a bit then shoots forward and repeats that until I get tired of riding it. I have been told it is transmission problem, so should I try to swap it with a friends bike which is used for a parts bike? (The same 426 as mine) or bring it in to rebuild? Not worry and don't use 5th gear???