I agree most likely a pinch, but do check the glow plug and make sure it's the right one for the engine. I find the 4 ports like a slightly warmer plug and to not have a low idle. If you make the idle perfect it won't be after a few tanks and or a low tank. Bearings- I've seen some crappy bearings in the last year or so. Mostly rear ones. fuel tank- I had some issues on my mbx-7 lids not sealing properly just a thought. Fuel- if it's good it's great if it sucks it sucks.