YZ250 Blaster Build Log

Here is an example of an MX engine in a Blaster with the carb angled too much and the solution:
29013-1aafee8382184fa9c1bfc0c5ae787cce.jpg
29012-1c1253873df9310db9524707270f1f81.jpg

It ran with the angled carb, but it ran and started so much better with it corrected.
 
Here is an example of an MX engine in a Blaster with the carb angled too much and the solution:
29013-1aafee8382184fa9c1bfc0c5ae787cce.jpg
29012-1c1253873df9310db9524707270f1f81.jpg

It ran with the angled carb, but it ran and started so much better with it corrected.
 
Five degrees shouldn't cause that problem. You'd know because after sitting a couple of days the fuel leaking into the case would evaporate leaving mainly oil. When it finally starts it would belch white smoke and run like garbage for a while till the excess oil is purged.

Hot or cold doesn't matter...now that's really strange, but try this and see if it helps any:
If your jetting is in the ballpark, then you will have to choke it when cold. Kick Slowly two or three times to get some fuel and find just barely past TDC. Crack the throttle, reset the lever and kick once but kick FAST. If it doesn't work, ease past TDC and hit it again. One problem is that in a dirt bike the kick shaft can rotate almost 180 degrees but in a repowered blaster, it rotates less than half of that. For every 90 degrees, your motor will barely make one rotation. Inirtia is not our friend and half kicks will almost never cold start any bike, new, old or otherwise. I'm about a buck 75 and have to jump on it and kick down at the same time.

The weird thing about this engine is it is incredibly hard to get one full kick it, almost like it is catching on something but it's not, I pulled the clutch cover and everything is fine. If you get it pass the first 1/4 kick then you can kick straight through most of the time. It's probably just because I'm not use to kicking dirtbike engines, I've never owned one.