So I just rebuilt my Scrambler 400 engine (top & bottom) and would like to know what I should do to break it in so I don't screw my piston up. And also if I should keep the oil pump in? It looked like it was in excellent condition (including cable). I've heard a lot of mixed opinions with the 400's oil injection system.

Thanks!

 

If the pump is in good shape,you can keep it out of mud holes and you trust it,keep it. It's just that so many pumps corroded up over the years and froze is why people are afraid of them. On break in procedure I'd do just like we did on new ones straight out of the crate. Set up instructions called for the first tank of fuel to be premixed at 50/1 ratio with a good synthetic oil that you use in the tank.No wide open throttle for the first hour or so,but vary the throttle response.You shouldn't have to baby it and just putt around.The extra oil will cause the machine to smoke a little more,but helps protect the engine in case the pump lines have air pockets.After the first tank any air should have been purged from the oil pump and then you can run straight 87,89 fuel in the tank. If you decide to get rid of the pump,premix fuel 40/1 with a good synthetic.

 

Ok, thank you very much for your help!