I just put in a new Wiseco piston in my Scrambler 400 after having my cylinder bored .020 over and having it ported. I just fired it up this morning and it will idle but when I give it any gas it dies. It looks like it's spitting the gas back out the intake side. I checked my compression after putting in the new Wiseco and it was about 140 PSI. Does anyone know if that sounds right? I was expecting it to be higher than that.
I made no changes to the carb or anything and it was running great up until the piston went south on me. I'm running a 350 main but like I said it was running great til the piston problem. I don't think it's carb related but the piston went in without a hitch so I'm not sure where to look.

A 350 sounds a little big , even on a ported motor , but still , it should rev up . Did you have the carb apart at all ?

Well, besides not being a very good mechanic I also can't type. Yeah, a 350 main would be a little fat. That was supposed to be a 250 main is what I'm running in there right now. I must have beem thinking about the Chevy engine I'd like to drop into my Scrambler. I didn't do anything to the carb other than remove it to get to the piston. Last nite I pulled the carb out though and took it completely apart and cleaned all the jets and checked my float and choke. Checked my reed cage and it looks good. Put it back together and exactly the same problem. It's like the motor is just chokin on the gas. It runs great at idle and I can turn up the idle to a fast idle and it is fine until I give it gas, then it chokes and bogs out. I have to admit Rick I wanted to have the porting & headwork done by RCR and I ended up having the work done somewhere else because I got a good deal on the price. I hope that old saying you get what you pay for doesn't come into play here. I'm on vacation this week so I'm going to play with it today and see if I can figure this thing out.