300ex

[RichM1983]

Hey guys Ive pretty much finished my brothers 250x/300ex. I need to know where to start with jets. I have a 125 Main and a 38 Pilot. The motor is a 300ex motor with a 12:1 250x 2mm over piston. Im running a foam uni filter, white bros exhaust and a header that I think is stock. Am I ok with the jets? I believe that head has some work because the valve springs look larger than stock ones.

My next question is how much time should it take to pump oil through the line up to the head? The motor was bone dry before I put the oil in it and Ive cranked it over a lot and still no oil comes out of the hole in the clutch cover where it should. Since the motor was dry should I poor some oil down through the hole to help the system start pulling oil?

I also need to know how to adjust the valves. They are really sloppy because I adjusted them wrong before. I follow the instructions in the Clymer but it says that it has to be the compression stroke and the way you tell if it’s the compression stroke is if there is play in the rockers by hand then its the compression stroke when at TDC. Should I just put the motor at TDC and adjust them to specs?

Thanks a lot guys. Ill get pics of the project up soon. Have a good one.

[Ghost-Rider]

I noticed you really haven't gotten any replies so i would ask this in the powertrain section of something if the likes.

[250X_project]

I'm too good with jetting, but I would take a wild guess that your just a few mains over stock. Also it sounds like you have HD valve Springs. This means they were ran with a high lift cam.

When the motor is dry it sometimes will take a bit longer than you like to get the oil pumping. Once distributed, it comes much faster. Also you may have clogged oil ports. If it comes down to it, drain the oil and use break clean and compressed air to flush out the oil system. Then when you get oil flow and can fire the engine, soon there after, drain and replace the oil and filter.

Yes, you must be at TDC, and your cam should be facing down (4 and 8 O'clock) giving you rocker play. Then adjust the .004" on both intake and exhaust. Then rotate and check. Good luck with the build!

[dork]

take the plug out and kick the motor over with the ignition off until you get oil flow. it may take 3+ minutes.

[RichM1983]

Thanks a lot guys. I got everything figured out. The oil eventually started pumping to the head once it was cranked a long time. I got a 125 main in and I it runs good on top with no sputtering so I guess its not to rich. I hope its to lean though. How would I know by looking at the plug, Im used to 2-strokes when it comes to this stuff.

The only problem I'm having now is that my cheapo small battery doesnt pump enough amps to turn over the motor with the high comp piston. I guess Ill have to go and invest in a bigger more powerful battery because the one I have is smaller than what a stock 300 should have.

Also when the motor first started up it sounded like metal was rattling in the motor somewhere. I couldnt identify where at though. Eventually the sound went away and I havent heard it since I first started the motor.

I dont know if its jut in my head or what though but this thing seems like it has 10x the power my old 250x had. I dont know if the 12:1 2mm over 250x piston in a 300ex would cause that much more power but it sure feels like it to me.