400ex carb on a 300 ex

[Braff1]

I need to know what jetting you guys running a stock cylinder are using (pilot and main jet).

Thanks

[Braff1]

anyone?

[465Stroker]

Should be a stock needle on #3 with 160 Main jet. Fuel screw arond 2.5 turn out.

What's wrong? Are you having trouble?

[dirtmomma]

WEll my head isn't stock(ported) but I'm running a 150 main, not sure where the needle ect is cuz I didnt' adjust it at all when we first put the carb on, we just got LUCKY for once & it ran fine. I am going to try to go down to a 148 though cuz it's running a little rich. BTW I'm @ 500'-1000' elevation:) Is this for Lil Braffs???

[Braff1]

Yea this is for Lil's quad.

Rick, We had the porcelin from the inside electrode break off and bounce around trashing the cylinder sleeve and piston. I have been trying to get a new 330 kit from TC racing for over 3 wks but they are out of stock and don't have the time to machine one piston, seems the same with everyone else too. The GNCC break is when the local series here picks up, racing every 2 wks for about an month and a half now. Anyway came across a deal on a stock cylinder w/weisco piston and gaskets for a good price and just went with it to try to get her through this season. Next season Lil is going to start nationals but it will be after the break and I am going to rebuild her bike with a 330 or 350 kit.

I have her bike back togather now but it don't want to start. We got good gas, good spark (checked it on myself). I am going to have John take a look at it and see if he can find anything wrong.

[300exOH]

You may want to double check your timing.

Have you tried GT Thunder for the rebuild? I have heard nothing but good about them and it isn't too far away so shipping times/cost shouldn't be bad.

[cals400ex]

from what i hear, the stock jetting on a 400ex isn't that far off on a 300ex. so, i would start with a 148 main, needle clip in the 3rd position, and somewhere between 38-40 on the pilot jet.

[465Stroker]

Dan, Your jetting should not really change that much that it would not start. There are several things that can make it act up.

1st - make sure you do not have it out of time since it is very easy to have it 180 degrees out. At top dead center the cam lobes should be pointing down.

2nd - valve clearance for TC cam is .006 intake and .008 exhaust. It may also be time for a valve job too. If you valves are shot or clearance too tight you may not be losing compresson.

3rd - Main jet - this will not make it start any easier unfortunately. The reason the 330EX takes a larger main than a 400EX is that the 400EX head is way more effecient and draws much more volume than the 330EX. If you go any lower than a 152 you will risk overheating / damaging the motor.

Good luck,
Rick