need help with bro's 250r, sputtering on bottom end (vid)

[mineralgrey01gt]

Me and my brother went riding yesterday at a new area and it was a great time! Both bikes were doing great. His 250r runs great on top end but on bottom end it stutters. I took a video but will not link it to here as we didnt have helmets on at the time when it was video'd and I know that is frowned upon on this site. So if anyone doesnt mind going to youtube and searching for my videos under (mineralgrey01gt's channel) you will see the video of him running it. Can anyone help to get this little problem figured out? The mods are:

ESR 370 top end with +4 stroker crank
ESR trx5 centermount
brand new Airstryker carb (52 pilot, 185 main he thinks)
not sure what reeds are in it
ESR filter kit
running rich also

I think thats all performance wise. The motor is fresh, not even probably 7 hours on it yet if that much.

EDIT: when you go to look for the vid. Click on my name on the video LTR450 in mount hermon, la. It will be under that

[machwon]

Mineralgrey, I didn't watch the vid but its becuase the jetting is too rich. The high compression on a motor will cover up rich jetting. I'm not sure which carb size he has, but 185 is likely too large. Do you have a good close up of the plug?

[mineralgrey01gt]

It's a 38mm sorry about that. It's just black, no close up of the plug. Sorry

[machwon]

If its black, I'd go to a 48 pilot and 175 main to start. It will likely need to go a bit lower on the main but I would start there. Just make sure it has the right octane fuel too.

[mineralgrey01gt]

He runs the recommended fuel that ESR said he needed to which is 110 or 112 cant remember which.