I would like to share this, for other users with same model (Kyosho Ultima GP Type R).
The plastic piece, first I through it was probably made for the original engine, but when I removed it, even when it looked like nothing changed, It is a very important support for the clutch bell gear and the spur to stay in place, otherwise if I try to "bend" the car they slightly separate, enough to strip the gear on power. Later I tryied putting the piece back in place, and the "flexibility" was gone.

The fix was to loosen the not and reposition the throttle arm.

The problem now is, or may not be a problem (sorry I am newbie). On the idle position the carb has a 1mm gap which is fine after reading the engine's manual, but on full throttle the card doesn't open completely, it reaches the 70% of the whole capacity. I guess this can be limited by the servo, a futaba s3003.

Any ideas??

Thank you