MX Yamaha

2006 Yamaha YZ250 (Tom Morgan YZ315 stroker),46/2006-YZ250-TMR-YZ295,1345261

Part list:

  • DEP works pipe, R304 shorty silencer,
  • 2008 CRF450R front brakes,
  • Vforce 3 reeds, new plastics,
  • chain and sprockets,
  • brand new 2018 YZ250 wheels,
  • Tusk 270mm adapter to get 2008 CRF450 calipers,
  • Red Label is making the graphics,
  • GUTS seat,
  • Tom Morgan 295cc ported, milled head,
  • Magura Clutch,
  • R-tech kit, blue Luxon clamps, and 18 YZ450F front plate and fender,
  • R-tech tank,
  • Acerbis blue frame guards,

Owner found one in Yamaha for less then $2,000 and it was a bit of a mess. Front brakes barely did anything, didn’t run right, chain was shot… just a mess.

Frame was really bad shape, slow spinning wire brush on the end of a drill was used, a Dremel and some scotch brite pads.

Had to order the Tusk 270mm adapter to get the 2008 CRF450 calipers mounted. Brakes work fantastic now that it’s bled with new system!

After Magura Clutch install pull feels quite a bit better and reduced effort to pull.

After bottom end modification it will be 76mm stroker that will make YZ315. Tom Morgan was building it, along with flow benching reed cage and carb. He uses stock crank, balances it and uses OE Yamaha rod kit since OE is proven reliable.

A big bore pulls more air volume thru the intake tract and also requires a smaller throttle opening to create the same torque. This raises the vacuum in the carb which causes a larger pressure differential between the float bowl and the venture. This pulls more fuel thru the same size jet. The A/F ratio is the same but people mistakenly believe that it is leaner because of the smaller jets. The main change that you will make when increasing the engine displacement is in needle clip position and air screw setting. The main jet stays very close to the same as with a smaller bore

Carb setup

185 Main
N3EW #2
55 Pilot
1-1/2 out on AS

By Ivars Naglis

Bucci F5 owner.

My day job is web development.

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