04/16/2022
Our Next build here at Bubba’s Motosports And Racing, is our Yfz450 carbbed style frame we designed that starts with a custom 6 point sub frame The coolest thing about this frame similar to what LSR did for Apex Racings 250MXR which was a custom built yfz450 Carb Style frame but was shrunk 3/4 of a inch and set up factory for a Carbed and modded Yz250F engine! So we did something similar but made a few changes we shrunk ours 1inch, so it can be used for a shorter rider or younger rider and have better control over the machine. I’m 5,4’ so needless to say it’s perfect for me lol. Then we changed the geometry a bit sharing a bit of Trx250r/04,05 Trx450r for better and lower bump steer and slows us to utilize 04,05 Trx450r Honda spindles with yfz450 LT Arms. And we added mudslide mounts for the upper A-Arms like all other machines in the big5 versus the single bar upper arms that Yamaha used. we also kept i mind keeping it a option to run a pro tracks set up for Yfz450 using lower protracs arms, while matching the uppers with a dual mounts and a bit shorter then lower and a hole joint for the use of yfz’s protracs upper arm male threaded joints!
As far as the power plant for this beast we will be staying with the Yamaha theme using a 1999 Yz400 Bottom end we gutted it started with all new custom bearing sets to handle a high rpm rev range between 11,000-13,000 rpm’s and be able to take the beating along with custom cut g and welded chromoly gears then dlc coated to keep the wear and heat down then next was to increase oil pressure so we bored oil ports in the low end and on case for the classic exterior 3 way oil pipe. We ran a custom made oil 3 way to increase oil flow, we then installed a Hinson aluminum clutch basket in comparison to its competitors it does the same job, light cooler better flow we then used a pressure plate hub from a raptor 660 since one was never produced for the Yz400f. We ran with heavy duty clutch plates from Hinson for the raptor as well they seem to really bite hard on torque of the atv versus the Hinson bike set. We made a few little tweaks to the oil pump to increase oil flow as well as dlc coated the pump gear for heat purposes. We then had a custom crank designed by one of the legend builders we know out in Arizona. He does a custom crank modification where he adds basically a pump design around the journal for the rod which puts mini teardrop buckets in a thin circulation around the journal so as oil builds up around the journal and the bearing the oils not pressed out the sides of the bearing but shut up into the underneath of the cylinder keeping the machine cooler and creating more horsepower. We use a custom bearing which is sealed and able to handle RPMs up to 30,000 RPM, versus any other bearing out there we then added a Cp Carrillo Billet Dog Bone Style Tod which is 3+ making this bad boy a serious stroker. The jug we are using is from a yz426 that is Re sleeved to accept a 96mm high compression piston l/ring set by Cp Carrillo with a custom oil flow design we did allowing extra oil flow over the yz450f piston and we tweaked the flame pattern a bit moly skirted and wrist pin is dlc coated to help the heat of the beast. We also installed a wet kit to no longer use the oil tank we squeezed 1.2 quarts with all of our oil mods, lastly we have worked with a few old school Yamaha Race team engine builders who helped us come up with the correct head design for porting and polishing and fuel flow. So the head was poured heavily to give us great low and mid range over it being a bike engine which allows us to play with gearing for the top end we also did a ring in the head similar to how you see done on a diesel engine to guarantee perfect combustion and compression in the engine. Timing and cam chains were done DLC coating Again to keep temperatures down and wear at minimal. And lastly we chose a set of custom WebCams to tweak in tune the retarding around the build, And used a 450 exhaust cam to make starting I have a lot easier. We are still doing some testing on whether it is going to end the fuel injected or it will be ran with a large FCR carburetor. And we are going down to Dasa they have a custom pipe made in tune specifically for this build, To pull out as much horsepower as we possibly can I will start posting pictures as we’re putting it together step-by-step and you can let us know what you think. Once again thank you for supporting Bubba’s Motosports And Racing….
