My mission was to build the most effective, do it all 2 stroke race bike that I could. I used only the best aftermarket parts and services available and here is what I ended up with.
I purchased a new 2009 Yamaha yz250 from Colorado Powersports, I chose a 2 stroke due to there reliability and low maintenance cost and a Yamaha because in my opinion the best of the 2 strokes still being made. And here it what I did to the bike.
Enduro engineering evolution hand guards and roost shields
MSR heavy duty aluminum skid plate
Works connection radiator braces
MSR a o f clutch perch
Cycra front disk guard
Renthal RC high bend fat bars
GPR v1 steering stabilizer
Boyesen shokout flex grip system
Renthal sprockets 13/51
Renthal r1 gold chain
Tm Designworks chain guide
F M F gnarly pipe- for technical woods riding/racing
F M F turbine core 2 spark arrestor muffler
Pro circuit works pipe-for higher speed hare scrambles/mx riding and racing
V force 3 reed valve system
IMS zip ty edition 3.2 gallon tank
Motion pro lite loc rim locks
SDG seat
Sunline sl-1 foot pegs
Works connection aluminum rear caliper guard-anodized red
MX bonz reversible axle blocks
Works connection master cylinder caps-
MX bonz oil fill cap
S F B 9 0z flywheel weight
STR fork bleeders
Custom suspension re valve by Jim Sumner at airborne MX suspension
I chose the IMS Zip ty edition tank because it hold 1.1 more gallons of fuel but retains the same width as the stock tank and doesn’t have the raised lip in front of the seat that can interfere with forward body positioning. The 9 oz flywheel weight makes the bike less prone to stalling on slow technical obstacles and even in tight corners at the track and felt it didn’t hurt the top end power or revs much or at all.
I like the FMF gnarly pipe for tight technical riding because it gives the bike more low end grunt and torque but does sacrifice top end and revs so for higher speed riding and racing like hare scrambles and MX. I like the Pro Circuit works pipe because it mimicks the great stock power band but adds a bit of power and revs slightly longer.
The V Force 3 reed valve added a good amount of mid range power and throttle response and didn’t sacrifice the power anywhere else. I went from the stock 50 tooth rear sprocket to a 51 because it seemed to tighten up the shifting just enough to make the power more usable without hurting the top speed of the bike.
The bike seemed a little twitchy at high speeds and I didn’t want to change the offset of the triple clamps and lose the great steering response of the bike so the GPR stabilizer was a must and works flawlessly.
The biggest modification was the suspension and Jim at airborne MX suspension set it up perfect for me .the stock spring rate was right on for my weight and ability but he managed to set it up so it works great for me at the track as well as the woods with nothing more than a click or two on the compression.
I choose not to modify the motor in fear of hurting reliability so I run OEM Yamaha top ends and a Wiseco crankshafts because I know I can depend on them not to fail and leave me pushing. Woods riding in the Rocky Mountains can be very hazardous to a bike so items like hand guards, skid plates and radiator braces are mandatory. The Enduro engineering hand guards are in my opinion are the best ones out there. There super strong and protective, they fit great and have never failed me. The MSR heavy duty skid plate is bulletproof and can take whatever I can throw at it and despite having to slightly modify the works connection radiator braces to work with the bigger tank they work great.
The Sunline sl-1 foot pegs are wider than stock and due to there concave shape allow for a better feel and more precise foot positioning. The most underrated aftermarket part the I find to be mandatory is the Boyesen shokout grip system. It gives you the ability to chose from three different rubber absorbers within the grip housing depending on how much or how little flex you choose. I have used this same unit on my last 4 bikes and couldn’t ride without it.
The MSR a o f perch is a very high quality unit that uses a CR bend clutch lever and pull ratio and uses a bearing in the lever for a smoother pull and works great. after destroying many aftermarket heavy duty aluminum chain guides I decided to try one from TM Design works. The guide looks great and its totally functional and due to its strong yet flexible plastic construction I am yet to destroy it.
It has taken me over a year to build my YZ just the way I wanted it and I’m more and more impressed with it every time I ride it. Id like to give a shout out to Shannon and Zak at Colorado Powersports for always getting me what I need and there continuous race support and Jim at airborne MX suspension for his great work and continuous support.
I hope to see more 2 strokes like mine make a comeback and less loud 4 strokes digging trenches that I have to jump over.
