Nicholas Fluhart

September 18, 2010

Honda TRX350XX (TRX250X – ATC350X Conversion) TRX350X

Filed under: Bikes, Trikes, ATVs — Nicholas Fluhart @ 12:01 am
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From the ATC era of the mid 80’s up until the end of the following decade Honda and most of the ATV industry was void of any heavy-hitters, performance wise, for trail riding. Of course there were still some thoroughbred race bikes (although none from Honda after 1989), but for off-the-track trail riding you were very limited. The Honda options of the day were the TRX250X and later the TRX300EX, both only middle weight bikes. The 250X was a kick start model with a nice 4-valve single overhead cam engine with a 5-speed transmission. The subsequent 300EX was an electric start model with basically the same engine but with a lengthened stroke making the displacement a little larger. Yamaha had a leg-up on the industry, really in all categories race and trail, and the king of the sport trail bikes was the 350 Warrior which had a stout 2-valve single overhead cam engine with a 6-speed transmission. The paradigm shift occurred in 1999 with Honda’s introduction of the TRX400EX. But up until then, no manufacturer had produced a 4-stroke trail ATV with the bulk power, torque, and speed of the ATC350X last produced in 1986. The industry had decent four-wheeled chassis but no major power plants aside from the Warrior, which was not superior to the 350X. So during that period, what could be done?

The answer: Well, in this case you can have your cake and eat it too. My choice, and the choice of many others before me, was to combine the best of both worlds with the exceptional, time-tested ATC350X power plant within the stability and performance of a four-wheeled chassis, specifically the Honda TRX250X. And thus the infamous Honda TRX350XX is born.

Mine of course has some major upgrades…

My project started in the winter of 2002, and although by that time there were some high-end four-strokes available, i.e. the Honda 400EX, Yamaha Raptor 660R, and the newly released Suzuki Z400, as a 19 year old, full time college student I didn’t have the means to go down and purchase a brand new ATV. Besides, it’s not my style to buy new machines; I like to build my own, and my favorite thing is to combine the past with the present. This was the ideal project for me.

As discussed in my 350X post, I got my hands on some ATC350X crate engines. The next step was to find a suitable ATV chassis, preferably something requiring minimal fabrication yet sporty enough for my riding style. While researching it on the web, my brother and I got some tips at Powroll and thus decided that a TRX250X chassis was the way to go. Fortunately, I knew someone who had a non-running 1991 250X. I easily obtained it for $500. We then ordered the Powroll conversion kit including the Shotgun series Supertrap 4 exhaust which at that time was priced at $565.00 total (the header was not stainless steel).  And the project began.

The engine:

The 350X power plant is a kick start, 4-valve, single overhead cam engine with a 6-speed transmission (no reverse). My goal was to have an ultra-durable and super dependable bike that I could put lots of fun miles on with minimal maintenance. With this in mind, I wanted to keep the engine as close to stock as possible, but I installed some strategic upgrades. Although my engine had never been used, it had been setting on a shelf since 1986 so I wanted to freshen up the cylinder. I bored the sleeve and installed a Wiseco oversize piston kit which not only enlarged the displacement but also increased the compression ratio from 8.5:1 to 10.25:1. The next thing I did was upgrade the clutch with EBC friction plates and heavy duty Barnett springs. Then the engine was ready. These were moderate modifications that would increase performance without sacrificing dependability.

Intake and fuel delivery:

Initially I went with the 250X carburetor and a K&N air filter. I removed the lid from the air box for maximum air flow and jetted the carburetor accordingly. Later I installed a 400EX carburetor which has a larger diameter throat and got a noticeable power gain.

The chassis:

The chassis was pretty much stock when I received it. The only upgrade was a Dura Blue heavy duty rear axle. I left it that way initially but soon found it lacking, specifically in the suspension department. To remedy the issue, I installed front A-Arms from a 1989 TRX250R and front shocks from a 1999 TRX400EX. This widened the front substantially and gave me a lot more suspension travel. On the rear I installed an aftermarket mono shock with a remote reservoir and I added 6 inches to the width by installing Dura Blue polyurethane wheel spacers on the axle. For rear wheels I settled on 20×11-8 Maxxis Razor tires mounted on Douglas polished aluminum 8 inch rear rims. On the front I stayed with the stock rims and mounted a new set of radial directional tires that boasted a smooth ride with great handling. For the operator, I recovered the seat and installed Tusk brand aluminum handlebars with a padded cross-bar and gel hand grips.

At less than $1800.00 total investment, I had a good, competitive bike that easily held its own against the new $6,000 bikes. At that point it looked like this:

In the prime of my riding days, I took many trips and fun rides. We took trips to the mountains…

…and rode many trials and homemade race tracks doing tricks and big jumps.

But alas, as my core group of riding buddies slowly married and moved away our weekly rides had come to an end by early 2005. I rode the bike sparingly until about mid 2006 when it was placed in storage and remained there until a sunny spring morning in 2010. That day I pulled it out of moth balls, not to ride, but to reminisce. It was still fairly clean but it was much in need of cosmetic TLC. It hurt me to see it that way, so I trailered it to my shop and got to work. I removed all the plastics and began cleaning, polishing, and painting on the chassis components. But I didn’t stop there. I ordered all new plastics for it to give it the clean cosmetic finish I always wanted it to have but never had the chance to do it. Plastics for this bike are unusually expensive, more so than most other models.  And at last, after almost 10 years I finally put the final touches on one of my favorite personal projects. I still have this bike today (back in storage) and it looks like this:

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