Area51 Project - Mike's ATC 250sx - The Weapon:


Machine Specs:


1985 Honda ATC 250sx

250cc Single Cylinder Four Stroke

5 Speed Manual Auto Clutch Transmission

Electric & Kick Start

Shaft Drive

22x11x8 Tires

Drum Brakes Front & Rear

Single Rear Shock


Ever since I finished restoring Bassan's '85 Big Red I've been looking for my own ATC project. After doing a bunch of research I decided on a 250sx, it shares the same reliable power train of a Big Red, 250cc four stroke, 5 speed auto clutch manual with reverse and shaft drive. The SX is a sportier model with smaller tires, a taller rear differential ratio, and no racks. This won't be a work machine, simply an occasional trail cruiser.

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   December 24, 2017


In February 2016 a continuing search of our local classifieds listing finally found me a reasonably priced, in this case cheap '85 250sx.





The machine I picked up today is far from mint,  has alot of missing/wrong parts, but the important bits are there.




I bought the bike as "recently stopped running" which was reflected in the very cheap purchase price, it lost spark and wouldn't start. The wiring harness on the bike was chopped to hell, so I ordered a good used replacement on EBay.




The gas tank was literally laid in place and gravity was solely dependant to keep the rear fenders/seat in place. Ebay has been a fantastic tool to source cheap readily available used parts for my project. I had a set of seat/fender brackets and gas tank rubber mounts arrive an bolted in place. The fenders will be replaced, but I still needed the original mounting hardware regardless.




The bike was ran for a considerable amount of time with no air filter so I stripped down and thoroughly cleaned the carb and installed a complete rebuild kit which jets the bike to the revised 1986 spec. EBay also sourced me a factory air box with filter and snorkel tubes.



For some reason the original front forks and triple trees had been replaced with parts from an '82 250r. The air adjustable forks were in hard shape and the triple trees didn't fit. The steering stop is wrong, they are 1.75" too wide, and there is no headlight mount. Luckily EBay came to the rescue again with these proper 250sx triples & headlight bracket, and a local  ATC enthusiast sold me a proper pair of forks & a front axel.




I greased and temporarily installed the triples with the OEM ball bearings, but they will later be replaced with a set of aftermarket tapered roller bearings.












Test fitting with the 250r forks which are way too small in diameter.








EBay also came to the rescue with the electric start. With my replacement wiring harness installed the starter worked but the reduction gears were missing, after searching I eventually found a reasonably priced set in the states and had them sent up. They fit perfectly and I now have working electric start! In the future I'll install an EBay starter rebuild kit as mine sounds a little rough.




The engine that came in the bike wasn't running and the outside cases were cracked partly because the motor was loosely bolted in place with only 2 bolts as opposed to the proper four mounting points. I bought a used supposedly good motor locally and bolted it in place.




My new wiring harness was delivering spark and I was getting gas through my rebuilt carb but the bike would still not start. I left the 250sx project for awhile to tackle other projects around the house.





August 2016:   Recently I got back at at this project and took the valve cover off to check timing, then removed the head and jug to find the piston and cylinder completely toast. I didn't have a metric adaptor for my compression gauge, but no compression was the reason it wouldn't run.




Luckily the engine that came in my bike (with damaged cases) has a great piston and top end.




I removed the engine from the frame, and between the two motors I made one decent one. Its not perfect as there are a couple bolts cracked off in the head, but it has fresh gaskets so it no longer leaks oil and it runs!  I ran the bike around the backyard to make sure the engine was OK and all the transmission gears worked, I was glad to find all was good! I will paint this motor and use it for awhile, eventually I'd like to swap in a 300 Fourtrax 2wd motor.




I've been contemplating the color scheme for my project and have dreamt literally hundreds of combinations. With this test spot of Amour Coat Oxford Blue I think I've finally settled on my design. Blue Frame, black accessories (engine mounts, swing arm - basically anything that bolts to the frame) and white plastics with the '86 blue/light blue decals and a black seat.




September 2016:   The gas tank was in rough shape. It was originally red and at one point had a very good white paint job but had since been coated a couple times with cheap white paint.  It was peeling, cracking and in terrible condition.




Since there were so many coats I decided to use a chemical stripper to peel off the old paint which worked great.




With the paint removed I found a couple pin hole leaks in the bottom of the tank which I repaired with a resin epoxy repair kit.




When I got the bike I found that the rear of the frame had been cut off at some point, and the Fender Support Brackets and Rear Grab Bar were missing. With decent used parts purchased via EBay, I mocked them in place using online pictures and pics from the factory repair manual. I will have to fabricate and weld approx 4-5" of frame back in place to bring the bike back to stock.




Gas tank stripped and ready for bodywork & paint. The resin tank repair kit wasn't great, I checked into having the tank coated inside locally at a cost of almost $300! I now have a Gas Tank Kreem kit on the way via EBay which is a do it yourself product. The kit strips and cleans the inside of the tank, and the last stage is a coating that creates a plastic liner on the inside of the tank. Online reviews are good so I will give it a go.




The resin epoxy repair kit that I repaired pin hole leaks with earlier started to leak again. I've since removed the Epoxy product and installed a Permatex putty repair kit which seems to be working well. My Kreem kit finally arrived so I'm looking forward to properly repairing this tank from the inside to prevent future leaks.




October 2016:   I also started fabrication on tubing to replace the missing rear frame section. The final result will be squat completely just like the original was from the factory.



Part of working on a project like this is constantly checking EBay and local classifieds for deals. I found these fantastic Factory Honda 8" Aluminum rims originally from a 200x on our local classifieds. These will look great and eventually replace the tired steelies in the back. 3" wheel spacers will be needed for them to fit with the drum brake and will provide a little more stability as well.




Work continues on repairing the rear frame. The new tube was squat and shaped like the factory piece was and then welded in place.




The repaired frame now allows the fender support and grab bar to be bolted in place.




A previous owner cracked off two bolts that held the mangled foot peg in place and welded it on instead! I cut off the bent up foot peg, drilled out the old bolts and temporarily bolted my EBay replacements to check fitment before removing them for paint.





The OEM battery box was missing and someone welded one to the frame. I cut off the incorrect piece and ordered a proper replacement from EBay. Unfortunately they are very hard to find (cheap) with the hold down strap included.  Luckily with a spare Honda rubber strap and some sheet metal I had one fabricated in no time.




This should hold the battery good and secure on the bumpy trails around the house!




With frame repairs all complete it was finally time for paint!




The frame is now coated in Armor Coat Oxford blue. Parts like the rear swing arm, foot pegs, battery box etc will be painted black to break up the color and mimic how Honda paints the frame and accessories in the factory.




November 2017:   The year is not a typo, its been awhile since I got a chance to get back at Project 250sx. Last December I completely disassembled the bike partially to start working on the swingarm and partly to make room for my Skidoo & ATV in the garage over the winter months. Its been a busy year and next thing I knew a year went by! This month Steve was home for a visit so we got a chance to get project 250sx back on track.




The first item was laying out and organizing all my existing, new & used parts and properly cataloguing and bagging them. Then we started disassembling the rear swing arm. A few of the bolts were in horrible shape, I got a chance to try out these specialty sockets (received years ago as a gift) and it actually worked to remove bolts (that weren't seized) with rounded heads!




Inside the differential was a mess as expected, and all of the bearings are toast.







It took awhile but all the parts were soaked and scrubbed in a makeshift parts washer. The axel bearings & seals were removed, but I need specialty tools to do the pinion bearings. I may drop the unit to my local dealer to have these replaced as opposed to buying all the tools.




I also cleaned up and readied for paint my locally sourced 250sx forks, they were chemically stripped of their previous poor paintjob and thoroughly cleaned.




I got a chance to try out my new small sandblaster which worked very well stripping paint and rust from my swing arm parts.




My moose hanging rack doubled as an awesome painted parts drying rack. In addition to my swingarm parts, I coated everything else I wanted black with a couple coats of Gloss Black Tremclad paint.




The swingarm itself was cleaned, then there were some extra bits previously welded to it including a terrible trailer hitch that I cut off and cleaned up. A fresh coat of paint will make the piece as good as new.




I previously discovered the rear brake aluminum brake panel was in very hard shape. It was cracked and even the piece that the cables mount to cracked off and missing which would mean no working rear brakes. I sourced a good replacement on Ebay and had it sent up last year. The brakes on my bike contained a brand new set of shoes, all the parts were simply cleaned up and new seals installed.




The brake drum itself was in good shape and just needed a though cleaning with a wire wheel and a coat of black high temp paint on the outside for a fresh appearance. This was the very first step in actually putting a part of the bike back together!




The washer and cotter pin for the rear foot brake were missing so I found a large washer, drilled it to the proper size and installed with fresh seals and grease.




As mentioned last year I temporarily installed my replacement proper 250sx triple trees with the OEM bearings and they were very rough.




I picked up an All Balls tapered roller bearing kit and installed it with the included directions.




The old races were popped out with a long round punch & hammer, the new races installed with ease.




The lower bearing is a press fit, not having a press I used a piece of pipe larger than the steering stem and tapped the bearing in place with no trouble. Be sure to follow the directions and install the included washers if called for on your model bike.




The new bearings are a huge improvement over the stock worn out bearings and as I properly packed them with grease they should last the life of the bike.




Next up was replacing the complexly shot, seized, rusty swingarm bearings.




The races (as usual in swing arms) were seized solid to the frame I had to cut them with my Dremel tool, then split them with a chisel. This allows them to fold inward and come free.











New bearings installed and ready to go. I taped up this whole area while the frame is stored awaiting final assembly.



After a year of storage and only having one coat of paint I decided to give to give the frame a thorough second coat of oxford blue. With the bike completely disassembled this time, it was much easier to give all the nooks and crannies a thorough coat.  I also painted the triple tree lower Gloss Black.



December 2017:   While experimenting with the new Triple trees & old 250r forks last year I manage to snap out a bolt in one of the lower bolt holes. I had tried drilling the bolt from one side last year snapping off a couple bits and later an easy out bit.  This week I successfully managed to drill the bolt from the opposite side and remove the broken piece with a new easy out tool, now the forks can be properly re-assembled!



Also this past week a super deal on our local classifies came across my screen a pair of hard to find rear mud flaps for the back fenders which were missing from my bike. They arrived on DRL bus from the west coast and came with all the special hardware Honda uses to bolt them to the fenders and were very reasonably priced!



So project 250sx is back on track and will continue after Christmas as I have lots of parts in stock now to keep going forward. Stay tuned for updates!


Cheers, MIKE

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Copyright 2011 Michael Smith