School's out for summer and my teenage daughter was looking for a project to keep her occupied:
- find a bike on Craigslist for under $1K;
- disassemble and inspect all the major components; and
- rebuild the bike from the ground up.
Here's the Craiglist find she chose for her project: KTM200MXC
absolutely filthy, probably last washed 3-years ago. Engine runs first kick hot or cold, smooth shifting through all gears. Magura clutch OK, no clutch drag/slip. Brembo Brakes OK. Radiators, and plumbing are fine but need coolant replaced. No cracks in frame. DID rims straight and true. Tires need replacement. Missing kick stand spring and exhaust/silencer rubber. Throttle rubber cover ripped, Seat cover rip and covered with duct tape.
Aftermarket items: Acerbis hand guards, Acerbis large capacity gas tank, E-line CF pipe guard and rear disc protector, Works Connection frame guards, Devol radiator guard, Pro-Taper fat bar (CR Hi-bend) and Scotts bar risers, Galfer Wave brake rotors, Renthal sprockets, Guts racing seat.
Identified replacement items after dis-assembly and inspection: kick start spring, countersprocket oil seal, fork seals, wheel bearings, a front spoke. Seized rear axle needs to be polished and greased. Brakes need to be bled. Faded and cracked plastic. Exhaust pipe dented and rusty. Seat cover. Miscellaneous rusted, mismatched or missing fasteners. Promptly put in a parts order to RockyMountain ATV MC
and trolled eBay Motors for deals.
She's now up to speed with every component and system of 2-stroke dirt bikes.
As strong willed as my daughter is, I pretty much had to step back and let her do the work. I'd limit my involvement to describing the nuances of each system and provide guidance: How to measure a clutch stack; Piston ring end gap; inspect a conrod lower end bearing; burp the cooling system; measure for static and race sag; reverse bleed a clutch; clean and oil an air filter; do the oil change; adjust the powervalve; set carburetor idle; align front forks; etc.
Replaced piston-rings (Vertex). Used a wire brush and Naval Jelly to restore FMF Gnarly pipe w/ Turbine Core 2 SA. Replaced waterpump O-ring seals. Replaced counter shaft seal. Clutch friction plates were at 10%-50% wear; con-rod/crankshaft/clutch basket and hub/transmission inspection = OK. Cleaned and rebuild carburetor. Reed block was fine. Chain, sprockets, and brake rotors were OK.
Set Powervalve to Langston modification: http://motocross.transworld.net/1000...the-ktm-125sx/
Quite a lot of corrosion control: After a thorough degrease and wash; Replaced all chassis bearing w/ All Balls (shock pivot, swing arm pivot, steering stem, F/R wheels); Replaced rusty fasteners. Note: the wheel spacers where seized to the wheel bearing - had to be cut out! Copious amounts of waterproof grease, anti-seize, WD-40, silicone grease, chain lube to lubricate every moving part and metal fastener. Replaced footpegs with IMS SuperStock footpegs.
She learned how to manually mount the Dunlop MX51 Front and Rear tires using the ISDE technique. Replaced front and rear brake pads. Degreased and lube O-ring chain. Replaced air-filter (No-Toil). Replaced brake fluid and Magura clutch mineral oil. Running Shell Rotella T 15W40, Putoline Coolant, NGK Spark Plug.
Revalved and changed springs on WP forks and rear shock. Thanks to Joel @ 707 Racing Suspension
. The cartridges and valve stack shims were an absolute mess, and the fork seals were due for replacement. To achieve correct suspension sag for my daughter: changed fork springs, and changed rear shock progressive springs to linear rate.
FX seat cover, shaved 2.5" off seat. Cleaned the plastic (razor blades and heat gun); taught my daughter to plastic weld to repair the cracks. I let her customize the bike graphics with decals left over from previous projects.
- Chassis and wheel bearings are consumables: Most owners don't maintain and replace bearings. If the bearings have not been replaced in more than 2-years, odds are your wheel and rear suspension bearing need replacement.
- The piston, piston rings, and the clutch plates are consumables: Perform a compression and leak down test. Disassemble the top-end and clutch on every purchase of a used bike and inspect and replace all items beyond maximum tolerance limits.
- Suspension fluids need to be replaced frequently: Most owners don't adhere to the suspension maintenance schedule.
Break-in and function check: Saturday. Riding Sunday!
Post Ride Report:
My daughter absoultely loves the bike. It needs carburetor fine tuning, and even softer suspension springs.