Bottom End Rebuilds
One of the most critical maintenance items for two-stroke racing engines is a properly installed crankshaft and all its related bearings. The very nature of the job is somewhat intimidating to most do-it-yourself mechanics, and while the job isn't overly complicated, it is extremely important to have it done right. And not just right, but with precision.

At MCE, absolutely no corners are cut during the reassembly of a bottom end. Every bearing is replaced, and every last little part is critically inspected for signs of wear. MCE builds engines with such care and precision that no MCE motor has ever failed from an assembly error. Ever. It's a bold statement, but it's one of great pride. That is why no replaceable components are ever re-used in an MCE rebuild. From bearings to seals to gaskets to sometimes even studs, every little item is replaced. The little pieces are often overlooked as unimportant or non-critical for replacement by some mechanics, but not by MCE. "Failure", to coin a phrase, "is not an option."
Reliability is one thing, but performance is another. An MCE rebuilt motor is, for all practical purposes, a completely blueprinted engine. The cases are verified to be completely true, the bearings are inserted with aerospace precision, and the cases are aligned to within 0.0001" for a supremely free spinning crankshaft. Each engine is leak tested before leaving the shop.

It is not an overstatement to say that your engine will be better assembled and closer to the engineer's specifications than it was when it was brand new.

What's involved in a complete rebuild:
  • Complete dismantling
  • Analysis of the engine's condition
  • Etch washing of all parts to oil and dirt free condition
  • Inspection and micrometer measurement of all wear-related parts
  • Measurement of bearing bores for misalignment and out-of-round conditions
  • Measurement and adjustment of new crankshaft runout to within 0.0001" (TIR)
  • Measurement of cylinder bore, height, and parallelism
  • Inspection of crankcases for cracks, warpage, worn threads, and bearing bore alignment
  • Zyglo penetrant and ultraviolet inspection of engine components for evidence of cracks, stress, and abnormal wear.
  • Replacement of all bearings
  • Replacement of all seals and gaskets
  • Replacement of transmission circlips (if required)
  • Replacement of all springs and circlips
  • Replacement of dowel pins (if required)
  • Replacement of cylinder studs
  • Replacement of all lock washers
  • Replacement of piston and related top end components
  • Measurement and adjustment of crankshaft runout after final assembly
  • Adjustment of ignition timing (some models)
  • Adjustment of clutch actuation
  • Pressure test of crankcase

    • NOTE: Yamaha rebuild includes a rebuild of the crankshaft

Plan ahead for your rebuild and save time: Pricing:

Please note that all rebuilds include crankshaft run-out adjustment. This service is available seperately at the standard shop rate of $80 per hour with a minimum charge of $50 and a maximum of 6 hours ($450) depending on the difficulty in the adjustment.

The typical labor costs (in US dollars) for rebuilds are as follows:
Make, Model and Year Engine Rebuild Crankshaft Rebuild Only Engine Removal & Installation
Yamaha TZ125 $1470.00$170 $313.00
Honda RS125 (1995 or newer) $1280.00N/A $80.00
Honda RS125 (1994 or older) $ 715.00N/A $110.00
Aprilia RSR 125 $ 990.00N/A $220.00
Yamaha TZ250 (2000 or newer) $1897.00 [new crank]
$2282.00 [rebuild]		 $385.00 $450.00
Yamaha TZ250 (1999 or older) $1760.00 [new crank]
$2145.00 [rebuild]		$385.00 $387.00
Honda RS250 $1327.00N/A $533.00 [includes shims]
Aprilia RSV 250 $1020.00 $300 $330.00

Please keep in mind that the above does not include parts, and that the actual cost is dependent upon the amount time spent on the job. Engines with warped cases and other problems will require more time. Cost is based on a standard shop labor rate of $80 per hour.