I'm putting together a companion bike to my 2008 CR500. Like the 500, I'm throwing everything
but the kitchen sink at it to try to achieve the equivalent of what Team Honda would be fielding if
they were still racing 250 Ts.
With that in mind, I thought I would do a series of post detailing the "care and feeding" of an all
out CR250 race engine. The goal is 57-58 hp with a broad useable MX powerband. I'll post a
segment each week for a total of four weeks.
Here is a list of the specialty work and components:
Everything that rotates has been treated to a Cryogenic REM Isotropic process. The cryo treatment
strengthens the metal components at the molecular level and the REM removes the peaks and valleys
present on all metal surfaces to yield a much lower coeficient of friction. The results are nearly bullet
proof gears, etc. with less heat, drag and wear.
Large Steel tranny gears replaced with Titanium gears
Crankshaft and piston assembly balanced as a unit by Crankworks
Cylinder and cylinder head ported and machined by Tom Morgan Racing
Wiseco GP single ring piston
Complete Hinson clutch with ti springs
Ceramic bearing in clutch hat
VForce 3 reed
Keihin 38mm quad vent air striker PWK with TPS and power jet
Vortex digital multi map IC with auto swapping
Here is part one of the prep and assembly:
The first step to putting everything together is to prep the cases. Honda
castings are generally of high quality, but there will always be flashing and
burrs with anything mass produced. Areas of concern are the crankshaft well
and oil drain hole.
The first step is to remove the bearings to eliminate the possibility of
contaminating them with metal debris. Once the bearing are out, remove
any scratches, flashing or burrs with whatever you feel the most comfortable
using. I used an 80 and 120 grit flap wheel followed by a Brown Scotchbrite
drum on a Dremel, then finished with a Grey Scotchbrite pad and WD40 on
the crankwell. I chamfered the oil drain hole with a carbide burr on a die
grinder.
It?s important to clean the flashing and burrs from the cases, because that
metal will eventually break off and be free to mix with parts you don?t want
it to mix with. Casting flashes and scratches are also great places for metal
fatigue and cracks to start from stress and vibration.
Once the cases are cleaned up, put the left and right case together and use
a .002? feeler gauge to check the case face for warpage. If you can insert the
gauge anywhere between the halves, you will need to lap the surfaces of the
cases. This is known as matching the cases and is important because you
want to eliminate any possible source for air leaks.
Lapping is a machine process where the case half is held against a known flat
surface that contains a special slurry of free abrasives. The desire is to
machine the case half face to a high tolerance while removing as little
material as possible.
Once the case halves are matched, they are ready for bearing installation and
installation of the internals. After the bearings are installed, check each one
in a quiet room for silent and easy rotation. Lube up all the bearings,
especially the shielded mainshaft bearing with gear oil before installing the
gear clusters as a set.
This pictures shows the main and countershaft gear clusters. For this engine
I had all of the washers and snap rings REMed so that everything that rotates
has an extremely low coefficient of friction. Less friction, less heat and less
wear. I?m also using a very high grade synthetic gear oil that is ultra slick
while still retaining all the qualities desired in a gear oil. It features a film
thickness of 75W90 but a friction level as low as ATF ? best of both worlds.
Once the gear clusters are in place, I install the left side case half and check
to make sure the transmission gears spin freely. This is a functional check to
determine if the clusters were assemble correctly.
If everything spins freely, remove the left side case, shift drum, shift shafts,
shift forks and the two gear clusters.
As always, questions and comments are welcome. Conversely, if no one is interested,
let me know that as well.
dogger
