The Mr Turbo way
This mod was sent in
by Dazbos from his records dating back to 1993. It has become
clear that the 750 turbo suffers from a less-than-perfect
lubrication system. This often leads to turbocharger failures,
even with the stock turbo unit, and on many engines spinning of
the big-end shells (rod bearings) wrecking the crank. This mod is
designed to improve both pressure and flow to the engine and to
the turbocharger. Highly recommended even for stock bikes.
The M6NTL
way
Drill out the
oil cooler bypass (as per diagram 1), to 5mm. This will increase
the oil supply to the entire engine as well as the turbo, and at
5mm it will NOT stop oil circulating through the oil cooler (the
bore of the standard oil cooler lines is 7mm). Increasing the oil
flow here will protect the turbo and help prevent the big end
damage which sometimes occurs.
Check and
de-burr the main oil passage where it meets the oil cooler and
bypass area (also diagram 1). Note that this is stepped, and
cannot simply be drilled clear, but must be carefully filed with a
needle file through the oil cooler supply hole in the front of the
sump pan. This is the main oil supply to everything, and must not
be restricted.
Using circlip
pliers, remove the circlip in the top of the Oil Pressure Relief
Valve (diagram 1), and install a washer approx 1.5mm thick on top
of the existing washer, and replace the circlip. This will
pre-load the spring in the valve, increasing the pressure at which
the valve opens.
Drill out the
turbo oil supply passage (as per diagram 2), to 7mm. This is
angled down and back at approx 45 degrees. Take care not to drill
too deep causing damage to the banjo bolt threads, or to allow the
sides of the drill bit to damage the top surface of the sump pan.
This will remove the restriction in the oil supply to the turbo.
Cross drill the
banjo bolt (at the shoulder) with 3mm holes, and drill down the
full length of the bore to 6mm, all the way to the head of the
bolt (but obviously not through the head!!). Leave the filter
screen out of this bolt on reassembly.
I personally
replaced ALL the O-rings and gaskets in the sump pan, and sub pan
area, and I strongly recommend NOT using any sealant around any of
these O-rings or gaskets…..
