With the engine completely assembled and installed in the motorcycle, it was time to start the clock.  The odometer was reading 24,926 miles.  It’s probably a good time to tabulate exactly what I was getting ready to test.

-Wiseco 94mm flat-top piston, .040” quench

-94mm cylinder, stock height

-Stage II head, 33mm intake valves, 28mm exhaust valves, 1.5” D-port, 56cc chamber

-DR650 cam, stock late-model rocker arms, Cagiva valve adjusters

-Floating cam chain tensioner, 12mm extension, .06” back-travel

-Six-inch flywheel

-Stock 5-speed transmission

-Hybrid clutch, 13 plates, stock springs, Sneezy release cam

-Knock-off PWK40 carb (actually 38mm)

-K&N 3” x 5” cylindrical air filter

-Mac 1.79” exhaust header pipe

-LCGP 2.5” muffler with 1.75” ID baffle, 288 holes

-Stock final drive pulleys


The engine was close to the 94mm flat-top engine that I originally built in February of 2021.  The only significant changes were:

-PWK carb

-Big flywheel

-DR650 cam

-Floating cam chain tensioner

-Larger baffle in muffler

-Ignition timing retarded 2°

First 3500 miles.

It had great power.  Seemed just as healthy as it did before I started the Evolution of a HotRod project.  Audible noise and vibration were normal.  The new muffler was quiet and seemed to be making good power.  There was no discernable change that could be associated with the heavy flywheel, and power characteristics felt identical to the prior setup.  The two cams run about the same.  So do the carbs.  I really can’t feel any difference between the VM and the PWK.

Oil pressure & temperature remained the same.  Usually about 8 psi and 200°F at 4000 rpm.  CHT was about the same or possibly just a bit hotter.  It ran about 280°F to 300°F.
 
Fuel consumption was a bit higher, even with the less restrictive muffler.  It was still getting excellent fuel economy, but it wasn’t deep into the 70 mpg zone.  It was averaging mid to high 60s, with an occasional 70 mpg ride.  Still stellar mileage, but not as good as it was before.  The increased fuel consumption could be related to the carburetor, flywheel, ignition timing, or the cam.  I’m gonna guess it’s the cam.

Although the milder DR650 cam would generally be associated with improved fuel economy, this motorcycle has extremely low gearing which seems to favor the hotter 340b cam.  I think the hotter cam, with more overlap and TDC lift, compliments the gearing.  Its more efficient at the LS650’s high cruising rpm.  Just a guess on my part.  I suspect the retarded ignition timing didn’t help either.

Oil consumption was up.  It used about 6 to 8 ounces every 1000 miles.  That was a significant change.  The first iteration of this engine didn’t seem to use much, if any, oil.  Now it needed oil every 1000 miles.  Not a big deal, but it was a change that I couldn’t explain.  Maybe re-using piston rings has something to do with it.  My guess would be the cast-iron oil scraper (2nd ring).  Maybe I should have installed a new set of rings.  However, I don’t consider 8 ounces every 1000 miles as anything to worry about.

All went well.   The engine ran great.  On 4/26/22 the odometer was reading 28,654 miles.  Time to change the oil and do an inspection.

The spark plug looked fine.  It had a little more color than I would like but nothin ugly was goin on.  I have no idea how many miles are on this plug.  You can see that it’s pretty old.

The cam chain tensioner looked fine.  It was at 12.5 mm, so it had only gained about 0.5 mm.  Rather than tweak it back to 12 mm I left it where it was.  Again, I want to see how it looks at 7000 miles.

Cranking pressure was 225 psi.  Pretty much the same as it was on the original 94mm flat-top.  I was happy with that.  I guess the compression ring was holding its own.

I moved the ignition pickup .102” to add 2° of advance.  Every .051” equals 1°.  When it’s all back together I double check with my little timing wheel and a strobe light.  I was lookin for 5° at idle, right on the factory spec.

Having to wait 8 weeks for my cylinder head is killing me!  I am really anxious to get my engine back together.  The head is the last piece of the puzzle I need.  As always, great write up, DBM!