I let the paint cure for a few days and then took the left and right engine covers off as well as the camshaft cover, cylinder head and cylinder. Then installed the rotor, stator, front sprocket (15 teeth in replacement of the original 14), and various small parts before screwing both side covers back on, this time for good.
Now we’re ready to get the top end mounted on the engine. The work is straight forward as Honda engineered everything rather superbly for the XR500 engine. Let’s animate the steps through a slide show and see how everything is coming together:
The cylinder is bored 1mm over to fit the 90mm Wiseco piston (see previous post for details on this piston). I’ve ordered a new set of corresponding piston rings — let’s verify that they fit. The end gap should be between 0.30mm and 0.50mm and not exceed 0.65mm. The measured end gap is 0.60mm, so we’re borderline. I inherited this piston and cylinder and unfortunately I don’t know who machined it. It was bored in the upper limit, but within tolerances. Crossing my fingers that we’ll not have too much piston rattle (!).
Let’s mount the piston rings. I’ve had a few unfortunate accidents in the past and now am hyper cautious during this operation and always use the help of a piston ring installer.
Piston is mounted in the engine. The new Wiseco pin fits too tightly so I have to make a few adjustments to make it slide in properly. The ring ends are positioned according to the chart provided by Wiseco.
The next step is to mount the valves back into the cylinder head. Over the years I’ve used all sorts of valve compressors which were for the most part designed for large engines and thus were incredibly frustrating when applied to smaller valves and cylinder heads. This time around though I got myself a new tool, and this one is killer, making the job a real joy (Genius Tools valve spring compressor).
Valve side of the cylinder head. The camshaft bearing journals in the XR500 engine are known to easily get scored and show signs of seizure. This cylinder head bearing journals though are in great shape.
Starting to look like an engine. Final step is to adjust the cam rocker clearance and then manually rotate the engine to make sure that the 10.5:1 Wiseco piston offers enough clearance for the valves. Everything is good.
This was fun! Next step is to clean and paint the exhaust and then we’ll start focusing on the frame and suspension components.