Frame and engine mounts: what a 650 needs in the CX500E frame

The short version

My CX500E and the CX650E Eurosport use exactly the same engine-mount bolts, nuts and torques. The torque tables in the CX500E, CX650E and GL500/650 manuals all agree.

What changes:

• The front hanger plates. My bike has 50310-MC5-000 and 50320-MC5-000. The CX650E uses the GL650’s pair, 50310-ME2-000 (right) and 50320-ME2-000 (left). The bolts through them stay the same.
• The cooling. The 500’s hanger plates carry the shroud for its engine-driven fan. The 650 has no engine-driven fan. It runs an electric fan on its own radiator, so the radiator, shroud and water pipes change with the hangers. See cooling.

No Honda manual I have shows any machining.

Mount by mount

Mount	My CX500E	With a GL650 or CX650E engine
Rear lower	12 × 308 mm bolt 90110-415-000 and 12 mm nut	Same parts
Rear upper	Two 10 × 70 mm bolts 95800-10070-00 and nuts	Same parts
Front hanger plates	50310/50320-MC5-000	Change to 50310/50320-ME2-000
Front hanger bolts	12 × 225 mm 90111-MA1-000, two 10 × 40 mm 95800-10040-00	Reuse mine
Final drive	41300-MC5-000, 3 nuts	Keep mine

Sources for that table: Honda’s CX400EC/CX500EC Parts Catalogue 1982 (frame groups F-29 and F-30), the CX650E Eurosport 1983 Parts List (frame group F-31 and the hanger page), and the torque tables in the CX400E/CX500E Sports 1982 Shop Manual (page 1-4) and the CX650E 1983 Shop Manual Addendum. I’m citing them, not reproducing them.

Why my own 500 plates won’t do

Honda gave the 650E a different bracket even though every bolt into the frame stayed the same. The forum adds that the 650’s top studs sit too far out for the 500 plates, and that the 650’s water pipe passes through the hanger.

A German seller lists a “650 into 500 frame” hanger-plus-adapter kit. It isn’t a Honda part, and nothing shows it suits the Pro-Link E frame, so the genuine ME2 pair is the documented route.

Still to check, on the bike

1. Offer the ME2 brackets up to the frame’s front lugs: the 12 × 225 bolt line and both 10 × 40 holes must line up.
2. The ME2 brackets against the 650 engine’s front studs.
3. Which lugs the two 10 × 70 bolts actually use. Honda’s frame drawing and the shop-manual photo disagree.
4. The 650 radiator’s three mounts against my frame tabs.
5. The 650 water-pump cover, which sits about 12 mm further back, against the U-joint boot, swingarm and Pro-Link.

The frame tubes and steering geometry aren’t identical either: the library has 25 mm vs 29 mm backbone tubes (the GL500 and GL650 figures) and 27° vs 28° rake (CX500E vs CX650E). Those are published specs, not my measurements.