How I'll convert my '79 Honda CX500 Custom into a trike . . .

Honda CX500 Custom Q Q Q Q A stock Honda CX500-C motorcycle Q

According to the service manuals:
V-twin engine (4 pushrod-operated valves per cylinder, 10:1 compression ratio)
50 horsepower, 32 foot pounds of torque
5-speed transmission with shaft drive
57.3" wheelbase, 452 lbs.
106 mph top speed.

CARCENTRIC CX500 Trike Q Q Q Q ROXINANTE* - Our CX500-C trike Q

The PaintShopPro sketch to the right shows how our trike will look when finished:
Wheelbase increased about a foot and the front lowered a couple of inches
CX500 swing arm and final drive replaced with a Triumph Spitfire rear suspension
and a Triumph GT6 differential
Late-'60s VW Beetle rear fenders trimmed to fit

Picasso's Rocinante Л----ЛЛЛ art for top of tank courtesy of Picasso
* Rocinante was Don Quixote's faithful steed - the "x" in Roxinante is from the CX500.

SPECIFICATIONS	TIRES					FINAL DRIVE		OVERALL
	tire W	tire AR	wheel D	tire D	tire D	ring/pinion	r/p D	DIFFERENCE	axle H

CX500-C FRONT	3.50"	90	19	25.30"

CX500-C REAR	130mm	90	16	25.21"		3.09:1
Roxinante REAR	205mm	70	15	26.30"	+4.3%	3.27:1	-5.5%	1.4% lower	up 0.54"
			circumference:	82.6"		(GT6)		v v v
CX500 Custom	Circumference	Revs/mile	Trident	Roxinante				v v v
(stock bike)	79.2"	800	police trike	(trike)
		Speed D>	10.8% lower	1.4% lower	<<<	<<<		<<<
3567	rpm @ 40 mph in 5th		4000	3618
4458	rpm @ 50 mph in 5th		5000	4523
5350	rpm @ 60 mph in 5th		6000	5428
6242	rpm @ 70 mph in 5th		7000	6332
7133	rpm @ 80 mph in 5th		8000	7237

TRIKE CONVERSION DETAILS

REAR SUBFRAME MOUNTS. The subframe will be bolted to the CX500 frame at three pairs of points (see drawing to the right):
the top crosstube of the main frame member (C),
at the footpeg locator crosstube (E), and
where the bike's coil springs and shock absorbers were mounted (A).
Crosstubes (C and E) will have solid steel cylinders welded inside, and those cylinders will be drilled and tapped for Grade 8 mounting bolts.

REAR SUBFRAME MATERIALS. Front-to-rear tubes and the crossmember above the swaybar will be made from 1" x 2" square tubing (1/8" wall). Both the horizontal x-brace (X1) and the diagonal x-brace (X2) will use 1"square tubing (1/16" wall). The parcel shelf frame will use 3/4" square tubing (1/16" wall).

Color coding in the rear subframe drawing below:
Honda CX500 frame (only the rear section is shown)	VW SuperBeetle front swaybar used in the trike to locate rear uprights
Triumph Spitfire rear suspension and Triumph GT6 differential	Fabricated subframe, parcel shelf, and custom driveshaft

REAR SUSPENSION. Part of the frame from a 1980 Triumph Spitfire will be used (click here for a photo), along with its shocks, swing axles, suspension uprights, and transverse leaf spring (a leaf or two of which will be removed to soften the ride). Instead of the Spitfire's stock radius rods, however, the front swaybar from a VW Super Beetle will be substituted - it will provide the extra advantage of resisting outward lean during cornering. This lightweight setup has a rear track with stock wheels of only 50", so its width won't overwhelm the fairly small size of the CX500 donor bike.

REAR WHEELS. A rare pair of Compomotive FH1570 alloy wheels (15" x 7" with a 4-on-4.5" pcd and an offset of 10mm) will be mounted to the oddball 4-on-3.75" pcd Spitfire hubs via a pair of adapters machined from 6061-T aluminum.

REAR BRAKES. The CX500's rear brake pedal will actuate Spitfire stock rear drum brakes via a Spitfire single circuit master cylinder.

DIFFERENTIAL. A Triumph GT6 differential will be substituted (the two models share the same third member case and flange sizes) because its 3.27:1 ring/pinion ratio is better suited to the trike than the Spitfire differential's 3.89:1 ring/pinion ratio would be.

OVERALL GEARING. While the Triumph GT6's final drive ratio is a little more than 5% "shorter" than the CX500 bike's 3.09:1, the larger diameter of the rear tires compensates for most of that difference. The trike's overall gearing will be only 1%-2% lower than that of the CX500 bike because the 205/70R15 tires that will be used have a 26.3" overall diameter (4.3% taller than the CX500 bike's rear tire).

DRIVESHAFT (or propshaft, for those in the UK). Since the differential needs to be centered left-to-right and the output of the CX500 transmission is offset several inches to the right of center, the trike's driveshaft will have fairly large working angles - and those angles can lead to destructive vibration at highway speeds. Rather than throwing something together myself and hoping for the best, I intend to bring a CX500 driveshaft and a Spitfire driveshaft to a driveshaft speciality shop, supply the necessary dimensions, and pay them to provide me with a balanced, custom part ready for installation.