A Minor Suspension Eureka

[panteradave]

Long story......

I've been gradually working through the suspension of my '82 Prolink over the last year or so. This is a very original, low mileage bike but one with some subtile handling issues - mainly a mild but annoying wobble when banking though high speed corners. To start, nine or ten months ago I rebuilt the front forks out of necessity, replacing the leaking rubber seals (which took the front brake pads with them by drowning them in fork oil) and I also flushed the brown goop that once upon a time had been fork oil (refilled with 10w, 6 inches from the top). While that rebuild improved the feel of front end of the bike dramatically, the high speed wobble was still present. Then, last month I opened up the triple clamps and greased and detorqued the steering stem nut, which eliminated a minor low-speed, hands-off the bars wiggle. The high speed wobble was still there.

To digress slightly, I've always prefered the cleaner look of the Prolink fairing minus the bags and I'd recently found a small (20 litres), water proof tail bag that slips into place easily over the passenger seat. Yanking the hard bags and mounting brackets and installing the tail bag became my project for last Saturday afternoon. Sunday morning I took the now bagless CBX out for my semi-normal high-speed cruise though forested back roads northeast of Houston. I'm not a knee dragger by any means but I do tend to push the bike a fair amount. To my surprise, the high speed wobble had virtually disappeared. The CBX is now much more comfortable (almost planted) zipping through the same 80-85 mph sweepers. It's practically confidence inspiring.

This is a most welcome outcome but also surprising and somewhat puzzling. None of the suspension settings on the bike were changed from the previous wobble times. For spirited riding, I generally run the front forks with about 7psi and the rear shock with about 50 psi and the shock adjuster out to maximum stiffness. The tires are newish but nothing fancy Bridgestone Spitfires with 38 and 40 psi, front and rear. I'd experimented with various pressures for the front and rear shocks and while higher pressure seemed to help somewhat, the wobble was always still there. ????

At any rate I can only guess a couple of things that might somehow be responsible for handling improvement: 1) maybe there is some weird turbulence generated by the bags that makes the rear of the bike wave around slightly at speed or 2) the combination of bags and brackets throws the back of the bike over some weight threshold (even though the bags and brackets aren't really all that heavy) that the monoshock (and/or linkage) suddenly can't handle. Both seem like a reach so basically I'm stumped.

So I'll throw it open to comment. I'm very curious how this might have happened. Any and all ideas are welcome.

Dave

[daves79x]

Dave:

Guys usually notice a difference without the bags and brackets - glad to hear yours was pretty dramatic. Only thing I can offer if you must stick to the stock shock is to put about 70lbs of air in it. I know, Honda's max on the sticker is 58, but back in the day, guys routinely ran 80 or more with no issues. Not saying a 30 year old shock will stand what they did back then, but they weren't much good even new. A Progressive unit or other aftermarket shock will transform the bike.

Dave

[panteradave]

I've been considering a couple of additional suspension changes to my Prolink.

The RaceTec cartridge/spring setup for the front forks seem to have gotten universally good reviews from CBX owners. I'll probably go that way once my budget catches up to my ideas. Also a heavy duty fork brace (such as the one Randakk sells) might also help stiffen the front a bit, though my sense is that the larger Prolink forks probably benefit less than earlier CBXs from a fork brace.

The recent improved handling after removing the hardbags suggests the rear monoshock/linkage is perhaps the bigger problem. I've heard several times from experienced CBX owners that a Progressive shock can make a big difference on a Prolink bike. I'm not a big fan of the variable spring rates that would come with a Progressive shock, however, I guess I'm still open to it. Are there other aftermarket monoshocks available for Prolinks with a linear spring rate, adjustable preload, and a nitrogen canister - or is that just an expensive custom build?

A second option for the rear (one that I've strongly considered) would be to have the stock Prolink shock rebuilt by someone like Mike Nixon, with a shimmed spring to increase the preload (less air pressure required) and fresh, heavier weight oil filled to a higher level. I've really grown to like the hydraulic push button that allows instantaneous changes in compression/rebound on Prolinks. Or the flip side, are the Honda monoshocks just not worth messing with?

Last, is there a benefit to be had in rebuilding the rear monoshock linkage by replacing the stock bushings (6, plastic??) with brass or needle bearings?

Where do diminishing returns kick in? This CBX is never going to be a race bike. I don't want to spend a fortune chasing my tail, but within reason I would like the CBX to be 'all it can be' handling wise from a high performace street bike perspective.

Any comments/advice to my rambling thoughts would be greatly appreciated....


Dave