Please help me understand my suspension

First off, I have a manual and have read it, what I'm looking for is a better understanding between cause and effect. 1982 XJ750 Maxim 31K+ miles and stock components (I know...a complete rebuild/refurbish is in order and don't skimp...progressive all the way).
I hope I haven't sounded too arrogant...just don't want you to waste your time about what I should get...but rather please explain what I currently have.
Seems my rear shocks have 2 ways to be adjusted (a 4 position dial at the top and a "step" adjustment on the bottom)...what exactly do these two dials control? How do they work in relationship to each other? What is "preload"? As my bike is older is it better to compensate with higher/stiffer settings, or keep them as the manual suggests?
The front, similarly, has a dial adjustment (4 position) and an air pressure adjustment...I have a Windjammer full fairing...should this be compensated for? What is the relationship to higher air pressure and the dial control?
Lots of stuff...thanks in advance for any light you can shed for me, and anyone else interested.
Pat

Oh Yeah, I normally ride 1 up (200lbs), and I'm no daredevil...just cruising and occasionally some "spirited riding

 

Let's start with the rear shocks. The little numbered dial at the top is there to adjust "damping" but I'm not 100% sure if it's 'rebound" (probably) or compression damping that's being adjusted. Likely it doesn't adjust much any more, since at the mileage you're at the shocks are probably not doing much damping anymore. The "step" adjustment at the bottom is to increase or decrease spring preload.

"Preload" being the amount of compression a spring is being held in at rest. More preload effectively "stiffens" up the suspension.

As for the front, again I'm not sure which direction the little dial was trying to adjust (compression or rebound) but it's a "damping" adjustment.

Adding air is like adding a springier spring.

Hopefully some Windjammer-on-Maxim experienced owners will chime in with some tips on that aspect (I'm not a "windshield" kinda guy.)

 

On the rear, stepped adjustment on the bottom is the preload, top dial is a dampening adjustment. Dampening adjustment only works if there is oil in the shocks and the seals are in good order. Since they aren't rebuildable, most just replace them.

Pre-load sets the ride height, and what force the springs "start" to compress. Which means, if you put 200 lbs of pre-load, the springs don't compress until they "see" 200 lbs, and from there, the spring rate is the same as it would have been without preload.

Spring Rate is only adjusted by changing the springs. It refers to the amount of travel per unit load. Pre-Load DOES NOT change this.

For the front forks, the dial is the dampening adjustment, air adjustment is like adding another spring force, stiffening the spring rate. Preload is adjusted by adding spacers between the fork cap and inner spring. Dampening can also be adjusted by changing the fork weight oil.

I'm starting to get into suspension adjustment, and will likely play more when I get my current project on the road, but from what I understand, there are several short comings of our 80s suspension system:

No-independent adjustment of compression vs rebound dampening. The oil basically flows through the same orifices in both motions, so if you can set one, you give up on the other. I've read (and I'll be interested in trying soon) cartridge emulators can decouple the dampening in the forks, allowing you to fully adjust the compression dampening while adjusting the rebound dampening using different weight fork oil. In addition to that, there are a lot of cool ways to make the initial dampening forces plush, while preventing bottoming out. The 750 secas tried to accomplish this with anti-dive forks, but those have been phased out for a reason.

Again, the rear shocks aren't rebuildable, so there isn't much you can do with them (hence replacement). But I think the complaints are basically the same as to compression vs rebound dampening, and when the seals fail, you get no dampening.

Proper dampening severly affects handling and traction, so it really is important no matter what kind of riding you do.

 

How do you like that, 2 for 2! Two replies, two of the more "experienced" members!
Thanks....I feel smarter now.

 

Great Thread!

 

Just what i was looking for!

 

http://www.gostar-racing.com/informatio ... set-up.htm

 

I would start with your tires and make sure they are in good nick and properly inflated. I have found with too much pre-load in the rear it feels like the front is pushing in the turns and bouncing too much over rough spots, too little and the rear end feels like it's squishy and wants to oversteer (slide out). I keep adjusting my setup (in tiny increments) until it 'feels right'.

+1 to the dampening comment from ManBot, it keeps you tracking when things change too quickly.

Keep us posted on what you end up with and how it works. Good subject with these older bikes and the old tech with regards to suspension.