Rear Suspension System

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There are two different suspension systems used on the CX/GL models. The CX's use a pair of conventional shocks mounted externally to the swingarm. The GL's use a single air shock (Pro Link) that is mounted internally behind the airbox that uses a parallelogram linkage arrangement to provide the suspension for the rear wheel. We will look at both types, and share a article on refurbishing the "Pro Link" rear suspension on the GL models.

CX Model Shocks:

The CX models use a pair of 12-1/2" long pair of shocks with a four position preload adjuster and an external spring. To my knowledge, these cannot be rebuilt, but can be disassembled for more effective cleaning. The preload is adjusted by the special wrench that was supplied by Honda, but is now missing. A pair of Channel Lock pliers with padded jaws will works as well. Just turn the lower sleeve with the ramps to a higher or lower ramp for different levels of preload.

To disassemble this shock for cleaning, first place the lower eye firmly in a vise with the shock vertical. The next step is much easier with a helper. Making sure that the preload is set to the weakest position, pull down on the upper cover, exposing the lock nut below the top eyelet. Using a open end wrench, slip it over the lock nut. Then with a long, sturdy screwdriver in the top eyelet, and holding the wrench, unscrew the eyelet. You don't have to hold the cover down once the wrench has been inserted. There will be a slight bump when the threads come apart, but nothing to the extent of parts flying. Now you can remove all the parts for much easier cleaning and polishing. Reassembling is not difficult, just reverse the removal.

A number of members have used a different length pair of shocks to reduce the seat height or otherwise lower the rear for styling effects. Caution must be observed that you still have adequate space between the tire and the inner fender when using these shorter shocks. A 1" shorter model from Harley doesn't seem to be a problem for medium weight riders.

GL Model Shocks:

    • The Pro Link style monoshock used on the GL series bikes have the shock mounted internally in front of the rear fender. The system works well, and only has two areas that cause concern. The first is the seal leaking on the shock allowing air pressure to bleed off. This will cause handling problems and needs correcting as soon as possible. Luckily, this is not a common problem. The seal is not available from Honda, but the CX/GL forum details several members finding and using a aftermarket seal.

Item: 91257-MA2-003

    • The other issue is squeaking of the suspension. This is very common after 30 years and while not usually life threatening still needs to be corrected. The areas that this suspension lives in is one of the wettest, dirtiest, and hardest to get to on the bike. Lubing requires that the Pro Link be removed from the bike in order to access the various bushings and sleeves. This is a full afternoon job, as most bolts and nuts are large, and invariably rusted and dirty. Patience and lots of rust buster is the key. The best way to assure future lubing of this systems is to add Zerk fittings to the bushings of the suspension.
    • The following article explains how to do this. Thanks to Ofapar for the following description of installing Zerk fittings:
    • Here's a seperate page for the adding grease zerks to the ProLink. ProLink


Installing grease fittings to the Prolink. The Prolink on the Honda CX/GL V-twins are prone to seizing if they are not stripped and cleaned regularly; factor in twenty-plus years, multiple owners and the neglected Prolink can end up in a sorry state! If you hear that dreaded squeak as you sit on the bike you know some spannering time is overdue... The removal procedure of the various parts can be time-consuming and can test your mechanical skills to the extreme if they have been allowed to deteriorate. Expect seized bolts, inaccessible fixings, rust, previous bodges, seized bearings/bushes, seized other stuff and some other bits that have also seized to previous seizures.... Get the picture? This is how i have fitted grease nipples to my linkages to help with the problem, but i still advise a thorough strip-down every so often.It`s a pleasure to remove a Prolink and take it apart after it`s been properly serviced and everything comes apart as it should! The pics/text here may give you an idea of what to expect if you decide to do it yourself. The bolt that goes through the pivot that is nearest the centre stand mounting lugs is the one most likely to give problems, and it`s removal is hindered by the exhaust preventing the extraction of the through-bolt. A CX with an original collector box means half the exhaust system has to come off, and it`s the same with some other aftermarket pipes too. The nut end of the bolt (nearside) is inaccessible because of the side stand bracket, which prevents easy access for tackling a seized bolt with a drift and hammer. If this bolt is seriously stuck the best way to see what you are doing with this one is with the chassis upside down, with everything stripped off the frame. Of course, this might be a bit drastic if all you are planning to do is service the linkages, but in my example pic near the bottom of the page where the bolt was stuck fast, it was lucky that i was in the middle of a frame-up rebuild (i had to strip it right down to fix some tin-worm in the hollow sections of the frame) , which made it all lot easier. . It`a bit extreme to go this far just to remove one bolt, but if you are doing a frame-up resto job its a good place to start. I had to cut the bolt out on the one in the pic.. If the bolts come out easily and the linkage can be removed from the bike thats the biggest hurdle over - getting the thing on the workbench where you can see what`s what makes things a LOT easier. Honda supply a high-content moly paste especially for lubricating the Prolink. This isn't suitable for applying with a grease gun so a conventional strip-down is the best way to apply it. I reckon giving the linkage a squirt of `ordinary`grease every few thousand miles via the grease fittings should keep the Prolink in a serviceable condition. It`s done OK on my bikes. Applying grease to the collars and bushings before installing them into the linkage pivots always seems to wipe off the vast majority of the grease leaving very little on the bearing surfaces - the oil seals don`t help with this. The grease fittings at least ensure that some lube is placed where it`s needed. Having just done three grease-nipple installations in the past few months on various project bikes i thought i`d take some pics this time to show the procedure. It`s a straightforward job,but you have to place the fittings in a position on the linkage that will not be obscured by various parts of the frame/swingarm and so that a grease-gun can easily be used. You may find that the linkage bolts have seized,did i mention that...? The joints consist of the bearing `tube` (Honda call them `collars`), a phosphor-bronze bush interference-fitted into the linkage arms,a dust-seal either side of the joint and the nut/bolt. I have noticed that Honda seem to have used various designs during production in the swingarm-to-linkage-arm pivots,with one-piece bronze bushes(the ones with the grease-holding diamond-shaped voids) and two-piece bushes that appear to be made from plastic/nylon (I've seen this in a GL linkage, so it may be for that model only or a Honda design improvement) and another version similar to the plastic type but made from a sintered material.The two long pivots usually have the bronze type,but two in each joint for the extra width. The linkages live in a harsh environment underneath the swingarm in the full force of the weather and road grime - out of sight, out of mind, until a problem comes up (usually at MOT time when excessive movement at the rear wheel is discovered!). Do yourself a favour - service that sucker while you're in the mood, not after MOT disappointment! Here`s a new bush and bearing, and my GL having a squirt of grease; Photobucket Photobucket View of a typical Prolink pivot showing the nut & bolt, dust caps, bearing, and bush; Resized to 65% (was 814 x 615) - Click image to enlarge prolink.jpg

Here`s a pic of two different types of bushing, plastic/nylon on the left. The third version i have seen is similar to the left one but made from a sintered metallic material;

The Prolink has rising rate/progressive suspension set-up which means a lot of movement at the wheel equals a moderate compression of the shock absorber (i think the total shock travel is only about 45mm or so). This is great system for improving a bikes handling and comfort but when wear takes place it works the other way - a little bit of wear in the pivots means a lot of unwanted suspension `slop` at the other end. This seems especially true of the top shock mount, which is another hidden/difficult to access pivot that is often forgotten about. To check overall play in the linkage try standing at the rear of the bike leaning over the tail/seat (bike on centrestand), reach down either side and grab the wheel rim with both hands. If there`s any freeplay you`ll feel it move up and down before the resistance of the shock is felt. To see where the wear is coming from will mean getting on the floor and feeling/watching the linkage while moving the wheel up and down with some kind of suitable lever (tyre iron/breaker bar/jemmy/crowbar) placed under the tyre, or get your wife/girlfried to do the wheel-lifting thing while you look for the movement in the linkages!! To check the condition of the top shock bush jam a finger between the shocks body and the frame bracket while operating the lever. Having noticed exessive freeplay in the rear suspension of the CX-P (the lengthened swingarm will exagerate any wear) i traced the play to be in the top shock mount. After stripping it out the collar showed wear of about 2.5 `thou compared to the new one and the bush looked fine, but there was freepaly at the wheel of about 20mm. A new bush`n`collar completely eliminated all play, which was good!;

Photobucket Photobucket Photobucket

Here`s an overall pic of the finished grease job;


And new bearing with clean grease;

The part of the Prolink that goes from the frame to the linkage `fork` only requires one grease nipple installed. The wall thickness here where the nipple is installed is relatively thin, so either place a washer under your grease nipple fitting or do not screw it fully in otherwise it may foul the bearing - they are made with a tapered screw-thread anyway so a good,firm fit will still be made. The nipple needs to be angled rearward to clear the frame and enable your grease-gun to locate easily. The red line in the pic indicates the angle at which the fitting is to be placed.


The L/H fork-to-swingarm pivot is slightly obscured by the extra-long swingarm bracket, so the grease fitting needs to be angled back - the red line in the pic indicates the postion.

On this side the nipple has to be located on the radius of the casting, so to facillitate the installation i ground a small flat on the linkage fork - you can see this clearly on the first pic above.


The R/H side has better access - the fitting can go in at 90 degrees;


The bottom pivot is easy to get to,fit the grease nipple at approx 45 degrees. Note:the shock absorber mount (at the top in this pic) is the resiliant-bonded rubber type and does not need any modification.


These pics show the bronze type bushes which were seized to the bearing and came out with it during dissasembly, they usually stay in place.. The other pic shows worn versus new bearing `tubes`.

Fit some caps to the grease nipples to protect from road dirt and corrosion.(or improvise some from 10mm or so of suitable plastic tube the end of which is plugged with glue. Replace the dust seals if necessary. Grease the bolts when assembling to prevent them seizing- the grease from the nipples will not get to this area. When drilling into the linkage parts remove the burrs from inside of the pivot bushes with a small needle file. Don`t forget to service the top shock absorber mount - this one is often forgotten about but a small amount of play here = a lot of play at the wheel. This is what you`re trying to avoid!; Photobucket

Another project,another Prolink problem...

I have removed the linkage from the CX-periment (all the bolts came out easily....) but the bearings were in a bit of a state and one was seized in place.No surpises there then. The method i used to remove this seized bearing was to get the arc welder out. I welded up the centre of the bearing tube - this did two things; it put some heat right at the point of the problem (applying heat is always one of the first things to try when removing stuborn fixings or parts) and provided a good solid point onto which i could use a parrellel punch to knock the bearing out. If force is applied to the end of the bearing directly it can deform/bend over making it even tighter in the linkage arm/bush and more likely to bind when driven outand damage the bushes. Of course this renders the bearing scrap but if it has seized to this degree it is unlikely to be usuable anyway.

After the linkage had been cleaned up i pressed the bushes back into the arm in the vice - a Euro grab-rail bobbin made an ideal tool for this job;

For more information see

Pro-Link Shock Rebuild

(Sidecar Bob)

I re-built the shock on my GL500 many years ago and wrote this up because I found the FSM's instructions confusing. When I did a shock for my CX650E based sidecar machine a few years ago I found that everything was exactly the same except that I had to re-use the original seals because they were NLA now.

- You need to start by disassembling the shock and cleaning it all out. Over 30 years, a lot of moisture can get past the seal and combine with the fluid - use a solvent like mineral spirits and make sure you don't leave any lint behind. When I drained mine, I clamped it in a vise, hose end down, removed the valve, and let the air force the old fluid out. In retrospect, this may have been a mistake. I also replaced the seal. The manual says to remove the seal by filling the shock completely with fluid (same method as below), replacing the valve, and pressing the shock so the fluid pushes the seal out (don't forget the retaining ring). I removed the seal by a slightly more dangerous method - put a plastic bag over the seal end of the shock, put it in a strong cardboard box, and apply air pressure until it goes pop!

When it is all put back together again, you need to put in fresh fluid. According to the Honda GL500 manual , the Rear shock capacity is 669cc (you will need at least 1L - see below) BUT it would appear from the method Honda recommends that the actual amount of fluid in the shock is less important than the amount of space left for the air.

Method for filling (these are my words, the manual is not very clear) (assumes shock is empty):

1) Place shock in press with hose end up (FSM says hydraulic press with adaptors, I did it on an arbor press at work, no adaptors were needed).

2) Place end of hose (valve removed) in a container of fresh fluid (ATF or fork oil)(I use a 50/50 mix of motor oil and ATF), compress shock (do not overcompress - 45mm max.) and release so that fluid is drawn into the shock. Repeat until shock is completely full (no more air bubbles).

3) Press the shock and measure the amount of fluid that is removed. When you have removed 200cc, replace the valve and re-pressurize the shock.

Tip: baby food jars (the ones from juice, with calibrations on the side so Mommy can tell how much the little monster has consumed) are great for measuring how much oil you have removed from the shock (also for measuring how much oil you are putting into your forks and many other uses around the shop), and can usually be obtained free, in quantity, from anyone with an infant. Or just buy a measuring cup at the $1 store.

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