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Cracked Engine Case; older Ducatis not rated for Pillioning=> Suspension Upgrade


It is a journey I have just been on. Short story, all ST's and undoubtedly a lot of other Ducatis, are not rated adequately for pillioning with anything more than a pair of jockeys on board. The long story is told here, but putting a condensed version up for reference. The problem happens, A LOT - eg: Although nothing newer than 10 year old (unless "operator error" in the mix) so presumably Ducati fixed the casting & design issues behind the problem.

ST ratings are all the same, from 2000 ST2 up to 2007 ST3 anyway as I have collected all the owners manuals (where you find this info) over the years. ALL say 420kg max total combined and say luggage cannot be more than 23kg of that, which leaves 397kg for bike plus rider. A 2000 ST2 therefore, at 212kg dry, so let's assume 237kg wet (20l fuel, 5l oil), leaves 160kg for humans, or up to 183kg more if no luggage. Wow eh, and the ST4 / ST4S are 3kg heavier. No wonder I broke my case as I was 180kg peeps AND bunging on an easy 30kg luggage!

The minimum you need to do if you are a pair of "decent sized" folk is replace the rear spring with one a bit stiffer, and it is sensible to do this at the front as well. Oh, and check you still have a bump stop rubber in the bottom of the rear shock, plus that no cracks have started already at either front or rear bolts. A chat to Shock Treatment and they will soon sort out what works for you; I did the full service upgrade and preliminary riding says it was worth the cost / effort of a trip to Wallacia. Sending them bits in the post works well, but so does riding down for the day and letting them work their magic as you will leave with a properly set up bike.

So why did this happen? As it turns out, if you are overloaded and hit a decent bump mid-corner, the rear suspension "goes solid" and that breaks the case, just like a nut-cracker principle. The bike just goes "a bit springier" initially, and I didn't notice that - next thing is to hit another bump and goodbye to the back wheel (totally bolted to the engine, if you hadn't noticed), as it would swing up and twist, so put you in an instant corner not of your choosing. Lucky eh, but the evidence is I did 100-200km on this crack and I know some of that was some pretty bumpy twisty stuff, so a lucky escape.

I have posted a few pics of "the journey" below, note the "too tight to buy head gaskets" approach Lee Wright originally mentioned. This system of putting the cable ties on then tieing them together keeps everything tensioned, but be careful not to screw the bolts you add for the cable ties in too far so as to interfere with the threaded portion of the head studs or you will have a devil of a time before you figure it out. Don't ask me how I know....

Note the reason the alternator is sitting in the frame is because maintenance 101 on these ST's is to fully solder your connections to the alternator and rectifier. Absolutely a when not if question about this stopping you when you least want it to. The connections are grossly under-designed and you MUST solder them up (ie cut out the connections and solder the wires directly) . Same deal with starter cables - go buy expensive well made ones if you like, but the Ducati ones are good too if you just run cleaning acid in then solder the terminals on properly. It helps to go to the extra trouble to make a bracket to mount the rectifier behind a lower fairing opening, so it is still cooled properly but not trapped in the headlight if soldered up, so working on the bike is not a problem, whatever is going on.

Note on disassembly there is ONE bolt under the clutch housing assembly, so the right side case has to come off to get at it so can split the cases.

I got the repaired case half back and, after a bit of agonising over it, went back to get more done. The initial repair was beautiful, but I would say only about 60% - 70% of the original strength. Mostly because the bottom two mm of the fracture faces can't really be welded (as it just melts through and falls away) and the extra bit of thickness added to the top isn't really enough to compensate for that. Plus one failed section is inaccessible so it misses out entirely - more a loss of cross-sectional area issue to cope with serious overloads, than joint strength.

Whilst I am hoping the suspension work has removed the primary causative factor, plus adding an actual bumpstop to reduce impact of any overloads, I needed the case to not crack again, EVER. And didn't want to confront having to dive this far back in to fix something that an extra bit of time and cost now could have avoided. You can see the stiffening added.

After a 110km run out to Cessnock, my initial conclusion was the suspension upgrades made the bike "somehow easier". Going into 45's I know at $1.20 I am normally comfortable I have an easy GST to spare, but now it felt like an easy two GST's in reserve. I tried to identify what exactly I could feel / sense that was noticeably different, but couldn't really pick it - the basic sense was that the "this looks like trouble" point had moved out a ways from where it was before. But crikey the bike ran great, and wasn't that a load off my mind!!!


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