After my belt mishap last year, I finally got my ST4s back together and running. The bent exhaust valves on the horizontal cylinder were further compounded by the dreaded rocker wear problem and I had to change all four inlet closers. So, after what was essentially two heads rebuilt, a new gasket set, a complete clean up of pistons and combustion chambers, all new pulley bearings, new belts, new coolant, new battery and some general fettling, cleaning and dabs of paint, I have just got through the second tank of petrol since and found that she is averaging 17km/l in mixed mode of half urban half motorway, which isn't bad. I think I'll need to get the throttle bodies sync'ed, as there is a little bit of vibes at certain parts of the rev range, but the good thing is that at motorway speeds (and above on a closed road, professional rider, blah, blah, blah) there are no unexpected vibes so it feels like the big ends are OK. So, lessons have been learned and now I am fully confident to do the belts myself, and measure, if not set, the valve clearances. As of this month I have the bike five years and fully expect to keep it for another two, by which time it will be worth more in parts than as a runner! A
Nice to hear you're back on the road, and have obviously gained some valuable maintenance experience! Good luck, and fingers crossed that all your troubles are behind you!
Indeed, it was valuable learning experience. At this stage, the only bits I haven't had apart are the crank cases! Still, after a week riding it again, I realise why I persevere—the Desmoquatro is the nicest road bike engine I have ever ridden, and for my usage, the 4s is best package in which it is available.
I'm curious what happened the belts. Were they over the recommended time, or distance? I know the later Ducati belts, eg 749, MTS, etc are wider and thicker. My ST4s now has 59k miles and runs stronger than ever! Belts must be changed on time/distance on this engine due to the narrow belts and the contortions the run through. Pat
The belts were about 18 months old but what had happened was that in June I looked at the belts and realised they were a little loose. So I set the tension on them, but I turned the tensioner pulley clockwise instead of anti-clockwise. That tends to push the belt downward for some reason. So the belt run meant that the inner edge started chaffing and it began to fray to the point where the belt began to disintegrate a long its length. When I took the cover off, there was loads of fluff that had come from the belt fraying and about a 3mm wide strip had actually split and begun to flail about too. The weakened belt could no longer hold the tension and the exhaust cam hopped a tooth and that caused the bent valves.
Nah mate, no gods need apply. Though I did invoke some by name during the resurrection of sweet Isabella (ST4s)
