is there any reason to go for any of these air cooled engines over another? What options are there? Easier to fit? Cheaper to buy? More reliable?
Hmmmmmmm... not quite... A 2v motor will bolt into a 4v frame HOWEVER the bracing in-between the bottom tubes is different and would have to be modified. The bracing on the 4v (S4R in your case) frame will sit exactly where the 2v throttle bodies want to be. As Attila says, the ST2 and S4R frames are pretty much identical, the differences are mainly at the rear (there are other small differences like foot-peg and fairing mounts). If you're building a RAD-style bike then I'd imagine you'll be modding the rear of the frame anyway? In that case, if I were you I'd use the ST2 frame. One more thing to consider... most (maybe all?) 2v engines have 10mm engine bolts, most later 4v frames (ST and Monster) have 12mm, so you may have to either sleeve your frame or drill out your engine mounts, no big deal just something to be aware of. Having said that I have a very early ST4 frame with 10mm holes so you may be lucky. Hope this helps and looking forward to seeing some pictures! Darren
A picture paints a thousand words... The ST2 (and all other 2v variants of the ST and 2nd gen Monster) has a diagonal brace across the bottom tubes, a single brace across the top tubes and another diagonal from top to bottom. The ST4 (and all other 4v variants of the ST and 2nd gen Monster) has a single X-shaped brace that served the top and bottom tubes, no diagonal brace. This doesn't affect bolting the engine in but 2v throttle bodies foul the 4v bracing and vice-versa. It always annoys me when I see an ST2 frame on eBay with "will also fit ST4"... It just won't! Darren (Ignore the photo below, I mislabelled it as ST4 and now I can't seem to make it disappear!)
now i see it in a photo its pretty obvious isn't it :smile: as for an aircooled engine i reckon a 1000ds from a multistroodle would make for a nice lump, its long stroke so its nice and torquey and they could be picked up for a reasonable price. I'm not sure if the S4R swingarm is a straight fit though?
I have a multi 1000 SS swing arm for sale if your interested You would have to use your hub out of the S4R swinger though.
Cheers Phill, won't take you up on your offer at the moment but thanks anyway. Thanks to Atilla and Badgerface too. Basically I don't want to have to machine too much - basic skills, basic knowledge and basic tools is the reason for this. If I use the ST2 frame which air-cooled motor will bolt straight in and allow me to fit the S4R swingarm too? Will the whole swingarm and shock assemly go straight in or do I need some bespoke shock linkage? Anyone know of issues bolting an S4R front end straight in to the ST2 frame? I'll get some pictures up soon, the tear down is happening quickly. Cheers
oh yeah and i'll have loads of S4R bits for sale soon: Engine Exhaust system Frame Plastics & tank Basically everything except the suspension, swingarm, brakes and hoops Let me know if you're interested in anything
You can cut out the centre bracing then reweld it back in, in another place to accomodate your inlets.
Anything from an SS or aircooled Monster will fit for sure. The whole suspension set-up on the ST2 and S4R is the same apart from the swingarm, so the S4R swingarm, shock and linkage will bolt straight on to an ST2. One thing to consider is how you'll secure the swingarm pivot in the absence of the S4R footpegs, this has been discussed at length before. Here's something I mocked up a while back: ST4 frame, linkage and shock, S4R swingarm, 900SS motor. Notice that there's no inlet on the vertical cylinder because the frame-bracing is in the way. If I'd gone any further with this then (as I've already said) I'd have had to modify the frame bracing so the carbs/TBs would fit. If you use an ST2 frame then you won't have this problem. Never tried it but AFAIK the 2 bikes are almost identical at the headstock so I see no reason why not. Darren
Nice one Darren, Really appreciate your input on this. I know it must be frustrating for you guys going over all these questions again but being a total Ducati novice this advice is invaluable. So it sounds like I need to get a swingarm pivot mounting point welded on to the frame? I can get this done when the rear subframe area is being modded. I've spoken to John at Racefit about doing this but i'm not far along enough in the dry build to give him any real info. Apart from that most other bits will bolt straight in. I'm hoping to have the forks, swingarm, shock, brakes and wheels all bolted on to the frame in a week or so. Then I need to sell / swap all the remaining ST2 and S4R bits to raise some cash for an air cooled motor, gear box, loom etc. I wish I had bought a 900ss complete bike and just an ST2 frame but the ST2 was too cheap to pass up. hey-ho you live and learn. Does anyone have an air cooled motor, gearbox, loom they want to swap or sell for a running ST2 motor? Or I'll have some juicy S4R bits soon, running engine, frame etc
Not frustrating at all mate, happy to help however I can! No, the problem is that the swingarm pivot (the 'axle' that goes through the swingarm and engine that allows the swingarm to pivot) is held in place on the S4R by the footpegs. If you fit that swingarm to the ST2 frame there will be nothing stopping the pivot sliding out as you're riding along... bad times! You just need to come up with some way of stopping the pivot coming out, on other bikes (like your ST2) this is done with circlips.
Enjoying reading the thoughts here - I wish I was brave enough to embark on something similar - when I had the plastics off my ST4 for I saw the potential, but I lack the skills to build it. Anyhow, when you're looking for a donor do consider my bike Ducati ST4, excellent, v low miles - Ducati Forum Classifieds Low miles, plenty of bits to use, plenty bits to sell off, and its the classic 916 engine of course...
God knows why the pics are going in upside down and sideways!? That's not how they appear on my machine! Might try and drop in the s4r front end today, depends what the wife says! Oh yeah has anyone else ever gone to undo the main engine to frame bolts and found they are quite loose!? I suspect there is moreto the history of this bike than meets the eye but the i thought its an unloved v-twin that may rattles itself loose!? Any ideas? And finally, the horizontal cylinder exhaust flange nuts literally flake off in your hands, is this common?
