Hi there, My new old engine (888SP3) is coming along nicely but I am running into problems I don't see a simple solution for. Hope some one can shine a light. I was anticipating I would run into tensioning problems because I did mill 1.2 mm from the base of the cylinders. That's why I bought a pair of golden fixed pullies which are supposed to be a bit bigger than the original one (SP3 engine). Unfortunately with these pullies I am still not able to tension the belts like they should (95 teeth). Don't want to use a thicker base gasket, squish is currently 0.95 mm. SP3 fixed pullies have a diameter of 39.5 mm, the gold coloured ones I bought are 40.5 mm. I also tried some 748 pullies which have an even larger diameter (42.05 mm), but that doesn't help either. Also tried to fit 93 teeth belts from a 748 low cam Ducati, but that's too tight. Does somebody know if there are 94 teeth belts available? Heard that the Exactfit belts might be a bit tighter? Does somebody know about this? Any other ideas other than longer conrods and/or pistons? TIA, Jacco
Don't understand your problem, exactly and not really familiar with the bike. You have adjusters to adjust the tension in order to correctly set it. Are you saying that the mods you have made render this impossible? Normally, you can go from sh1t loss to too tight, just on the adjuster. Shaving off 2 mm on the base wouldn't stop you being able to get the correct tension. Not on my bikes , anyway!
I think it's probably down to the different type of adjusters and the amount of range they give. On the desmoquattros it's an eccentric, whereas the 2Vs and ST3 use a sliding pivot arrangement. As regards belts you probably need to contact a few manufacturers to compare specifications. Dayco, Gates, Flennor and Contitech.
True, On the desmoquattro there's just a limited range of adjustment. Because of the mods I did I anticipated that I would need a larger fixed pully to compensate for the 1.2 mm that was milled from the base of the cylinder. But it turned out that it is still out of range. Probably because of the different crankcase (S4) that was installed combined with the carrillo conrods. I understand that the ExactFit belts fit a bit tighter, that will help a little but might not be enough. So alternative belts with 94T could be the way to go if I can find them. Does anybody know what the specs should be? I know 17 mm wide but there are different shapes of teeth (rounded, squared) and what pitch size. There's probably some code for these spec belts?
One of the Gates references is 5192XS. There may be more.. According to one seller on EBay (in Amsterdam) the standard 95 tooth belt has the following specifications: Width 17mm Length 905mm Pitch 9.525mm
Thanks all! Decided to go the ExactFit route. Already ordered them through exactuk.com. They seem to give a bit tighter fitting, fingers crossed!
You haven't mentioned setting the valve timing, which will be 'wrong' because of your 1.2mm skim. Just sayin'
True, need to redo the cam timing. But first things first, without properly tensioned belts I can't time the cams. Already needed to set the cams since I've got 748R head and cams fitted, not the SP3 ones.
Hmm, got the exact fit timing belts but still can't get the belts properly tensioned. I feel I need to bite the bullet and raise the cylinder / replace the cylinder, but that would also mean replace the piston since I want the quish and CR to meet certain specs. Cases are S4 monster cases. Can somebody tell me up front if these cases are suited to fit 96 mm bore cylinders or do the cases need to be machined to get these cylinders to fit? Don't want to split the cases to have them machined, too much of a setback. Otherwise I need to raise the current 95mm cylinders with bigger base gaskets and buy non standard 95 mm pistons (pistal) which will cost me since I need to order those in batches of 4...
Not familiar with 888 engine but my 916 also had 1.2mm removed from the cylinder height: 1mm from the head and 0.2mm from the base, to both increase compression and get the squish to 1mm and I can get the tension with the gold idler pullies - though the teeth of the belts do sit close together at the pinch point but it's been like that for many years with no problems. Have used both Ducati and Exactfit belts BTW and both worked fine.
___________________________ I think my vertical cilinder/belt is exactly like yours (teeth close together but doable), but my problem is the horizontal one. Don't know why there's this difference. Can you tell me the diameter of that golden fixed pulley you have installed? I already use oversized pullies but I understand there are even bigger pullies than I currently have fitted. The OEM pulley is about 39.5 mm diameter, the oversized one I fitted is 40.5 mm.
Hi, I am too pleased with the service. Quick delivery just didn't happen. Not because of Stuart, he did send it very quickly, but because of this Brexit stuff it took almost 3 weeks before I could pick it up here in the Netherlands.
Not sure of the diameter, it's not accessible until I remove the covers/airbox etc. but they were standard Ducati parts from another model of Desmoquattro. I would think the same as yours? AFAIK the pullies are designated by colour: black, silver, gold - my originals were black. Front cylinder has the same clearance as the rear on mine.
Have a read up on this thread... https://www.ducatiforum.co.uk/threads/748-853-build.67837/page-3#post-1319348
______________________________ Sev, Kept the cam wheels the same size, just fitted a bigger idler pulley so no problems with teeth being increased in size I guess. If I did understand what you were writing. Bigger idler pulley didn't bring me enough on the horizontal cilinder. Didn't skim the heads but the base of the cilinder. That was because I machined 1.3 mm from the deck of the pistons, since I wanted to reduce the depth of the valve pockets. These do cost compression and don't need to be this deep since I fitted more modern cams (748R). The deeper pockets are needed for the older cams, like the g cams, which open earlier and have a bigger duration. So with a squish of 0.8 mm this will give me a CR of about 12.2 : 1 (95 mm JE pistons). I was turning the tensioner anti clock wise. My engine was at a friend place who also tried even bigger idler pullies (42 mm diam) but that too didn't solve things. Guess I will borrow these to see for my self, just to be sure. He doens know a few things though, can't imagine he got it wrong.
