Or just some mongrel with a torch bringing more work?
Dragging the ol' girl home post dyno tune took less than an hour, but the whole way I was chewing over the possible limitations like a cow chewing it's cud. As mentioned in the previous post I wasn't just disappointed by the lowish headline figure, I was also confused by the torque peak at a lowly 7000rpm. The things that were rattling around in my head were:
- the Pipercross "sock" type air filter that envelopes both intake trumpets. It was an easy solution with good for filtration, but was it hurting performance?
- The crappy OEM 851 inlet trumpets, with only a barely there inlet radius
- The "new and not so improved" exhaust
- Cam timing
The torque peak at such low rpm had me thinking cam timing would be a good place to start. Now for some reason I had it in my head that the 748R, like the 749R, had adjustable cam pulleys as OEM fitment, so I could have kicked myself when I removed the belt covers only to see they are fixed. If the cam timing was out I might as well have just burnt the dyno dosh in a giant spliff: IDJIT!
That's all in the past, how do we check/fix it in the here and now? It's extremely difficult to measure the top dead centre position of the piston with a one off measurement. Due to the time the piston spends at or very close to TDC it makes it almost impossible to pinpoint the exact moment the piston is at full travel. So we use a piston stop, rotating the crank one way to to the stop, then the other way to the stop, with a degree wheel mounted on the end of the crank showing each relative position: halve the degrees between the two and you have an accurate position for TDC.
We face the same difficulty measuring cam/valve lift. Using my 748R cams as an example, those figures of 110/102 (inlet cam centreline is at 110deg ATDC, exhaust cam centreline is at 102deg BTDC) are really only theoretical points which aren't much use to us. Instead, we use an arbitrary 1.0mm lift point as a datum, simply for ease. We then just compare the position of that datum against the degrees of crank rotation. There's a little more to it removing or allowing for valve clearance etc but that's the guts of it.
Being polite here, Ducati can be a little.....loose....with their cam timing, and some handy gains have been seen simply resetting the cams to the OEM spec. But how does all this affect my ol' girl? Advancing or retarding the cams, max lift earlier or later in the cycle, can be used to tailor where we want the grunt. Bottom line? Retarding the inlet cam should push the torque further up the rev range.
So I made a lil' bracket for my DTI, and bent up a wire extension to sit down against the valve shim to measure valve movement:
Which at first glance looks perfectly adequate, who needs those fancy schmancy factory tools, eh?! Ok, now imagine it on the vertical cylinder exhaust cam....where will the face be pointing? Not so adequate now ya numpty, jammed up against the shock rocker/subframe/breather tank etc and completely unreadable...bugger. But unbolt the mufflers, unplug the P8 ecu, pivot the subframe, remove the breather tank and I could finally get a mirror in there to get the job done.
Bottom line? The vert inlet cam was 8deg out from the ever-helpful Brad Black's suggested cam timing of 104/108. I didn't even bother checking the rest, obviously I needed the adjustable pulleys I didn't have.
The desmoquattro heads use 18 tooth pulleys where the testastretta use 20 tooth. Finding an adjustable 18T set is easy enough.....finding an affordable set? Not so much. The dead sexy aftermarket alloy/ergal sets had me licking my lips like Sylvester checkin’ out Tweety Bird, but also had my wallet looking desperately for somewhere to hide. Leading up to the financial ground zero of Christmas I made do with OEM steel, available on some 2V engines, so I just bought 2 x 2V sets. Combined, the steel pulleys were half the price of the alloy sets, but the later 20 tooth pulleys are far cheaper again, parking meter money, simply because they are so plentiful. Supply and demand sucks!
FYI, the 748R (as per the heads I was using) employs wider "RS-style" pulleys and belts, to cater for big revs in competition. Trying to find the equivalent adjustable version would be nigh on impossible, but I'm not going to rev the thing to 13000rpm and/rebuild it every other weekend, so I was comfortable enough to revert to "common or garden variety" pulleys/belts with a more modest redline.
Another reason we “enjoyed” instant noodles for Christmas dinner? I got a call from Justin at Pro Twin: he had repaired the damaged 749R crank/rods!
As you can imagine I was off like a bride's nightie to collect them, and I could have kissed him when he placed the rebuilt crank/rods assembly in my trembling hands. The bill dampened my rampant affection somewhat but given the alternative was throwing the crank/rods in the bin I was still more than happy to hand over my credit card.
Rather than handing over a collection of expensive titanium and forged steel bits and pieces he had actually assembled the components and he made it clear, "Don't check it, it's good to go, just bolt it in", and given the limited torque cycles (throw away after 3 torques) of the crazy expensive Ti rod bolts I wasn't about to pull anything apart. I'll never forget the sensation of rotating the rods on the crank: silky smooth, with just the slightest hint of well-oiled resistance. It wasn't an attractive thing to look at but it was a sublime thing to feel, hard to believe given the almost-junk I had handed over.
I have no idea of Justin's age but he looked like a naughty 10 year old when I asked him how he'd done it, going decidedly coy while suddenly finding his shoes intensely interesting, just mumbling something about a Sauron-brew of custom crank grinding/polishing and Suzuki bearings. Fair enough too, his skills and knowledge are hard earned so why would/should he give them away?
So, while waiting for the cam pulleys to arrive I turned the pile of 749R bits into an engine again:
Shown above with RS "Corse" rocker covers (the cast-in logo is on the title page of this blog) fitted as dust covers, the magnesium R covers are on the RS engine in the bike. Strangely, although I'm sure there is some method to their madness, the cutting edge RS uses old-school separate frame mounted ignition coils and HT leads, where the 749R uses more modern integrated "stick" type coils. The stick coils don't really fit the RS covers, hence the swap (see below).
749R/999R type magnesium rocker cover, note that both front and rear are identical:
The RS/Corse rear cover bolts as above but the front (shown below) has only 4 mounting bolts arranged slightly differently, meaning you have to do a bit of juggling with the mounting posts when swapping between R and RS. Note the difference in spark plug ports:
Holy quacamole, that's the 749R engine ready to rumble...now what?
Bearing in mind our only full size track is still closed to bikes and I haven’t raced in years. Logic has never been my forte but all things considered the lil’ 749R seemed like an all-around smarter/easier way to get back into it, so reluctantly out came the big daddy 999RS and in went the wee fella.
