Into the fourth week of Ducati ownership and after treating the machine to an oil, filter, air filter and spark plug change, went for a 20km jaunt around my neighbourhood. By the time I was heading back down our street, the motor was getting decidedly lumpy and grumpy at anything below 3k RPM. Pulled the plugs and they were as black as the proverbial really black thing... Hmm - more than a bit rich. So - off with the carbs - easier said than done, but after removing fuel tank, fairing, battery, battery box and air box I had them sitting on my bench. Disassembled one and saw that the PO had, as advised, fitted a carby kit before sale, but apparently the kit didn't include new o-rings for the float and main jet. The o-ring for the main jet appears particularly hard and flattened, resulting in a rather loose fit in its bore, and I am of the opinion that at least some of the richness encountered is due to fuel bypassing this o-ring. (see pics) I've had a good search on here and with Google but have not been able to find a source for these. Can anyone help with this? Thanks in anticipation...
Allens carbs in the UK should be able to sort you out but a bit of a pain for Ozz? Wish I could help with the diameters as they are only standard fuel impervious O-rings. Similar carbs are fitted to many Japanese machines Yamaha in particular and I've seen kits for these including those O-rings
As Chris said........Allens Performance in the UK should have what you need........but depending on what the Yamaha models are called in Oz, the XTZ 750 and the TDM 850 should be the same carbs. I can't be sure but I think I also spotted that you don't have a Dynojet kit fitted to the carbs (the main needle in the top pic seems to be OEM).
Thanks to both of you. I'll try the Yamaha shops. BTW tell me more about the Dynojet kit - see it mentioned a bit, but assumed it accompanies some mods...
Dynojet.........Improves performance. It comes with thinner / more tapered main needles and lighter throttle slide springs, plus increased size main jets..... There are three DJ Stage kits. St 1.......Basically for standard airbox and zorts. St 2.......For an opened up airbox top and free-er breathing zorsts. St 3.......Not that common, largely for full race bikes. The OEM Mikuni parts will have a little square logo near the size figure. PS......I'm not entirely sure about the Yamaha models that have the BDST38 Mikunis (particularly in OZ) so check your old O rings and seals against what the dealers may have.
Check the plastic choke plungers for wear also. It caused rich running on my old 900. TRX850 also used the same carbs.
Rob, Couple of posts on here. Mikuni service kit | Ducati Forum Carby Strip Down | Ducati Forum Cheers Gaz
As it turns out, I only had to walk 50m to my next-door-but-one neighbour to source some o-rings. He restores old Suzuki motocrossers and Weber carburettors and has a stock of Viton o-rings that would choke a small horse. Found the correct size rings, now just need to set float levels (starting with 14mm - they look to be ~13mm now), assemble and install carbs. Al - I've read your diatribe about adjusting mixture screws on the bike - any progress since then? mcr998 - checked the emulsion tubes and they are very round... Al - I'll see how it goes with the standard set-up before going to the Dynojets.
I wouldn't adjust the float levels if I were you........At some stage they must have been about right as you have them set at the moment. The 14mm is only a guide and in my opinion, it makes the fuel level too low.......The fuel level on these carbs forms part of the pilot circuit and adjusting it can p*ss up the low revs running quite badly.......and the lower the fuel level, the more you have to unscrew the pilot screws, probably until they are too loose for the spring to keep them set. ....when I first insected mine, one was 12mm and the other about 9mm..........It ran OK then, but setting them both at 14 and then 13 wasn't good......they are now both 12.5 and I reckon 12mm would be better. Pilot screw setting on the OEM set-up should be approx 2.5 turns out, if I recall correctly.
