I was at Carl Harrison's (the Ducati Guru in the East) workshop today purely out of curiosity. I learned a few things which may be useful and I certainly am going to try out. 1) Belt tension - He reckons the 5mm Alllen key method leaves the belt too tight especially when the engine has got hot, because the cylinders expand so much........this can cause stress on the rollers and can cause them to shriek at certain revs......He says an 8mm key should be used instead. 2) The pilot screw or idle screw is not really either, but a metering screw........A lot of the time what we think is an engine out of balance or an engine is hard to balance; it is usually down to one of the screws needing half a turn more than the other......... 3) Fuel height - measuring the float above the gasket face isn't the right way to do it. The correct way is with the bike upright is to push a clear tube on the drain spigot and hold it upwards........then undo the drain screw so the tube can fill..........Carl says as long as the fuel is in between the two lines on the float bowl, it should be AOK. NB!......Having looked at the two lines, when the carb is in the correct position, the lines are 22mm approx vertically apart..............In my mind that is a lot of variation. I have seen an example of external fuel height measurement for a Yamaha with BDST38 carbs and the range appears to be 5.2mm - 6.2mm above the bottom line. I shall be checking with Carl on that point.........but it makes more sense to me that they should be checked externally. 4) Definitely junk the carb heaters - Although they may work in cold weather (mine do) when in heavy traffic, they can cause really rough running owing to the fact the fuel can evaporate quickly and cause weak mixture; although I can't see it myself, because the pump must be filling the carbs more quickly than fuel can evaporate. 5) Apparently Dynojet once stated that the overflow tubes to the carbs can cause an air imbalance, therefore the tubes should be removed..........In my mind, that still leaves the overflow stubs open. Plus there are also the two breather pipes the vent into the triangular plastic boxes on the left hand side.............but I think they have non-return valves on them.
All good stuff al, only thing I i don'nt seem to have the lines on the float bowls, I've got 5 here and non have a lines on that I can see. Might do all this as its running dealtealt bad after the carb change, can't get the carbs to balance.
Very interesting, though an 8mm for belts? That seems a bit too loose for my liking? surely 6mm at most. I'll keep with my tried and tested 5mm for fear of belts skipping teeth etc
I was told by Gates Technical that belts must have some tension when cold, but I have to admit, when the 5mm Allen key method is used, the belts are really bloody tight when the engine is hot.......
Another 'tip' Carl uses, is that when fitting and shimming the swingarm, always leave a tiny amount of end float (I think he said 1 thou, but he might have meant 0.1mm).........otherwise when the engine gets hot, the swingarm can nip up.........
First time I did the belts, I used 6mm on the vertical and 5mm on the horizontal. As the vertical gets slightly hotter I had read someplace that this would help ?
Ah.......and something else that sprang to mind...........(well, there was a lot to absorb at my age)..... The belt rollers, fixed and adjustable...........don't Loctite them....... ....Apparently the drillings in the castings are factory helicoiled.........Loctiting them could pull them out and ruin the casting........ I don't Loctite them anyway........
Hmm.. bugger! I've always loctited them with the wonderful 'red stuff'! Red for stuff I don't want coming undone (belt tensioners) Blue for stuff I don't want coming undone, but might undo axle nuts, sprocket fasteners) copper slip for stuff I will almost certainly undo or is going into ally (engine casing bolts and the like) Never failed me so far... BUT now I know that, I will most certainly bear that in mind next time! cheers for that one
