Can anyone help? Having big problems on cold start after fitting high comp Pistol pistons along with other mods. Bike is a 99 with older starter ratio. Thanks Darren.
Hi Steve, I hope thats not true!! I believed that I need to swap the idler and the main(flywheel) gears. Ive searched about and theres mention of using 999/1098 gears in the 996 engine on US forums? I need to do something, my mates are falling out with me on track days pushing me about the pits.... I have the larger battery already fitted(not dry cell) Darren.
Hi, i possibly have what you are looking for but there are about four different ratios, problem is they all look the same but count the teeth and they are different, btw the 1098 gears CANNOT be fitted as they are too large, this is an issue that i am dealing with at the mo. THE IDLER AND SPRAG GEAR MUST MATCH. There are three combos here, then the little starter gear must match the idler, this gives another two combos. Leading you astray, are you sure of the starter, the brush gear when worn does tilt to the adjacent segment giving twice the current drawn and poor performance. By all means pm me for my number, Last q. What sort of compression are you now running?
Thanks for reply Spike, you have confirmed what I did know and few of the questions I have. I was aware of what gears need to be replaced as a set. Starter motor is ok, Ive inspected/checked that when I assembled the engine March last year. ( bike has been sat since October) Gear teeth: Starter pinion: 13t Idler gear: 13/56T Main/sprag: 70T Engine details: 996 Biposto, 50mm Leo Vince system, Dynojet 3 set up on dyno, standard injectors and throttle bodies. Standard 996 heads with 36/30 valves, Std A1 cams. 128.9 Hp, cant remeber torque figure as not home till tomorrow night but will update that later. 13-1 Pistal pistons. .4mm base gaskets Approx 3 thou skimmed off heads to clean them up. .96mm squish In cam 11° advanced Ex cam 9° advanced Bike is brutal in lower revs with torque but smooth due to flat power curve, lot of fun to ride but you always want more, tis good to harrass people on later bikes..... getting it to start would be god tho, only when its cold or first start its a problem. I really do need a ignition re map...... Darren.
Hi Darren, my sprag tooth count is slightly different at 71 tooth for a 996, the lower ratio one is also 71 tooth but does not mate with the 13 tooth idler, it only mates with the 11 tooth idler, i do have both. the differenc in ratios is from 5.45:1 to 6.45:1 so gives about 15% more torque. If you could fit the 1098 ratio you are looking at about 75% more torque. I dont want to put you on a downer and whatever you choose i will sell these gears but you really need to check the compression ratio, aftermarket pistons are quoted with comp ratios at nominal squish values, the 996's squish is adjustable with different base gakets so how much squish are you running? note here that some, including myself turn the bottom of the barrel to get the squish correct with a 0.4 base gasket, has this been done? This is a long road that i have also been on, there are ways to fix these problems but if the comp is too high the std ducati 996 will not turn these over properly, when they do they dont last long. As i said, if you want these gears, or a different approach p.m. me. but re count that sprag gear, if it is a 70 well thats another ratio!
Forget my q on squish, i missed that but re check comp ratio. I did some working out with the calculator, if the squish is quoted at 1mm for 13:1 and you reduced this to 0.95mm this coupled with a 3 thou skim could have removed just under 2cc from the chamber vol, this could give a comp of 13.8:1 instead of 13:1, do the math! this is if your starting point is 13:1. I just fitted some JE pistons that were advertised at 11.5:1 and when measured were nearer 13:1.
Ok thanks for your thoughts spike, may just pull heads to inspect it, was going to pull cams to check rockers etc anyway as its been all track riding since rebuild, not encountered any probs so far, it only just doesnt start, its fine after the first cold start of the day. Teeth count is correct btw. Darren.
Steve, you used the right word "claimed", I am looking at a motor this week with 95mm pistals and i think the comp is much higher that "claimed". My own motor with JE Pistons had a chamber volume of 41cc, good job i checked as it worked out at 12.5 with a piston that is 11.5:1.
Thanks again chaps for sharing knowledge, its much appreciated, am going to run it till May then pull heads and cc the chambers and will report back. In the meantime after a little more research I believe I have the gear combo that Im told will go into early engine. 11/57 idler and 71t as stated earlier in thread by Spike. (You have a pm btw) Thanks, Daz.
