Hi all! Without silly answers like ' because its an SS' , why is my Duke 750ss so slow? help! I have after blowing my 600 engine, fitted a 750 engine into my bike, and when fitting etc, cleaned the carbs (the carbs are the 750 ones) and fitted a new air filter and plugs etc. it runs nicely, though lumpy low down, and flat out seems to run out of puff at 110mph - that is slow, even for an SS. what might the issue be? I have tried other plugs, and different pipes and filters to no avail.... where can i look next? I am not hoping for 150mph+ as it isn't built for and never would hit it. but my old 750 did 130 with ease, so this is rather disappointing . please help!
hi,have you put the 750ss exhaust on the bike? or are you still using the 600 one,also the 600 carb manifolds are a smaller diameter so you will need 750 manifolds.
it is the same with the 750 and 600 pipes... However I was certain I had read and was told the manifolds were the same... Id better get on eBay, I've restricted my bike and not even known it... Muppet! Thanks for that
Yes, mine are stamped 6 (not that I needed to check - they came from my 600 engine). I have now sourced a pair of 750 ones from eBay, which should be here very soon and I can unleash the poor engine's power! Thanks for the pointer though, I appreciate it, even if it has made me feel a right muppet! Cheers! Ben
No problem Ben i nearly made the same mistake,you will notice the diffrence between the two when you get them.
I think its your gearing. If the motor is running fine, it will go through its natural rev ranges fine but if the gearing is out it will not drive the wheels to full advantage. The standard gearing for the 600 ss was specified as 15 f 36 r for the 1994 model and 14 f 41 r for the 1995 on model By way of contrast the 750 ss was specified as 15 f 37 r for the carbed models If the exhaust option doesn't work, check the drive sprocket sizes.
I can confirm that the 900 inlets are different again. I fitted a 900 motor to my 750ss, and kept the 750ss inlets, which looked to be the correct diameter, only to find that the lengths must be subtly different, so the carbs didn't go into the airbox. Here's a wild card possibility... You might have a 'wrong' speedo and speedo drive combination? A 17mm front axle speedo drive, coupled with a late model speedo would under read, by quite a lot. Loads of folk, especially on Ebay seem to assume that all the bits that go on the 600/750/900ss family are all the same fitments, but there are lots small differences to trip up the unwary.
I once had a Honda 400N that accelerated fine but topped out at 85 instead of the 105 it should do. I did everything to find the problem including a full engine strip with friends. It turned out to be the regulator/rectifier. Don't ask me why. I bolted on a different one from a breakers for a tenner (literally 2 bolts) and hey presto - 105 mph. I rather wish we'd tried that from the off. In fact, it was months after the bike was put back together again.
The speed is accurate (as accurate as it can be) - I double checked with a friend on his Gixxer beside me - and it felt dog slow! The sprockets are the standard gearing as specified by JHP 15/37 sounds about right. Thus, at least for now the manifolds sound the most likely cause after all they're differing sizes, thus I've effectively restricted my bike! thanks all - will update when I've tried it
well, manifolds fitted couldn't test as the bloody starter switch is playing up at the mo, but by bypassing it, the bike starts a lot easier and sounds a lot more healthy when revving For a comparison of manifold diameter .... left is 750, right 600 Thanks all for helping me out now anyone got a starter switch?
is it the solonoid you need or the relay,if its the relay nr the head light you can take the top off and give the points a clean with wet and dry.
I have two solenoids and tried the spare (known good) and got nothing. I ill try the relay tomorrow I assumed it was the start button itself playing up. worked fin until today! Ducati's- they're great, but my lord they keep you on your toes
Well, it is all good now! The starting word being due to a tiny wire that bridges the contacts on the white plug in the back of the solenoid- it he broken just at the 'resistor'? - soldered and we are sorted! Still not as quick or responsive as my old one ,but much much better Thanks to all who helped
Cleaning the connections might help unless the solenoid is getting tired............and that bl**dy white plug, well.......... ..........mine is held in and sealed with some clear silicone.........
Al. That's where my frustration with the thing came from. I tried cleaning the pins, I tried another solenoid, only to find that stupid wire broken. When I return from my enduro holiday in going to strip all the wires to it, and renew as neccessary!
Is it a little insulated link wire between the two pins in the white plug? If so, I believe that is a diode................it is supposed to prevent something occurring............God knows what........
