Had my Monster for 3 years and done 7000 miles on it. Back in June last year I noticed it was developing quite a jerk on the throttle. I've done 1800 miles since. 1) For the first 20 mins or so of a ride, the bike feels fine and smooth 2) When the jerking starts it's quite noticeable at around 4k. There will sometimes be a slight drop in power as it briefly comes and goes. 3) I've changed back to stock end can after having my SC project can on there: no change 4) I've deleted the exhaust servo: no change 5) It happens at any level of fuel 6) Happens with E5 and E10 7) Had a new air filter on annual service about 1 year ago Bit stuck as to where to go next. Friend has suggested it might be a coil pack on the way out, esp as intermittent. Motah is an 821 Testastretta 11* which was also used in the hyper. Does anyone have any suggestions or things to try? Or is this something that happens all the time and I only noticed it last year?
It really needs to be plugged into diagnostics and run so you can see what’s going on, otherwise you’re just guessing and potentially throwing parts at it.
Can you see live data on that, while the bike’s running? Eg APS & TPS values? Injector pulse length? MAP sensor values? Air & engine temp sensor values? If there are no error codes stored and all the various parameters are in line with where they should be when it’s running and up to temperature then it may be a failing spark plug or plug cap/HT lead, they don’t cause errors to be stored in any of the control units. If a coil were packing up and firing intermittently it would leave an error code.
You certainly can get a lot of live data from it, certainly all you mention above although I'm not sure about the injector pulse length - I will check what I can get against what the values should be. As I mentioned, the jerking occurs after about 20 mins of riding so I'll have to head out for a ride with the OBDStar and pull in where safe to check. The TPS was replaced in November 2023 by Ducati Stoke and didn't do many miles until I first noticed the problem. I did wonder if that might have had something to do with it and performed a reset about a week ago, but the problem has come back. Thankyou for the suggestion about the spark plugs and plug caps/HT leads, and useful to know that a failing coil would leave a code. Very useful, I'll get to work with that information, thankyou
