Evening all, Following on from previous thread (https://www.1000rr.co.uk/threads/how-to-stop-fuel-line-kink.42109/#post-562506) my bike is still being troublesome and so looking for any other ideas on what to try. Fundamental problem is between 8k rpm and 10k rpm, at max/high throttle, the bike looses acceleration/power and rpms become very choppy. Happens in all gears and reducing throttle input doesn't seem to significantly improve condition but it's hard to tell with the bike jumping around everywhere. It does continue to accelerate slowly past 10k rpm where the bike suddenly regains its expected performance all the way to the redline. Items confirmed since the issue started: Multiple refuels so not bad batch of fuel Valve clearances checked - some near edge of tolerance so changed shims. This had no impact on the above issue New set of spark plugs - no change Cylinder compression is OK Air filters cleaned Fuel pressure at idle confirmed around 3.5bar - tried revving and stayed at 3.5 but wasn't exactly redlining it under load. Fuel hose from tank to 1st injectors replaced - noticed this looked kinked (hence previous thread) but this has had no impact Had a look at the fuel pump through filler cap and looked OK but difficult to see No power commander on the bike Stock downpipes - Delkavic slipon The only remaining things I can think of is to replace fuel pump or injectors. The thing that's confusing me is the bike recovering above 10k rpm. If the fuel pump or injectors were bad surely it wouldn't do this? Just looking for any other (cheaper) ideas before I bite the bullet and buy a new fuel pump... Cheers
Do your “choppy rpms” ever feel like she’s cutting in and out ? Maybe consider the cam pulse generator.
Is it every time you give it some or intermittent. Mine was intermittent, sometimes I could go a couple of months before it would do it again. It felt like a flick of the kill switch off n on then full power. Only did it with a full twist in the lower gears. RR7
Pretty much every time without fault I get the problem. I wouldn't say its as forceful as kill switching. Its more an unstead hesitation like someone is putting a slight kink in a fuel hose.... Mines RR6 for context (missed that in original post) I've now ordered a new fuel pump as a decent deal came up on a very low mileage, known functioning one.... Will report back on results but in the meantime any other ideas are still welcome
Have you checked the fuel filter inside the fuel pump? Might be clogged. This is what was happening to me (01:53):
Haven't had the fuel pump out yet so not had a good look at it. Entirely possible it's a cause but again not sure how the bike would manage to recover it's power after 10k rpm if the filter was blocked? Surely if it was blocked it would restrict the max flow rate through the filter and so once it hit that threashold it would never get higher? Thanks for the video too but that doesn't look similar to my problem unfortunately. Mine maintains the rpm rather than the sudden drop in your video, it just fluctuates +/-100 rpm as it continues to slowly climb to 10k rpm... Once I've got the fuel pump out in the next few days will share some pictures to see if anyone can spot anything.
Another possibility maybe. I've not tried swapping them with another set but I'm certain they're seated correctly. If the fuel pump swap doesn't make a difference it's definitely something I'll look at... It's now snowing which is mildly infuriating as I failed to get a video of the behaviour!
Have you got an alarm immobiliser? Had very similar problem with my old 600RR, kangarood like mad at high revs - found out the alarm was wired into ignition not starter system and at high revs some electrical signal caused it to cut in the immobiliser, which then cut back out as revs dropped. Odd issue but rewired and sorted.
No alarm system or aftermarket electronics apart from some heated grips (no impact if they're turned on or off) On an electrical theme, battery seems perfectly fine as it starts up OK and both terminals are secure.
Coil on cap do degrade more than the older remote coils through vibration and heat, it would be worth trying another set, I’d look at a dyno session if you have one near as they’ll detect it on the dyno, bsd found similar problem on my zx7r a few months ago, does it still have the exhaust servo valve fitted?, it should be fully open at those revs but if it’s partially closing it will cause misfiring.
Exhaust servo removed for the delkavic slip on that's on the bike. Also intake flapper mod done so that's not moving anywhere. I do have a dyno nearby and was considering getting them to have a look if I'm truly stuck...
Does it do it when stationary and revved up? Had a bike once where a wire was earthing out, didn't misfire when stationary only when riding. Garage had replaced CDI unit, head gasket, carbs under warranty - I found the wire when washing the bike!!
Id clean the tank out change the fuel filter. Modern fuel is crap and it's easier than changing the plugs. Also worth checking the charging voltage.
So had a thought today that the likely problem is the fuel pressure regulator. It explains how the bike recovers past 10k rpm. From idle to 8k rpm the engine fuel demand is low enough that the pump builds enough pressure to open the regulator and bleed off internal pressure until it meets nominal 3.5bar. When the engine gets to 8k the fuel demand is high enough that the regulator should only be slightly open but for some reason the one in my bike has too much resistance and actually closes fully. This means internal pressure in the pump builds and so changes the A/F ratio - hence the reduction in power. Very quickly it raises the pressure enough to re-open the pressure regulator and the cycle of open/closing repeats - causing the jittery acceleration. The key is when it gets to 10k rpm the fuel demand from the engine is high enough to not build up enough pressure to reopen the regulator and so the A/F ratio recovers and performance returns. Received the fuel pump today so will know either way once it's fitted - although the snow isn't making it easy to test.... Hard to tell as when its up on a stand it's got no load on the drivetrain so revs really fast. Generally doesn't feel like intermittent connection on the basis of repeatable rpm range 8-10k but can't rule it out. Fuel tank looks clean from the filler cap but I have done a few thousand miles using french/italian fuel so who knows! Already changed the plugs recently and they didn't look too bad but already ruled that out. Charging voltage is OK too.
Problem has been resolved with a new fuel pump assembly as predicted. Fitted a second hand fuel pump from an 07 yesterday. When I removed my current one general condition of the pump looked OK but when I pulled back the packing to see the strainer it's clear there is a lot of sediment held in the strainer. I think probably a combination of slightly blocked strainer and some of the sediment has made its way into the pressure regulator and jammed it. With the new pump assembly on the bike its back to its mental self and pulling all the way through the rev range as expected! I'll try to rebuild the old fuel pump anyway to have a backup or sell it on. Thanks everyone for the suggestions, hopefully if anyone had the same problem in future this thread will help to diagnose!
