Won't pull past 6,800 rpm

[Timothy]

Now here's one for you chaps.

What with all the problems with my relatively newly acquired NTX (see NTX top end woes) I've not really had the chance to give the bike a good thrashing until recently. On doing so I noticed that it just won't pull past 6,800 rpm. Almost as if it had a rev limiter.

Obviously the first thing I did was pop on this forum to find a similar thread of a chap with exactly the same problem. But as is so often the case no conclusion. Having experienced an XJR1300 many years ago with the same symptoms I assumed it was air intake related so tools out to have a nose for anything unusual. Air filter out and all looked well but, after stuffing my hand down the air box I could feel that one of the rubber boots/tubes that go from the air box to the throttle bodies was twisted against the other tube to the extent I was surprised any air was getting to the right hand cylinder at all.

So air box out for a good nose. The problem could be alleviated by rotating the hose in the air box to change the angle thereby making both inlets free of each other but on replacing the whole assembly I soon realised that the hose no longer aligned with the throttle body. If that all makes sense

After an hour of twisting and stretching without success. It dawned on me. And a quick look on the parts diagram confirmed it.There should be a left and right hose with different part numbers and my bike from the factory has been fitted with two left hand hoses so it's been wrong since day one.

Correct part ordered and fitted and it now sails up to the the real rev limiter with vigour. Just need to get the throttle bodies re balanced now..... F**king Italians eh

[Mi_ka]

Could by any chance your italian luck had something to do with the top end failure by some very strange pathway?

[Timothy]

Could by any chance your italian luck had something to do with the top end failure by some very strange pathway?

I'm probably not technically advanced enough to work that one out for sure as I'm not clear how all the injection, air flow monitoring, gas analysing blah blah blah all pans out in the end . I doubt it though as the left hand cylinder had the little end failure but the right cylinder was the one starved of air

[draidt]

Could by any chance your italian luck had something to do with the top end failure by some very strange pathway?

I'm probably not technically advanced enough to work that one out for sure as I'm not clear how all the injection, air flow monitoring, gas analysing blah blah blah all pans out in the end . I doubt it though as the left hand cylinder had the little end failure but the right cylinder was the one starved of air

Actually I can make a case that it could have caused the Left cylinder malfunction, Think about it , The left jug was doing all the work. That cant be good, the motor was unbalanced. How the throttle bodies could have ever been balanced by the factory or shop is beyond me. Did you re balance the TB's after the fix and was it way out ?

[Timothy]

Did you re balance the TB's after the fix and was it way out ?

Only fixed it yesterday so no had the TB's done yet. Booked in for next Saturday and will be interesting to see how far out it was.

Although as you set the TB's at low RPM I'm not expecting it to be massively out as the engine's not breathing very hard at that point. Any restriction in air flow is only really going to show at high RPM...I think

[draidt]

Not so ! The TB's are balanced at idle via the bleed screws and I agree that it will not matter to much with the restricted intake, BUT Throttle Bodies are balance at speed as well 3200-3600 rpm and are balanced via the throttle body balance screw That has to be way out in order to compensate for the previous restriction, TPS should be reset after each adjustment as well. If your dealer is NOT balancing the TB's at the higher RPM via the balancing screw on the connecting rod then they are doing YOU and all other customer's a great disservice.

[Guzzistaracing]

Have you checed that you do not have the "run in" rev. limiter engaged? I do believe that You can select this by entering the menues on the dash. I do not know about the new NTX but on my Griso there was something like that.

[GT-Rx]

Have you checed that you do not have the "run in" rev. limiter engaged? I do believe that You can select this by entering the menues on the dash. I do not know about the new NTX but on my Griso there was something like that.

Not true... that is simply a rev limit light for break in. There is no adjustable rev-limiter on the bike, only programmed in the ECU.

[Timothy]

Have you checed that you do not have the "run in" rev. limiter engaged? I do believe that You can select this by entering the menues on the dash. I do not know about the new NTX but on my Griso there was something like that.

Not sure you read my post properly. I said "it felt like a rev limiter" not there was one. There is no way to set an actual rev limiter just the ability to set an indicator that comes on at certain revs. A rev limiter wasn't the problem anyway but a restricted air flow which is now resolved.

I posted not looking for answers but to assist anyone that may have a similar issue in the future and to vent my disappointment that such a basic mistake could have been made in the factory and went through several checks at a dealers only for a mechanical numpty like myself to discover the resolution.

Who ever put that part of the bike together must have known it was wrong because as the part fitted was not only the wrong shape but too short as well. To get the tube to fit properly over the throttle bodies they'd actually had to pull it out of it's seating at the air box. This whole error not only cut off the air supply to one cylinder but actually broke the seal of the air box meaning unfiltered air was leaking in. I doubt it's done any lasting damage in only 1500 miles but it could have been a whole different scenario if I had used the bike on dusty tracks

[Guzzistaracing]

See, I learn something new every day! First my memory of the Griso and second: read full post before answering!
Just made a fool out of myself and have to go and get another beer as punishment! Never ever am I going to make THIS mistake again.