2006 919 hornet stutters/surges under acceleration between 3k and 5k. - Wrist Twisters
 
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post #1 of 11 Old 06-14-2015, 08:34 PM Thread Starter
Tirone
 
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2006 919 hornet stutters/surges under acceleration between 3k and 5k.

I have a 2006 919 Hornet that runs like a champ except for one thing. It has this surging stutter thing around 3500ish to 5500ish when accelerating. It feels almost like a bounce, like I am running over very small smooth speedbumps. I have verified it isn't tire pressure or something like that.

Basically, regardless of how fast I am going, if I steadily roll on the throttle it will surge/stutter starting slow and increasing in frequency until I get past 5500rpm. If I crank the throttle and rocket through the rpm range I will never notice it. If I never come below 6k I also never notice it. However, since 1st gear is soo high I find I am hitting the 4500k in 2nd - 4th gear whenever cruising (which is probably by design.

Another way to describe it is that kind of chain-lash you get when closed throttle in 1st gear and you are just barely on the throttle or just chopped it. You know how the engine braking and then rolling on causes a no-load to load situation. Well, it is almost as if the engine is dealing with chain lash at that rpm range.

Those are the best ways to describe it. Other than that, it runs like a dream, it idles and runs smoother than any other bike I have owned (including a VFR800fi and a CBR900RR). Any ideas on what I should be looking for? I have not properly adjusted the suspension for me yet, not enough hours in the day so far and I don't commute like I used to so I haven't gotten around to it yet :-( But seeing as how it appears to be RPM dependent I doubt it is suspension related.

Any help I can get will be much appreciated!

JP

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post #2 of 11 Old 06-15-2015, 05:06 AM
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Do you have a power commander installed? If so remove it and see if that helped. Another possibility is the Fuel pressure regulator. Pull the vacuum lines to see if they have fuel in them. Tighten battery cables and check the spark plug wires. Not sure if these things will help but it's worth a shot

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post #3 of 11 Old 06-15-2015, 05:57 AM Thread Starter
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I don't think I have a power commander, at least I didn't install one.

Should I check the vacuum lines after a ride or after idling in the garage for a bit?

I will check the cables.

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Originally Posted by redline919 View Post
Do you have a power commander installed? If so remove it and see if that helped. Another possibility is the Fuel pressure regulator. Pull the vacuum lines to see if they have fuel in them. Tighten battery cables and check the spark plug wires. Not sure if these things will help but it's worth a shot

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post #4 of 11 Old 06-15-2015, 06:00 AM
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If the FPR has failed there will be fuel in the vacuum line. Probably from the last time you rode it still.

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post #5 of 11 Old 06-15-2015, 06:06 AM
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Apparently you need to pull the vacuum line from the fpr and turn the engine over with the starter button. If fuel comes out the vacuum line. The Fpr is bad

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post #6 of 11 Old 06-18-2015, 04:22 PM
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Any mod affecting the breathing of the motor like air filter or exhaust, requires remapping the injection table. 919 does not have a closed loop system, the table is hard wired for the stock config. The straight forward way of doing it is via PowerCommander. But tuning is NOT TRIVIAL! You cannot rely on someone else's table. Tuning equipment and a basic knowledge about AFR is required. At minimum you also need an instrument to measure AFR. The cheapest and still my favourite is the NGK's with numerical LED display. I do this process with all my bikes, even carbed ones. Result is great fuel economy and flawless throttling.


Quote:
Originally Posted by jptechnical View Post
I have a 2006 919 Hornet that runs like a champ except for one thing. It has this surging stutter thing around 3500ish to 5500ish when accelerating. It feels almost like a bounce, like I am running over very small smooth speedbumps. I have verified it isn't tire pressure or something like that.

Basically, regardless of how fast I am going, if I steadily roll on the throttle it will surge/stutter starting slow and increasing in frequency until I get past 5500rpm. If I crank the throttle and rocket through the rpm range I will never notice it. If I never come below 6k I also never notice it. However, since 1st gear is soo high I find I am hitting the 4500k in 2nd - 4th gear whenever cruising (which is probably by design.

Another way to describe it is that kind of chain-lash you get when closed throttle in 1st gear and you are just barely on the throttle or just chopped it. You know how the engine braking and then rolling on causes a no-load to load situation. Well, it is almost as if the engine is dealing with chain lash at that rpm range.

Those are the best ways to describe it. Other than that, it runs like a dream, it idles and runs smoother than any other bike I have owned (including a VFR800fi and a CBR900RR). Any ideas on what I should be looking for? I have not properly adjusted the suspension for me yet, not enough hours in the day so far and I don't commute like I used to so I haven't gotten around to it yet :-( But seeing as how it appears to be RPM dependent I doubt it is suspension related.

Any help I can get will be much appreciated!

JP

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post #7 of 11 Old 06-18-2015, 04:34 PM Thread Starter
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Wow... that is a bit beyond my skillset I am afraid. Right now, it is too hot here to work on a bike (85 in Anchorage is death valley weather for Alaskans). So... once it cools down I will probably tear into at least checking the FPR... in the meantime I am going to enjoy the ride and keep it over 5k

Thanks for the replies!

Quote:
Originally Posted by vonkas View Post
Any mod affecting the breathing of the motor like air filter or exhaust, requires remapping the injection table. 919 does not have a closed loop system, the table is hard wired for the stock config. The straight forward way of doing it is via PowerCommander. But tuning is NOT TRIVIAL! You cannot rely on someone else's table. Tuning equipment and a basic knowledge about AFR is required. At minimum you also need an instrument to measure AFR. The cheapest and still my favourite is the NGK's with numerical LED display. I do this process with all my bikes, even carbed ones. Result is great fuel economy and flawless throttling.

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post #8 of 11 Old 06-18-2015, 04:37 PM
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Quote:
Originally Posted by vonkas View Post
Any mod affecting the breathing of the motor like air filter or exhaust, requires remapping the injection table. 919 does not have a closed loop system, the table is hard wired for the stock config. The straight forward way of doing it is via PowerCommander. But tuning is NOT TRIVIAL! You cannot rely on someone else's table. Tuning equipment and a basic knowledge about AFR is required. At minimum you also need an instrument to measure AFR. The cheapest and still my favourite is the NGK's with numerical LED display. I do this process with all my bikes, even carbed ones. Result is great fuel economy and flawless throttling.
Steve?

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post #9 of 11 Old 06-18-2015, 05:30 PM
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OK - here is the next best thing. Firstly, do all the mods you want to do that affect combustion (exhaust & intake) then find a PowerCommander tuning service with a good reputation (the hard part). Be prepared to spend $500 on he bits to be added to your bike plus the tuning session. A good tuner will alert you that there is more than one way to tune a bike. For example to get best fuel economy or to get best throttle response and power. PowerCommanders can hold more than one map, so you can have various maps pre-programmed by the tuner and shown how to change by pressing buttons on the Commander unit.

Quote:
Originally Posted by jptechnical View Post
Wow... that is a bit beyond my skillset I am afraid. Right now, it is too hot here to work on a bike (85 in Anchorage is death valley weather for Alaskans). So... once it cools down I will probably tear into at least checking the FPR... in the meantime I am going to enjoy the ride and keep it over 5k

Thanks for the replies!

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post #10 of 11 Old 06-18-2015, 05:36 PM Thread Starter
Tirone
 
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That does remind me that there is an aftermarket can on there, so if there was a cat it might have been removed as well.

I was blessed with a full parts bike with a broken front wheel, smashed tank and cracked bottom case otherwise totally intact (minus levers and mirrors of course). So I should compare next time I go out to the shed.

Not sure if I trust anyone in Alaska to do any tuning honestly, most of the cycle dealers have a pretty poor reputation for price gouging and general douchebaggery.

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post #11 of 11 Old 06-18-2015, 05:41 PM
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Quote:
Originally Posted by vonkas View Post
OK - here is the next best thing. Firstly, do all the mods you want to do that affect combustion (exhaust & intake) then find a PowerCommander tuning service with a good reputation (the hard part). Be prepared to spend $500 on he bits to be added to your bike plus the tuning session. A good tuner will alert you that there is more than one way to tune a bike. For example to get best fuel economy or to get best throttle response and power. PowerCommanders can hold more than one map, so you can have various maps pre-programmed by the tuner and shown how to change by pressing buttons on the Commander unit.
This is not his issue. Why steer him down the wrong road? You don't need a power commander for an exhaust or filter. He owns a 919 it's probably something simple.

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