Need Help Loss of power in 6th gear

[Dollar Bill]

Riding back to San Francisco from Colorado last week, the engine on my 2013 NC700X DCT suffered a severe loss of power, primarily at highway speeds in sixth gear. The throttle had to be held full open to achieve even 60mph. Fuel mileage dropped from the mid-60 mpg level to low-40 mpg. This loss of power was most noticeable at elevations around 9,000 feet (felt like it had a carburetor rather than fuel injection) but also on level roads near sea level. I've experienced a similar loss of power on previous trips but attributed it to a weak engine riding against a headwind or uphill.
My bike is well maintained, has 29,000 miles, valves were adjusted and air filter replaced 3,500 miles ago, and has 233 psi compression in both cylinders.
The bike ran fine in the Colorado mountains but upon leaving I dropped it on its right side pulling out of a driveway. The low power condition seemed to be exaggerated after that. The engine started right up once the bike was lifted upright so I don't think the Bank Angle/Tip Over sensor is causing a problem (it worked properly by turning off the engine when the bike was on its side).
The service manual suggests the problem to be with the fuel pump, fuel injectors, or MAP sensor. The engine idles smoothly and does not stutter. It also pulls strongly in lower gears. However it requires the throttle to be held full-open to maintain highway speeds, usually needing a downshift into fifth gear.
I'm suspecting the problem may be due to a faulty sensor pack on the throttle body but would appreciate any input you all could provide before I go to the time and expense of replacing it.
Thanks in advance!

 

[Saturday Morning]

Great write up and description of the issue, quick question (perhaps I missed it) but, would it be accurate to say the engine RPMs dropped as the power decreased when the bike struggled in 6th? I'm sure you already know where I'm going with this. Just want to rule out the possibility of a slipping clutch.

 

[hulkss]

My guess is you stirred up some sediment in the gas tank and partially plugged a fuel filter (if there is one) or the fuel injectors.

 

[NickV]

I've run into a similar issue with the powerband since relocating from 2000ft elevation to 7000ft; I can run all day in 6th at highway speeds but when I drop down to under 5k ft then try to climb back up I loose power in 6th; dropping to 5th makes up for it and I can get back up to 75+ no problem. For reference, Flagstaff is at 7k and Sedona is around 3k in elevation, and it's only about 40 minutes from one to the other on Hwy 17.

 

[Dollar Bill]

Great write up and description of the issue, quick question (perhaps I missed it) but, would it be accurate to say the engine RPMs dropped as the power decreased when the bike struggled in 6th? I'm sure you already know where I'm going with this. Just want to rule out the possibility of a slipping clutch.

Thanks for your reply. The RPMs did decrease as the speed dropped. The bike has the DCT transmission and I feel no clutch slippage. In fact, when I drop to 5th gear the speed / power picks right up.

 

[Dollar Bill]

My guess is you stirred up some sediment in the gas tank and partially plugged a fuel filter (if there is one) or the fuel injectors.

Thanks for your thoughts on the fuel filter or injector. I've not disassembled the fuel pump / filter system but I'm inclined to think that is not the problem because the engine runs strongly when I drop to a lower gear, idles smoothly, and generally runs well around town. I'll certainly check this out in the next week.

 

[Dollar Bill]

I've run into a similar issue with the powerband since relocating from 2000ft elevation to 7000ft; I can run all day in 6th at highway speeds but when I drop down to under 5k ft then try to climb back up I loose power in 6th; dropping to 5th makes up for it and I can get back up to 75+ no problem. For reference, Flagstaff is at 7k and Sedona is around 3k in elevation, and it's only about 40 minutes from one to the other on Hwy 17.

Thanks for sharing your experience, Nick. Have you been able to determine the cause of the power loss?
I suspect we're both suffering from a faulty MAF/MAP/throttle position sensor because of our bikes' reaction to variations in altitude. My power loss was extreme at/above 9000 feet and only slightly improved when I got back down to sea level.
I took a gamble and ordered a new throttle body and sensor unit and will post the results after I install it.
BTW...no warning lights (DCT/MIL) have flashed or illuminated on the instrument cluster (they all light up when I turn on the key so I know they're functional).

 

[MZ5]

No matter what anyone claims, DTCs aren’t very useful diagnostic tools in terms of reliably indicating a problem or indicating the actual problem UNLESS there’s a total, outright failure of a directly-monitored part.

 

[Dollar Bill]

No matter what anyone claims, DTCs aren’t very useful diagnostic tools in terms of reliably indicating a problem or indicating the actual problem UNLESS there’s a total, outright failure of a directly-monitored part.

I didn't realize that, but it makes sense. Thanks for the info, MZ5.

 

[showkey]

There have been multiple prior posts on this statement:

“I've experienced a similar loss of power on previous trips but attributed it to a weak engine riding against a headwind or uphill.”

The prior posts were variations of common or similar conditions :

Fully loaded ( luggage, side bags, gear,passenger), going fast, wind, Altitude, big wind screen and hills/mountains …….

Mid size bike 50 HP, wind and running fast resulted in 30-40MPG, bike went faster in 5th gear vs 6th. Unable to hold speed in 6th gear.

 

[NickV]

Thanks for sharing your experience, Nick. Have you been able to determine the cause of the power loss?
I suspect we're both suffering from a faulty MAF/MAP/throttle position sensor because of our bikes' reaction to variations in altitude. My power loss was extreme at/above 9000 feet and only slightly improved when I got back down to sea level.
I took a gamble and ordered a new throttle body and sensor unit and will post the results after I install it.
BTW...no warning lights (DCT/MIL) have flashed or illuminated on the instrument cluster (they all light up when I turn on the key so I know they're functional).

Probably (as Showkey implies) it's due to the small engine. I've not ridden loaded for travel since I got here, so weight isn't the issue. I did go to a larger vStream windshield, so that may be a contributing factor; additionally, I've not been able to source non-ethanol gas since I left the Coeur d'Alene area. Ethanol could be an impact as I've not used it previously to as great an extent as I do now.

No warning lights for me, either, but no issues when rolling the throttle when not fighting a grade.

The only time previous to this when I had to really run in 4th and 5th to maintain speed was riding Westbound on Hwy 84 in Southern Idaho against a heavy wind and loaded for a trip. East to understand why in that scenario.

 

[Dollar Bill]

My experience has been similar to Showkey's.

Two years ago I rode the bike 11,000 miles around the perimeter of the USA. As with my recent trip back from CO, the bike was fully loaded (Honda side and tail hard bags, tank bag, and Moose soft bag across the rear seat). I experienced a loss in power on hills and in headwinds and also attributed it to a somewhat underpowered engine.

However the power loss was significantly greater this time returning from CO. Riding up and over the Vail summit I stopped to check if a spark plug wire had popped off or some other obvious problem had occurred. I actually had to hold the throttle wide open going downhill to maintain highway speed. Granted, this was around 10K feet elevation but performance only slightly improved at lower elevations. Dropping to 5th gear allows speeds up to 85mph but they can't be easily sustained in 6th gear.

Aside from this current issue, I've found the NC700X to be an excellent solo touring motorcycle. The handling is quick yet stable, and with the addition of Race Tech Gold Valves in the forks, slightly lower foot pegs, and a Shad seat with a modified mount to raise its nose, the NC is comfortable enough for up to 700 mile days...and I can't offer enough praise for the DCT transmission. Add excellent fuel economy and for me it's the perfect do-it-all bike. That said, once I get this bike back to normal, I'll be looking for the 750 model as a replacement...and perhaps wishing Honda will come up with an 800 version

 

[Dollar Bill]

Oct. 3 UPDATE:
Installing the new throttle body/sensor pack solved the problem. The engine is now more responsive and feels more powerful in all RPM ranges.
Could it be the sensors gradually failed? The power loss issue had been going on for so long it seems like I simply assumed the 700cc engine was a bit weak (aside from the significant power loss in sixth gear riding up hills and into strong headwinds). Also, I pulled the sensor pack off the old throttle body but could detect no blocked orifices, etc.
Oh well, I'm glad the problem is fixed. Well worth the $460 price of the throttle body/sensor pack. Had I taken the bike to a dealer, simply removing all the bodywork, battery, airbox, etc. to access the throttle body would have put the total repair well over $1,000.

 

[wheel_of_steel]

Oct. 3 UPDATE:
Installing the new throttle body/sensor pack solved the problem. The engine is now more responsive and feels more powerful in all RPM ranges.
Could it be the sensors gradually failed? The power loss issue had been going on for so long it seems like I simply assumed the 700cc engine was a bit weak (aside from the significant power loss in sixth gear riding up hills and into strong headwinds). Also, I pulled the sensor pack off the old throttle body but could detect no blocked orifices, etc.
Oh well, I'm glad the problem is fixed. Well worth the $460 price of the throttle body/sensor pack. Had I taken the bike to a dealer, simply removing all the bodywork, battery, airbox, etc. to access the throttle body would have put the total repair well over $1,000.

I'm glad you got to the bottom of it, I'm also worried about that failure mode. Expensive guess if it did not fix the problem. Did you test any sensors to see which voltages were out of range?

 

[Dollar Bill]

Thanks. I did not test voltages of the sensors but that would have been the correct first step toward identifying the problem. The shop manual said to test voltage and resistance of the MAP and TP sensors and then check the readings of known good sensors (which I didn't have). Since I do not have the Honda HDS pocket tester recommended by the manual, and was uncertain I'd get accurate readings with a multi-tester, I based my decision to gamble on buying the throttle body/sensor pack on the manual's list of three likely causes of poor engine performance/poor fuel economy: MAP sensor; fuel pump; fuel injectors. Since engine performance was good in lower gears and at idle, and since engine performance varied with altitude, I rejected the fuel pump/injectors possibility and went with the MAP sensor. I'm embarrassed to admit my amateur mechanic approach but luckily the gamble paid off.

 

[NickV]

My experience has been similar to Showkey's.

Two years ago I rode the bike 11,000 miles around the perimeter of the USA. As with my recent trip back from CO, the bike was fully loaded (Honda side and tail hard bags, tank bag, and Moose soft bag across the rear seat). I experienced a loss in power on hills and in headwinds and also attributed it to a somewhat underpowered engine.

However the power loss was significantly greater this time returning from CO. Riding up and over the Vail summit I stopped to check if a spark plug wire had popped off or some other obvious problem had occurred. I actually had to hold the throttle wide open going downhill to maintain highway speed. Granted, this was around 10K feet elevation but performance only slightly improved at lower elevations. Dropping to 5th gear allows speeds up to 85mph but they can't be easily sustained in 6th gear.

Aside from this current issue, I've found the NC700X to be an excellent solo touring motorcycle. The handling is quick yet stable, and with the addition of Race Tech Gold Valves in the forks, slightly lower foot pegs, and a Shad seat with a modified mount to raise its nose, the NC is comfortable enough for up to 700 mile days...and I can't offer enough praise for the DCT transmission. Add excellent fuel economy and for me it's the perfect do-it-all bike. That said, once I get this bike back to normal, I'll be looking for the 750 model as a replacement...and perhaps wishing Honda will come up with an 800 version

Just catching up on this (and your subsequent replacement of the sensors). I've not had the decrease in power downhill, so I suppose that I'm not experiencing the same issue. Thanks for all the info!

 

[Dollar Bill]

Just catching up on this (and your subsequent replacement of the sensors). I've not had the decrease in power downhill, so I suppose that I'm not experiencing the same issue. Thanks for all the info!

I should have clarified that the loss of power downhill was when I was descending from a 10K feet elevation. Riding up to the summit the bike would barely do 45mph with the throttle wide open. Downhill I could get up to 55. However at lower elevations I could achieve 85 mph downhill but would have to hold the throttle full open to maintain 65 on flat ground. With the new throttle body/sensor pack the bike easily accelerates up hills it would previously struggle up. I've not ridden against a strong headwind but am confident the bike can now maintain freeway speeds in this situation.
If anyone else has had this problem and fixed it, please let us know your experience and solution.
Thanks!

 

[wheel_of_steel]

Thanks. I did not test voltages of the sensors but that would have been the correct first step toward identifying the problem. The shop manual said to test voltage and resistance of the MAP and TP sensors and then check the readings of known good sensors (which I didn't have). Since I do not have the Honda HDS pocket tester recommended by the manual, and was uncertain I'd get accurate readings with a multi-tester, I based my decision to gamble on buying the throttle body/sensor pack on the manual's list of three likely causes of poor engine performance/poor fuel economy: MAP sensor; fuel pump; fuel injectors. Since engine performance was good in lower gears and at idle, and since engine performance varied with altitude, I rejected the fuel pump/injectors possibility and went with the MAP sensor. I'm embarrassed to admit my amateur mechanic approach but luckily the gamble paid off.

I see your logic, nice troubleshooting. Sometimes it's impossible to be 100% sure and we take the educated guess, hopefully this thread helps others out as the same batch of sensors gradually ages out and causes similar problems.

 

[Dollar Bill]

I see your logic, nice troubleshooting. Sometimes it's impossible to be 100% sure and we take the educated guess, hopefully this thread helps others out as the same batch of sensors gradually ages out and causes similar problems.

Thanks. I do hope my experience can be of help to some other riders. It would be interesting to see if others have had similar low power issues.

 

[Dollar Bill]

I'm glad you got to the bottom of it, I'm also worried about that failure mode. Expensive guess if it did not fix the problem. Did you test any sensors to see which voltages were out of range?

Correction: The throttle body/sensor pack cost $363 with tax and shipping (not $460 as I mentioned previously).