Help! I Need Diagnostic Assistance

Phil Tarman

Site Supporter
Moderator
Joined
Dec 12, 2010
Messages
9,367
Age
81
Location
Greeley, CO
Bike
2010 Silver NT700VA (ABS)
I noticed this once or twice on my way towards Portland and during the 3-Flags Classic, but it got much worse during my Kansas journey. Thursday night when I turned off I-70 and onto I-135 southbound towards Wichita, I was bucking a headwind and couldn't hold the speed limit with my cruise control. It's always disconnected if the throttle had to open past a certain point, but up until this started, that was almost always when going up a fairly steep grade at speeds of 75-80mph. But Thursday, it wouldn't hold 70 and when I tried to take over manual control, I realized that if I opened the throttle past the point which is usually good for 70-75mph on level ground, the bike would start to miss and slow down. That got really bad in the strong winds I was in Monday afternoon and evening and was bad today until I got to Colorado and the wind quit. Even with no wind, a speed of more than 70-72 would cause the bike to feel like it was missing until I backed off the throttle. Then it would accelerate up to about 70-72 again, but that was the max.

I've been thinking about what could cause this and my first guess is bad spark plugs. I guess it could be something else in the ignition circuit. I'm inclined to think it's not bad gas -- that was my hunch when it happened in Oregon and on the 3-Flags Classic because it always seemed like it happened after I'd filled up. Not this time!

What else could it be? What would you check first?

Any suggestions are greatly appreciated!
 

JQL

Growing old disgracefully
Joined
Dec 19, 2010
Messages
831
Location
Val de Marne, France
Bike
2010 NT700 & 2019 FJR1300
Could it be a faulty TPS (Throttle Position Sensor)?

See: https://www.youtube.com/watch?v=N_sqen6hSbQ

If you think it's plugs the quick and cheap "fix" (way to check) is to change the spark plug caps or make sure they are correctly seated. Always use the NGK ones.

As an aside, I had the NGK caps and one was slightly corroded/tarnished inside which caused an interesting fault when the ambient air temperature was high (OK otherwise!).
 
Last edited:
OP
OP
Phil Tarman

Phil Tarman

Site Supporter
Moderator
Joined
Dec 12, 2010
Messages
9,367
Age
81
Location
Greeley, CO
Bike
2010 Silver NT700VA (ABS)
John, I guess I should have mentioned that I don't have an MIL light. So I don't think it's the TPS.
 

mikesim

Site Supporter
Joined
Jun 7, 2011
Messages
3,331
Age
74
Location
Union, MO
Bike
NT700, Red, #989,
At this point, without a MIL to guide you, it is a crap shoot. At 70, you are turning about 5K rpm. How does it act at 5K in other gears? Does it lose power at 5K in 1st, 2nd, etc.? Could be spark, could be fueling.... sorry I can't be of more help.

Mike
 

junglejim

Site Supporter
Joined
Apr 26, 2012
Messages
2,119
Location
Northern WI
Bike
Tiger 800, NT sold
I agree with Mike. And, from your description I still don't know if it is consistent or intermittent. I believe Mike is on the right track to first determine if it is related to rpm or load. Inconsistent/intermittent faults are a real bugger to diagnose. If the miss is regular and steady it is probably an ignition problem on one cylinder. If the miss is not regular it is more likely a fuel problem. But as mentioned above the spark plugs are the easiest and least expensive place to start. Note the condition of the old plugs when you remove them. Next I'd take it to a shop and have them measure your fuel pressure - that's pretty easy. After that your friends at Sun Honda should be able to help. Good luck.
 
Joined
Jun 5, 2011
Messages
630
Location
Western Washington
Bike
2010 NT700V, 2015 CB500X
The only simple thing to add that hasn't been mentioned is the air filter.

There is a good troubleshooting guide on page 24-3 of the service manual for "Engine lacks power" to get some ideas. A few of the ideas are tire pressure, wheel bearing, clogged fuel line or muffler or air filter or oil passages, worn out engine or bad compression, spark plugs, low oil level, ignition timing & faulty ECM or CKP or TPS, and overheating.

Just because you don't have a MIL doesn't mean that the TPS (or some other sensors) is sending a correct position to the ECM for the actual position. It may not be the most likely suspect, but don't eliminate a sensor because you don't have a MIL.
 

Mellow

Admin
Joined
Dec 12, 2010
Messages
1,881
Location
Carrollton, TX
2024 Mileage
000540
Bike
21 R1250RT
I'd start with the simple stuff.. bad-ish fuel... get some seafoam in there and run a tank through from a good dependable gas source and go from there.
 
OP
OP
Phil Tarman

Phil Tarman

Site Supporter
Moderator
Joined
Dec 12, 2010
Messages
9,367
Age
81
Location
Greeley, CO
Bike
2010 Silver NT700VA (ABS)
I'll add some Seafoam today.

The miss seems to be consistent in all gears and is more related to throttle position than rpm. I think. I'll check that too.

Thanks for the suggestions!s
 

OvO

Joined
Mar 29, 2016
Messages
27
Location
Pittsburgh
Bike
2010 Red NT700
My money is on the ignition, especially if you've never replaced the plug wires. I'd be guessing that everyone's NTs are going to be due for plug wires pretty soon. I don't understand why but it seems that marginal spark is only a problem under load - like climbing a hill or into a headwind.

It wouldn't hurt to replace the fuel filter if that hasn't been done recently.
 
Joined
Jan 25, 2012
Messages
709
Age
62
Location
NSW, Australia
Bike
2013 DL650/A & CX500 Euro
As it is happening at around 5,000 RPM in all gears my first thought is lack of fuel. I have seen this previously on various vehicles.

The second possibility is spark plugs or plug leads and the third is the air filter.

I would try the spark plugs first as they are cheap and fairly easy to replace. While replacing them check the air filter and replace if necessary.

Seagrass
 

mikesim

Site Supporter
Joined
Jun 7, 2011
Messages
3,331
Age
74
Location
Union, MO
Bike
NT700, Red, #989,
I'll add some Seafoam today.

The miss seems to be consistent in all gears and is more related to throttle position than rpm. I think. I'll check that too.

Thanks for the suggestions!s
If the throttle position (twist grip rotation) seems consistent, then that would perhaps be a clue to the TPS. Usually, the TPS doesn't fail in its entirety though. They seem to develop a bad spot and the problem may seem to go away after you twist through that bad spot. If your tech has an old fashioned analog volt/ohmmeter, it's quick work to check the TPS with a sweep test. On the NT however, it is NOT quick work getting TO the TPS.

Mike

I would first try the Seafoam cure. BTW, how many miles on the plugs? I usually change mine at 16K intervals. Even though mother Honda recommends 8K when I pulled mine at 8K and they were still pristine. They still look pretty good at 16K with minimal electrode erosion.
 
OP
OP
Phil Tarman

Phil Tarman

Site Supporter
Moderator
Joined
Dec 12, 2010
Messages
9,367
Age
81
Location
Greeley, CO
Bike
2010 Silver NT700VA (ABS)
Well, I bought the Seafoam today. Didn't get it in the tank. I'll try that tomorrow.

Thanks for the suggestions, everyone!
 
Joined
Jan 6, 2011
Messages
1,945
Location
Aurora, Colorado
Bike
19 Versys 1K SE, 14 FJR
FEED THE Hamsters.:rofl1: All the previous ideas are good, Has the bike kicked up any codes, to help in the trouble shooting. Maybe a newer less traveled NT is in store for you Phil. Aurora Honda has a 2011 used unit on their sales floor.
 
Joined
Jan 23, 2011
Messages
1,285
Location
Arkansas
Bike
2020 Kawasaki Versys
As mentioned it is mostly a crapshoot at this point. It sounds as higher loading causes it to surface which can be many things such as lack of fuel, lack of air, weak ignition, even a clogged muffler (cat converter). I would let the seafoam work, check the air filter, and maybe plugs while in the air cleaner area.
I don't suppose some linkage on your cruise control has slipped or something and is preventing the throttle butterflys from opening all the way up is it?

Good luck,
Brad
 
OP
OP
Phil Tarman

Phil Tarman

Site Supporter
Moderator
Joined
Dec 12, 2010
Messages
9,367
Age
81
Location
Greeley, CO
Bike
2010 Silver NT700VA (ABS)
I don't have any MIL codes showing and when the cruise control is disengaged (or even when it's engaged, for that matter) there isn't any change in the feel when of the throttle when I turn the grip all the way open.
 
Joined
Jul 1, 2014
Messages
148
Age
81
Location
Bettendorf iowa
The only other thing I can think that may cause the problem could be the charcoal Canister / vent system..I have never experienced any related issues with this setup, but have heard that the canister can get flooded with fuel..which effectively restricts the venting....Maybe ride with the gas cap loose may solve the problem temporary..
 
OP
OP
Phil Tarman

Phil Tarman

Site Supporter
Moderator
Joined
Dec 12, 2010
Messages
9,367
Age
81
Location
Greeley, CO
Bike
2010 Silver NT700VA (ABS)
The only other thing I can think that may cause the problem could be the charcoal Canister / vent system..I have never experienced any related issues with this setup, but have heard that the canister can get flooded with fuel..which effectively restricts the venting....Maybe ride with the gas cap loose may solve the problem temporary..
I hadn't thought of that. I'll give it a try and it's a cheap fix. Thanks!
 

DirtFlier

Site Supporter
Joined
Dec 13, 2010
Messages
3,332
Location
Troy, OH
Bike
2010 Silver NT700V/ABS
This is all ancient history to me but I recall the function of the charcoal canister is to accept gasoline vapors after the engine is shut OFF and once the engine is started the next time, it draws those vapors back into the engine for normal combustion.

On a car, it's much easier to ruin the charcoal filter by overfilling the tank because it has a line near the filler neck that can send raw gasoline to the charcoal canister but on our NTs, the overflow just dumps onto the ground. :)

Having it lose power at nearly the same RPM in each gear points to a fuel feed or perhaps ignition/TPS problem. The NT does have a fuel filter and it's integral with the fuel pump and not offered as a separate part.
 
Last edited:
OP
OP
Phil Tarman

Phil Tarman

Site Supporter
Moderator
Joined
Dec 12, 2010
Messages
9,367
Age
81
Location
Greeley, CO
Bike
2010 Silver NT700VA (ABS)
The "mechanic-in-a-can" has sorted my engine issues that I was talking about after my Kansas trip. I've only ridden the bike about 240 miles since I got back from Kansas and I had put 5 oz of Seafoam in before I rode it out Ft Morgan and back (113 mile roundtip). It had seemed as if the "missing" and lack of power that I had endured when I was coming back from Wichita, seemed better by the time I got back from Ft Morgan. Today I had added another 3 oz and topped off the tank before I headed to Front Range Airport for my meeting with Chuck. As far as i can tell, the bike was running normally! Yea!!

I had never used Seafoam before. Techron has been my go-to product for engine tuning but Seafoam may have won my loyalty from here on out. Chuck says that all these products are basically diesel fuel mixed with alcohol. I don't know about that and Chuck has proven that he knows way more than I do about all things mechanical. But since I'm always looking for the easy way out, Seafoam will work for me!
 
Top Bottom