can anyone diagnose engine ‘surging’ prob?

[toowired]

The heat probably isn't helping the issue, but it's still most likely a connector needs some cleaning. It's not like you're boiling out coolant, so I don't think there's wires melting anywhere.

yeah it was pretty chilly here today when i went riding. why do you think bike runs fine first half hour though? that’s been the case every time.

are there pics / diagrams in the service manual that show the connectors? i know there’s instructions in the link provided earlier about how to access ecm.

 

[NewTo700V]

As for the connectors, I didn't take photos but the TP sensor is on the right side of the throttle body. Its connector is blue, somewhat behind the coolant expansion tank. You'll want to pull the right side plastic. I looked at a Honda parts diagram for the NT to ease my initial search. Specifically "Wire Harness / Ignition Coil" MEW4F3100. Part 11 is the throttle body subharness, the point where it joins the main harness is what I'm calling the mid connector. On the left side of the bike, follow the main harness some inches forward of the ECU once you have the gas tank raised and supported. You'll find a gray connector clipped to the inside of the main frame rail.

 

[toowired]

As for the connectors, I didn't take photos but the TP sensor is on the right side of the throttle body. Its connector is blue, somewhat behind the coolant expansion tank. You'll want to pull the right side plastic. I looked at a Honda parts diagram for the NT to ease my initial search. Specifically "Wire Harness / Ignition Coil" MEW4F3100. Part 11 is the throttle body subharness, the point where it joins the main harness is what I'm calling the mid connector. On the left side of the bike, follow the main harness some inches forward of the ECU once you have the gas tank raised and supported. You'll find a gray connector clipped to the inside of the main frame rail.

of course my tank is just about full. i’ll take a look at the tank assembly. if i recall on a really old (‘74) honda i had it more or less just rested on large flexible bushings. is tank detachment pretty easy? am i gonna need to drain the tank first? if so i’ll probly draw the line there and get the pros involved. first i’ll try the other two connectors, who knows, could be just one loose connection and not the frame one. of course that violates some sub theorem of murphy’s law

thanks so much to you and all. super pleasantly surprised at all the friendly help and quick response times. i’ll have to hang around here and visit the more ‘fun’ forums ...

i do love my bike and i’ve had a number of honda sport products over the years. this is the first time i’ve ever had an issue, and even if i have to take it to a dealer i can sure test their acumen first. def gonna try on my own though. pray for me ...

 

[NewTo700V]

You don't need to remove the tank. Just loosen the nut and bolt at the "hinge" near the seat end of the tank a little. Remove the two black hex bolts at the front of the tank by the bars. You'll then need to remove the left and right fairing pockets before you can raise the tank, the owners manual has that info for removing plastics.

Instead of propping up the tank with a rod, you can tie off a small rope like paracord, or even bungie strap hook ends to the bolt holes at the front of the tank and run other end back to the grab rails. That will keep the tank raised up enough to gain access.

 

[toowired]

of course my tank is just about full. i’ll take a look at the tank assembly. if i recall on a really old (‘74) honda i had it more or less just rested on large flexible bushings. is tank detachment pretty easy? am i gonna need to drain the tank first? if so i’ll probly draw the line there and get the pros involved. first i’ll try the other two connectors, who knows, could be just one loose connection and not the frame one. of course that violates some sub theorem of murphy’s law

thanks so much to you and all. super pleasantly surprised at all the friendly help and quick response times. i’ll have to hang around here and visit the more ‘fun’ forums ...

i do love my bike and i’ve had a number of honda sport products over the years. this is the first time i’ve ever had an issue, and even if i have to take it to a dealer i can sure test their acumen first. def gonna try on my own though. pray for me ...

oh hey, another question, what’s the name of the engine? i assume it’s 700 cc. are there other bikes/products that use the same engine, or is it unique to this bike? if so my guess is it’s not super familiar to most techs. although with the information you’ve all provided any decent tech could probly handle. hopefully

 

[toowired]

oh hey, another question, what’s the name of the engine? i assume it’s 700 cc. are there other bikes/products that use the same engine, or is it unique to this bike? if so my guess is it’s not super familiar to most techs. although with the information you’ve all provided any decent tech could probly handle. hopefully

still gonna try to fix myself first!

 

[DirtFlier]

You wrote "I downshift back to 1st below 30 mph."

1st gear at 29 mph would make the bike very touchy and overly-sensitive to any minute movements in the throttle. Once moving, I rarely downshift to 1st unless I'm at a stop.

I rarely get above 4000 rpm when riding on secondary roads that are flat and I'm mostly in 5th when the road speed is above 40-45 mph. If there are hills, then I'd use a lower gear but only as necessary. Let the engine tell you what it wants. And of course on The Slab, the tach is reading well north of 4000 rpm.

Going through curves in a higher gear or on bumpy roads can also give you a lot more control because the bike isn't jumping around so much. There is really no reason to rev the engine to have fun and often times all those unnecessary revs can be counterproductive!

 

[ARKNT]

It sounds like you may need to familiarize yourself some before digging in too deep. For instance since the bike is fuel injected the fuel pump is in the tank and there is a procedure to relieve pressure if disconnecting the pressure hose. You most likely don't need to do that but my point is a service manual may be much help.

One simple thing to check. Is the battery/charging system in good shape? If the voltage is low the TPS supply is low and can then give bad output and throw a code. Probably not the problem but a good simple first step.

Brad

 

[Phil Tarman]

I'd recommend buying the factory service manual before starting to locate and clean/reconnect/repair the TPI connector.

 

[Phil Tarman]

I think I'm like most people in the way I ride the bike. I usually don't shift into 1st once I'm moving unless I'm in a very tight hairpin-type curve with elevation change thrown in. Otherwise 2nd works for most of the really tight stuff. I like 3rd for tighter twisties in the foothills and mountains. If I'm running where there are sweepers with little speed change or any open highway, I'm always in 5th unless I'm accelerating fairly hard.

 

[DirtFlier]

Checking battery voltage and also cleaning and greasing the battery terminals/cable ends is a no-cost procedure - always do the easy stuff first!

ps. keeping the revs up is an ancient idea that is no longer valid, especially with the softly-tuned NT700V.

 

[toowired]

It sounds like you may need to familiarize yourself some before digging in too deep. For instance since the bike is fuel injected the fuel pump is in the tank and there is a procedure to relieve pressure if disconnecting the pressure hose. You most likely don't need to do that but my point is a service manual may be much help.

One simple thing to check. Is the battery/charging system in good shape? If the voltage is low the TPS supply is low and can then give bad output and throw a code. Probably not the problem but a good simple first step.

Brad

i keep a battery minder on it constantly, it always starts right up. next time it’s running i’ll check the battery gauge. does anyone know if a pdf of the service manual exists?

yes, i am most nervous about screwing around w the gas tank. i think i will try checking the two easier to access connectors first and hope i get lucky. if i go at the tank i’ll take it slow and proceed w caution, making sure i don’t just pull at stuff willy-nilly.

 

[Phil Tarman]

AFAIK, there's no legitimate pdf of the shop manual. Spring for the whole deal and avoid violating copyright laws. It's about $60, but it's well worth it if you're going to be fiddling around with any maintenance. It's the only source for a wiring diagram that I know about.

 

[DirtFlier]

I've been underneath the fuel tank for many reasons and have never once disconnected the high pressure fuel hose. Long ago, I decided to spend a few minutes making a simple prop to hold up the nose of the tank. I used an old broomstick handle and sawed an angle at the end and attached a piece of plywood onto which I mounted some long machine screws to act as locating studs for the front mount on the tank. It works every time and only cost about 15-min of my time.

 

[NewTo700V]

I like tying off the top of the tank to grab rails behind, that way the work area under the tank is clear.

As for fuel lines, there's no gas tank connections to be messed with for this task.

 

[toowired]

thanks for the continuing flow of support and info dirtflier, the tank looks almost perpendicular in the photo. i assume it was empty or almost empty? how high will i need to raise the tank in order to be able to access the connector? my tank is almost fulll, and it’s unpleasant to ride w current problem.

i googled and there’s a very legit looking pdf of the service manual online for $20. i buy my music from i-tunes. i don’t want to alienate anyone, but i’m cheap and this is a discontinued bike. i feel like it’s very low on the piracy scale if current owners of the machine were to share this pdf. if no one has it and can share, i’ll spring for it. i’m sure some folks who already have the printed manual might want a version to pull up on a device. DMs open, as they say

 

[Brillot2000]

It sounds like to me that you are not building up enough pressure on the fuel rail to support the engine under a load. This could be directly related to fuel flow. A restricted fuel flow will not allow the pump to build up to the required normal operating pressure.

I would suggest that you do the Fuel Flow Inspection called out in 6-41 in the OEM Honda Shop Manual.

 

[Phil Tarman]

Bruce, his symptoms sound just like the ones I had when the issue was a connector between the ECM and the TPI. Fixing (whatever that involved) the connection completely removed the symptoms -- at least for the last 500 miles since the repair.

 

[Brillot2000]

Bruce, his symptoms sound just like the ones I had when the issue was a connector between the ECM and the TPI. Fixing (whatever that involved) the connection completely removed the symptoms -- at least for the last 500 miles since the repair.

Certainly a possibility. The manual does go into some level of detail on how to Test the Throttle Position Sensor, refer to 6-23 through 6-25. The MAP (Manifold Absolute Pressure) Sensor might be worth a look. Inspect the hose leading to it and away from it for any loose connection or cracks in the hose. A vacuum leak could affect how the engine runs.

If the problem was after the engine came up to operating temperature and then the engine started to sputter. I would suspect the IACV (Idle Air Control Valve) located on the throttle body.

 

[Phil Tarman]

Mine didn't start to sputter until it had been ridden a while. His acted the same way.

Last year (late '17 until late summer of '18) I had a fuel pump issue. It behaved similarly, but it was different from this deal that got fixed by repairing/reconnection/replacing a connector. The fuel pump never threw an MIL code -- this did: 8 short flashes, which pointed to the TPI. "toowired's" bike showed the same code. With the fuel pump issue I had, the issue showed itself when I opened the throttle past a certain point a little past 3/4 throttle, IIRC. When I'd do that, the bike would act as if it had a choke that had been activated. I tried Techron and some other fuel additives and would get improvement. I rode all the way to WV and around there with the WV Rally group, then to Columbus and back to WV for Eric Trow's Stayin'Safe rider's training course and only had the symptom a couple of times. But then when I got into Kansas, it got worse and worse. I rode about 1800 miles to Grand Junction and then a good part of the route for the How the West Was Won Rally and home and the bike ran fine until the next week when I took a shorter ride.

By then I had decided that it was probably the fuel pump and when I took it to the dealer for repair, the tech told me that there were several other things it could be and that all of them were cheaper than the fuel pump. He suggested that if I wasn't in any great rush I could leave the bike with him and let him "fiddle" with it between other jobs. I don't know what all he tried, but I do know that he had the bike on their dyno at least twice. Finally after nearly a month, he told me he was baffled and was going to try the fuel pump test. It turned out my pump had adequate pressure, but less than half of the specified flow. So, he replaced the fuel pump and the bike ran great until after the last service (which took quite a while and cost quite a bit because of stripped valve cover bolts which took HeliCoils to fix. When I got it back from that service was when the TPI code and the sputtering started.