Dealer claims it has a broken timing chain. I doubt it.

jtanner

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Here's the short story version:

I picked up a 2012 NC700x with around 9k miles on it. Newish tires, full luggage set, center stand, tall windscreen, engine guards, hand warmers, etc. It's a great setup! The guy I bought it from (who owned the bike for less than a year and didn't seem mechanically-inclined) said he was riding in stop-and-go traffic and it just died. He noticed the fuel light was blinking and suspected it was just out of gas. After getting to a nearby station and filling it up, it started up and ran fine, but only for short amounts of time. He took it to a dealer and after looking into it, they reported that the timing chain was broken and that replacing the entire engine would be the most cost effective.


Now, correct me if I'm wrong, but there's no way a bike with a snapped timing chain would start. Right? Seems like the dealer he took it to must have been pretty shady. They even told him that they tore the engine apart to look at it.

In any case, I now have possession of this beauty and wonder where to start. Fuel pump? Injectors? I'd love to hear your guys' thoughts.
 
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1wiseguy2

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Well right off the bat I was thinking that maybe you are drawing a vacuum on the tank (as in a clogged vent)and gas isn't flowing to the engine or something is heating up and not allowing fuel to get to the engine.
Is the tank vented through the cap? Start it up with the gas cap removed and see if it runs longer than before.
Timing chains open valves. If no valves open then no engine will run is my thinking.
Hope you got it for nothing or almost nothing if the chains snapped[emoji6]

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jtanner

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After a short bid war with another interested party, I snagged it for $950. I wouldn't have paid that much if it weren't for my suspicion that the problem isn't as bad as suspected!

Thanks for the tips! I'll try pulling off the cap and see if that helps.
 

dduelin

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It would be impossible for the bike to start at all with a broken timing chain but often the children's game "Telephone" best describes a mechanic's diagnosis that has been through 2 or 3 people before it hits the interweb. Perhaps a broken timing chain is not at all what the mechanic said or meant to convey.

How long does it run? 5 seconds or 5 minutes - hey it makes a difference! Can you put it in gear and get enough power to smoothly ride it up through the gears efore quitting or does it sputter to life and run for 5 seconds in neutral?

Start with making sure the battery tests good and the connections are tight. With the key switched on, you should hear a faint whine under the seat for about 10 seconds as the fuel pump pressurizes the fuel delivery system. The fuel pump audibly runs a few seconds then cuts off. Good? Now is there fuel in the bike and is the fuel fresh - less than 30 days old? Is the inside of the fuel tank that is visible clean and shiny or pitted and rusted? Immediately after it quits, turn the key off and right back on. Now does the fuel pump make the same noise as before? Will it restart immediately? Does the instrument pod blink or flash any trouble codes?
 

jtanner

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Good point about the communication that can be lost from the mechanic. I suppose it won’t be too long before I find if it does have serious engine damage or not. Thanks for the pointers! I’ll be playing with it in the garage more comprehensively in the next few days.


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dduelin

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We hear that a lot but vehicle manufacturers don't warn operators about maintaining fuel above certain levels. Fuel running through the pump would cool it as well and when fuel runs out the pressure regulator cuts off the pump.

My daughter when she was a teenager to early 20's provided abundant anecdotal evidence. Everytime I got in her Honda Accord to move it in the driveway it was on an 1/8th tank or so, it seemed she never put more than $5 at a time in it. Totaled at 230,xxx miles on original fuel pump which is a direct replacement for many Honda motorcycles.
 

670cc

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If fuel pumps were ever being damaged from low fuel level, fuel pump manufacturers have had ample opportunities over the years to correct that defect. I can’t recall any vehicle owner’s manual I’ve ever had warning of potential pump damage from low/no fuel.
 
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jtanner

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Thanks for the follow-up.

We're in the process of preparing to move into our first home, so bike stuff has fallen onto the back-burner.

I'll be sure to post an update here when I get a chance to investigate!
 

jtanner

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In the meantime, here's a picture of both my NC (red) and the new one in question. Needless to say, the overall plan is to take the aftermarket parts from the upgraded one and put them on mine. After fixing the one in need of repair I'll sell it for a little profit (assuming the problem isn't too severe).

NCs.JPG
 

davidc83

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If fuel pumps were ever being damaged from low fuel level, fuel pump manufacturers have had ample opportunities over the years to correct that defect. I can’t recall any vehicle owner’s manual I’ve ever had warning of potential pump damage from low/no fuel.
My 1983 GMC Safari minivan had the warning in the owners manual...stated something like continual usage below 1/4 tank of fuel could damage fueling system....I do know my wife at the time continually ran it low and the fuel pump did go out (and it was in the gas tank)...just so happened...I had just filled it up when it went out...you know how heavy 29 gallons of gas is????
 

TigerDude

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My 1983 GMC Safari minivan had the warning in the owners manual...stated something like continual usage below 1/4 tank of fuel could damage fueling system....I do know my wife at the time continually ran it low and the fuel pump did go out (and it was in the gas tank)...just so happened...I had just filled it up when it went out...you know how heavy 29 gallons of gas is????
1983 was a real low-point for US auto manufacturers. That era is basically what made Toyota and Honda a thing here.
 

davidc83

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1983 was a real low-point for US auto manufacturers. That era is basically what made Toyota and Honda a thing here.
Besides the fuel pump and a whole in the radiator (big rock thru front grill), no other issues...sold it with 250,000 miles on it...that minivan probably best vehicle I have ever owned (have a Toyota now)....got pulled over doing 130mph outside of Little Rock Arkansas....got let go with a warning (Air Force at the time, and the police offier was former Air Force SP)...and yea, I was going that fast...oh, and it was an 87, not an 83...My 83 was a Pontiac Sunbird (piece of crap).
 

jtanner

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Hey all, apologies for the very long delay on getting to this. We moved into our first home and have been working on renovations for months as well as prepping for a baby (also our first).

I finally had a chance to take a close look at the bike this past Saturday. Here's a quick summary:

The battery was dead and deemed "bad" by my battery charger, so I put in the battery from my good NC and turned the key. The fuel pump primed normally and the gauge display was normal as well. After hitting the starter button I was surprised to find that the bike started up immediately with no hesitation. However, it was immediately apparent that the idle was choppy and weak. I pulsed the throttle to keep the bike alive, and it continued to run as long as I was feathering it (total of maybe 30 or 40 seconds). I tried to rev it up, but the RPMs stumbled and tripped. No odd sounds coming from the engine from what I could tell. The bike did not die until I completely released the throttle, and then within 2-3 seconds it was off. I did take a video, but I'm not sure if I can share videos on here? Anyway, maybe I'll try later.

I pulled the plugs (see picture) and will be putting new ones in soon.
Air filter had a little debris but nothing substantial at all. Overall clean.
Fuel injectors are fully functional and shoot strong fuel streams. This also seems to prove that the fuel pump is okay

At this point here are my top suspicions:
-Contaminated fuel
-Spark plugs

My current plan is to put some new plugs in and then check for any improvement.

Thoughts?
 

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ROBERT DOSS

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I WOULD CHECK THE PUMP RELAY FIRST.
THEN, CHECK THE TIMING PICKUP, HAD A BIKE ONCE THAT WOULD START AND RUN FINE, UNTIL YOU PICKED IT UP OFF THE SIDESTAND, JUST A NICK, BUT ENOUGH TO GROUND OUT THE IGNITION.
 

670cc

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From the photo, the spark plugs look fine. Are they both the same color, and was either one wet?

Before any shotgun part swapping might begin, it might be a good idea to go through the valve adjust procedure, paying attention that the cam timing marks align as expected. Also, although it does not fit the description of the original failure symptoms, could someone have done a botched valve adjustement on the false TDC? If you know the engine is entirely adjusted correctly to spec, then you can approach the problem as a part failure.

We have seen a couple cases of problems with the engine’s idle control device (Usually an IAC valve, but I forget Honda’s name for it). The idle control can’t manage air flow to maintain idle speed, so idle is uneven or the engine dies. What happens if you actually try to ride this bike? Does it run normally off idle?
 
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jtanner

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From the photo, the spark plugs look fine. Are they both the same color, and was either one wet?

It might be a good idea to go through the valve adjust procedure, paying attention that the cam timing marks align as expected. Also, although it does not fit the description of the original failure symptoms, could someone have done a botched valve adjustement on the false TDC?
The left spark plug was definitely wet. I remember noticing that. Color was about the same for both.

Not a bad idea to check the timing. I'll put it on the list.
According to the previous owner's story, the bike was running fine for a long time without any issues before it started acting up mid-ride. He didn't have any work done on it other than having a dealership put a new chain and sprockets on.
 

670cc

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If the left plug was wet, but the right was fine, it may indicate an ignition problem on the left cylinder. If one cylinder is cutting out, it probably can’t idle smoothly or for long on one cylinder.
 
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