Cam Chain Tensioner Failure

[KDRider]

I wanted to share this in case anyone else has the same thing happen.

SYMPTOM
I was riding along about 50mph not pushing the bike at all, on a hot 90+ degree day here in FL. The bike was running great. It's a 2012 bike with about 14,000 miles. Without warning, it sounded like the exhaust had developed a hole in it (???). I stopped took of the helmet to see where the sound was coming from. It was coming from the airbox!!??!!

At idle it sounded normal, but under any kind of load it had a ton of noise coming from the airbox. A noise that sounded like exhaust noise.

The bike ran like crap as I nursed it home.

CAM CHAIN HAD SKIPPED A TOOTH
The only thing that made any kind of sense was that I had a problem where my intake valves were remaining open at the wrong time. ….and sure enough that was exactly what was going on because I found that my cam chain had slipped a tooth. (Yikes!)

To find that the cam chain had skipped a tooth I pulled the plastic over from the right side of the engine that allows you to see the timing marks on the end of the cam shaft, and then I rotated the engine to where the #1 cylinder was at TDC. The timing mark on the end of the cam was of by a few degrees from where the factory manual shows it should be. I rotated the flywheel so #2 was at TDC and not surprisingly the timing marks on the cam were off by a few degrees again.

FAILED TENSIONER
I didn’t see anyone on the forum with a slipped cam chain who had posted. But I did see itlives posted where he had a cam tensioner fail. I pulled my tensioner out, and found that the spring in the tensioner had broken. This was certainly the reason that my cam chain had slipped.

Even with cam tensioner out of the bike, I didn’t have enough slack in the cam chain to slip it back. (I tried from the cam sprocket end, as well as the crankshaft end). I had to take the sprocket off the end of the cam shaft and move the chain back one tooth, and put it all back together. I confirmed that the cam timing marks were perfect once again at TDC for both cylinders.

BACK TO GOOD AS NEW
I bought a new tensioner (about $100) and installed it per the factory manual instructions, put everything back together, crossed my fingers and fired it up. I’m happy to say that it runs a good as new now.

Actually, the engine is now a bit quitter than it was before, and I suspect it must have been running with a loose cam chain for some time before the slip actually happened. I'm definitely going to check that tensioner each time the valves are adjusted from now on.

 

[HONDABIKEPRO]

i have not seen any cam chain problems with nc 700.. Always listen to your motor if the motor sounds different then normal, always take it to your dealer and have them listen to it. The cam chain has a very distinct noise, if you roll on the throttle in neutral the chain will be quite, as you let off the throttle, as the motor comes to idle the chain will make a lot of noise as the slack moves towards the tensioner. DO not run the motor any more if it makes this noise. Dale

 

[Deleted member 1183]

I did notice one other mention on this forum of a tensioner related failure. However as far as I can remember the chain did not slip any teeth. From memory also the actual slipper broke on that tensioner as opposed to the spring. I suspect that in both cases this is just a one off. Many thanks for the warning though as we can keep an eye out for such issues having been warned.

 

[KDRider]

Question: Anyone know if the NC700X engine an interference engine, where the valves will hit the piston of the cam gets out of time far enough?

 

[itlives]

Good question KDRider. I would also like to know.

In your picture, the arrow points to the piece of metal (the part that is not there) found in my crankcase with a magnet. That spring was also MISSING on my tensioner when I pulled it out. I never did find it. I imagine someday, if the engine is pulled apart, someone will say "You'll never believe what I found in here!".

 

[KDRider]

itlives -your post about your tensor failure was a big help to me when I was researching in my issue. That is crazy that the spring is hiding in your engine some where.

My spring was off the tensioner, but fortunately I found it right away when I pulled the right side engine cover. I surely dodged a bullet given the fact that that spring could have gone through the gear on that side of the engine.

 

[buckshot]

I've never liked that style of chain tensioner. Same sort of thing was in my Dad's XR250 dirtbike. Pain in the but to work with when the engine is apart, had to replace his at one point too.

 

[itlives]

itlives -your post about your tensor failure was a big help to me when I was researching in my issue. That is crazy that the spring is hiding in your engine some where.

My spring was off the tensioner, but fortunately I found it right away when I pulled the right side engine cover. I surely dodged a bullet given the fact that that spring could have gone through the gear on that side of the engine.

I never pulled my engine cover. If you read my thread, I was "looking" for the rivet(with a magnet) that failed and fell into the engine. I didn't even know the spring was missing until I compared the new tensioner to the old one. I bought it used and am thinking whoever had it before me ran the dog snot out of it because of the rev-limiter. I could see a young crotch rocket rider trying to get the same performance out of the NC, failing, and trading it in. I picked mine up at the local Suzuki dealer (I was looking at the Wee-strom)I got disgusted and just put it all back together and fired her up. I figured it would either break or run. She runs, and quite well.

I'm glad my thread helped!

 

[di_]

Hello! I`ve got some sort of trouble above. With similar symptoms.
A first time while I was riding, engine suddenly started stalling at idle mode. My friends told me that cam chain to noisy and suggested to inspect condition of chain and tensioner (by the way bike traveled 15 000km totally)
After couple days I rode to bike service, and when I was ridig i heard silent click somwhere out from the engine and it stalled down. I could not start engine anymore.

In the service we put off top cap and clutch side cap of engine. Bottob cap too. Inside we sighted a lot of metal filings. And we found a source - it was a inner side of engine body right wehere the cam chain are moved. About 1mm grinded.

Here is the photo of removed tensioner:

As you see metal plate (blue color) in the inner side of slider cracked (marked by red color). After that rubber (or plastic?) slider was decayed.

And some curious questions:
1.Where is a derbis of the damaged slider?
2. How could this metal plate got broken? Metal quality fault? Defective?

ps^ I`m russian, sorry for my english ^ )

 

[Grey1one]

Your english is fine, if you're lucky the debris drained out with the oil and filter.

 

[Lou Wambsganss]

When the tensioner failed, it could have let the timing chain get loose enough that it jumped a tooth (or a few) on either the crank or cam shaft sprockets. This would have caused the bad idle and engine stalling. It might have also caused damage to the valves and/or pistons if it was far enough off time. You might want to at least do a compression check to see if the valves are OK.

That's certainly odd. Heat can damage plastic tensioners, but on a water cooled, fuel injected bike like the NC, it is unlikely that the engine got hot enough to cause the problems shown. Have you ever noticed an overheat condition while riding? Does anyone know if the ECU will go into a "limp mode" if it senses coolant temp too high? That would prevent serious damage.

Another possibility would be the oil. Running the engine with insufficient oil level, or with oil of a poor quality or incorrect viscosity could lead to premature wear of tensioner components. Have you ever grossly exceeded the oil change interval?

If it were a manufacturing or assembly mistake, I would think it would have shown up before 15,000 km. The engine RPM is electronically governed, so I don't think that would cause the damage here.

These are just a couple of ideas. I'm really not sure. Damage to the tensioner like you have shown is more common to see on old engines with high mileage (or high kilometerage in your case) that have been used or abused.

 

[itlives]

I'm not sure but when it stalled on you it could have been broken then. It could have allowed enough slack to affect the timing and stall the engine.
Glad you found it when you did.
Make sure the timing is all ok and do a compression check (as suggested above).
I ended up putting mine back together with a new tensioner and just RIDING! Mine is still going strong.

di_ - welcome to the forum. Stick around!

 

[Rennie]

What does Honda say about this? Did you call customer support? This should be a goodwill fix covered by Honda?

 

[Hondafan]

That looks like the typical cam chain tensioner Honda has been using for years. They are generally reliable. The spring takes up slack as the chain loosens, and there is a steel wedge that locks the tensioner in the new position. The pulses in the chain do not act on the spring when everything works as it should. If that wedge jams, and does not lock the tensioner, the resulting pulses on the tensioner will act on the spring. This could cause it to break over time. It would also cause excessive wear on the friction material. This could be what happened.
Loose cam chains are noisy at idle, and get quieter as rpm's increase.

 

[itlives]

I would still like to know if the NC has a non-interference engine. Anybody? Dale?

 

[di_]

I never had any troubles before that.
I often ride in a dense traffic at low speed, sometimes fan start runing. But engine temp indicator doesn`t turn on (except check when I switch on ignition).
New oil every 4-5k Km.

I have no official guarantee because bike was bougnt in japan and brought in my contry for me.
We do like that because japan close enough from (I live on east coast) us and vehicle from japan market has more functionality and sometimes more reliable (haha ... not in my case ^ ) ) for the same money or even bit cheaper.
for instance - japan Honda NC700 has 525 chain.

But anyway I have an idea to notice them by mail ^ ) I wonder if they answer me? who knows. Does anybody have their email ? ^ ) can`t find it


Now the things I gonna do is put all back with new parts (waiting parcel from Japan with new goods) and tweak timing (I almost sure chain skipped a tooth).
At first time after breakdown we tried runing engine by a starter of course it did not start. But that was usual sound when I push start button like every time without any strange noises so hope valves and pistons are Ok ^ ) But anyway I`ll check compression asap as you suggest.
Then if the engine start normally I let it run 5-10 minutes and drain oil to get rid of the filings as much as possible and fill with the new oil (and put new filter of course) again.

I hope all that was just accident and such troubles will newer disturb me in future
I`ll keep you informed )) 3 month to go for the new riding season so I not gonna be hurry and don`t mind to discuss all this stuff ^ ) thank you

 

[L.B.S.]

Welcome to the Forum, by the way, di_

Sorry it had to be to report a bike problem, though!

I hope that is the only hiccup you have, and everything is perfect from now on

 

[di_]

Thanks !
Finally, I`ve got new parts I hope that will help ^)

 

[L.B.S.]

Good stuff! Are you going to install yourself, or have a workshop do it?

 

[itlives]

Don't pull that little wire thing out until you have installed! I would think your chain is fine. But since you have a new one, put it in and keep the old as a spare.