RC 36 , knocking noise

Hello, I hope someone here can give me some opinion about the "knock noise" my vfr developed a few days ago.. Here is the youtube link Honda VFR 750 -Strange clicking / ticking / knocking /tapping noise? - YouTube . I hope its not a rod or something serious.. The bike is running fine, but when cold the noise is loud and with warmer engine temperature the sound is muting..

 

While you are at it, with all the plugs pulled out, check the compression on all cylinders. If you find the piston that has a bad bearing as tinkerinWstuff explained, compression test should confirm this.

Another thing to check to confirm bad rod bearing after compression test is to look for metal shavings in your oil. Not sure if you have one of those fancy magnetic drain plugs, if you do not, you could put a magnet on the drain plug and run the engine for a minute or two.

 

Ok,so I was riding the bike for about 300miles after the video ,and the sound is not changing (it is not louder or quieter),there is no power loss, or any affect on performance :S.. As I said, the sound is much more louder on the camera than for real..But it is pretty loud when the bike is cold, and for the first 10 minutes is the loudest..After some time riding it, it just disappears, you can maybe hear it if you listen very closely,.. So I drained the oil,and there is no trace of any metal shavings or anything, the oil looks normal.. Maybe too black for the miles, but ok,since the bike is running rich..I removed the clutch cover, and nothing suspicious there either! I will remove the clutch tomorrow to see oil pump etc.. Any ideas? Thank you!

 

Not sure if you will pull the oil pan or not, but if you do, you should be able to rotate the crank and reach the bottoms of the con rods and check for play.
I assume you checked all the gears and little springs in those spring loaded ones.

 

I think we are focusing here on a spun rod bearing, since that is the most obvious thing that can cause knocking when cold, before metal had a chance to expand and seat.
I am not sure what else could be a culprit, since nothing else I know would produce such rhythmic, consistent, rmp-dependent click when cold, but not warm.
Just for kicks, what happens when you put it in gear, but with clutch disengaged? Or when you drive it around when cold and shift through a few gears? Same noise, regardless of bike sitting or driven?
A good stethoscope might help you in tracing the source of clicking more accurately, although I had so-so experience with it when noise is buried inside the engine.

 

To my inexperienced ears, it sounds like the valve tap/tick I was getting on my 86'...

 

That is a vile.....ugly.....sound. :fear: I would think that would be super easy to locate the source of in very short order. Granted some tools and beer will be required.

 

Wouldn't a valve tap be present even when engine is warm, and even be louder when warm than cold? Ticking in this case goes away once engine warms up ...

 

maybe pilot idle screwa or carbs badly out of sync?

 

I think you are right. Thanks for the correction. I missed that in his first post.

 

Thank you so much for answers people!! So here is the thing, I had a very bad gas mileage when I bought the bike , and loud pops from exhaust (There is other thread where I explain this). When I figured that I can't sync the carbs myself since I dont have manometers (Don't know how you call it) I gave the bike to a shop.. The bike was there about month and a half :S ,and when I picked it up everything was basically the same.. The consumptions is maybe just a slightly better..Long story..Ok so I removed the clutch yesterday and now I have some questions. There are springs on the clutch outer (6springs, not clutch springs ,there are 5 of them) And those springs are not having some tension,and I can basically rotate some of them.
So should those springs have tension when engine stationary?
I noticed that oil pump chain has a big slack.. Is that normal??Also ,the oil pump shaft (where the sprocket goes) has some clearance in and out (you can hear click when pushing it in and out, and when you rotate the pump there is slightly more resistance than it should be by my opinion..
I droped the oil pan but could not drop it entirely since the exhaust has to come down (and we all know what pain in the ass of job can that be).
So I tested the right rods trought space I had, there is some clearance left-right but I think its in tolerance (less than half of mm by aprox meassure), and there is no free play up-down.. So I think that's good! I can't test the left ones right now, but since the sound was clearly coming from the clutch cover, I am really focusing on the right side..
Also there are some springs on the gear of the right crank side, and this looks all good.. I forgot to mention that starter clutch had some very strong burnt smell, but everything looks normal, and it grips just by rotating it by hand.. hm..

 

What exactly do you mean by clutch outer? Clutch basket, the part that clutch plates sit in and that has a big gear on the back of it? If this is the case, I believe indeed it does have split gear with tensioning springs embedded in it, and these springs should be tight at all times. If they are not, somehow your gear under tension has skipped a tooth, and is now rattling. But I am not sure if these are the springs you are talking about, a picture of what you mean would be good if you can post it.

Oil pump chain should have some slack, but not a lot. Like 5mm or so. It could be that the chain stretched under the chatter and banging from the big clutch basket gear, if it is indeed a problem as stated above.

 

Yes, I meant clutch basket, and the springs on the back of the clucth basket!!
This springs:

.
Here is the video of the springs free play: Clutch Basket Springs - YouTube (Im not a ghost, I was just sanding lol)
Sound of the clutch basket while shaking it : Chaotic Clutch Basket Shake - YouTube (warning,can make you dizzy xD)

Oh and the starter has some free play (which is normal), but is this much normal? : Starter - YouTube

The oil pump maybe has little more slack ,maybe 6mm, but nothing looks damaged or worn out..It doesn't look like it could slip of the sprocket by itself ,it just has a little more "free play"..

 

Awesome videos! It brings a whole new perspective to "online mechanic", and gives us idea exactly what you are talking about! Wow, I wish people were as good as you about posting details of their problems.

I would say that starter play is OK. There are shims (thin washers) inside the starter that are supposed to limit this axial play, but over time they wear out a bit. This should be no problem, as long as you do not have large left-right radial play. It looks to me like your starter is OK (I hope it is not clicking itself , I have see much worst and still operational. You can always test the starter directly by getting battery voltage to it's terminal, like with jumper cables or some similar thick wire (it will draw a lot of current .

Now, for the clutch basket, I am not sure it is bad, but I am not sure it is good either. I never really shook mine like you do in 2nd video, but I think I did have similar rattle noise when I moved it around. Tension of the springs (free play if you want) inside the big gear also seems OK, since gear is off the shaft. Again, I am not sure, so if someone else can chime in, it would be great!

What I did not see clearly is the relationship of the teeth of the two split big gears on the clutch basket. There should be a little offset, where gear further away from the clutch plates should be a little "back" from the main gear, like ~1 mm or so. When you install the basket, this offset gear needs a bit of force to align it to the mating gear on the crank, and this is where inner springs get tension, when you align the gear. I am not sure I am explaining this correctly, so ask if I am not making sense

What I did not see from the video is if there is "offset" between these two gears.

Since you are fairly good with mechanical stuff, I am sure you can see how the whole contraption operates. If the gears indeed do not have offset, it could be that little tabs that springs rest on, inside big gear, are a bit bent, or it could be that springs themselves just compressed and lost their "length". This could also be the source of your rattle, but I would expect the rattle to change as you operate the clutch, since then you take load off the basket.

Lastly, based on what you said about chain for oil pump, I also think it is OK.

 

Rising the topic from the dead =D .Thank you mastergregor for your answer, Im sorry for the late post, didn't see it before.. Anyway I decided to answer and help the people who may have the similar problem in the future! The problem was in clutch basket indeed! I was working on a bike for looooong time (when I got free time and money) , there was a lot of complications followed one by another and thats why I'm answering the topic now.I'm not sure how to explain this correctly but I will give my best , if someone has some questions feel free to ask! So , when I took apart the clutch basket I realised that there should not be that lot of a free play between springs and basket.. So looking at the system and how It works me and my friend realised what the problem was.. The clutch basket has inside some sort of a "cone ring or shim " whatever you want to call it.. That ring is puting tension to the whole basket system, so that here is no play.. What on the other hand does springs do is absorb the engines torque , hard accelerations etc.. Something similar to the car clutch.. If there where no that cone ring , then springs cant do their job well and there is that free play.. What happened in my case was next : The cone ring reverted (fliped) itself to the other side ( as you where press it with hands to it kind off pops to the other side and stays that way) and because of that it was not making any tension causing clutch basket to rattle.. My guess why this happened is because one day I was reeeeeelay late for work so I maybe pushed the bike too hard when still not on a operating temperature.. Since the rattle started that day after the bike started later when cooled off, and that cone ring is very thin and could be forced to flip on the other side by suddenly applying a lot of heat , thats only conclusion I got to..

Anyway bike purrs like kitten now, but I'm still having old consumption and some stalling problems now.. -.-
Will get to that problem in another topic when I get some time
Cheers