Help! Weird knocking noise

I own a 2007 VFR800 with 16,000 miles on it. In general, the bike runs/rides fine. However, about a month ago I started to hear the faint noise of knocking somewhere in the engine. Unfortunately, in the last month the knocking sound has gotten much louder.

In general, the knocking is kinda like the sound of a very worn piston rocking back/forth in the cylinder bore. However, the sound is not more pronounced during cold start-up (which is very common for piston knock) and it does not change in frequency or intensity as engine rpm goes up/down.

The other day I pulled in the clutch around 30 mph as I was coasting down to stop. While the engine rpm went to idle (around 1,000 rpm) the knocking sound continued. With the clutch still in I revved the engine fast and slow but it did not affect the frequency of the knocking sound. I have since tried this test many more times and the result is the same. Clearly, the knocking is based on road speed ... not engine speed. Thus, the knocking is likely coming from the transmission ... not from the engine.

In general the transmission shifts fine with no issues. However, when pulling away from a stop and during light throttle the knocking is far more pronounced. During medium acceleration there is less knocking and during hard acceleration there is no knocking sound. In addition, at higher road speeds (60+ mph) there is no knocking sound. Thus, I am guessing that during hard throttle or high road speeds (with lots of wind drag on the bike) there is much more load on the gearbox which eliminates the knocking sound.

Again, the bike runs/rides fine. The chain is adjusted and the sprockets look fine. The brake pads were recently replaced and the tires (and psi) are good. I recently changed the oil/filter and there was no debris in the oil. The bike starts fine, idles fine, and has no leaks. The clutch actuation is smooth, there is no clutch chatter, and bike shifts fine.

Thus, does anyone know what the gearbox noise can be?

Are VFR’s known for having gearbox issues?

Help!

 

Can you duplicate the issue on the center stand?

 

This won't help your problem, but your idle is a little low if its at 1000. Should be in the 1300-1400 range.

 

I can try that later today. Hopefully the bike won't come off the center stand as the rear wheel is spinning a 30 mph!

 

I'm not so sure that's what Toe had in mind? I know I wouldn't be too keen on running my bike on the center stand.

 

I know you said the knocking does not go up with the rpm's but does it increase with the speed of the bike? If so, it could be your chain. A link could be seizing up. Mine just started that recently and I found the link that was really tight. Problem solved when I put on new chain and sprockets.

 

The noise is most prominent between 0-40 mph during light/medium throttle. When I coast down from 40 mph to a stop, the sound is a bit different as it has a little more of a grinding sound to it. I don't think the grinding sound is coming from the brake pads dragging on the rotor ... but it is possible.

Regardless, it is more of an on-throttle issue than an off-throttle issue.

If a link in the chain were seizing up ... why would that cause a knock-knock sound when under throttle??

The only chain related thing that makes sense to me is a faulty bearing or seal for the shaft that goes through the side case where the front sprocket mounts. If that shaft were wobbling around then maybe it could be causing a bad sound.

Again, has anyone out there had a similar knocking sound in the transmission during light throttle?

 

You will know if you have a link that is getting tight. Put the bike up on the center stand, NOT RUNNING, in neutral and slowly turn the rear wheel in a forward moving direction while watching the chain on the lower side. A link that is stiffening up will readily be visible as it will not lay flat like the rest of them. A simple thing to rule out. I thought my issue was deep inside the bike's engine because I felt the knock on my feet. Seems to be more prevalent on light acceleration than deceleration though. But was there for both.

 

OK, so I just put the bike on the center stand and then fired it up. I gave it light throttle in First and Second gear and ... wow ... was there a lot of clunking/popping noise coming off the chain and gears. I put my ear next to the transmission and heard some clunks/knocking ... but way louder was the clunks/knocks at the rear sprocket.

With the engine off and the bike in Neutral, I slowly spun the rear tire while watching the chain. I saw no link(s) that were not laying flat. However, as I spun the rear tire at one point there was a pronounced bind as one of the links curves around the front sprocket. When the link connects with the rear sprocket there is a low squeak sound. I tried this many times and the same tight spot and squeak occur.

Thus, I think that 34468 Randy is correct! I will order a new chain and rear sprocket today.

Questions:

1. Do you think I need to replace the front sprocket as well?
2. Is the factory chain a "press fit" or does it have a removable master link?
3. Is there a chain brand/model/style that I should use ... or just stick with stock?

 

Stock is fine. A quality chain that lasts the usual 20-25,000 miles ain't cheap + 2 sprockets, but sometimes you gotta spend. See if you can borrow a chain press tool cuz if you trend toward worriyng, a removable-link might not be best.

 

Alright then. We have gone this far, I suggest we do a couple other tests. Same as before rotate the wheel, forward motion engine off. When you hear the clunk, mark a spot on the chain with a felt pen. You will obviously need to clean the chain link first. Then rotate the wheel a few times and see if that sound always comes as the mark comes around to a specific spot you are watching. Now you have narrowed it down to a specific location. From this point, you can now see just where on the chain, it crosses the sprocket. Mark this spot as well and rotate the wheel so that the spot in question is now along the bottom run of the chain loop. You can examine the chain more closely now and determine if in fact it is a tight link on the chain. Over kill? Maybe but it would be nice to confirm it is the chain before you spend the money on it.

Answering your specific questions:
1. I am a believe in changing chain and both sprockets at the same time. I do buy in to the theory that you don't put a new chain on a worn sprocket. Most here do as well yet some are adamant that this is not necessary.

2. I do not believe that the factory chain has a removable link. You will need to press a new link on the new chain. There are links available on line that are removable but I am not a believer in those either. Again some here are. You may need to borrow or buy a chain tool. There are all sorts of videos on YouTube that show you how to change a chain and sprocket set. They are pretty good. I changed mine for the first time only a month ago by myself with a borrowed tool and other than an issue I had with a corroded well nut, it went fine. All the other chains were either replaced by the shop at a stupid cost, or a friend did one change for me. I borrowed his chain tool.

3. D.I.D. is very reputable for chains. You can buy cheaper but you get what you pay for. I think all my chains since the first replacement have been D.I.D. I got mine from here: Sprocket Center. Find the specs on your bike's chain and sprockets and they send you everything you need all matches up nice and neat. I don't know which bike you have but mine had a 16 tooth front, 43 tooth rear and a 110 link 530 chain. This time around I bought a heavy duty chain with x-rings rather than o rings.

 

Sorry. Just re-read your original post and see you have an 07 so your chain and sprocket will be the same as mine.

 

Today I ordered new front/rear sprockets and a new DID chain. Hopefully the new wares will fix the problem. I will chime in later to inform of the results.

 

Can of chain lube on the shopping list could not hurt.

 

Last night I installed new front/rear sprockets along with a new 530-style chain. The result is ... insert drumroll here ... the clanking/clunking noise is gone!

I inspected the old (original) chain that had 16,000 miles on it and there were no fused/stuck links. However, there were numerous links that were significantly stiffer than others. I am shocked that a few stiff links could make the bike have such a terrible "the tranny's ready to blow" sound. However, 34468Randy was right!

 

Glad to help. See. Sometimes I am right. Please tell my wife of this. Now. Keep the new chain well lubed and you should get 25K or so out of that chain.