Knocking sound, please help

I've posted about this problem before but couldn't describe the knocking (who could) so now I have video. Its a 1992 VFR 750 with 77,000 miles on it. First some background.

I wasn't riding much so just disregarded the problem but once in a while I would hear a knocking sound consistent with engine speed, only at low idle like lower than 1200 RPM, only in neutral, usually only when warmed up, coming from possibly transmission but hard to pinpoint, and the weirdest part... it would go away when the clutch was pulled in. I was only riding like two weeks a year, so ignored it. It was suggested it could be a carb sync issue causing vibration so that was what I was going to try. It did this for like 5 years and was doing it before I stopped riding it so its not from sitting.

I am now trying to fix the bike up because its now going to be my primary bike as I sold my other one, so first things first, changed oil and filter, change air filter, flush radiator, valve adjustment(within specs), replace plugs, new battery, and the bike ran 100 times better, but still had the slight knocking described above, so I decide to fork out $70 for a sync.

I had the carb sync done by my local shop, and now ITS 100 TIMES WORSE. The idle response is a lot better and the engine runs smoother, but now instead of hearing the knocking every once in a while its almost constant, and a lot louder, and happening at slightly higher RPM's as well (still only below like 1300 RPM though). I still can't figure out where its coming from. It doesn't make the noise when the clutch is engaged. It makes the noise in neutral and when in gear and the engine speed is close to 1000RPM. I've tipped the bike forward, backward, and side to side, doesn't seem to affect the noise at all. It happens more readily when warm rather than cold. I need to know if I should just rip into the transmission or completely remove the engine to get to the heads or sell it and buy something else because its going to need a complete rebuild.

I have two videos. First is when the bike is cold. I just take it off choke and you will hear the knock every once in a while, but not often. Thats how it was all the time before the sync.

In the second video I just took the bike around the block to warm it up and removed the side panels to better pinpoint the sound. Sounds like its transmission or rear heads. It never makes the sound when I pull the clutch. Toward the end it will go in and out like I'm pulling the clutch but I'm not, sometimes its just not continuous but cuts in and out.

What could this be??? I'm thinking something loose in the transmission, piston slapping a loose value in a rear cylinder, crankshaft vibration, I just don't know. Wondering if it could be a clogged carb pilot jet or something feeding the wrong mixture to only 1 cylinder at idle. Bike runs great, doesn't have any problems at RPM's higher than idle, and still idles smooth aside from the knocking, so definitely its not affecting performance. Please help.

http://www.jtasolutions.com/videos/Bike1.AVI

http://www.jtasolutions.com/videos/bike2.AVI

Thanks,

~Todd

 

Did the shop notice it when they did the sync?

 

77000 says something for Honda.

 

yeah, the shop wasn't too interested, and just kinda said they didn't know what it could be. Nobody seems to want to touch these older bikes, especially for someone that doesn't want to shell out $1000 for repairs. I'm going to take it to a honda dealership and have them give it a listen and give me opinions but they already told me they wouldn't work on it. Thought I'd see if anyone here recognized the sound.

 

It's normal, both my 1990 and 91 models did this. My 97 does it too but not so much.

Ride the bike and enjoy.

 

Yeah, as Sye said, that is normal. That is actually the clutch pushrod (the rod that goes thru the case from the slave cylinder to the clutch basket) making that noise. It is very normal and I'd venture to say it goes away, or at least is not as loud, when the bike is warmed up and youhave a few miles on it for the day. My 93 did that all teh time and I had no issues at all other than it being annoying until the engine warmed up and it quieted down.

 

Thanks for your replies. I've owned this bike for 5 years and never heard the noise for the first 3 so I'm wondering if its normal maybe it has to do with something wearing down and it can be silenced. The noise I'm having occurs more when the bike is at temperature and doesn't occur so much while cold and its also a pretty hard clunk, and can be felt through the handlebars. I had the pushrod out a month ago while rebuilding the slave cylinder, and it didn't feel heavy at all, and fit pretty snug through the center of the bike. Also I thought the pushrod was under a constant slight pressure from the slave cylinder spring at all times and that should be holding it steady. I'll look into it though. Can you run the bike with that push rod out? I don't think there is a direct path for oil to travel out the hole it would leave, but can't be sure. Also, if it is the cause, would smothering it with grease cure the problem? And why would the problem have gotten A LOT worse after a carb sync was done? I'd really like to fix it because it sounds like something is seriously wrong, and even if its normal I'd like to bring my bike back to its nice throaty steady smooth idle that I used to enjoy during the first 30,000 miles I put on it. I hate being embarrassed when out on the bike I love because it sounds like its about to blow a valve or something.

 

I have just litstened to the second clip and yes it does sound odd.

Put the bike on the side stand and remove the right hand engine cover. Make sure you have a replacement gasket. With the bike on the sidestand you will only lose about an egg cup full of oil.

Once it is removed, check the tightness of the spring bolts and condition of the inner clutch hub pegs. I think one of them may be loose causing something like in the attached picture.

Good luck.

 

See, I was thinking it was something loose in the transmission area, like a loose and wobbly starter gear or something, so that makes perfect sense. It wasn't until the noise got a lot worse after the carb sync, and my buddies started saying things like "it sounds like piston slap" and "could be hitting a valve" that I went into panic mode and started doubting my original ideas. I just didn't want to tear into the bike until I was pointed in some intelligent direction because I always seem to break something so wanted to cut down on how much fiddling I did. I'll probably see about ordering that gasket and taking a peak inside the cover. Do you have to remove the clutch plates to look at that? If I do do you think I'd need to replace the plates? I've never serviced the clutch in the 40,000 miles I've had the bike, but it works perfectly fine. If I remove and reinstall the old plates would I be introducing problems and should just replace them? No point in removing the clutch cover more than once if I don't have to.

Yeah, this motorcycle is a true testament to Honda's reliability and endurance. I don't know how it was treated before me, but I neglected it. I've put about 40,000 miles on it for a total of like 77,000 with minimal maintenance, meaning just oil changes. Had to replace the chain once, had to replace the RR once, just recently rebuilt master and slave clutch cylinders because the fluid turned into a thick sludge, but the engine has remained rock solid. Even after sitting for 6 months at a time outside in the winter it would fire right up. I even ran the original air filter the entire time (yeah I know, bad me, but I was in college and had bigger fish to fry, and young and stupid, yadda yadda yadda). Boy was that thing black when I replaced it. I love this bike and hope I can restore it to its original glory. Thanks for the help.

 

I have a 92 VFR made for Japan only. Don't sweat it much but the noise you hear is the clutch. Same same here.

Get back with ya on this later.

 

To fix this. adjust your idle to the correct rpm called for and you will notice it will go away or will be a slight annoying when starting in front of all the posers.

 

Undo the 5 bolts, number 22. Undo them a little at a time in a criss-cross pattern until they are all out and remove the springs. You should then be able to see the condition of the posts. If they are OK then I would remove the clutch plates and friction disks and keep them in the order they are removed. Once everything is out then you can give it a severe looking at.

It will be very obvious if there is a problem. For example, deep grooves as a result of the springs not being held tightly in place or a snapped post.

It's up to you whether you replace the plates or not. If you intend to keep the bike for a long time then it makes sense. If not then why bother?

It's very cheap to check this out. The only cost you will have is the replacement gasket. It then depends on what you find on inspection.

 

Hi,

I was wondering about that sound as well. I just bought my VFR 08 ABS, and the sound is every time with me at slow speeds while releasing and pulling the clutch.

 

Yeah, I'm going to order a gasket from the local shop, and when that comes in I will tear into the right case cover and see if anything is amiss... I will keep you informed. Probably won't be till next week (although hopefully this weekend).

 

Sounds like clutch chatter, I get that on my 08 with only 300 miles. Hear it on lots of bikes, especially ducati. The R6 does it something fierce. You hear it really well if you set the bike on the side stand and let it idle out of gear. Soon as you pull the clutch in it goes away. Weird that it took 30k to show up though. Most bikes that do it sound like that from new.

 

I've got an 08 purchased new 04/2010. Never noticed this noise til last year maybe. Currently has 52K on it. Noise goes away when clutch is disengeged. I assumed it to be pushrod because plates shouldn't rattle when engaged.
It does make a slight "popping" sound when in gear and stopped sometimes. The shop said that is normal(pushrod alignment).