I have a metal scraping noise coming from my left cylinder. Can anyone diagnose this? Is it me? http://youtu.be/hCYqMKFK0IM
Wild guess would be timing chain, but it's hard to tell from a video. You may want to post this up in the Airheads section where the real experts hang out. Best of luck.
Kinda hard to tell what's going on, but has sort of a piston slap or piston making contact with a valve sound. Does it idle or only run by giving it fuel like that? ie: not good, but it could be various things going on. I'd do a compression test. If it's low in that cylinder you'll need to investigate what's going on. Damage to the valves, piston, broken rings, etc... would all be possibilities.
It needs gas when cold... I can adjust the carbs to not need this, it depends on temp and time of year. I am also revving to demonstrate the noise I am concerned about. Compression is great, 160 in each. Had the cylinders honed and re-ringed pressionally by Engine Dynamics. Timing chain looks great and the sprocket looks brand new. Though it sounds to me like a timing chain issue. I'm thinking it may also be the rocker arm bearing or something related. It does it on acceleration only around 2k rpm to about 2.2k rpm. Thing is that it runs great. Though airheads will run good even with major damage. I'm not sure I have major damage. What I am talking about is more of a pinging sound and is more of an annoyance if anything. Could it be the gas I'm putting in it?
It probably happens as resonation, but as to what exactly it is, someone would have to be there in person to hear it since it's hard to diagnose from the short sound clip. The only two times I've heard that sound in my garage it was due to two similar but different reasons. In the first case, the piston skirts were slapping the cylinder walls because the skirts were broken and the rings were also broken. In the second case the pistons were too small in the bore on a bike I tried to save with new rings and a hone job. The only answer was new pistons and an overbore. But in both cases it was the skirts of the pistons slapping the cylinder walls at a really narrow/specific RPM range. The fact you said it was honed and re-ringed caught my attention. I just got my new-to-me '75 R90 and I honed/re-ringed it with 58k miles on the clock. My bike is working fine with about 135psi compression in both cylinders, but my standard piston rings BARELY cleared spec on ring gap. The bore of the cylinders is worn enough that I'm approaching the limits on piston gap. If you didn't replace your pistons and rebore (I don't blame you, it's really expensive) you might be hearing piston slap. I could be completely wrong, (so don't panic) but just sounds similar to the two times I have had it happen though. 160psi is higher than specification, I believe. Did your engine guy do something to up the compression? You might consider running the highest octane gas just on that one point alone.
Here's an idea: either RIDE that thing or GO INSIDE IT. One way or the other, you will eventually discover the cause. (Or perhaps you'll learn not to be concerned.) Either way is much more productive than to spend hours and days going back and forth speculating about it.
I love how annoyed Hammerfist7 is every time I post. His anger is the energy that powers me and motivates me to get out of bed in the morning. Birthed from his mother's loins as a master mechanic, I seriously suggest you listen to him.
Your words were much more helpful than speculation. Thanks for them. I'm sure OP's bike is back to tip top shape now that he opened it up and fixed the problem.
I don't know where you get the idea that I am following you around or "getting annoyed every time you post" - I haven't responded to a single thing you have said on this site YET. As far as your above snide remarks, you are NOT doing ANYTHING towards solving the problem which simply RUNNING that motor - or LOOKING INSIDE will eventually disclose. I have been rebuilding engines for several decades (for a LIVING) and am sure that my hands and eyes have been inside far many more of them than yours have - often while surrounded by jabbering "experts" who rarely had any more to offer than their GUESSWORK and OPINIONS. I gave the owner of that bike some plain, SIMPLE advice - either run it or open it up, and quit wasting his time wondering. YOU are the one who got his panties in a bunch, not me - and you are the one annoying everybody with your pointless posturing. .
See, technically you're wrong on the first point. You've replied to me in this post. Mentioning how long you've been at it sounds like pointless posturing to me given that your posts which are devoid of any useful information. You're just another ineffectual, angry old boy on the internet. The answer to any motorcycle related question is, "FIX IT IDIOT." Congratulations, you've figured out the most intellectually lazy solution to every motorcycle problem on the internet.
It's usually the personality of the old guru to blame. I believe that you know all sorts of things. Yet I've only ever see you share insults and too-much-to-the-point information that doesn't help anyone that's looking for help. I'm sure you were angry long before I got here with my snot nose. I've seen the same thing happen on other car/bike forums but it's almost always 100% because the old guru doesn't know how to get along with anyone if there is a disagreement of any kind. There's volumes of useful knowledge dying off every day, but it gets re-discovered by young people as time goes on. Then they get old and angry and say screw it and go into retirement. Or they stick around so they can repeatedly post READ THE MANUAL! I enjoy speculating because every once in a while it leads to either a new discovery or it is much more likely to get someone to think about their problem and start working on their bike versus just yelling at them to take it apart and fix it. It is also just normal social behavior as opposed to barking down from on high any time you see something that annoys you. I'm not sure I follow the "trolls who have the most to gain" given the fact nobody around here is getting paid.
I followed the advice to ride it. It seems like a knocking.sound.is appearing. Im.thinking a rod or rocker bearing... Im going to keep riding it til its more obvious. Its pretty much a daily rider, and I do not want to guess and start fixing random things. Im purely a city rider so I will not be stranded. The thing is its rides great outside of noise, so Im just going to block it out for now.
I recommend you ride the bike over to some experienced airhead mechanics who can evaluate the noise you are describing. My crystal ball has a crack, and I pissed off my local voodoo priestess, so I am of no help. If the mechanic has a mechanical stethoscope, that is a very good sign (but not a requirement). I hear there are some very good airhead mechanics around the SF area, so be grateful you have that resource. I expect a few can make time to listen to that noise. Good luck! Edit: if it were my bike I would try (while waiting to see a mechanic) 1. Put in the highest octane fuel and possibly add an octane booster. 2. Change the engine oil and see if the noise changes (this is always my go-to since it costs little, is easy to do, and won't make anything worse). 3. Pay attention when the noise occurs (i.e. up hill, downhill, accelerating, decelerating, rpm, gear, etc.) and take notes off the bike. 4. Also, an experienced engine mechanic (doesn't have to be airheads) may be able to diagnose the noise in person - if you know of one (or a friend of a friend knows one) they will likely be happy to listen to the engine and give you an opinion. Edit II: If I read the information correctly, the noise occurs between 2k and 2.2k? Again, I am no help because I don't ride my airhead in that rpm range.
A metal scraping sound. Hmmm. Ride it? What, until permanent damage is done? I wouldn't. I'd take it apart to find the cause, fix it, THEN ride it. These engines don't "knock" unless there is something very wrong. Just my $0.02. If this was a Ducati, it would be a different story.....
a bent pushrod can make a nasty sound but not always since they have a tendency to turn....but it also can point to a larger problems. I would check rod bearings and peek at you PR and lifters.
I changed the oil. to Castrol GTX and it seems to have nearly eliminated the issue. When the bike gets hot from city riding (waiting at lights) it comes back again but not nearly as bad as it did. Previously I may have had generic oil in it. I imagine once this new oil breaks down a little it will come back again. Maybe an oil additive will help for now? Despite many being against it. It does however seem like lubrication is helping so why not try to put something extra in? If I was not riding in the city, there may not be an issue. It really does seem timing chain related. It sounds like a chain. Its probably worn just enough to make a noise when very hot. Maybe not needing a new chain quite yet under healthier riding conditions.
Were it me, the pan would be coming off and I'd be looking at big end berrins. I dunno from BMW's but if they have shells I'd have a look at them ASAP. While perhaps bluntly presented, some previous advice about getting in there is correct, IMO. Fresh oil may mask it, but it won't heal it. If you hear a sound it's trying to tell you something.
I had an r90 that made a similar noise and it turned out to be the rocker shaft bearings, not hard to have a look, might take 30 minutes.
