I have just put my bike back after a top-end resto and a left cover swap, so now I have had the chance to actually drive a little I noticed a loud knocking sound when giving it the beans when in any gear, right around 4k rpm. The weird thing is that there was no sound before the rebuild, so I am bit stumped. I have read about the sheared woodruff key but to my understanding the noise should be in any gear and all the time, not only when giving it some throttle.
Could it be the cam chain being to loose/tight? Ill check the automatic cam chain tensioner asap.
I don't know what your process for reassembly was so I'm going to assume you adjusted your valves? Cam chain could be loose though the tensioner is auto adjusting, or it could be tight if the spring wasn't removed during install. Also did you make sure to reinstall the circlips on the wrist pin? Sorry if this is basic stuff. Tell us more about your rebuild.
Nono, the basic stuff is just right for my mechanical abilities!
I have adjusted the valves to the best of my abilities, I just had a gut feeling that this kind of knocking sound could not just be badly adjusted valves (since it is also quite loud). The cam chain tensioner is adjusted as instructed, put in and fastened without the spring which is then put in afterwards. Wrist pins were put in, and I took care in checking that they actually seated in the groove on the piston.
One thing I did note was that the auto decomp was maybe a bit on the tight side, I will have to run it again after I have loosened it off a bit. Could incorrectly set valves really make a knocking sound?
I will try and see if i can cowboy together a video of the whole thing.
When you say at 4000rpm is this only when the bike is ridden? Is the noise there when stationary? I had large knocking noise on rebuild and it turned out to be a loose top frame mounting bolt. the noise only appeared when engine was under torque and the engine was vibrating in the mount but was masked by the tank and I was convinced it was the piston main bearing!
Only when ridden, couldn't replicate it when the bike was stationary. After reading about peoples experiences with knocking sounds off that character I am mentally preparing for the worst and hoping for a loosened off bolt in reassembly. I was quite thorough with the torque wrench though
Did it yesterday, just drove to work. You weren't wrong in saying that they needed a tightening, but the noise is still there.
I slackened off the decomp cable a bit and that might have helped some, so I think I will have a look at the valves over the weekend. I am not noticing anything out of the ordinary with regards to misfire/backfire, a little popping on high rev downshifts, but i'm assuming that is to be expected.
I'll try to get that video before the weekend, at least for historical evidence of my incompetence in valve clearances.
Possible it could be pre detonation(not highly likely if high comp piston wasn't used, but a quirky cdi may cause it) , put in some higher grade fuel once and see if it changes.
Valves are easiest to get proper clearance with the bent feeler gauges rather than straight ones forced in . make sure to use a tool to hold the adjuster stud while tightening the nut. I've used a 3" deck screw/ construction screw with a #2 square head bent at a 90 to hold the stud(it fits the square stud tip nicely) if you don't want to buy the special tool.
Piston/rod/bottom end type stuff usually has a low-deep knocking that goes in tune with rpms , topend/valves are more clattery/ tinny sounding .
I noticed a loud knocking sound when giving it the beans when in any gear, right around 4k rpm. The weird thing is that there was no sound before the rebuild, so I am bit stumped. I have read about the sheared woodruff key but to my understanding the noise should be in any gear and all the time, not only when giving it some throttle.
