After what looks like a successful fix of the balancer (it's not cutting through the case anymore \o/ ), my 2008 with about 89k km and dubious service history developed a new worrying noise.
Just as a precaution before I give it to someone who actually knows stuff (end of the week at the earliest
), I'd like to have a try at locating and fixing the problem, and would appreciate any pointer if there are obvious things to check/do first.
I know, it's considered a black art to troubleshoot stuff from noise (even worse when you only have a description of the noise!), but juste maybe someone will have had the very same problem around here.
About 50km of urban driving after the balancer fix, I noticed a faint rustling sound (like a piece of paper on a desk, continuous when the engine is running, low correlation with RPM, no correlation with anything past the clutch), from the general area of the engine. Oil level was slightly low (i.e. only 60-70% of the looking glass, instead of the 95% I used to run at) due to my forgetting to top up the oil after the balancer fix.
At that point I changed the clutch cable (probably unrelated to the problem) and went on a ~200km trip with a friend. Most of it around 80-100km/h, plus some dirt roads @ 50km/h and wet sand (that was a first, pretty fun). Along the first 100km I noticed a gradual increase in noise, from the gentle rustling to a more rythmic sound that evolved to a fast ticking, pretty loud at 4-5k rpm. No overheating, no other symptoms.
Next day when I start, for the first minute, no noise at all. And as the engine warms up it returns to full force (all the more when stuck in traffic). Same the next day.
Tonight I took the oil out, it's gotten very dark in only 300km, though I read somewhere it was not uncommon with Castrol GTX. Small bits of rubber are present, but that's expected (rubber of one of the balancer sprockets had a pretty rough finish in some places, I removed only the worst of it before assembly). A little bit of magnetic metal particles (enough to cover my magnetic oil plug with a ~0.5mm layer of stuff) and some non-magnetic metal too, but very little.
No metal chips this time, at least
The oil filter took a much darker shade, from its original yellow-ish to a dark brown. Not much in terms of metal here either.
I put the oil back, topped up, and got the same behavior.
Basically, as long as the exhaust can be touched, there is no strange noise at all. Then it gets worth (louder for a given RPM) with general engine temperature.
I tried poking stuff all around, found a couple of things loose that I fixed/changed without impacting that particular noise.
I might just record a thermal video with sound, see if I can correlate the sound with anything more specific than "general engine temp".
More likely to help, I should also receive a stethoscope soon, to try to locate the origin more precisely. I feel like it might be closer to the top end, but can't even be sure of that.
Might be relevant or not : I forget sometimes to disengage the choke when riding around (urban, <10km).
So here, any idea is appreciated. I always like a good puzzle but right now I would prefer to ride when the weather is still fine :/