Maybe a pertinent story - maybe not - but this all took place in the last month or so. A close friend of mine has had two distinct engine noises since his bike was new (2010 SEUC). A hammering bottom end sounding noise and clattering top end noise. He has constantly been at the dealership - actually a couple of dealerships. First the dealership diagnosed it as "normal". Suprise!! So I went to the dealership with him and had them start 2 or 3 new SEUC's on their floor side by side with his. They quickly agreed his engine noises were not "normal" noises. They speculated a bad crank bearing, piston slap, bad lifters, bad rocker arms, rocker box interference, timing... all kinds of guesses. The motor only had about 400 miles on it. They inspected the top end (rocker boxes and rocker arms) and found nothing. They claimed to have replaced the lifters - but I don't think they actually did.
After two months of them having his bike more than he had the bike - with no progress, he asked me to look at it - I reluctantly agreed to look at it for him. I hate working on anyone's bike but my own. Working on someone else's bike (especially a new bike under warranty that has a problem) is a lot like loaning money to family - more potential downside than upside.... Anyway, he's a friend, so I agreed to... I looked in the cylinders with a borescope. The cylinder walls and pistons looked perfect - like new. No way there was piston slap. I listened all over the motor with a mechanic's stethescope. There were without doubt two sources of noise. The first was easy. The heavy bottom end sound was a leaking rear exhaust gasket. I could not feel it leaking, but I squirted a bit of WD40 at the header/head connection, and the noise immediately changed. It was leaking. When I pulled the gasket out, it was obvious the header had never sealed to the head. If they replaced the lifters, they would have had to remove the exhaust. The exhaust gasket showed no sign of being disturbed since new - hence me doubting they replaced the lifters. I replaced the exhaust gaskets with Cometic exhaust gaskets. That eliminated the "bottom end" noise. It's not the first time I have run across this problem. And trust me, maybe hard to believe, but leaking exhaust gaskets can sound like a crank bearing.
I next pulled the pushrods and lifters. The top end noise was definitely coming from the rear cylinder. I found the problem was a pushrod. An exhaust pushrod on the rear cylinder had a loose "cap" on the lifter end of the pushrod. Other than the stethescope pointing me there, the other clue was the wear marks on the pushrod where it was contacting the pushrod tube. The other three pushrods had no signs of contact. I replaced the pushrods with SE tapered pushrods. I replaced the lifters with the new Woods directional lifters that Deweyheads overnighted to me. And then I put it all back together. I used Redline 20-60 motor oil Once back together, I fired it up. As soon as I started it, he smiled. He has a quiet motor. The next day we left on 1500 mile trip. He was happy with his new bike for the first time.
The other problem he had been having was when downshifting, it would frequently not drop into gear. Again, it was first diagnosed as normal by the dealership. (he needed more experience downshifting was their claim) I saw him downshifting multiple, multiple times (I suspected he had a twelve speed or something - lol)... So I pulled the primary cover off and found the primary chain with no freeplay at all. Almost guitar string tight. So I adjusted the primary chain to spec - and put it back together. He can now downshift like a mere mortal (turns out he only has a six speed like me...hehehe...)
So there's the story... I often think all the reports of noisy motors are potentially simple fixes. Maybe lots of causes - but it's all mechanical stuff...
By the way, what the heck is "piston slap caused by a tight flywheel"?
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Topic: Noise from rear of primary (Read 7635 times)