Loud Noise Under Acceleration; UPDATED
 

EDIT 9.28.11 - I popped my flywheel off to see if the noise was coming from the starter clutch area. The starter clutch is working fine, no odd wear or anything. I'm curious if the starter primary gear should have this much play in it. Take a look at the video.

Video Here.

The reason I took everything apart is the noise got WAY worse last week. It's a clacking under acceleration, but I've noticed no loss of power, just the noise. I can't reliably reproduce the sound when it's idling, so my efforts with a mechanic's stethoscope haven't been useful thus far.


I ride my bike everyday, 70 mile commute so I have a good idea of what it sounds like normally. Last week it started making a distinct ticking noise when accelerating and when engine braking, I very very rarely get one little tick at idle. Bike has ~32500 miles.

Over the weekend I tore it down to check valve clearances, which were all in spec except for a barely out of spec rear intake valve. I also replaced all the seals in my exhaust, including the crush gaskets at the headers. Eliminated the PAIR valves as well. Manual CCTs were installed ~6k miles ago.

It is still doing the same thing after all of that, so I'm thinking it might be knocking caused by bad fuel. I added two gallons of Shell 93 this morning hoping to fix the issue, but wanted to run this by you guys first.

Uploaded a video, but the mic on my phone kinda sucks. You can hear it at 06 seconds after I let off the throttle.
VID 20110918 104005 - YouTube

Actually it kind of sounds like the carb slides bouncing around.

It is a rather common sound on a SH.

Though it is kind of hard to tell over the net ;)

I guess it's just hard to hear from the video, but I've put over 8000 miles on the bike in the past 5 months and it's definitely a new noise. Most noticeable when slowing down.

Or I'm just paranoid, :D. Either way, thanks for the input.

I'd try to isolate it with a stethoscope. I hear it and don't like it, although it doesn't sound fatal at this point.

well,for shits and giggles,try a lower octane,the superhawk is made for 87 octane.
these bikes have low compression,so it only requires 87 octane,89 at the most.
i use to run 91/93 octane when i first bought the bike.it ran good,but than i found out it only requires 87 octane,so when i started to use that,i noticed a little difference on the first tank,but it was noticable once the second tank went thru.
I did hear a ticking at first and it went away,the only other noise i think i heard was maybe the water pump bearing going bad,but never heard it again.
its a cheap route,and on full tank,put 3oz of sea foam.clean it all out.

Bump. Please see the edit to the original post.

Where in Washington are you?

I am in Port Orchard.

I'm about 10 minutes east of the Fauntleroy ferry. I'm not sure how soon I could get over there to take a close up listen. I do have an electronic stethoscope that can be pretty useful for isolation of the sound.

That would be a great help, whenever you can make it. The bike isn't my number 1 priority at the moment. I'm dropping a new transmission in my pickup this weekend, it's been on the backburner for a while but now that the bike is down I need to get it done.

I'm about 10 minutes off the Southworth Ferry and will definitely pay for gas/ferry/favorite beer ;)

I'm mostly retired, so maybe mid week next based on your schedule.

Does the air box have the 2 small foam filters in the corners?

No it doesn't. I had a K&N filter that I recently replaced with a stock style but I didn't know anything went there. Looking at the fiche, I can see what you're talking about though

:shock: Did I suck something through that vent?

After looking at most of my internal components for the source of my noise, I happened to look down the intake on my front cylinder. I saw what looked like some serious carbon buildup. So I popped the head off today and look what I found. The patch on the piston is large and raised off the surface. What is the best way to go about cleaning this off without removing the piston?

Attachment 33225
Attachment 33226

Try just wiping it off with a cotton rag first, and a little oil if necessary. I was surprised at how much I could get off of mine just doing that.

I'll give that a try, thanks.

use a wire wheel that hooks onto your drill.... that is what i did and it came off really easy. just put the piston a TDC and zip it right off.

I have watch your video, for about an hour, and have to ask -
-how many miles on the bike/or engine?
When you adjusted the valves- Did you rotate the engine as the manual states in the procedures..To check your process....
I would agree with a cheap prcedure, and run a couple of tank fulls of 87 octane thru your bike... YET I would recommend running Seafoam thru your system "At least not at first"
If the carbon is built up, and you run SeaFoam thru, could be worse, than better...Break all that carbon loose at once...
I would run a bottle of Suzuki "FACTORY" fuel injectoe,carberator cleaner thru... At least with the two tank fulls of 87'.
Then I would consider using Seafoam-To the recommended mixture to fuel ratio...
IMO

Bike has 32500 miles on it. 8500 have been put on it since I bought it in April.

I have a physical copy of the manual, I followed the instructions on value adjustment as they were printed and am confident it was done correctly.

The knocking sound got progressively worse during the course of a week of riding, so about ~350 miles. After tearing into everything(both side covers, oil pan,carbs, new chain/sprockets) and checking it, I pulled the head and found that carbon build up. Seeing as nothing else was out of spec, I'm think the buildup is causing predetonation, assuming it is allowing hot spots to form as well as bumping up the compression ratio(It is quite a large chunk of build up).

I'll clean the front piston and head up, put it all back together and see where I'm at.

Sorry, Got caught up in the videos.... Those were your pictures...
Did you clean the ports for the EVAP system? That are in the corners of the Factory air box.. Which I don't think would make that noise.. IMO it is still a "Spark Knock"...
Really appreciate communicating, with a person that has a clue / what there doing?
The small foam filter are part of the EVAP system ..
Strange your bike sound exactly like my 2001...(In the videos)

I have the little filters on order, should have them tomorrow. I cleaned out the vacuum pistons in the carbs, the area those filters are for, and there was no debris visible.

The videos don't show the issue correctly. I should have filmed with my GoPro while riding, as I only really get the knock under load. It doesn't really happen at all at an idle. I have to really try to get it to do it.

I'm pretty confident at this point it is spark knock, but I like to bounce ideas off of others just to be sure. Thanks for the input, I appreciate it.

Silly as it seems, I am waiting for a member to suggest that your CCTs are failing( which is causing the timing to fluctuate) and causing the "Spark Knock"
Now being that your bike is a 1998, Please tell me that you have consider changing the CCT(with factory/or manuals)
The cylinder head looks fine, (some carbon/ I have seen worse) Top of piston looks fine- you can tell from the burn pattern of the 93 octane use..
How do you feel about -Putting it back together/and attempting the cheap fix procedure??

I have had manual CCTs for the past 7500 miles. The piston actually has a significant amount of carbon where that burn pattern is, it is probably 1-1.5mm tall. I'll knock that off before I put it back together.

You're suggesting running a few tanks of 87 through, with a carb cleaner mixed in?

Reading above- Ya know I have the BMC filter, Dr.Honda Velocity stakes, main jet shimmed, Full exhaust sytem. and the octane of fuel varies(IMO) that the bike has wonderful throttle responce one tank full/ then a hope in a bucket the next... and run 93 two tank fulls, then 87 the next- then back to 93... those valves still need the lead... And never use any of that "DAM" Ethanol fuels... SAY good by to the valve train....