Topic: 550f making strange noise at high speed

[ieism]

So i've been driving my 550 on Germany's Autobahns yesterday all day, I thought I try out how fast it would go . It did pretty good exept for a strange sound that has me worried a bit. It only occurs when driving in 5th gear at high speed for a long time, and then easing off the trottle to slow the bike down a little for a car or corner.
It sounds a bit like a small rubber ball being shaken i a large tin can, and it only last for a few seconds. The sounds seams to come from the lower part of the engine, but it's hard to pinpoint at that kinda speed.
I can't reproduce the sound at lower speeds, under 80 mph it doesn't do it at all. When I go much over 90mph it either stops or I can't hear it anymore from the windnoise.
Anybody know what could be causing this sound?

[putnaja1]

I don't have any useful contribution here..  I'm just wondering how fast you got your 550! 

[78 k550]

Not sure what it could be.
I have had my 550 up to 102 mph 

[ieism]

It did 170 km/h (105 mph)on a flat road. The previous owner never had it above 120, so it needed a bit of time to get used to my driving style 
Germany is great though, i drove 880 km (550 miles) in 8 hours! 

[Ernie]

your chinstrap smacking your helmet  srry i couldnt resist ! but have you checked your chain tension?

[putnaja1]

your chinstrap smacking your helmet  srry i couldnt resist ! but have you checked your chain tension?

Hahaha!  Good point- I've had a strap on my backpack start to slap my leather jacket at speed- first time I heard it I wondered what the f*** it was!

[ieism]

  I see what you mean, but i'm not that retarded.    I wish i could descibe the sound better, it's not a scary sound like something has come loose, more a mysterious noise that haunts you at high speed. I've already checked the chaintension, but it's more of an hollow metalic sound anyway.

[Kevin400F]

I believe there's a thin metal guard that wraps around the front of the chain, inside the left engine cover.  Take a look and see if it is cracked or loose. 

[VitaminCB550]

It did 170 km/h (105 mph)on a flat road. The previous owner never had it above 120, so it needed a bit of time to get used to my driving style 
Germany is great though, i drove 880 km (550 miles) in 8 hours! 

Any mods? I had to get mine going down hill to hit the century mark...

[78 k550]

I had a buzzing I couln't figure out. Turned out to be. I only put the top screws in for the plate and it was only doing it at a certain speed.

Paul

[merc2dogs]

 possibly unburned fuel popping in the exhaust/mufflers.

 Had a car, and a bike  that would do that when diving fast then slowing down stronger vacuum would pull extra fuel through the engine and it would ignite when it hit the mufflers, kind of a tinny bloop sound.

 first happened on the bike, and I spent most of the summer tearing into it at various times to figure it out, then one night while racing a buddy down backroads it did it, when my buddy caught up he said that almost every time I slowed down for a turn he could see dim flashes in my mufflers.  went cruisng again while he followed, compared notes and they synched.
 when it happened in my mustang it was a pretty close match in sound just slightly louder.

ken.

[Rushoid]

 possibly unburned fuel popping in the exhaust/mufflers.

 Had a car, and a bike  that would do that when diving fast then slowing down stronger vacuum would pull extra fuel through the engine and it would ignite when it hit the mufflers, kind of a tinny bloop sound.

 first happened on the bike, and I spent most of the summer tearing into it at various times to figure it out, then one night while racing a buddy down backroads it did it, when my buddy caught up he said that almost every time I slowed down for a turn he could see dim flashes in my mufflers.  went cruisng again while he followed, compared notes and they synched.
 when it happened in my mustang it was a pretty close match in sound just slightly louder.

ken.

My buddy's old Chevy truck would do that. We always heard the popping and couldn't figure it out. He had Cherry Bombs bolted to his headers. I was following him one night and could see flashes. I thought it was pretty cool. 

[Mark M]

It's the bottle caps in the spokes matching the sign wave of the suspension deflection at the specific rotational varince devided by velocity.   

[ieism]

Any mods? I had to get mine going down hill to hit the century mark...

No mods that I know off really, i bought it like this. I only added electronic ignition, and iridium plugs. I'm also pretty lightweight, so that may help. I'm talking indicated speed, not sure how acurate the speedo on these bikes is. 


@ Merc2dogs: That makes sense. The pipe is a big hollow piece off metal, and little bits of petrol exploding in it could very well make a sound like that. Any reason why it only does it in top gears though? I'll try and have somebody drive behind me at night next week, maybe it's visible too. Would you recommend changing carb-settings to prevent this, or is it harmless?

[putnaja1]

Did you check your spoke tension?

[gar]

I have had my 550 up to 102 mph 

I didn't think my 550 would go 100mph.  But I have to ask: Are you guys nuts?    I've gone 100+, well, 100's of times (I won't admit it to anyone but you guys....don't tell my wife)....but not on my 32 y.o. motorcycle.  I would be concerned about high speed wobble, stress on old steel and welds, an old cam chain, tire balance (mounted myself, didn't have them professionally balanced)...

On the other hand, there is no better sound than a 4-cylinder running at those speeds IMHO

[ieism]

What's the worst thing that could happen      But really, 100mph didn't seem that fast. It's pretty stable at high speed. Of course with only a single disk in the frontwheel, you need half of Germany to come to a full stop again.

[78 k550]

Mine was real stable at 102. I don't do it all the time. I hit 90 in spirts but stay under 75 most others. Nothing like winding out a inline 4   I can't wait to get my 750SS running. That will be a fun bike.

Paul