Strange "Moan" at 4500

S

SinNH

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Mar 17, 2009
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NH
I'm getting this low pitched moan only when coming down into the 4-5000 rpm range and then feathering back up. It goes away at about 5000 and never does it if I go back to idle and feather up to speed. I can't make it do it going up just coming down to about clutch engagement r's and slowly back up. Does not sound or feel like any of the three are missing, feels smooth. Otherwise it runs/starts great. Have taken plug checks at 6000 and they look they way I like them. Sled is stock.
Carbs are set at factory specs except the air screw is out a bit over two to stop the idle hang.
It sounds like a loud purr and instantly goes away if I hit it. Seems like something isn't quite right.
Any ideas ?
thanks
Steve
 
check your airbox boots make sure they are attached firmly to carbs, sometimes leaking air can cause weird noises.also check your belt, it may have some inside teeth missing or worn.hope this helps!
 
ebayfreak said:
check your airbox boots make sure they are attached firmly to carbs, sometimes leaking air can cause weird noises.also check your belt, it may have some inside teeth missing or worn.hope this helps!
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thanks, whenever I pull the carbs or air box on first start and run I use a Butane tank with hose to check for leaks around the boots, I don't want to cook the mill .
But, I am running a beat up belt, not old or cracked it has a divit or two in it from trying to break free a frozen track, I will check the teeth too!

Steve
 
not on the brake when it happens, right ?
I assume not, had to ask.

I have a low sort of growl when I decelerate too.
Mine is comming from suspension though, track or wheels.
Maybe its in your suspension, check the wheels on the track for play.

My 2 cents
 
Whammy said:
Bearing getting ready to go............
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thx all for input-
this summer replaced the four bearings in the two shafts when installed new track--it's a engine symptom I'd bet my something on it thx
 
On a 18 mile ride last night when the rpm was coming down to idle from about 7000 it back-fired thru the exhaust four different times--that just started happening too.
thx :confused:
 
:shock: oh oh..better start saving a few $$$..something is starting to happen..warning signs are there.I wouldn't take it far from your house now.Check all you can..compression,leak down test,plugs,carbs,gas,oil usage,piston wash..etc...
 
bluemonster1 said:
:shock: oh oh..better start saving a few $$$..something is starting to happen..warning signs are there.I wouldn't take it far from your house now.Check all you can..compression,leak down test,plugs,carbs,gas,oil usage,piston wash..etc...
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Scare tactics? or do you really think so--runs great otherwise
 
are your pv's clean? mine would make strange noises like that when they were getting sticky. not sure about the backfire though....
 
one thing about us running our sleds.We basically know how they sound since we ride them alot.When something changes or a certain sound shows up that wasn't there before..we start to panic a bit..for good reason.Just be cautious..don't ride to far from home now until you can identify the sound.I had a new sound last year show up on my SX600R and it bugged me to hell.It wasn't there prior season.It sounded like something was loose in the motor..couldn't identify it..but I was worried something was gonna blow apart on a run..At idle was fine,as soon as I got rolling the clanking sound shows up.So one day I decided to run it on the stand and reved it and listened.Started to pin point the sound..yet sounded like coming from motor.I finally found it..it was one of my front heat exchanger protectors.I guess the rivets let go and it was barely hanging on,but as the track started moving it would bump the track back against the exchanger and so on.I was lucky I caught this before the whole protector decided to fall off into the track and ram against the exchanger..maybe an instant stop..for sure a wrecked exchanger..but you have to find where a certain noise is comong from and try to find it..otherwise a surprise.
 
Check your exhaust donuts at the manifold and at the silencer. When mine were finished I couldn't hear it at wot but when I slowed down after a 35 mile high speed run it was noticeably louder.
 
03viperguy said:
are your pv's clean? mine would make strange noises like that when they were getting sticky. not sure about the backfire though....
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Yes cleaned them right down to bare metal everywhere about 800 miles ago, and have been running Interceptor oil since which is supposed to be good for keeping the valves clean. Rode 30 miles today no backfiring, did fill the fuel tank before leaving and added Startron, just like what was in there.
thx
 
bluemonster1 said:
one thing about us running our sleds.We basically know how they sound since we ride them alot.When something changes or a certain sound shows up that wasn't there before..we start to panic a bit..for good reason.Just be cautious..don't ride to far from home now until you can identify the sound.I had a new sound last year show up on my SX600R and it bugged me to hell.It wasn't there prior season.It sounded like something was loose in the motor..couldn't identify it..but I was worried something was gonna blow apart on a run..At idle was fine,as soon as I got rolling the clanking sound shows up.So one day I decided to run it on the stand and reved it and listened.Started to pin point the sound..yet sounded like coming from motor.I finally found it..it was one of my front heat exchanger protectors.I guess the rivets let go and it was barely hanging on,but as the track started moving it would bump the track back against the exchanger and so on.I was lucky I caught this before the whole protector decided to fall off into the track and ram against the exchanger..maybe an instant stop..for sure a wrecked exchanger..but you have to find where a certain noise is comong from and try to find it..otherwise a surprise.
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That's true on your machines and it doesn't make any diff what it is, sled, bike, tractor, saw, etc, when there is a noise change we hear it. I know I do, because I am the one who fixes all my stuff. No backfires today after refueling and adding Startron, just like what was in the tank. I'm not going into my carbs again because I was getting the "Moan" ( for the lack of a more descriptive term) last year to at the end of the season. Went through the carbs in the spring and still the moan, so I doubt it is carb related because I don't think I would make the same mistake twice.
Compression check today-warm engine- WOT--
Muff side--103
Center-----109
clutch------101
Butane gas check around boots for 2 min--no leaks.
Leak-down tester ordered.
thanks
 
Stephfg said:
Check your exhaust donuts at the manifold and at the silencer. When mine were finished I couldn't hear it at wot but when I slowed down after a 35 mile high speed run it was noticeably louder.
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Thanks for the reply, I did check those, because that is somewhat like the sound I am getting,metal to metal vibration that seems amplified by something hollow.
They are in good shape, thank God, they cost stupid money.
I think I am going to remove the belt, and use my stethascope ( can't spell it) at 4300 rpm to try and narrow it down.
Supposed to go on a four-dayer next week---I 'd like to find something.
thanks
 
bluemonster1 said:
one thing about us running our sleds.We basically know how they sound since we ride them alot.When something changes or a certain sound shows up that wasn't there before..we start to panic a bit..for good reason.Just be cautious..don't ride to far from home now until you can identify the sound.I had a new sound last year show up on my SX600R and it bugged me to hell.It wasn't there prior season.It sounded like something was loose in the motor..couldn't identify it..but I was worried something was gonna blow apart on a run..At idle was fine,as soon as I got rolling the clanking sound shows up.So one day I decided to run it on the stand and reved it and listened.Started to pin point the sound..yet sounded like coming from motor.I finally found it..it was one of my front heat exchanger protectors.I guess the rivets let go and it was barely hanging on,but as the track started moving it would bump the track back against the exchanger and so on.I was lucky I caught this before the whole protector decided to fall off into the track and ram against the exchanger..maybe an instant stop..for sure a wrecked exchanger..but you have to find where a certain noise is comong from and try to find it..otherwise a surprise.
Click to expand...


I learned that if I wear earplugs, the sled goes 2,000 miles without wrenching. Your choice.
 
SRX_700 said:
I learned that if I wear earplugs, the sled goes 2,000 miles without wrenching. Your choice.
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I hear you
:lol: , but I usually can't live without hearing the triple run.
The only time I wear earplugs on my bike ( full face on ) is when I am going to make a long Interstate run, otherwise, it is just way, way to easy to ride way, way too fast without hearing the power plant.
thx
Steve
 
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