Loud knock at cold idle

Mcgyver74 · Aug 14, 2009

Having wierd issue with my 09,

When I first start it up, it runs very rough (Which from my research is due to lean condition from factory, Jumper mod should fix) but it also seems to "hiccup" every so often until it warms up and the idle drops (it starts idling at 1500ish then drops when the engine starts to warm up) but when it does that hiccup it make a loud knocking sound, almost but not quite like a valve knock, it's hard to describe except to say it's almost like the entire rotating assembly comes to halt for a split second then resumes rotating....

When the idle drops it stops doing this and the motor is smooth as silk, if I hold the idle at 1500 with the throttle manually it doesn't do it.

From my searches it sounds like I'm hitting the lean setting from the factory and should look into Barbarian mod or PCIII but I've never heard that sound from a lean engine before .

Should I be worried? Take it back to stealer for them to check?

Thanks

vroompuppy · Aug 14, 2009

Mine does it too; and others have posted that theirs also does this. Sounds like something's about to break doesn't it.

What I have found helps is to give it a little steady throttle just after crank up for just a second or two and it doesn't bobble/hiccup.

Mcgyver74 · Aug 14, 2009

Thanks man, I'll try that....I was just nervous because it DOES sound like something's going to break

johnny80s · Aug 14, 2009

I have not seen anything like that on my 07. Sounds scary.

kaitsdad · Aug 14, 2009

Mine did it until I adjusted the warm/hot idle to 1200.

No more "THWOCK"

Bustanut joker · Aug 14, 2009

You kids an' yer "new bike" problems are aboot to kill me.. ****, what ya think dealers are for.. Tires? Take 'em back an ***** to them.

Hey! My nuts get hot when i ride .. Kan U hep me oot? Fer Gawd's sake ya fruits GET a fukin clue..

Gawd I'm glad It's Friday.. :huh:

:jester:

fjrob1300 · Aug 14, 2009

:crazy:

Bustanut joker said:
You kids an' yer "new bike" problems are aboot to kill me.. ****, what ya think dealers are for.. Tires? Take 'em back an ***** to them. Hey! My nuts get hot when i ride .. Kan U hep me oot? Fer Gawd's sake ya fruits GET a fukin clue..

Gawd I'm glad It's Friday.. :huh:

:jester:

Snicker.... What? I didn't say a thing! :crazy:

Sagebrush · Aug 14, 2009

Your dealer probably did not adjust the idle on your new bike. Mine didn't.

Get a couple bars on the temp guage and look on the bikes right side looking forward. Look for a metal knob with a philips screw style head above the engine. Turn that sucker up to 1200 rpm. Mine came from the dealer set at 1,000 rpm and everytime it stumbled when cold it would make a knock noise as the engine fought to stay running.

You may also want to check the bike over for loose fastners, tire air pressure, fluid levels... my coolant was low and my saddle bag locks had no Lock Tight... My tires were 36 psi front and back, the usuall stuff.

jhedges · Aug 14, 2009

Bustanut joker said:
You kids an' yer "new bike" problems are aboot to kill me.. ****, what ya think dealers are for.. Tires? Take 'em back an ***** to them. Hey! My nuts get hot when i ride .. Kan U hep me oot? Fer Gawd's sake ya fruits GET a fukin clue..

Gawd I'm glad It's Friday.. :huh:

:jester:

LOL, fruits get a fukin clue! LOL

Mcgyver74 · Aug 14, 2009

Thanks everyone (Ps, Thwock is the exact sound!!

)

I'll check the idle tomorrow morning, I think it idles around 1k, (I try not to spend too much time at idle

)

As for the dealer, the first thing I did when getting ti home was check it over, mine too was low on coolant, Overfilled on oil etc,but the rest was ok,

The only thing I have not checked is the bags for loctite, not even sure HOW i'd check that other then pulling the screws out and checking, but if they were already loctited can you loctite twice into plastic?

johnny80s · Aug 15, 2009

Mcgyver74 said:
The only thing I have not checked is the bags for loctite, not even sure HOW i'd check that other then pulling the screws out and checking, but if they were already loctited can you loctite twice into plastic?

Yes you can locktite twice with no ill effects.

user 213 · Aug 15, 2009

The loctite is not into plastic. Do NOT get any on the plastic. It will eat it. A drop on the screw, thread it back in and snug it up. You'll know on the first screw you take out if they are loctited. If they are, great, re-do the one and be happy. If they are not, do them all and you can forget about it forever.

You're simply securing the lock's tab to the lock itself.

Wee Willy · Aug 15, 2009

Mcgyver74 said:
Having wierd issue with my 09,

My '08 will do the same thing on rare occasion. I believe now, having experienced it about 5 or so times in the 5 months I've owned the bike, that this is very like a detonation event when the motor is running at low RPM under the engine control system's (ECS) choke settings. Only happens right after the bike is started cold and if I'm running regular fuel and I'm not in the loop twisting the throttle. If I go to a higher grade of fuel (mid or premium which I will run occasionally just to see the difference) it never happens. Detonation usually requires a hot engine, high compression ratio and low grade (low octane) fuel but such an event can also happen if the ECS fires the spark (timing) at or before a certain point in the compression stroke. My solution that seems to solve the problem is to use small throttle blips to surge the RPM from idle to 2500 at about 1 cycle every 2 seconds and do so for about 10 seconds after a cold start. This "bump" hasn't happened since.

Cheers,

W2

SCRider · Aug 15, 2009

Mcgyver74 said:
.... but when it does that hiccup it make a loud knocking sound, almost but not quite like a valve knock, it's hard to describe except to say it's almost like the entire rotating assembly comes to halt for a split second then resumes rotating....

That pretty much describes where the clunking noise is coming from. When the engine does the cold miss-fire, the transmission gears bounce off each other due to backlash and makes that "thwock" sound. Pull the clutch in and hold it before you start and you'll notice that it doesn't make the noise. This engine doesn't have much of a flywheel so the miss-fire is not dampened as much as on a car engine. Mine makes this sound once or twice every time it's started cold and has done it since day 1, even after doing the BJM. I don't think it's hurting anything.

dcarver · Aug 15, 2009

Good replies everyone.

no1passesme · Aug 15, 2009

I had the same issue with my 09, but it went away after I installed my Holeshot header system with the PC-V. It's been about a month and I haven't heard it since.

GPRIDER · Aug 16, 2009

My 08 does it at every start up. I tried adjusting the air screws on the throttle bodies and did the barbarian jumper. This was after I adjusted the idle adjuster as far as it would go to get the idle up. I'm sitting at 1,100 rpms but still does the low idle clunck at start up. There have been several other threads about this. I'm starting to think I'm out of options and will just live with it.

GP

SCRider · Aug 16, 2009

GPRIDER said:
My 08 does it at every start up. I tried adjusting the air screws on the throttle bodies and did the barbarian jumper. This was after I adjusted the idle adjuster as far as it would go to get the idle up. I'm sitting at 1,100 rpms but still does the low idle clunck at start up. There have been several other threads about this. I'm starting to think I'm out of options and will just live with it.
GP

Same here but mine does it at 1500 rpm during the cold start fast idle but doesn't do it when started after its warmed up.

Mcgyver74 · Aug 16, 2009

Thanks everyone

Loud knock at cold idle

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