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CLUNK!

1K views 5 replies 2 participants last post by  realshelby 
#1 · (Edited)
Hey guys,

I just picked up this (2007 reg) K6 Vee. It's (only) got 14,000 miles on the clock (You'll see that in the video), but it's running kinda rough.

I've got this crazy CLUNK coming from, somewhere. I've captured it on video - it's very intermittent - but it can result in a stall. It also clunks while riding around at around 2500-3500RPM (a constant speed); it appears to be okay above this RPM limit. The bike stalled during a first test-ride, but the idle-RPM was set to around 1000. It hasn't stalled since, where the idle has now been increased.

This clunk was captured from a cold start to warm. It initially rev'd at cold somewhere around 1200-1300, then I gave it a blip and it increased when it was, now warm, to where it is in this video - Skip to around 25 seconds in:

https://photos.app.goo.gl/AMqYrTR6bpyv4dpQ6

The CLUNK happens in the video after 25 seconds - you'll hear it and see the RPM dropping slightly. I let it record longer, to see if it would happen again, but it didn't - As I said, it's very intermittent. I also had the bike in, "Dealership Mode". The TPS is indicating bang-on centre and there are no error codes present.

I will need to see if the motor does this clunk with the clutch engaged/disengaged. There is feedback in the lever and the clutch does make some noise (rattling), I guess that's some of that early-stage, infamous, "Clutch Chudder" I hear so much about.

Any advice is appreciated! :grin2:

P.S
I haven't checked the throttle bodies are synced, any vacuum seals, spark plugs, air filter, or if either of the TPSes are firmly in place.

It's just that "Clunk" noise. I'm just at a slight loss. It sounds like the engine has "died" and has "caught" again. It's almost as if the fuel isn't burning during one cycle of the crank? Maybe? Possibly? That's what it feels/sounds like, since in the next cycle you're getting that pulse/explosion.

The actual fueling isn't an issue - the bike runs great above 4,000RPM - so it's definitely getting enough fuel. I had her running well above 100MPH, in various gears.

Just at or below the 3000RPM (and idling) mark it can feel "choppy". It doesn't inspire confidence when running around at lower speeds and trying to take a corner in 2nd gear; with the apprehension that the motor could stall, leaving you in an awkward situation.

I'd rather have this fixed than running around at MotoGP RPMs (in first gear), everywhere, to ensure it doesn't stall.

P.P.S.
I'm not entirely sure if this means much, but I noticed that the left exhaust output was warm (accompanied with mist/vapour), where the right was cold (and no mist/vapour).

I imagine that's something to do with the fact that the exhausts are linked, yadda, yadda.
 
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#2 ·
That is your fueling. Common early DL 1000 characteristic. Your statement about it running fine above 4000 also points to the lean fueling in the under 4000 rpm range.
The "Super Tune" for these is a change to Iridium spark plugs, triple check that the boots on the throttle bodies are in proper position and tight, valve check, TPS adjustment ( raises at 1700-1800 rpm ), idle to 1300, and a proper throttle body synchronization. This usually minimizes the hiccups, burps, and farts under 4000 rpm.
When right these engines are very happy from 2500 rpm and up. When fueling and tuning is as good as it can get, then you might find some vibrations when pulling under 4000. Then you need to look at the clutch basket. When modified those allow smooth operation when accelerating or cruising even in 6th gear at 2500 rpm.
Don't be concerned about vapor or temperature differences in the exhaust. They are linked and at idle they don't flow quite the same.
 
#3 ·
Cheers.

Couple of things I've checked:
I got some wire and prodded the hell out of the spark plug drain and sprayed a good amount of Dust Off up there to blast out any gunk.

The fuel pump is also delivering as promised. 3 turns of the switch and it filled up somewhere between 300-350ml (about 330ml).

I'm not sure what plugs are in just now, but I'll ask the garage to throw in the NGK CR9 (Iridium) badboys and ensure that the throttles/injectors are balanced correctly.

I spoke to their mechanic and gave him a rundown of what's happening, he said that he never experienced any hiccup issues that I described; they are so blatantly obvious that I dare anyone not to notice, but he would change the sparks. I did ask them to look at the throttle synchronization the first time around and they didn't bother. I'll mention it to the mechanic again, when I see him. I understand it's rather important in a big two cylinder to ensure they are matched.
 
#4 ·
Learn to do this yourself, or find a friend to help. For instance, the 1700-1800 TPS setting is lower than the factory service manual says but the collective here has found it to work much better. Taking time to do this, check the throttle body boots, and other stuff BEFORE doing the all important Throttle Body Synchronization makes all the difference.

Just to let you know, the "clunk" as you called it is exactly what can cause the throttle body boots to come loose! It is a true backfire through the intake track and that overpressures the throttle body assembly causing the boots to pop off.
 
#5 ·
Well, the bike is under a 90 day warranty, so I'm taking full advantage of it! I could do the work myself (but I'd need to get a CarbTune). I've serviced my bikes before, but if I cause some unintended damage (I.E a cracked fairing) then that's entirely on me.

With your help at least the root cause has been identified! Thanks muchly.

I'll get them to inspect the boots, change to iridium plugs and perform a throttle body balance. I'll can ask them about TPS adjustments, but if it's not actually faulty (it was dead centre in Dealership Mode) then I reckon they'd be hesitant to adjust it under warranty.
 
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