Kawasaki VN750 Forum banner

21 - 38 of 38 Posts

·
Registered
Joined
·
536 Posts
Discussion Starter #21
To your last point, when my ACCTs started to fail the noise always went away when the engine warmed up. I didn’t wait long before swapping them out.
I will put on my MCCTs this weekend, just to rule that out. It shouldn't hurt anything. I don't understand the mechanism by which these would make noise when cold, and not when hot. But just because I don't understand something doesn't make it so! (Just ask my wife :D )

Jason, I sincerely hope you can get this sorted out & it turns out to be minor.
Hydraulic lifter not keeping up? Or slow to pump up cold? Exhaust leak? Sounds to to be in the valve train to me. To many products claim to free up sticky lifters to recommend one .
I have heard of replacing some oil with an equal amount of marvel mystery oil, , running for bit and changing oil.

I’m sure you probably have ruled out exhaust leak by now.
I suspect something in the valve train too. I think lifter. I would think an exhaust leak wouldn't just stop like this noise does, returning with rev up and stopping momentarily after returning to idle. If it was a leak that sealed up with heat, I would expect it to gradually get quieter as everything warms up.

I spelled Rislone wrong. Don't know if it would make the clutch slip or if it works with synthetic oil.
The internet conciseness on use with wet clutches:
"DO NOT UNDER ANY CIRCUMSTANCES USE THIS WITH WET CLUTCHES!!! IT WILL DESTROY YOUR CLUTCH!!!" (usually followed by numerous insults flung towards those that chose to use it...)
and
"I have used this in my year brand model with every oil change for XX,XXX miles and never had a problem. It cleared up my issues immediately!!!" (Also followed by numerous insults flung towards those that chose NOT to use it...)

AND both sides claimed to have a brother that works at Rislone that they called and got direct approval to use the product with wet clutches.

Sometimes I hate the internet....though this forum seems to be one of the few good ones! Never-the-less, I'm no closer to knowing if it should or should not be used with wet clutches. I guess in the worst case, I have a spare clutch from my old bike...
 

·
Registered
Joined
·
8,187 Posts
Some clearances will get tighter as an engine warms up, while others can get looser.

My bike has a slight ACCT noise on cold start, but is gone by the time it's warmed up. Think it's the rear ACCT.
 

·
Premium Member
Joined
·
665 Posts
My “guess” for why the ACCTs would get quiet when hot is due to better oil flow and expansion giving the chain less play to slap the guides. I say this because when I did put on the MCCTs I overtightened them at first and as soon as it warmed up fully it stalled.
 

·
Registered
Joined
·
536 Posts
Discussion Starter #24
I did another level of analysis on the video. I took the audio from the video and looked at it in a sound editor (Audacity). The taps are ~109mS apart. This is 550 taps per minute, or every other rotation of the engine. In my mind, that rules out rod knock, as I believe that happens every rotation.

I filtered the sound wave with a low pass filter to eliminate the tap so only the exhaust pulses remain. I could see the exhaust pulses occurring with the expected irregularity (69 mS pause, 44 mS pause, 69 mS pause, 44 ms pause). The whole cycle takes 110 ms for two revolutions, corresponding to 1100 RPM. The time for a revolution is 55mS. The 44 & 69 mS irregularity lines up with the exhaust pulses happening at 0, (360+55), (720-55) etc, as we have a 55 degree engine with a single crankshaft throw. The exhaust valve opens 66 degrees before bottom dead center. This means the rear exhaust valve opens when the front is at 121 degrees BBDC (66 + 55 = 121) or 59 degrees ATDC (180 - 121 = 59) of it's intake stroke.

Then I looked at which exhaust pulse lines up with the tapping noise. The tap occurs between 14 and 17mS prior to the exhaust pulse that is followed by the long pause (the rear cylinder). At 55 mS per revolution, the engine is rotating about 6.5 degrees per revolution. That means the tapping is happening 92 to 110 degrees before the rear exhaust valve opens. This rules out exhaust leaks.

Putting this all together, the tap happens at 59 ATDC - (92 to 110 degrees) = 33 to 51 degrees BTDC of the front cylinder before it's intake stroke. The intake valve opens at 30 degrees BTDC.

The noise happens at the precise time the front intake valve is supposed to open!!! It's a noisy intake valve, and it occurs as the valve opens. This suggests a collapsed lifter as opposed to a sticky valve, as I would expect a sticky valve to slam shut, rather than make noise on opening.

Ok....so now what do I do?
 

·
Registered
Joined
·
8,187 Posts
That's quite an analysis, doctor!

If the intake valve was sticking, it would sneeze back through the air filter.

So I agree it's a lash adjuster on an intake valve. The trick will be finding which one. It might be obvious once they're removed. If not, I'd just replace both.

I've seen this before over the years, but lately there seems to be more posts about it.
 

·
Registered
Joined
·
536 Posts
Discussion Starter #27
It just so happens that I have somewhere between 4 and 8 good used ones in my garage...
 

·
Registered
Joined
·
536 Posts
Discussion Starter #28
Veronica is still sick. I took her out yesterday to see if the new oil would help. I'm tempting fate at this point, so she's going in on the September 14th for a professional eval. So I'll be riding in a cage for the next month.
 

·
Registered
Joined
·
764 Posts
That audio analysis post is killer! Nicely done. Noisy little engines these are, sometimes it's hard to tell what's just a noise and what's a scary noise that'll become something bad.

You seem to have nearly isolated it to being a noisy hydraulic lash adjuster. Do you think it's worth cracking it apart to replace it? The noise is definitely noisy, and excess valve lash would likely cause performance issues with lack of flow, but I can't imagine excess lash being catastrophic like a collapsed lifter would be. Aren't these 4 valves/cylinder, thus meaning it has a a 2nd intake valve through which to breathe?
 

·
Registered
Joined
·
536 Posts
Discussion Starter #30
I thought about that. Best case, I'd be down 25% performance as it's now breathing through 3 intake valves instead of 4. (I'm sure the math is more complex than that!). If that was the worst that could happen, I could ignore it and live with it.

Worst case, I do have a repeated hammering action in that portion of the valve train. That could cause a fatigue crack in the valve train over time.
That could lead to the valve retainer to crack, dropping the valve into the cylinder. Or the rocker arm to break, potentially jamming the valve open or flying around and damaging the other good valves in that head. A jammed open valve could cause total loss of compression or interference with the piston. Perhaps an alarmist viewpoint, but I can't say it's impossible.

Fortunately, it's not terrible removing the valve cover and camshafts, once the engine is out. I use that time to do an ear shave too!
 

·
Registered
Joined
·
536 Posts
Discussion Starter #31
The nearby shop gave me a VERY conservative estimate of $500. My wife's asking where I'm going to get the money for that! Please buy my used parts, so I can pay to have my good bike running again! 😎
 

·
Registered
Joined
·
536 Posts
Discussion Starter #32
Guys, you're never going to believe this, but it was the cam chain tensioner! Veronica lives again!
 

·
FREEBIRDS MC CENTRAL NY
Joined
·
16,197 Posts
Awesome

Sent from my A501DL using Tapatalk
 

·
Registered
Joined
·
8,187 Posts
Dodged a bullet!

Now I need to hear that video again.

So she's all quiet now?
 

·
Registered
Joined
·
536 Posts
Discussion Starter #36
Well how about that! Glad she’s back in business. I hope that didn’t cost you $500.
No, that was the upper range rough estimate if the shop had to tear into the heads! The shop I worked with was really awesome. They just charged me the diagnostic fee and gave me the option to swap out the ACCT with the MCCT from my old bike on my own, saving me that labor charge!

Dodged a bullet!

Now I need to hear that video again.

So she's all quiet now?
No more ticking! First run after installing the MCCT, I had it too tight. The engine normally "rocks back" a bit when shutting off. I'm not quite sure how to describe it. Like bounces off the compression stroke? It wasn't doing that, but stopped almost instantly. I loosened up the tension and it sounded more normal when shutting off. I think I hear a bit of chain noise still (like constant) that reminds me of a bad power steering pump, only a fraction of that. But it's very soft and just barely there. I might still have the chain too tight. What's the guideline for tightness?

I still need to replace the rear tensioner. I need to put some sort of oil sealer on the threads, because the rear one always dripped oil on my old bike.
 

·
Registered
Joined
·
8,187 Posts
Don't think there's any definite guidelines for adjustment, it's just how it sounds and feels. Maybe just sneak up on it, let it tick and tighten until just the point it stops ticking.

With a stethoscope you might be able to adjust while running, but you'll want it close before starting.
 

·
Premium Member
Joined
·
665 Posts
I think it’s safe to say the “sweet spot” for the tensioners is dependent on the bike. If you make it way too tight the idle will drop and it’ll stall ( been there). I loosened them, started the bike, then loosened them just enough to hear the chain start to clack then went in about a half to 3/4 turn and the bike went quiet. That was in March and I just checked them the other night for the first time because I noticed a slight tick on the front cylinder. Maybe it’s because the weather is cooling down.
 
21 - 38 of 38 Posts
Top