[heloego]

Camera head is only about 7mm, and the unit comes with several attachments including a right-angle mirrored one.
Great little tool to get a good look before you tear anything apart. Records stills, video, and can be connected directly to a Laptop.
I have one of the older ones without the pistol grip and have had zero problems with it.

[ace.cafe]

My decomp isn't out.  It's installed and working, according to the dealer who fixed it.  Again, I'm not sure what it's doing exactly, based on how much more difficult it is to push it through than it used to be.  Maybe it's fine?  I haven't tried another kick-start model to compare.

Exactly!

I have been made aware of this, more than ever since riding a few other models late this summer.  Remarkable differences between them.  Different shift feel, wildly different vibrations, even among broken-in bikes...

I hope to try this first, of course, because it's easy, and it means I get to ride it, too!    But, it's going to be difficult to reproduce the conditions with my current time restrictions (very little available) and weather conditions (much colder than earlier in the season).  Remember, this is an intermittent thing; "the hill that causes the problem" doesn't always cause a problem.

Let's just say for the moment that higher octane does solve the problem: does that suggest that no further investigation is needed?  Is it reasonable to assume that some bikes might require premium as a matter of course, where others might not, and accept that it's "normal" for my bike?



Thanks for the leak-down test info, guys!  I'll check it out, and file it for possible future use...

heloego - Harbor Freight to the rescue, again? 

If the higher octane fuel cures the pinging, then you either have higher compression than usual for these engines(for some yet undetermined reason), or you have very crappy regular grade fuel. Or both.

If higher octane fuel doesn't cure it, then it is most probably some kind of pre-ignition issue, most likely caused by a hot spot in the chamber somewhere. But there still would be some possibility for something else to be causing the heat.
Take it one step at a time.

[gashousegorilla]

Well, other than the tank being in the way, I can't imagine it's any more difficult than the heads on my old BMW /6... two valve covers, but only one cylinder head!

I will probably begin by pulling the plug, examining the chamber as best I can through the hole, and do a comp test while it's open.  With the understanding that the results could be affected by a number of issues.

GHG - is a leak-down test something that's done with the head on?

I feel another learning experience coming on... 

   Yeah Matt, much easier.   You can do a down and dirty easy leak down test , without buying the expensive and complicated gauge arrangement if you want, using the spark plug hose  from your compression tester....


  TDC on the compression stoke, both valve closed and piston at the top of it's travel. Bike in gear, rear wheel on the ground. And chocked on the front of the back wheel.    Remove the one way valve from your spark plug hose.... it's like a tires schrader valve.  Screw the hose in.  Set your regulator on your compressor to 15 or 20 psi.  Then connect the compressor hose to the spark plug hose.   Then listen for leaks from the intake.... open the throttle and listen through the TB. And listen for leaks at the tail pipe.   You WILL hear some hissing... but if all is good with the valves, that hissing will be past the rings.   You can also remove one of the inspection plugs on the side covers and listen for air blowing past the rings to confirm.   Some air going past the rings is normal.   If you want to get crazy with checking the valves ?You could remove the exhaust and intake, and spray the back side of the valves... through the ports.... with leak Detects or soapy water.    Your looking for bubbles , like a leak on a tire........

[mattsz]

If the higher octane fuel cures the pinging, then you either have higher compression than usual for these engines(for some yet undetermined reason), or you have very crappy regular grade fuel. Or both.

If higher octane fuel doesn't cure it, then it is most probably some kind of pre-ignition issue, most likely caused by a hot spot in the chamber somewhere. But there still would be some possibility for something else to be causing the heat.
Take it one step at a time.

Ah.  That makes sense to me.  Oh, how I wish I didn't have nothing but a few busy days of near-freezing temps left for the year!

Meanwhile...

I had a few minutes in the garage today, so I decided to pull the plug and do a quick check.

The plug looks perfect.  Using a flashlight and trying to peer into the hole, with the tank still mounted, was fairly futile, but I could see a little bit as I cranked the piston over with the kick start lever.  There's definitely some shiny, bumpy black crud on the piston, but I simply cannot tell any more than that.  From what I've seen and heard here, that's not unusual?

I disconnected the power to the fuel pump, and installed my compression gauge.  Electric start, wide open throttle, three different times: 160 psi, each time.  It only took two strokes of the piston to reach it, third stroke didn't budge the needle any further - I don't know if that's relevant.

A bit high?  I don't know is how accurate the gauge is.  Maybe I'll hook it up to my air compressor just to see how closely it matches the compressor gauges...

Regarding the auto decomp: when it lifts the exhaust valve, does it lift it enough so that you can see the valve movement, either through the plug hole or through the exhaust manifold?

[ace.cafe]

160 is a little high, but in a closed chamber with working squish, it should probably be okay.
However, in a scenario where your piston was maybe a little too far away from the head at TDC, and the squish isn't working too well, it might be enough to get it pinging.

From the test results, you don't have issues with low compression, which could indicate a leaky valve or something, so that's good.

I would surmise that if you start using premium grade fuel like 92 or 93, there's a very good chance that the problem will be gone.

[gremlin]

...... the auto decomp: when it lifts the exhaust valve, does it lift it enough so that you can see the valve movement, either through the plug hole or through the exhaust manifold?

action best viewed with the rocker cover off.

[Gypsyjon]

I never use any gas except Chevron Premium with Techron. Texaco has Tecron too. High octane! Hell the thing gets >65 mpg, gas is cheap.

[Arizoni]

160 psi?  That's interesting.
Either the pressure guage is messed up or the engine has about a 11 to 1 compression ratio.
(reading/standard air pressure at sea level = compression ratio = 160psi/14.5psi = 11.034)

11:1 compression definitely wouldn't like 87 octane fuel if the engine was being "pushed" at all.

About the only thing I can think of that would raise the compression that high would be a lot of carbon built up in the combustion chamber.

That said, and being a person who doesn't like to mess with stuff that's working, I still wouldn't remove the head if running high octane fuel stopped the pinging.

Besides, running an 11:1 compression ratio should give a noticeable horsepower increase over a stock 8.5:1 ratio.

  Can any of you other folks think of any other reason for the high compression readings besides a frinkled up compression guage or a lot of carbon? 

[Ducati Scotty]

The fact that the carbon he could see through the spark plug hole looked "shiny and bumpy" leads me to believe it may be excessive, rather than just a nice thin even coat over the piston top.

Scott

[mattsz]

Arizoni - I am about as close to sea level as you can get!  But - I can assure you I don't have any increase in horsepower! 

A reminder - this isn't a constant problem.  It only seems to happen when the bike is hot.  A 20 minute ride around town in 50℉ temps doesn't produce the pinging.  On long hills in this case, I can feel 5th gear just lose its oomph and not respond to the throttle before a downshift, but no pinging.  This is why I'm sorry I didn't start all this earlier, in the warmer riding season...

[ace.cafe]

It's not 11:1.
The compression ratio is based on volume, not on pressure.
We see similar test pressures from AVL and Iron Barrel engines with ratios in the area of 8.5:1 static.

Premium fuel with about 93 octane can withstand about 158 psi in an open chamber without any squish activity. So, anything higher than that needs some mixture motion help to get it burnt before any end gas detonation can occur. The squish function will be important in this case, and it is not always set right by the factory.

[AussieDave]

Speaking from my limited experience I would say carbon too. My piston had a good couple of mm build-up, and even more in spots. remote possibility could be a stretched con rod but that is highly unlikely unless Matt is a closet red lining hoon.

[gashousegorilla]

  Compression ratio's and what you see as psi on a gauge at cranking rpm's  can be two different things.  Depending on cam timing.   In particular intake closing time, and how much air , if any is lost through reversion.    Matts' bike to me, sounds like the compression test reading is a little high.  Some carbon build up and coupled with a relatively early closing time of the stock intake cam , I think would bump up his numbers.   I think he has also mentioned vibration and lack of performance ?    I'm thinking that could be from the effects of preignition ...... as the fuel/air mix starts to ignite early from the glowing hot carbon on the piston crown and in the chamber.   The Piston may be fighting it's way up the bore.

http://www.crankshaftcoalition.com/wiki/Cam_and_compression_ratio_compatibility

[mattsz]

remote possibility could be a stretched con rod but that is highly unlikely unless Matt is a closet red lining hoon.

 

No, no red-lining, closet or otherwise.  Much above 4000 rpm, and my bike rattles my fillings from my teeth and numbs my feet.  I don't ride there (unless I'm trying stop the pinging...)

[motorman2whel]

Matt didn't you say your auto decomp had been repaired once and it got harder to kick over after?. Maybe its not working correctly and causing higher readings at cranking rpm's. I went to a 8.5 to 1 comp piston in my IB, it was pretty extensively modified to reduce compression and with stock cam timing I still got about 175 psi.