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Hot valve adjustment


docc
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+ 5 hours from shutdown, engine temp 27˚C/ air temp 25˚C; valves have stayed 0.006/0.008.

 

Other than the hot (90˚C) valves being unexpectedly looser, and the intake looser than the exhaust, there are a couple other observations:

 

1) With the fans on the motor, it cooled almost 90% in 40 minutes and the valves returned to their "stone cold" setting. So, I would conclude that the motor simply needs to "cool down" for valve adjustment, but doesn't need to be "stone cold" or sit overnight; not even for hours. Notably, the valve cover was removed during the cool-down.

 

2) It's OK to remove the spark plugs from a hot engine. But best to replace them when cold.

 

3) guzzidiag is a wonderful tool for monitoring actual engine temperature/ air temperature.

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Guzzidiag is a wonderful tool for measuring temp as long as the temp sensor is in spec. Ask Meinolf haha....

 

Those results are interesting, as my valves seem to get louder as my engine warms up. Makes sense.

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Its always better to remove plugs from a warm head and install in a cold one, for reasons that seem obvious. Well to me at least

Ciao

Wait . . . why? :huh2:

 

Because an Aluminium head expands more than steel plug so removing will be aided. The opposite for installation.Its highly desireable to avoid installation and torquing on a hot head but if you have no choice then install the plug and let it sit for 5 min or so to absorb some heat before torquing. All falls under the umbrella of " good engineering practice"

Ciao 

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Its always better to remove plugs from a warm head and install in a cold one, for reasons that seem obvious. Well to me at least

Ciao

Wait . . . why? :huh2:

 

Because an Aluminium head expands more than steel plug so removing will be aided. The opposite for installation.Its highly desireable to avoid installation and torquing on a hot head but if you have no choice then install the plug and let it sit for 5 min or so to absorb some heat before torquing. All falls under the umbrella of " good engineering practice"

Ciao 

 

Thanks for that! Makes sense. In an engineering practice sort of way . . . :nerd:

 

(I edited the "best answer" post)

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So why not reduce to even smaller clearances...........? Just asking

I had always thought tighter clearance means more accurate fueling. With the downside being a risk to burnt valves. But my experience is that looser settings the Guzzi seems to run/start better.

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Just took the Rosso Corsa off the lift. The fellow's had it a couple years and it was right ready for a good going through. Guzzidiag is such an excellent tool to get base lines, zeroed the CO (his was minus 31 !) and  set the TPS all the while watching the engine temp and the air temp get closer.

 

Once "cooled down", the  valves were I/E: .007/.004 right and .011/.010 left. It was idling at 900 rpm with a throttle opening of 2.66˚.

 

I fooled with it about four hours in all including a very careful oil and filter change, throttle body balance, and fitting the missing cap on the left vacuum tap. :o

 

All in all, I do believe the good fellow is going to have a very fine ride home!

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Doc, did you get  a Rosso Corsa?

No, no, no - it's a buddy's bike that needed some luvin' :wub:

 

Made it MUCH better, but still need to "fine tune." :luigi:

 

(Trying to figure out this "guzzidiag" thing. :nerd: )

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  • 4 years later...

Just had to dig this thread up, where Docc found that valve clearances opened up slightly when hot vs common sense that says they would close up.

Great resource of info.

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4 hours ago, GuzziMoto said:

Just had to dig this thread up, where Docc found that valve clearances opened up slightly when hot vs common sense that says they would close up.

Great resource of info.

As a blanket statement valve clearances get tighter with the engine at operating temperature, however doccs test was a little flawed in that the engine isn't running. The valve temps on a running engine are wildly different to a warmed up engine sitting stationary for 5 min while you get the rocker cover off and measure the clearances. Also different materials expand at different rates. My VFR750 Honda during warm up had valve noise that went from silent to tappety and back to quiet again as the head and valves all expanded at different rates.

So measuring valve clearances with a warm engine doesn't actually tell you what the valve clearance is running at WOT with the valves running red hot. In that scenario you wont have more valve clearance than cold and thats what you set the clearances for,valve and head temp running at WOT at peak torque.

Ciao 

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dooc flawed?!? Say it ain't so . . .  :blink:

So, how in the wide world would one check valve clearances with the engine running? :huh2: Which is why we all assumed the clearances close up during operation.

Yet, the fact that the clearances come back to "stone cold" values after just 45 minutes or so was the point of the exercise. No reason to let the sun set and rise again to set your clearances, if I can be considered correct in this aspect of the matter . . . :luigi:

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1 minute ago, gstallons said:

IDK about a MG , but you can do it on a small block Chevy . It takes practice and patience or a lot of hubris .

Set the valve lash with the valve covers off and the engine running? Yeah, lots o' hubris and lots o' kitty litter and shop rags!?

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3 minutes ago, docc said:

dooc flawed?!? Say it ain't so . . .  :blink:

So, how in the wide world would one check valve clearances with the engine running? :huh2: Which is why we all assumed the clearances close up during operation.

Yet, the fact that the clearances come back to "stone cold" values after just 45 minutes or so was the point of the exercise. No reason to let the sun set and rise again to set your clearances, if I can be considered correct in this aspect of the matter . . . :luigi:

No docc not you, and your test did show useful results with regards to engine temp for clearance adjustment in that it doesn't need to be stone cold. I was commenting on GuzziMotos post about the clearances closing up when the engine was hot, which they do however its running hot. So he's right thats why if the clearances are too tight cold you will burn a valve due to it being held off the seat when hot and not cooling.  

I've seen valves being adjusted on a running engine docc, very messy.

Ciao

 

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