Is glazing a real risk with idling engines or a myth ?

[McCabe-Thiele (Ted)]

In the four years or so that I have been a sohc member there are occasional mentions about the dangers of "Glazing"if running an engine idling for long whilst making adjustments.

I've taken the comments at face value without asking what evidence this is based on and what it actually means.
How real is the notion and what causes it if inded it can happen?

[Johnwebley]

I believe if it is a rebuilt motor, the sooner you can load the piston rings, the better



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[Nurse Julie]

Yes, on newly rebuilt engines having had a rebore and new piston and rings fitted, glazing of the bores is a problem to be avoided by putting the engine under load, making the piston rings fling out to cut into the newly cross hatched bores. If this isn't done, by just letting the engine tick over, the bores glaze and the engine smokes. Also, idling without getting cool air around the fins can cause a newly rebuilt top end to seize due to heat retention.

[SteveW]

What about if you’ve just run a hone down the bores and fitted new rings?

[Nurse Julie]

What about if you’ve just fitted new rings?

Depends if you've crosshatched the bores and what the piston to bore clearance is.

[DomP]

For how many miles should a rebuilt engine be given raod miles under load before glazing isn't a risk?

[Laverdaroo]

It’s pretty similar to running in a new bike Dom, but I would give it 350-400m before picking the revs up and holding them a bit more. Rolling on and off and giving it load aids in the process rather than riding about all gingerly so the motor is being taxed but not ‘thraped’ in all the gears.
I’ve not run mine since initial set up for fear of glazing as I wait for the tank and seat etc. soon as they’re back I can get it out there but ll do 400 or so, drop the oil and do another 250m, check the oil and change if feeling frivolous. That’s just me but happy to be corrected.
End of the day I haven’t spent this much time in the shed to kill it in the running in process so probably do a little above what’s required but ‘belt and braces’ and all that.


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[SteveW]

What about if you’ve just fitted new rings?

Depends if you've crosshatched the bores and what the piston to bore clearance is.

Bores were crosshatched and piston to bore clearance was in spec.

[Nurse Julie]

What about if you’ve just fitted new rings?

Depends if you've crosshatched the bores and what the piston to bore clearance is.

Bores were crosshatched and piston to bore clearance was in spec.

Yes Steve, you still need to avoid too much idling as you're trying to achieve the same result as a top end that has had a rebore with new pistons / rings, bedding the rings in

[DomP]

What about if you’ve just fitted new rings?

Depends if you've crosshatched the bores and what the piston to bore clearance is.

Bores were crosshatched and piston to bore clearance was in spec.

I must get out on it then really Roo even though its not cosmetically ready, not many dry riding days left this year!

[McCabe-Thiele (Ted)]

I'm in the same situation Dom I need to go out for a few runs on my 500 before it's too wet & cold. I was planning a ride this afternoon but I've done a bit of gardening whilst it's still dry. Now I'm too tired,
looks like Tuesday might be dry here in Derby.

[Bryanj]

I can tell you that when Kawasaki came out with the Z 1000 quite a few were rebored under warantee due to people babying them far too much, basically lugging the engine is far worse tha reving it plus dont sit at a steady speed for long periods, us B and C roads even SHORT bursts to red line

[McCabe-Thiele (Ted)]

I avoid dual carriageways - my favourite run on the 400 has been to Ashbourne & out on the Leek road - its all very bendy & hilly so lots of up and down the gears with virtually no chance to run at a steady speed.

[K2-K6]

No myth here, but lucid look at piston rings in general and down to finer detail

https://youtu.be/EFfyWbi3APk?si=iWh1cmG6rd0jv1Ud

Quite informative, I think.

[magpie114]

Thanks for sharing that. Very interesting.


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