Say hyperthetically...

[chris-red]

...somebody put a good few tanks of unleaded though a bike that was supposed to take leaded fuel and now it will not start.

What sort of damage could have been done?
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Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.

[Kickstart]

Hi

Possibly valve seat recession, and left long enough the clearances will likely tighten up and it will burn out a valve.

First thing to try is to adjust the valve clearances.

What hypothetical engine?

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[chris-red]

A late 60's triumph 650 twin, It's not me by the way it my dad,
____________________
Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.

[Kickstart]

Hi

Should be easy enough to whip the head off and check. If needs be get the seats replaced with harder ones.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[.]

Usually it takes several hundred miles to remove the protective TET coating built up from using leaded petrol and then a lot more miles on top of that to cause damage valve seat damage through using unleaded petrol. But it's also dependant on the quality of the valve seats to start with.
Might be worth a few squirts of oil down each plug hole to seal the rings, then turn the engine over and check for (audible) compression loss via the exhausts.
If there is still clearance betwen the rockers and valve tip and compression is good, might be worthwhilst checking the basics first before opening up the top end, even though it's just a few hours work on one of those engines.

[Ariel Badger]

I myself have done 10s of thousands of miles on bikes that should have had lead in the fuel to no ill effect. I doubt it is unleaded that killed your dad's bike.
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Bikers make great organ donors, get 115 on your licence today.

[chris-red]

It probably has done about 500 miles or so, we really need to check it out but TBH it is far too cold
____________________
Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.

[tatters]

Bikes with alumium cylinder heads generally have hardened valve seats so are fine with unleaded fuel.


though l know people with pre unit singles with cast iron heads who have run unleaded fuel for over 20 years with no problems.
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[Kickstart]

[prawny1]

The ignition timing being set to still run leaded could do more damage in the short term than the actual lack of lead on the valve seat.

The different burn characteristics would likely need a minor plug heat range change too.