Engine bore wear

hello well This old girl must of done over a million miles for it to ware this much  and she need a new sleeve fitting now for another million miles  and long may she run and run  now have fun and keep safe  yours anna j

Hello, thats agood amount of wear. I had a Triumph twin that was on plus 10 at 170,000 miles. So Anna could be right if it has had regular oil changes. Its a wonder the rings have not broken due to flexing and bumping off the top ridge. I also had a Panther 120 that wore that badly, it used four pints of oil in one hundred miles, pretty smoky too, people overtook with lights on at great risk!

I read an article about Leland stripping one of their London bus engines, back in the late 60’s, and it had covered a huge mileage. The bore wear equated to .001”/100,000 miles which agrees with the above observations,

Regards

Dick

.....but I reckon running these old beasts without an aircleaner is the kiss of death.  Look at those vertical lines in the bore. Inhaled crud.

Surly it depends on the conditions it’s run under. Service intervals, load types, short or long journeys, air it breathed and throttle use. If it’s in a barn, farmers of the day we’re not too sympathetic to mechanics.  Any oil better than no oil... it’s running leave it.  And many other cringe worthy statements I remember from my youth. It could have had one careful owner, it could have had a budding TT wanabe.... check out the machine as a whole and read it’s story.  Levers, cables, gears, oil condition, sprockets, tin wear damage, finish, repair types etc, etc,...You will be able to gauge it.

cheers

Jon

This is from "The Modern Motor Engineer" , 1952 edition. It suggests it might be as little as 16000 miles. Modern oils (and air cleaners) have made massive changes to engine lives.

It amazes me how many 'restored' and or original bikes have little or no air filtration, apart from poor maintenance this is the cause of most bore wear.

The rudimentary gauze 'filter' often fitted (should be called stone guards!) will stop large lumps getting ingested but will not stop the fine dust that is always in the air, getting in and wearing the engine out. 

Also a decent air filter will act as a flame stop in the event of the engine backfiring. 

... don't do big mileages so air filters may be seen as overkill. I've always thought that an air filter was far more use than an oil filter however for the reasons outlined above.

The gauze fitted to bikes like my ES2 will in fact act as a flame stopper in the same way as a Davy lamp.

Hi all,

   You will probably find this bike hasn't done a vast mileage as an air cooled long stroke single with dirty air and oil wears the cylinder quite quickly compared with multi cylinder water cooled engines with good filtration. This was the norm for this era of engineering and is identified by piston manufacturers making so many oversize replacements, normally +.020, .040, .060. This means you can get through 4 pistons before having a sleeve fitted, and even then the bike had probably not done much more than 100,000 miles. Big numbers are banded about for effect, but to rack up a million miles you need to do 200 miles every week continuously for 96 years.

   The bore should be measured half way down the ring travel to get an accurate idea of the nominal wear amount. This is not to say it does not need a re-bore to remove the accentuated wear at the top ring travel area. This wear is caused by the whipping action when the con-rod reaches its reverse action point and slaps the piston from one side to the other. This is more prevalent in long stroke engines which gets worse with long term wear and slogging the engine at low revs in high gears. A regular re-bore will help to avoid this problem.