Friday 26 August 2011

THE ROOT OF ALL EVIL

Stripped the top end of the chop (again) the other day and while looking for possible sources of noise decided the pistons had a bit too much slap in the bores. Took 'em off and had the bores measured, i did it when i first built it but this time i took them to a local engineering company to have them measured properly. Fully expected them to be way oversize but max 2 thou wear on standard they said, pretty good. Took them the pistons, negligible wear they said and both the same but...they are undersize by about 6 thou ! these are standard original Triumph (Hepolite AE) pistons that the bike left the factory with. Couple this with 2 thou wear and we have the whole reason the thing has always blown a mist of oil out of the breather.
There are probably lessons to be learned here but when you have a totally standard size motor that has quite possibly never even been apart before and done very few miles (remember it was hung up in a bar for 15 yrs then has sat unused for another 18yrs since imported to the UK) and the bores and pistons look fine.....


New pistons and a rebore and we continue....

1 comment:

Hugo said...

Ohh , the good old British tolerances... Bless them.