mate of mine has has a scorpa sy250 2004 only ridden it last weekend started to make a loud knocking noise hes been useing good 2 stroke oil in the mix so yesterday took engine out and found the big end bearing scrap can any body tell me what can cause this i thought oil but hes using good brand any ideas by the way they are a pain to work on no room at all think i will stick to my beta was tempted to get a sy but not now

The usual reasons for a failed big end in a two-stroke:

Corrosion due to being stored with only fully synthetic premix oil for protection.

Corrosion due to motor being filled with water by accident and not immediately dried out.

Pre-ignition and/or detonation over an extended period.

Poor air filter maintenance practices (usually affects the bore and piston/rings first).

Its pretty hard to read your message without any punctuation but it sounds like either your mate only just bought the bike last weekend or you only rode it for the first time last weekend.

Any other clues about the bike ie how did it run prior to the failure and what sort of riding does the bike see?

by the way they are a pain to work on no room at all think i will stick to my beta was tempted to get a sy but not now

This is the first time i have heard anyone say the Yamaha engine is bad to work on.... these engines are as

good as it gets for all round quallity.. you just know every nut and bolt will be perfect, and all componants

strong and well made..

Scrumpy