Problem defined:-
• Rattle when cold at about 1500 rpm.
• Front cylinder only (rear cylinder runs fine).
• Either side of 1500 rpm no rattle.
• Rattle clears after warm up.
Changed front piston - rattle remains but at about 250rpm and louder this time.
Checks carried out and results:-
• Oil flow to cams good
• Cam chain set to correct tightness – no witness marks
• No piston to cylinder head contact – no witness marks
• No liner to big end bolt contact – no witness marks
• No piston rock (slipper pistons) - no witness marks on liner or piston
• Valve springs good – none broken, no binding
• Tappets set and checked at between 0 and 1 thou” clearance
• Piston to liner clearance = 4.7 thou
• Bore parallel at 98.000mm throughout (piston spec = 98mm)
• No big end play
• Small end play – oval on RHS
Small End – could this be the problem?
• Machined from both sides - detectable ridge 1/3rd in from LHS (this is normal apparently)
• RHS oval – evidenced with pin part in - rocks in vertical plane
Other thoughts?
• Is 4.7 thou” piston to liner clearance too big - bear in mind rear cylinder machined to same spec and doesn’t rattle
Otherwise it's a fabulous bike!
Appreciate suggestions for solutions or recommendation for further checks.
Thanks
DWS
