How often do you clean the sludge trap ?
( every time the engine has been striped down )
A more accurate answer, is needed
What is your experience in cleaning necessity, when using good quality oil, low detergent mono grade and very frequent oil changing ?
The sludge trap in my BSA SR was last cleaned in 2002. The old crank broke do to wrong side finish on the large journal (big ends).
The bike has been used approx. 10.000 miles since fitting a “new” / re-engineered crank shaft from SRM.
Oil change: Every 1000 miles, minimum 2. times @ year. SAE 40 spring, SAE 50 summer.
Use: Always warmed up correctly, but the engine is always used with plenty of throttle
(One of the reason for having a SR: quick and plenty of power).
In MHO if the owner does not know when the sludge trap was last cleaned it is good practice to use monogrades which are less likely to dislodge or wash through existing sludge.
If an engine has been stored and the history is unknown, I would be recommending a strip and clean of the traps along with a bearing review, however this would also be because I would want to know if the drive side bearing was on its way out and whether the shells were knackered…
If you have cleaned the traps, then their behavior is tied to the nature of consistent oil and filtration involved; so that the properties of the sludge build up are not interfered with by suddenly adopting a high detergent oil after the use on non detergent oils. I would not consider the sludge trap to be an item that you would be stripping an engine to directly address, rather an item to address whenever the bottom end is inspected which could arguably be every 100,000 miles and 30 years…
On my race engine I routinely replace the main bearing shells so take the opportunity to clean the trap, it invariably has little in it, but I have the motor down so it gets done.
Way way back in my youth I had a number of little BSA/Triumph 250 twins (the scooter) and ruined a motor because I fixed it up but didn’t flush the sludge trap. The fresh oil dislodged the sludge and ran the main bearings.
Personally I believe the answer “every time the engine has been stripped down” is adequate, because an engine showing no mechanical signs of distress does not need its sludge trap cleaning and with routine oil changes the trap will outlast the knock from a set of main bearings
Just my 10 cents worth.
