What is a Sludge Trap?
If you own a vintage 650 or 750 twin, then you've heard about the infamous "sludge trap". Like many, if you haven't been there you eventually will! Hopefully it's before your crank blows out the side of the case. Propaganda or preventative maintenance, you decide.
The sludge trap is located in your crankshaft and does just what it says - it collects sludge, a thick pasty mud made up of metallic particles, oil, and other stuff you wouldn't want to put in your mouth. When the trap gets plugged with this stuff, you have an oiling problem.
The following paragraph is out of an article from Silver Machine, Vol. 2, 1989, "Trumpet Tunes":
"...The standard cranks have a sludge trap in the middle which should be cleaned at least as often as the big end shells are replaced. Some say it's possible to do this with the crank in place by just removing the sump plate and turning the crank so that the bolt in the flywheel can be removed and with the timing cover off, blowing it through with an air line and some paraffin but this is not an official method..."
Thanks to HILLBILLYWVA from the BIR Denver for the following pics.


