Overfilled sump causes issues
Bike whisperer Kevin Hollingsworth reckons this scoot owner got off lightly
‘It’s not as fast as it used to be, can you derestrict it for me?” As nonsensical statements go, this one was right up there with ‘my tyres are empty’! Seeing as the rider was on a Daelim AM125 Othello scooter sporting a four-stroke single cylinder engine, it had never been restricted in the first place.
But when experienced mechanic Kevin Hollingsworth, AKA
‘Dr Tepi’ at Doncaster Motorcycles rode it down the street there was no denying that instead of a 5560mph top speed, the commuter was struggling to get over 30mph… once the engine had reluctantly fired-up in the first place.
When Kev started to look around the bike, the canvas showing through the rear tyre indicated that the rider wasn’t too bothered when it came to maintenance, but there was one area where he’d been over zealous: topping up the oil. “The sight glass was full and the guy was quite proud that he’d kept it topped up like his dad had told him to.
“But I think he thought he was topping up a two-stroke’s oil tank, because when I unscrewed the drain plug almost 1500cc of oil came out and its capacity is only 750cc,” explained Kev.
“I’m surprised it didn’t blow the seals out or the oil didn’t get pumped out of the overflow pipe.” There’s another issue if the oil level is too high on a multi-cylinder engine and it manages to start. The spinning crankshaft can aerate the oil, whipping it into froth or foam. This creates tiny air bubbles which form pockets of air in the oil galleries that feed bearing surfaces, or foam that sticks in place and doesn’t drain back into the sump so you end up with insufficient oil flow.
Luckily for our scooter boy, without the drag of that extra oil on the crankshaft the bike’s performance was restored with no ill effects. Lesson learned.
‘I’m surprised all that oil didn’t blow out the seals’