Exhaust bodge revealed
Mechanic Paul Knight uncovered a lot of corrosion and a bit of incompetence
‘The collets were doing nothing to seal the pipe’
When a 55-plate Kawasaki BN125 Eliminator came in as a non-runner it didn’t take long for Paul Knight, the boss of A55 Motorcycles in Penmaenmawr, north Wales, to work out that the problem was a lead from the regulator/rectifier that was so corroded the battery wasn’t getting any charge. But when he fired it up, an entirely unrelated problem announced itself with a loud ticking. “I can only think that the rider’s dad dredged up some mechanical ‘lore’ from the dim and distant days of his youth and thought the exhaust gasket was the problem for some reason. When I stripped it down the L-shaped exhaust collets that hold the downpipe tight against the exhaust gasket in the cylinder head were in the wrong way round, so they were doing nothing to seal the pipe up.
“As they were more corroded than the electrical lead I got some nice new ones, and a new cylinder head exhaust ‘crush’ gasket because they should never be re-used,” said Paul.
The job was made easier by a little tip Paul was taught years ago: masking tape. Holding those collets in position as you offer up the pipe is fiddly in a 125 single and can be a nightmare on a fourcylinder bike. But if you wrap a length of paper masking tape around each pair, it’s simplicity itself and the tape will burn off harmlessly. Paul added: “When you fit an exhaust, get all the nuts and bolts, from the downpipe clamps to the silencer bracket, engaged on their threads before you begin to tighten them, starting at the exhaust port studs. Slip joints further down the system can get a little loose over time; exhaust paste makes a good seal but be sure to wipe off any excess before you start the engine.”