ENGINE BUMP STOP REPLACEMENT
Many years ago it was common to fit a 400:10 rear tyre to increase the gearing to make Scooters faster! It was like adding the next size up front sprocket!
It sounds an easy job swapping the 350 to a 400 tyre! Some fitted, some didn’t, those that fitted had very little clearance – in use the tyre could expand and lock on the bump stop. SO it meant the engine bump stop needed cutting off to give tyre clearance to the casing.
In the 70/80/90’s it was common place to lay the Scooter down and cut off the bump stop! Cutting off the bump stop can be quite dangerous! If a shocker snaps the frame and rear mudguard drops straight onto the tyre, locks up and can send the rider over the handlebars!
Today it’s one of the most common engine repairs we do. Usually the casings are perfect and just miss the stop. In an effort to put engines back to how they should be we weld them back on using an old donor casing and then clean up the welding so you can’t tell it was missing in the first place.
Whenever you weld a bump stop or engine lug – the mag face always distorts so it needs milling all part of the work we do.
Donor engine lug fitted with our fixture
Not always an easy weld, the back side is a guess to see if its welded correctly
Once welded and cooled and mag face machined, the welding can be roughly cleaned up
Roughly grinding away can fine some blow holes hidden under the welding, its always best to drill these holes and grind away for more welding
More welding to fill in any blow holes
Once happy that there are no blow holes or that they have been re filled in, you can start to really clean up and fine grind the welding to disguise its been welded
And done! this customer didnt want the casings bead and aqua blasted, he wanted it to look old
Any questions ask mark@mbscooters.co.uk
Really brilliant article