Jordan from YGSC recently encountered a problem with his engine being underpowered and not revving properly. He first suspected jetting, but we soon set him on the right path, as he explains…
Recently, I’ve been struggling to diagnose a mysterious ‘stuttering’ of my engine, which is akin to having a rev limiter fitted when I try to rev out. I had several hunches — a poorly set up carb was one, or maybe it was my flywheel? So reading Editor Dan’s helpful tips in the April edition, it gave me an idea that the pick-up height might be misaligned. I tried the simple trick of warming my scooter up on the stand, and then revving the knackers off it in neutral for a few seconds. By listening to what happens, this allows you to rule out whether it was either jetting or electrical related. If it’s jetting it will rev but may be smoky; if it’s electrical it will ‘bounce’ as it hits an artificial rev-limiter. Mine did the latter. This confirmed to me that it was electrical, and having recently replaced all electrical parts I deduced it had to be the pickup alignment!
With the ever increasing ignition, crank and mag housing options out there for Lambrettas it’s no wonder these problems are starting to arise. I had a sneaking suspicion my pickup was sitting too high as the mag-housing gasket I’d previously fitted was the thicker type. So, I reduced the pickup height by 1.5mm and it now runs silky smooth.
A quick email to Dan and he helpfully explained to me how to go about checking and adjusting the height of the pickup. This is how I did it.
Image 1: Remove the flywheel cover and nut. Remember Lambrettas use a reverse thread, and then use the correct puller to remove the flywheel.
Image 2: Mark the firing points on the flywheel with white paint.
Image 3: Then mark the side of the pickup itself with two white stripes that align with the metal firing strips. After both the stator and flywheel have been marked up, re-fit them both. After this it is a matter of peering through one of the inspection holes in the centre of the flywheel and seeing how the marks on the pick-up line up with the marks on the flywheel. If the marks on the pickup sit high against the flywheels marks, you need to reduce its height and vice versa. The pickup needs removing before any adjustments can be made. It’s as easy as undoing the little screw out from behind the pickup.
Image 4: To reduce the height, I removed some of the metal laminates below the pickup. I made two slight cuts where the white lines are in the picture and peeled off a couple of the metal strips from the stator body. To increase the height, you can get in touch with a fellow called Anthony Tambs who makes some rather nifty stator packing plates. Alternatively, you could simply make your own little spacer to sit below the pick-up and adjust the height as necessary. Re-fit the pickup and add a dab of Loctite to the grub screw. Once you have adjusted and both marks line up, re-fit, torque, strobe and enjoy! It’s something I’ve never attempted before so I thought I’d try and help some fellow novices out.
This article was taken from the June 2016 edition of Scootering, back issues available here: www.classicmagazines.co.uk/issue/SCO/year/2016