Using Timing TDC Tool

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Posts: 37
Joined: Fri Jul 15, 2016 5:18 pm
ebay user ID: siskin40
Main scooter: Lambretta SX200

When i've done my timinig i've used the TDC tool which sits in the cyclinder head & as you do turned the flywheel in both directions until the piston hits the stop.

Have just noticed though the the piston will nudge that stop up.

So the question is should you use as i always have done turning the flywheel until it stops when hitting the tool or should you hold the tool 'probe' at the top so it cannot be nudged up.
registered user
Posts: 1272
Joined: Thu Sep 16, 2010 9:54 pm
Main scooter: SX 150 running in

its sometimes called a dead stop; don't think the tool should have any movement really; with a little bit of give your tdc finding marks should still be close to the same degrees before and after tdc so I wouldn't be to worried
C’est la vie
Warkton Tornado No.1
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Posts: 293
Joined: Mon Oct 17, 2011 6:16 pm
Main scooter: Lambretta SX200

The problem with finding TDC is that there is a large angular movement for very little movement even with a DTI (Dial Test Indicator) axially in line with the bore. The phenomenon is referred to as 'dwell' & even though I have the kit which I use with central plug heads or, with head off, a special bracket, it's a process that takes great care.

With what you have, you need to have a positive stop, so if you can lock the probe, or replace it with a bolt locked in place, you should be able to rock the piston both ways to the stop then mark the mag housing @ the two positions. Then, central to those two points make a mark that will be TDC. Of course, then you need to go ACW to mark your desired firing point for the ignition.

Ignition timing is made a lot easier if you invest in a tool such as Sticky's Buzzwangle. For less than £90 it takes the guesswork out of the process & is probably less than the cost of a new piston......
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