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Pull-start, Pullstart, Pull Start, 80cc, 70cc, 66cc, 60cc, 48cc,

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Pull-start, Pullstart, Pull Start, 80cc, 70cc, 66cc, 60cc, 48cc,

Post by Fabian on Sun Feb 05 2012, 07:00

After sorting out a few teething problems with the pull-start recoil mechanisms that are commonly available for centre mount 2-stroke bicycle engines, i'm happy to say that they work far more reliably than some of the negative press received on the internet.

A good part of the problem is the pull-start mechanism jamming up on itself and applying torque to the recoil cord, either breaking the cord or pulling the cord through the pull-start handle.
At first i used 2mm rubber as a gasket (on the ZM branded Pull-start) to space things out, though engine heat softened the rubber, allowing the pull start to snug down on the drive tangs; chewing into the aluminium, resulting in the Pull-start recoil cord tearing it's way through the Pull-start handle.
The same thing happened to the Unbranded Pull-start when i used a 3mm rubber gasket, but this time the engagement ramp bolts chewed into the aluminium disk, tearing the rope through he handle in similar fashion.

The fix is simple: provide adequate clearance between engagement hub and receiver disk, as outlined in the following photos.
In my situation, i needed 4mm of clearance to ensure the bolt heads were free from contact.
From my experience, non of these bicycle engines and pull start mechanisms seem to be (dimensionally) the same; you will most likely end up with a spacer of different thickness compared to mine.

Due to the extra material provided by the engagement hub, the spring washer that normally sits under the nut (holding magnet in place) will need to be omitted (loctite 243 being required) as there is not enough length on the magneto shaft to install both spring washer and nut.

Curiosity got the better of me as i wanted to place the "Unbranded" Pull-start internals in the ZM branded case, but dimensional differences prevented this from happening.

If you want any more info, i can be contacted by email: yldflight@hotmail.com


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Fabian
MxBF Power User

Posts : 338
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Birthday : 1970-09-03
Join date : 2011-06-08
Age : 46

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