i have a killer roto start miles and they are decent, but be aware the one way bearings do fail sometimes in the driver part, they can be changed but pain in the arse, always have a spare driver part with ya if ya get one

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i've tried most pull starts as well, i had a zenoah pum pull start on the twin and that was mint, right up untill it starts to wear, then it eats the secondary springs, tr pull start is total wank imo, never could get mine to work right and it ate the secondary springs all the time,
the rofun/zelda/spovan 45 has an ezi start on it and tbh thats quite nice and smooth, but heard there are issues with em and they need a slight mod to the pawls, but that wont fit your engines anyways,
i just fitted a full size alloy ezi start pull start to the twin ( its a chinese version but is well made) instead of the zen pum one, juries out on that one at moment till i get the dragon hammer finished and up and running again, but its smooth, but also had to mod it a tad to get it to work on the twin,
the fid ezi pull start looks good , but is expensive for what it is in my view,
nowt wrong wi normal pull starts though
reason i prefer the ezi start ones is cos , well imagine trying to start yer rig whilst being sat down and ya cant hold the car down wi yer foot,
thats me

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ezi starts make things easier in my case, but ya needs to keep em clean, same as any starter tbh though

