OzVMX Forum
Clubroom => Tech Talk => Topic started by: evo550 on April 10, 2009, 02:12:55 pm
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What are causes of kickback when trying to start?
250 two stroke, gives a serious boot back every second stab of the starter....
Would it be a timing thing?
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uhuh.
2T engines are set to fire a spark ON but usually after TDC by a few degrees .. specific vary for different engines and systems.
a 2T engine will run backwards if allowed.
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Hmmmm....not so sure.....many later twostrokes use a retard effect in the ign box that retards the spark from around 30 deg BTDC at low revs to around 5-6 degrees BTDC at high revs. If you are stuck without much in the way of workshop facilities, get your sidecover off and your plug out, establish where TDC is, and work from there with the spark at your plug. But if it's kicking back a lot, there's a big chance you're way advanced....in the end, your shin will be the judge... :D
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A 2 stroke fires before TDC not after, same as a 4 stroke.
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It's a mid 80's husky, it has a motoplat ignition, there appears to be two backing plates that you can loosen and rotate.
One smaller one seems to be set about middle of the slot the second one is set all the way round the slot, not knowing motoplats it's a bit of a mystery, manual shows nothing.
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Be careful as with motoplats most guys go to the wrecker and get a replacement when they give up and quite often they dont get the matching backing plate, so when you go to line the holes up ( which they will ) It dosent mean its at the correct time . Best get the dial gauge out. Have a KTM that did the same thing and thats what we found