4 strokes

Hi Guys---I am having trouble with a bran new Saito 91.She was ok all the time i was running in now as soon as i started to fly she has been a problem in running backwards.It has gradually been getting worse.It starts easy enough although i have to nearly flood her to start,then she runs backwards for 3-4 times before running correctly. Something not set up properly yes?

Hi Dougal,

Nothing really wrong. Four strokes have a tendency to do that. As they ware in the compression gets better so they tend to ignite slightly before top dead center. As four strokes have valves that close the compression they will fire before top dead and run backward.

Two ways to combat the problem. one is to use a heavier prop to continue the rotation against the initial explosion.

The other method is to flick the prop clockwise when starting. this has exactly the opposite effect to what is happening at present except instead of running in reverse it will be running correct.

And yes four stroke in general do need to be very wet to start. That's why they kick so bloody hard and take fingers with them. It also makes four strokes easier to start as the only need to be turned to fire.

So if possible start with chicken stick. Try not to use electric starter. using electric starter can cause damage as the engine fires with to much fuel and kicks back against the starter can cause bent valve rods or even smash the con-rod.

Remember 4 strokes start with a simple flick at very low revolutions.

THANK YOU FOR YOUR QUICK REPLY------- I do appreciate the damage that a 4 stroke kicking back can do.I always use a chicken stick with this one as I have many times felt the kick on the stick as it tries to whip it out of your hand,and have been very gtatefull that it was not one of my fingers.And of course know that if I use an electric starter this can do a tremendous amount of damage to the engine if it hydraulics and suddenly refuses to turn over.This is why I have been getting frustrated in the amount of time I spend flicking the bloody thing over,only to get it firing backwards. OK so now I will try to swing it in the opposite direction to the norm--ie-clockwise, and with less vigour.Think you got a bit mixed up there[you say swing it anti-clockwise] but that is the norm with 2 strokes. I also have a bigger prop to try,but will try the above first. I seem to always be in the way of the prop if I try and flick it too slow,so I obviously need to get into a different stance with a 4 stroke. I love the sound of it once in the air so I certainly have no wish whatsoever to put a 2 stroke in it,so I will persevere.Thanks again Dougal

Yes----got it.told it if it didnt start behaving itself i'd send it away to NZ.That did the trick. Instead of flicking like mad and wearing myself out----a gentle turn backwards after priming it and away she goes. Must admti I am amazed at the little effort needed to get it to fire up. Not sure who "ADMIN" is but many thanks---another satisfied customer!! Dougal