UK Karting - Notice Board (2-Stroke Karting) : Rotax no spark / misfire

Notice Board (2-Stroke Karting)

Rotax no spark / misfire
Posted by 'richpudd2003' on 03 Apr 2018 @ 08:49

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richpudd2003Joined: April 2003
Total Posts: 45
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Hi Guys,

After picking up a Rotax motor to go along with my old 100cc for some 'fun' test days, I finally got around to having a blat around last week. Seeing as 2 out of 3 people I asked at the track for advice looked at me as if I was trying to steal their top secrets from them (I was only asking for advice on jetting) I thought I'd come on here for some advice.

The motor ran fine for the first session of the day. After that, it made me wish I'd picked up a TKM instead. Second session it developed a misfire in mid range. The misfire would eventually clear itself if I backed off the throttle. This got progressively worse during the session.

From the next session onwards it got worse and worse till eventually at the end of the session it conked out completely. Having checked the obvious (Fuel mix was 100ml to 5 litres of fresh fuel, jetting was 158) I saw that there was no spark. A quick change to a new plug resulted in it firing straight back up. It then ran fine again for about half a session before picking up the same misfire. It conked out at the very beginning of the next session, and then refused to start again for the rest of the day!

So my question is, what are the common causes for no spark on Rotaxs? I have no idea. Coil? HT lead? Someone mentioned crank sensor to me, could it be this? Battery? Would any of these cause a misfire at the same time or is that probably something unrelated? Unfortunately I didn't have any of these spare so I couldn't try them on the day. I know the motor has about 25 hours on it but other than that it is unknown to me.

Any help would be appreciated.

Message Thread:

Rotax no spark / misfire by 'richpudd2003' << You are here!

Re: Rotax no spark / misfire by 'chrissawyer21' (03 Apr 2018 @ 12:56)

Re: Rotax no spark / misfire by 'alanrr' (03 Apr 2018 @ 13:47)

Re: Rotax no spark / misfire by 'richpudd2003' (03 Apr 2018 @ 14:19)

Re: Rotax no spark / misfire by '3190' (04 Apr 2018 @ 9:15)

Re: Rotax no spark / misfire by 'richpudd2003' (04 Apr 2018 @ 21:13)

Re: Rotax no spark / misfire by 'alanrr' (04 Apr 2018 @ 23:55)

Re: Rotax no spark / misfire by 'richpudd2003' (05 Apr 2018 @ 16:07)

Re: Rotax no spark / misfire by '3190' (05 Apr 2018 @ 18:19)

Re: Rotax no spark / misfire by 'Ditch' (04 May 2018 @ 8:34)

Re: Rotax no spark / misfire by 'Alan' (09 Apr 2018 @ 20:36)

Re: Rotax no spark / misfire by 'richpudd2003' (18 Jun 2018 @ 15:03)

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