Stuart Turner magnetos

If it's firing back through the carb I'd say the timing is wrong.

Now when I say 'wrong' I don't mean you've done it wrong - it may well be spot on to what the book says. I mean 'wrong' for the load (or lack of) it's running with. After all, the timing specifications were written with a view to the engine working somewhere closer to it's capacity.

Having a load would also have the same effect as a heavier flywheel...

Maybe try retarding it a bit?

Good idea Paul, thanks . I've been reading the instruction manuals I got with the engine and they seem to say that back firing through the carb means the mixture is too weak but what you are saying about load actually seems to make more sense. I just wish I had something to load her up with.

They also say that any water or oil in the exhaust will make starting more difficult and I could definitely see something shiny sitting in the bottom of the expansion chamber, don't know if it is oil or water but I don't think it should be there. Really that exhaust should point downwards, not up like it does, it should also have some sort of baffling, as it is it has no back pressure and I've always believed that two strokes like a bit of back pressure (as well as some load). I would like to get something sorted for that, something more like the original. I would also like to get a small radiator and fan set up for the cooling rather than all those silly looking pipes and tank.

I was actually going to say about the mixture too, but it was late (that's my excuse and I'm sticking to it!). A weak mixture would make it get hotter faster too.

I agree a 2 stroke needs back pressure - in fact it relies on it to work properly (I think any engine does unless it's specifically designed not to) I didn't realise that was just a straight through pipe - maybe also try just sticking 'something' over the end of it to give it a bit of resistance? (Another little bit of pipe with the end squashed?)

Not only is it a straight through pipe (with a slight expansion chamber in the middle) but it doesn't sit on the manifold properly and wobbles about. I've got an exhaust ring from my old car (when I changed the turbo) that I think will fit and help to tighten it down a bit but really that exhaust is all wrong. There's the back pressure issue, the fact that it is pointing skyward when it should be pointing down and the noise, it is pretty loud!

Plenty to think about. I'm also wondering now if the magneto plate and the magneto itself is clean enough as sometimes the spark doesn't seem that strong. I may send the magneto off to a bloke locally for testing, I still need to talk to him about what to do with the old mag. Do I pay the £75 for a new coil and try to sell it on or do I see if he'll offer me a few £s for the whole mag and he can sell it on. Questions questions questions, seems to be the story of my life

So we're back to Stuart Turner Magnetos!

I dunno, that was a big trip round the houses!

I'm not so sure about the timing, she didn't spit back much when we had her running that first time, & the timing hadn't changed, but we had been fiddling with the carb.

Have a look in that book of yours & see about that mixture adjust thingy on the carb (what they call a choke, I think. YKWIM). I think the mag should be tested, but I personally don't think you'll get good news. We (or rather I) could dismantle it first, give it a clean & see if I can test it. I don't know an awful lot about rotating coil magnetos, but I'm sure I'll learn. I can check up on line first, I know where I can get instructions on how to separate the condenser from the rest of the mag.

i use a battrie drill to start my r2 saves the arm quite a lot.

Diddy wrote:i use a battrie drill to start my r2 saves the arm quite a lot.

Now that is interesting. I've got quite a nice 18v Hitachi cordless, wonder if that'll be up to the job.


Matt, I was studying the books last night and they all say the same thing, weak mixture will cause back firing through the carb and oil or moisture in the exhaust will cause starting trouble. Also it has the wrong plug (I think, can't remember which plugs I bought Anyway, I've got my eye on the right one on ebay but it's looking a tad expensive. Personally I don't think there's anything wrong with this magneto, it might need a bit of a clean up but the spark still looks strong to me. I'll call the magneto guy tomorrow sometime and see what he thinks.