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Strimmer engine conversion


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Hi Joe

           How's the conversion going.?

I've just started on a Homelite 33cc chainsaw , ordered parts from wacker engines to do the conversion.

What are you doing with the carb.? mines got anti tamper proof needle that I need to modify ,other than that looks straight forward.

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I finished mine and had it running on a 15x8 prop, it started easily and then I stopped it to adjust the tickover and now it wont go, I seem to have a weak spark maybe the coil gone down? don't know what you mean about the carb first time I have heard this, can you give me a bit more info. The conversion is very easy you just need to take your time as the saying goes measure twice cut it once, lets know how you get on. Joe 

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Starting a magneto set up can be troublesome, have you tried putting a starter on it

You could go electronic route for easy starting, but then that put's the price up.

 The carb mixture screws are set back inside the housing of the carb, and a special tool is required for adjustment. However I managed to get them out and cut away at the housing to make them accessible,

just got to put an extension on the screws so I can adjust them easily without loosing my fingers..!!

It's all to do with emission control.

Just waiting for parts to turn up ,decided to buy parts in see how it's done.

This won't be the last ...!! these strimmers and chain saws are just to cheap..!!!

 Nobby

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Hi Nobby, You mentioned replacing the standard magneto for an electronic ignition when converting an industrial engine to model aircraft use. Positioning the magnets on the prop driver would be a bit of a challenge unless you knew where TDC was; considering most ignition systems have two magnets. Doug
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Hi Doug

             If you use the rcexl unit it only has one magnet .

Timing up is straight forward ,as an engineer by trade I shouldn't have to many problems with the setting up( famous last words..!!)

The biggest problem will be where to position the hall sensor,( and that isn't to difficult) then as Joe say's measure twice ,cut or drill once.

Having said that I havn't done it yet ..!! I am going to stay with the magneto on this one see how it works out ,and progress from there.

Although fitting a electronic ignition works out more expensive, there is big weight saving's to be made, plus they start easier.

The procedure is well documented on rcu along with loads of other mods .

Nobby

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I managed to get the engine started, it still won't start by hand but I have no problem when I use a starter, it starts every time, now all I have to do is figure out how to tune it as it idles far to fast, and fit it into some sort of plane and then bobs your uncle with a bit of luck. Joe
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I think the engine needs to spin somewhere near 500 rpm to get a decent spark to fire it up using the magneto, doing that by hand is quiet a tall order, as you tune the motor it might get better.

Thats one of the advantages of electronic ignition easier starting .

When it comes to tuning take a look here  http://www.flygsw.org/  under tech site everything you need to know is here.

Nobby.

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In the interest of experimentation I took the butterfly off which had two holes in it and replaced it with one I made without holes, the engine starts without problem and I can set the idle to whatever speed I like, I am dead chuffed and it cost nowt. Joe
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If I may come into your discussion?

I'm not familiar with the actual engine, but the two holes in the butterfly are to ensue adequate air velocity in the choke tube at idle, thus providing a suitable mixture for slow running. They also give a smooth 'pick-up' as the throttle is opened giving a steady progression to the main jet. Your modificaton whilst successful in enabling cold starting may cause erratic low/mid range performance.

 Was the origional butterfly closing fully?

Is the cold start functioning correctly?

Are the jet/air bleed settings correct?

Also ensure the timing is correct before adjusting the caburettor (many carb. faults are in fact ignition faults!) or you will just end up chasing your tail.

As I said earlier I'm not familiar with this engine but interested in the success of your project.

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Thanks for your response Brian, after the butteryfly mod the engine starts easier and idles so much better, it doesn't seem to have affected the performace although I will need a tacho to find the top rpm, and there is no problem with the engine response when throtling up, I thing it's getting near time to fit this baby to a plane just need to make a reasonable silencer. Joe

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Thanks for your response Brian, after the butteryfly mod the engine starts easier and idles so much better, it doesn't seem to have affected the performace although I will need a tacho to find the top rpm, and there is no problem with the engine response when throtling up, I think it's getting near time to fit this baby to a plane just need to make a reasonable silencer. Joe

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Been considering one, the Hanger 9 sopwith camel which was reviewed in the Sept 2007 RCME, 61 inch span with a short nose, the chap who reviewed it says that he had to add a lot of lead at the front due to it's short nose  which would not be the case with a petrol engine around 22cc, so this one sure looks like it may be in the frame, to tell the truth I really like biplanes, I have a World models Ultimate 40s and  a Ripmax Tiger Moth among my fleet which my dearly loved wife thinks the absolute world of? Joe

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