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Simonini Mini 2 Problem


wallboy
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I have a Simonini Mini 2 which starts and idles fine but wont rev over half throttle.

Have cleaned the carb with air compressor, fitted new gaskets etc, have also tried using another carb off a working motor and still no good.

There is lots of black oil/fuel coming out of exhaust flange but the spark plug is clean and dry

My mate thinks it could be crank seals, ideas anyone?

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If it is coming from the crank gasket, you should be able to find the source to confirm it. I would get some de gunker all over it, give it a good scrub so you have removed all the oil, fire it up for a little while and check the crank for new oil before it has a chance to spread and cover your entire motor again. :-(

SW :D

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If anything black were coming from the crankcase gasket of a 2 stroke, something would be very wrong.

A leak in the crankcase (gasket or crankshaft seals) will lead to poor running at idle as it sucks in air.

The spatter marks indicate a leak at the exhaust flange.

Have you checked that the exhaust is not clogged with carbon deposits? This would cause poor running at high rpm and leakage due to excess back pressure.

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Ahhhhhh, thats a very very good point!

I remember having to de-coke an exhaust on a little 125 2 storke many many moons ago but the end result was AMAZING !

Not sure you would want to do it in quite the same way as I did though lol (fill it with petrol and let it burn, tap it all out as it cools) but as I say, I would expect this is not the way it's actually done. LOL

SW :D

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Took silencer of left expansion pipe on still the same,going to try another carb.and check spark, on tick over it runs fine just bogs down when you gave it throttle,all the crap around exhaust but plug is very clean,ive put my 37 walbro of my f200 engine which runs perfect on mine still the same on the simonini no go after tick over.

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It will be the expansion chamber that is coked mate (If at all of course)

You would see signs by popping it off the barrel and looking. Well worth the effort I would say :-)

SW :D

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Not sure you would want to do it in quite the same way as I did though lol (fill it with petrol and let it burn, tap it all out as it cools) but as I say, I would expect this is not the way it's actually done. LOL

SW :D

That is exactly the way it's actually done in my workshop, but to some extent this may be a reflection of my contempt for 2 strokes :twisted:

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Could you elaborate upon the technical term "f***ed", so that others may benefit from your experience?

Unfortunately not as I just fitted a brand new Walbro carb and I am back to the same problem I had to start with so not a bloody clue what's going on.

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