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Polini 130 for Dummies


rsquared
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I apologise in advance for this being a long thread...but I really need help.

A brief history, my Polini 130 has 36 hours on it.....there was a downtime period of 6 months due waiting for new frame etc. When I started it after 6 months, to my surprise all seemed well. After 4 flights I had a semi engine failure after an hour flight...no response above cruise speed, landed, tried to restart...no joy.

Now I must warn you that I am one of the rare breeds that has never, I repeat...never been involved with engines of any type...I changed my first spark plug a few weeks ago in my 58 years of age. I astounded myself in taking apart the carb, and replacing the rubber things and needle thing with the spring thingy and filter which had a fair bit of gunk in it, plus renewed the fuel filter.

Next flight, engine started easy, but during warm up....it was "coughing" and "revving" without me moving the throttle. After a good 10 minutes of gently warming it up to full revs...it kept on decreasing revs when I held the throttle steady, but revved up again. Basically, imagine you revving the engine, but keeping the throttle in the same position...this is what was happening until I persisted and eventually it settled down and I flew....but only for 15 minutes.

In my limited brain, I know something is not right. After much research, I found that a lot of carbon build-up on the piston and the head usually results in "hard to start"...but mine starts easy. So I was thinking I still need to take the head off and check for carbon build-up. This scares the crap out of me...I only have basic tools, no torque wrench or other fancy gear...if I go down this road, what do I need to have?...spare gasket, O-ring...what surprises are install for me?....and then what about putting it back together again, do I need special sticky stuff to put on the gasket and threads?

Or is there some other simple reason that my motor is behaving this way?

Any advice is greatly appreciated, as I really need to get back in the air again....6 months was way too long.

Cheers Rsquared. 

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One rule of fixing things is to be careful to only do one thing at a time. 

You initially said would not rev above cruise speed...which does sound like carb issue....usually not enough fuel getting through.

Then you took the carb to pieces. Now you describe some new issues. These new issues are very likely to be due to the carb, since that is what you just played with. Before starting on new things first complete the carb set up. That "springy thing" is often a tricky one to set.

What carb is it? List details and then ask someone with same carb to help.

 

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Thanks for the replies....the carb I have is a Walbro 8, I received the carb rebuild kit and I thought I was meticulously careful with everything I did, even photographed evert step so as to be sure I put it back together as it came apart.

Not that easy for me to find someone with experience as I live out in the sticks in Thailand, and after seeing some of the way Thais approach things mechanical (not that I'm an expert...but I can tell the difference between competency and outright guessing), I don't feel I would trust a motorbike mechanic with something as important as my paramotor.

Anyway thanks again for the replies...Cheers

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A good resource for polini 130 advice is http://www.southwestairsports.com/ppgtechinfo/thor130/specs130200.htm  It has links to various strip downs re builds and testing methods etc. If there's no one local you could trust have a look on their see if there's anything that can help.

 

Heres a few others I've used in the past also

http://www.wind-drifter.com/technical/wg8walbro.php

 

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Although it sounds like a carb issue, the next time you have the carb off it's a useful opportunity to check the condition of the reed valves. The four  bolts behind the carb attach the reed valve assembly, look for any cracks or damage to the carbon flaps or petals as they are commonly known. 

Edited by paulg18
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