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Parajet plug


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Hi Guys and Girls

Anybody had my experience with engine cutting out ?

About to launch and get engine up to temp. then give it some revs to clear its throat and check thrust. Take off and climb for a minute or so then loss of power as though fuel starvation , dropping down to low tickover or stop . Hit the starter and straight up to max revs for about 10 secs , climbing but looking to land ! And repeat until back at home ! Once i managed to nurse it home feathering the throttle . I ve managed to safely land every time but its so frustrating .

Im posting this cause it happened again today . Just to say it isnt the fuel or the mixture or fuel starvation because i ve checked all of those previously...its simply the spark plug failing ! After 85 hrs im now on my 4th plug . The fault shows no signs in previous flights when it runs well and never misses a beat...On landing today i spent 1/2 hr on the ground trying to get max revs but to no avail...so new plug and its like a new machine again !

So my query is why is it eating plugs and why after having bikes of all shapes and sizes did you hardly need to fiddle with their plugs ( apart from a few KH triples that carried a spare set under the seat ! Remember?)


Thanks Steve

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Had this on my first and second ever paramotor flights!

Possible causes -

1) Plug cap worn oval and loose due to vibration

2) Unmetered air entering the system when warm (cracked or warped head or damaged head gasket)

3) Unmetered air entering below carb as carb retaining bolts too long (tight when checked with an allen key but carb still loose)

4) Carb needs cleaning or service.

Good luck.

Best regards,



Any news on the battery???

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Hi Steve

after 85 hrs of use have you thought about the fuel filter inside the tank ( It may clog up and the vacuum it causes may find a week point in your fuel line and draw air in causing your engine to run lean and cut out through fuel starvation)

hope this helps

Mark :D

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Could be a vacuum building in fuel tank at full chat, that eases as revs drop. Check all breathers.

I had similar with a ball bearing type non return fuel line valve that would actually shut off fuel in the 'forward' direction if the draw in the system was sufficiently high.

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I had a less severe version of your problem on a Parajet. Mine was caused by dirt in the carb. It would stay in the lower areas of the carb filter, and then on running and continuoius high vibration (take off) it moved and blocked the main jet. A good clean of the carb filter mesh cured it for me.



Same here, I used Tony's high hours Parajet for the instructors course. The carb was full of gunk, a quick clean and she was purring again.


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mine did the same as Phil-P .......check your breather...

or it could be the shitty petrol from the garage your closest to (I know) because I got 25 liters of worthless crap from there and it went into the microlight......they said you shouldnt be be using our petrol to put into a flying machine......I said that you shoudnt be selling water and passing it off as petrol... :x ...never been there since......

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  • 5 months later...

Should have replied before....

The problem turned out to be a partially melted piston !...Many engine hours before the reed valve decided to spit a piece into to cylinder .

I stripped the engine down and could nt find any damage apart from a few very minor nicks on the piston top which disappeared with a bit of Wet Or Dry ..

It ran fine for many hours after relacing steel reed valve with a carbon fibre one . :D

Then i encountered the problems i previously talked about...Called Parajet and they thought it was the settings on the carb...The piston must have received some damage which i had nt seen and the front had ever so slightly melted...sort of rounded a bit which took some finding .

The bore was spot on so just replaced piston and rings and head gasket .

Fine till next time !

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