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Black Devil M25Y local mechanic?


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Hi Guys

I'm looking for a local mechanic (to Worksop, Notts) to help me 'sort out' my manual start Black Devil M25y engine. I'm able to do routine maintenance and basic tuning, but I think I now need some help (please)

This engine has been quite problematical from new (2.5 years old) ... mainly engine starting problems / VERY hard to pull start ... sometimes requiring 30 + pulls, and VERY hard physically to pull start compared to my mates similar machine .i.e. it seems to be very stiff, almost like the 'automatic decompressor' is stuck (which it isn't).

There have been a few occasions where I've managed to get things to a point where I could pull start it fairly easily on my back (for maybe the next 10 flights), but just when I think I've 'cracked it', we get back to square one - not starting again.

I've changed & thoroughly cleaned the 'automatic decompressor' ... I've also tried the manual decompressor - behavior no different. I've changed the fuel lines, complete new carb', spark plug (including the new Denso), measured coil voltage (OK). Took the cylinder head off (looked OK), reassembled with new head '0' ring ... everything torqued to manufacturers spec'.

I've read and followed everything I can on the excellent AeroCorsair web page by Alex Varv (which has been my main source for getting this far).

So ... if there is anyone out there that can assist me, I would be most grateful ... and can either pay (real money) or barter my services as 'Computer Repair Man - Software Problem Solver etc".

Thanks for reading this rather long winded message guys :?

Happy Landings (& Take-Offs)

Brian 'Turbo' Tunnard

The Cloud Hoppers Paramotor Club

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Hi Brian,

I have one of these engines.

Firstly replace the plug, with a good quality one (NGK), secondly these engines like to run rich, so set the low to 1 1/4 turns from fully seated and the high to 2 turns from fully seated. Tune the carb from there, once its warmed up. Remember your looking for a COFFEE coloured plug after running the engine at full revs for 30 seconds.

There are loads of good info on the Alex Verv site (which I see you know about)

Mine was always difficult to start, mainly as I was flooding it when priming it. Its also non responsive to the throttle till its warmed up, this is normal. I blip the throttle whilst its warming up.

If its difficult to pull over firstly check then turn the engine over using the prop, is it still tight?

if so the strip the head off and the barrel and make sure the rings are not coked up with carbon. If the are clean them and free them up.

If its not tight then check that the pull chord / recoil mechanism is not binding.

Have you replaced the diaphragms in the carb? they can stiffen with age or there is 'fluff' in the filter in the carb - I'm assuming you have the warlbro wb37 fitted (most of them do), also if its a new carb / diaphrgams they take a while to bed in and work properly.

Another thought is that air could be getting in the line at some point and there is not enough fuel to start the motor. Have you used zip ties on the fuel line or proper metal clips that grip the pipe all the way round?


Have a chat with Paul Taylor - www.av8er.com as he supplies these engines on his Orbiter Paramotor.

His contact details are on his site. Paul is a good bloke who can help you out. He also has spares.

Hope that helps.......


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Thanks for your good advice Woody ...

I just (yesterday afternoon) stripped and greased all surfaces of my pull start, and that has helped . I also returned the carb (Walbro WB37c) to factory settings, and Permatexed the gasket surfaces of the carb flange (where it bolts to the engine).

Not only did I replace the carb diaphragms ... I actually ended up replacing the whole carb :? ... a bit over the top I know, but I was running out of ideas.

I had the cylinder head off, and the piston looks good and is running free (new 'O' ring) ... everything is torqued as per manual.

Proper metal clips already installed :roll: replaced all fuel lines with clear Karting fuel line (good stuff) so I could see if any air bubbles were being introduced. Also replaced the main primer bulb (in case it was sticking).

The 'pull starter binding' idea certainly had merit ... since I greased it, it certainly has made a difference. I am going to try it again tonight ... that is ... if the pain in my lower back stops twinging long enough .... I pulled a muscle in it yesterday, after the many futile pull start attempts (probably 80+).

Thanks for the AV8ER link ... not sure why, but I haven't come across them before? Nice One.

I've emailed Alex many times over the last 2 years (various problems - Good Bloke) ... he tells me that all the new Black Devil's are now being shipped from the factory with the Denso plugs ... which he says "start easier and are better quality than the NGK" (I have tried both - Denso back in at the moment). I've also spoke (emailed) to the 'horses mouth' (so to speak) Oscar Meschiari at JPX Italia (the designer of the Black Devil) .... a lovely chap and very helpful.

I remain totally convinced that this is a superb engine ... it's just my learning curve in maintaining it properly that's at fault. "I'm getting there". I naively thought that is would be just a case of buying the kit, getting properly trained then flying ... not appreciating for one minute that I would need to learn how to become a 'two stroke mechanic' ... oh well ... :D

Happy Landings (& Take-Offs)

Brian 'Turbo' Tunnard

The cloud Hoppers Paramotor Club

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No Problem Brian.

It is a good engine I have got about 4 litres per hour, just pootling around at 3-4000 rpm.

It has quite a lot of power, more than I'll probably need and I know Paul uses one of these machines for his Tandem rig.

As for becoming a 2-stroke mechanic, not something I planned on doing either, but its a good way to spend the non-flyable days pottering around in the garage!

Have fun and let me know how you get on.


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