I recommend printing this out link with the aircraft's papetwork https://www.kitplanes.com/magneto-timing/
Ian s is very good I recently saw aero VW (actually RAAus) with backup electronic ignition the little tit on top of car plug unscrewed itself and lead was hanging down. This guy does a lot of flying. So do up tit real tight. Ian McPhee 0428847642 On Tue, 30 May 2023, 3:57 pm Rob Thompson, <[email protected]> wrote: > Good work Ian.... Great explanation! > regards > Rob > > Rob Thompson > 0429 493 828 > > > > On Tue, May 30, 2023 at 3:24 PM Ian WIlliams <[email protected]> wrote: > >> Hi TMG team, >> >> Rob I hope u don’t mind me responding as well. Here in NZ we have to have >> the mag bench checked every 2 years and I look after 2 coming up 3 Dimona’s >> and 2 Grob 109’s so do this job with monotonous regularity. >> >> My procedure is as follows. >> >> - Disconnect battery >> - Remove the right hand Carb (from the front) and disconnect the >> choke and throttle rods. >> - Disconnect and remove the starter and remove spark plugs >> - Turn the engine so cyl *1 (The front right hand side one) is top >> dead centre on its compression stroke (Finger over the spark plug hole) >> - Note the little mark on the prop flange … it is set to 25 degrees >> so wont line up with the case centre seam at TDC .. it is used for >> retiming >> the mag >> - Use a long allan key and undo the 2 clamps attaching the Mag … the >> Alternator bracket and probably the throttle bracket are also attached so >> note how they are connected. I keep the bottom alternator bolt tight so >> it >> doesn’t move slackening off the belt. >> - Pull out the mag and remove the rear cap with the 4 HT leads (3 >> screws) >> - Get the Mag serviced >> >> Back on >> >> - The Dimona Mag is Right hand. So get a pin (an unused pop rivet >> works well) Look at the back of the mag and u will see 2 holes. Use the >> one marked RH Put the pop rivet into it and slowly turn the input until >> the rivet shaft slips right in. The mag is direct drive but has a 2:1 >> reduction inside and the pin / hole is in the smaller gear so u may have >> to >> turn it twice to make the pin go fully in. >> - Now the tricky bit. I use a length of masking tape crossed over to >> secure the impulse in a fixed position but in such a way that once the >> flex >> coupling is almost in place the masking tape can be pulled out. THEN >> REMOVE THE POP RIVET then reinstall the rear cap and the 3 screws >> .. note there is only one way it can go on. Taking care not to dislodge >> the masking tape. >> - Now Double check Cyl*1 is at TDC. Offer up the mag and the gasket >> as Rob has described. Be real careful here. You can see the coupling >> through the Alternator belt slot. With a torch. Once it looks as if it >> will >> slip in OK, remove the masking tape and reinstall the 2 mounting clamps >> but >> don’t tighten just yet. >> - Make up a small “buzzer”. I use a real cheap electric ceramic >> buzzer (about the size of your finger nail and a 1.5 volt AA battery) >> Write it up and use 2 flying leads with clips at the end. Check that >> when >> you join the clips together the buzzer makes a noise. Connect one clip to >> the “P” lead on the mag and the other to ground Now rotate the prop around >> the TDC point. You should hear a change of tone on the buzzer when the Mag >> points change state. It is not much of a tone change but is clearly heard >> - Now identify the mark on the prop flange and rotate the prop around >> it listening for the change of buzzer tone. Adjust the mag position so >> when rotating the prop in reverse (ie taking up any slack in the drive) >> the >> change of tone happens exactly when the flange mark is lined up with the >> split in the case halves. >> - Once you are happy tighten the 2 mag retaining clamp / bolts >> - Then slowly rotate the prop through all compressions and note the >> spark should correspond with that cylinder on its compression stroke The >> firing order is 1 3 2 4 ie 2 bangs on one side and 2 on the other. >> - Because of the impulse of course the firing spark is quite retarded >> when turning the prop manually and is roughly at TDC. This is a good >> way >> of confirming u have it correct. >> - Then put the leads back on the mag, reinstall the starter and Carb. >> And of course the plugs and battery >> - All should then make the usual noise . >> >> I hope this is of some help >> >> >> >> Best regards >> >> >> >> Ian Williams >> >> ZK-GCB >> >> >> >> >> >> PS… Is anybody else having big issues with Hoffmann propellors ?? >> >> >> >> *From:* [email protected] <[email protected]> *On >> Behalf Of *Rob Thompson >> *Sent:* Tuesday, May 30, 2023 9:38 AM >> *To:* [email protected] >> *Subject:* Re: [DOG mailing list] Magneto removal. >> >> >> >> 1 Line up the engine at the timing mark firing on #1 cylinder. >> >> >> >> 2 Remove the engine control rods and starter motor so you have room to >> get the magneto out and back in again. >> >> >> >> 3 Take the cap and harness off using a right angle screw driver. I >> replaced the slot head screws with Alan screws to make the job easier to >> refit the cap. >> >> >> >> 3 Loosen the magneto bolts with a long Alan key. I welded a long Alan key >> to a 1/4 inch socket and then used a small ratchet spanner in behind the >> magneto. >> >> >> >> 5 Follow the magneto install instructions in the manual. *It is >> important to get the gasket measurement right or the magneto may FAIL.* >> You can do a trial fit with plasticine or Blu Tac which compresses against >> the flywheel and then measure that you have the right clearance. >> >> >> >> regards >> >> Rob >> >> >> >> Rob Thompson >> >> 0429 493 828 >> >> >> >> >> >> >> >> On Tue, May 30, 2023 at 6:22 AM Tomasz Dzikuć <[email protected]> wrote: >> >> Dear Dimona users. >> >> >> >> The date of inspection of our magneto is approaching. >> >> >> >> The information I found on this list shows that the removal of the >> magneto can be done without disassembling the entire engine. >> >> >> >> Unfortunately, we don't know how to do that. >> >> >> >> Does anyone have any short instructions on how to do this or just can >> write some tips here. >> >> >> >> Thank you in advance and best regards from Poland. >> >> >> >> Tomasz Dzikuc >> >> >> >> TMG Team >> >> AZL Zielona Gora >> >>
