RE: Poulan 25 from FL trimmer
 

The Pipe and muffler sealer is rated to 2000F, so it is not affected by the heat, but it brakes on vibration. It cures to the solid hard mass and the engine vibration and expanding aluminum in the heat brakes it loose.

I don't think these pipes will get hotter than 300 - 400F. Aluminum is good conductor so the heat is distributed through the entire muffler and the surface is cooled quite efficient. I read somewhere that the rod is good up to 700F so if it flexes and expands together with aluminum it should be OK. The entire load is carried through the thread anyway, I just need something to keep the pipes from unscrewing in vibration.

RysiuM

RE: Poulan 25 from FL trimmer
 

Hi Rysium,

I've sorted mine with 35% glow fuel, 65% methanol and spent last weekend flying it. It ran great but really needs a 17 or 18x6 on my Pitts for a bit more thrust. Vertical is not bad, but not unlimited. I did the full aero routine with it and the engine ran faultlessly so I'm pleased with that. Only thing is I did the psiton side cutouts under the gudgeon pin and it lost 300 revs. I'm going to put a std pitson back in sometime and try it but I'd leave that mod if you've not already done it as I don't think its a wise one.

Also got the wacker engines muffler today so thats fitted, another 8oz off the engine. Total weight of the glow version is 920g now.

Next job is I'm developing two electronic ignitions for it, one fixed timing and one variable. Should have the fixed one running by weekend and a few weeks for the variable one.

Just as a side note when I got the muffler it had a note in saying if you send it back they will weld the pipes into the muffler for free, you jsut pay the postage. I have drilled and lockwired mine, and the mounting bolts, to stop them coming undone.


Let me know how you are getting on. I got another 2 engines the same too so will get into tuning them soon.

Cheers,
Rich

RE: Poulan 25 from FL trimmer
 

Hi Rich,

Wow, pure methanol - no gas. It must kick the but. Did you need different carb for that? Engine needs about 2 more fuel in the muxture than if you use gasoline. Did it start by hand?

What's the weight of your Pistts? If you can turn APC 18x6W at 8k rpm, it should pull around 12 lb unlimited.

That's a surprise. If you have other engine available you can try to replace just the piston with original sleve and check if this cut is the reason. I swapped piston/cylinder between engines and in short time therte is no much difference in there. They are manufactured with the accuracy that they wouldnt feel that. It's hard to believe that opening transfer ports does bad thing for the engine.

I just ordered VLACH from Pe for my experiments. I have one prop hub prepared for magnets so this willbe the one for electronic ignition.

Did it work? 'Whacker' might not like to see my muffler - faar away from the new look [:'(] It's all dirty in burned oil and tailpipe sealer. Welding this thing will not be easy. I will try set screws placed in the thread.

I was busy lately restoring Kyosho Cap 232 (40 size), so I didn't grab the Dremel yet. But when Vlach ignition comes there will be no more excuses for me ;)

RysiuM

RE: Poulan 25 from FL trimmer
 

opps, sorry to get you so excited, it was 35% glow, 65% petrol, my mind must have been somewhere else when I typed that! I've got 2 gallons of straight methanol on order though so will have that soon.

I have not run the muffler yet, maybe at the weekend I'll fly it again but lockwire should be fine until I save up for a TiG!

Pitts is just under 12lbs, and on the 16x8 APC at 8600 it pulls 13lb thrust when I measured it, so a 17 or 18x6 should be 15-16lbs thrust I would guess. I'll get one ordered tomorrow probably ready for weekend.

The other thing I did to my muffler was put a metal drift into the inlet hole and hit it with a hammer, mushrooming the top of the pipes thread to stop them coming out. A bit extreme but I don;t want them coming out[:-]

Cheers,
Rich

RE: Poulan 25 from FL trimmer
 

So I guess it keeps running without power on glow, right?


Even if I get one, I don't have room in my garage for it anyway[:@] I need smaller house and bigger garage;)

I have MVVS 1.6 on Powerline Hobbies Edge that weights 11.5 lb dry (12 lb full). APC 18x6W at 8300rpm i have enough thrust for unlimited vertical. However APC prop seems to be to heavy for fast throttle response. Mejzlik 18x6 is on it's way :).


Sure.[sm=cool.gif]. Keep me posted about the piston sleve tests.

RysiuM

RE: Poulan 25 from FL trimmer
 

Yup, turning the glow on and off makes no difference to the running except for the very low tickover where the glow on makes it run a little faster. Thanks to the thread about running on glow, its a nice neat and light way of doing it!

Cheers,
Rich

RE: Poulan 25 from FL trimmer
 

Hi

Many thanks for your tip ,
dave wallace in page 5, post 105
the piston skirt cover the transfer ports.

I have flown my STOCK weedeater for more than 4 hours when have a spark plug problem.
When check the plug I inspect visually the piston crown and see the path of fresh mixture from the transfers .
The back transfer have a shiny path of fresh mixture ,the polished surface of the piston is like new and the front path (where the counterbalance of crankshaft is) do not exist, the same black coloration of the all other parts of the crown.
I am running at 5% 2 stroke oil and extra gas. Venturi enlarged at 9.5 mm diameter
It make me to take the piston and with a file modify the skirt like in the photo of your post 105 , at a depth of 5 mm.Your depth is bigger may be 1/4 inch, refered to the ring in inside piston wall
I will make a test now.
I resist the temptation of start the dremel and enlarge the transfer and ports to the next time.
I am flying with stock air filter, have very much dust in "my airport"and have windy weather, a bit loss in performance but have no option.
Many thanks for your time to post photos.
Jose
Argentina