Bratpak

Now that I am finished with my 0% nitro glow fuel I was looking around for another project and came across this conversion forum. I have been reading here for a week or so and wouldn't you know it, my Dad's weed eater quit running and he went out and bought a new Stihl.
As fate would have it, I asked for the old one and he gave it to me.
I start tearing it apart and figured out it's a Poulan 25 cc. Four bolts in the back and springs holding the muffler on. The carb only has a low speed needle. The screen in the carb was plugged so I took it out and got it to run again.
I have another Waldbro carb coming with both high and low speed adjustment screws.
I have cut everything off that will not be needed. It will still have the coil and flywheel as this is going to be a low low budget build.
I couldn't get the muffler apart so I drilled out all the holes inside to 5/16" and also had room to drill a few extras. Drilled two holes in the top of the muffler, took the center pipe out of an old lamp I had , cut two pieces and welded them in. The welds are not the best looking....I only have a cheap wire feed welder, no mig, but it works ok for now
So far I have $9.00 in it (the cost of the carb and shipping).
Next on the agenda is a prop adaptor and maybe do something to get rid of the fins on the flywheel. I wish I had a lathe now[sm=72_72.gif]

I don't even have a plane for this engine but I couldn't resist the challenge of a conversion !!!! [sm=teeth_smile.gif]

Mark

jg4660

My Feedback: (1)

So far, so good.....

Bratpak

Thanks JG,
I used the shaft that was on the front of the engine for the prop adaptor.
The front half of the shaft was a square hole that the drive for the weed eater spool slipped into. I drilled that out and tapped it to 5/16 x 24.
I found an exhaust stud that was 5/16x24 on one end, smooth in the middle and 5/16x18 on the other. Screwed it into the shaft, found two thick washers and a nut.
Hopefully this will work.

Mark

buck1856

My Feedback: (49)

Thats a good job youve done so far but i wouldnt bolt a prop on the front of that thin a shaft,sticking out that far.Are you planning on using the washer agaisnt the shaft and then the second washer against the prop?That is going to wobble and then fail in my opinion.You need to take off the square drive and then put a proper hub on.After you take the drive shaft off post here as to what threads they are and one of us or me can point you in the right direction for a proper hub.I even make my own and purchase somtimes also.I have some made up right now.Im not critisizing you at all,as i said your doing an excellent job, i just want to be sure you or someone standing around you doesnt get hurt.Ive posted a couple pics of how mine look so you can copy them.

Bratpak

Thank you for the reply Buck, opinions are always welcome. That's why I like these forums.
The thread on the shaft is 5/16 X 24
That is a nice hub in the pictures.
Also while I got you here LOL what is your motor mount made of and what is the thickness???

Mark

rangerfredbob

My Feedback: (13)

for a low buck mount just get some long 10-24 bolts or allthread and direct mount to the firewall

Baldeagle

My Feedback: (7)

Mark Who did you get the carburator from? Thanks Rich

Bratpak

I got the carb off of Ebay store A Plus Small Engines. Nice guy to deal with. It was double packaged and he sent it out the next day after the auction was over.
I also got some aluminum plate given to me to make motor mounts from. Had to buy new bolts so that added a couple dollars to the project.

Mark

Baldeagle

My Feedback: (7)

Mark do you have a link to the seller? I tride a search but couldn't come up with it. Thanks Rich

Bratpak

I can't seem to get a link to work to the store but here is the ebay # of one of his carbs for bid. From there you can get to his store.

Ebay Item # 160262090004 Just type this number into the search and hit the search button.

Mark

buck1856

My Feedback: (49)

I made my mount out of 1/16th or 3/32nds.A decent source for aluminum plate is to ask the city dept for any damaged or unusable street sighns,ect...

Baldeagle

My Feedback: (7)

Thanks Mark I found it with your help. Rich

Bratpak

Buck, I got some 1/8" aluminum plate given to me to make motor mounts out of. The piece should be enough to make 12 mounts !!
Glad you were able to find it ok Rich.
Here's a pic of the velocity stack I made today.
I am also going to look for a proper propeller hub instead of the one that is in the pictures. A lathe is about the only piece of machinery that I do not have access to [:@]

Mark

tinsink

Can you tell me the model number of the Walbro carb that you are using? I have a poulan 25 and I am
going to need a carb myself. Also, do you have a link to the no nitro fuel?

Bratpak

The model # of the carb is WT - 263
The ebay number I provided to Rich ( Ebay # 160262090004) is an auction for that carb. I originally found a post that was asking for a carb for a Homelite 25 cc and it gave a number to this guys auction and store.
The intake spacer throat has to be modified as this carb has a larger throat diameter than the stock carb but it is not hard to do.
As for the link to the no nitro fuel, here ya go........

http://www.rcuniverse.com/forum/m_7580969/tm.htm

Mark

microsprint9

Did you flip the carb from the standard oem position?, if so look for the little hole that runs from the crankcase into the carb, when i flipped my carb this line was cut off and it would run great on the ground then deadstick in the air. If you looking to save some weight you could convert that engine to gas/glow, only an adapter and a 4 stroke plug is needed, it's well worth the weight savings.
Here's my little converted weedeater http://www.rcgroups.com/forums/showthread.php?t=793079

Bratpak

Nope, I didn't flip the carb. This is the oem position. I just went downstairs and took the carb and spacer off to make sure all the holes were lined up and they are.
I did read some of the gas/glow conversion and that may be doable in the future. The only difference is that when I run out of my gallon of 10% nitro fuel I have now, that will be it for nitro fuel for me as all my glow engines will be converted over to my homemade 0% nitro fuel mix.


Mark

Bratpak

A proper propeller hub has been bought and will hopefully be on it's way the first of this week .
Now for the propeller itself.
I have read these engines like either an 18 x 6 or a 16 x 8 propeller. This engine will more than likely go in an RC Guys Treehopper or a Hanger 9 Ultra Stick Lite. I am not much for doing any real trick flying (yet) just buzzing around the sky doing loops, rolls etc. if that makes any difference in the selection of one of these two.
Also what size spinner do you need for these props ???

Mark

microsprint9

I'd go in the middle with an APC 17x6, my friends 26cc converted stihl trimmer on gas/glow runs this prop quite well, i also turned some pretty good numbers on a weedeater conversion on this prop as well.

buck1856

My Feedback: (49)

I ran a 16x8 MAS,or APC on mine.You might get away with a 17x6 as said.I havent heard of any 25cc poulans spinning 18 inch props yet.At least at any decent rpms.

Bratpak

Thanks for the prop replies guys,
I think I will give the smaller 16 x 8 prop a try first and go from there.
But I need to know what size spinner to order for that prop.

Mark

buck1856

My Feedback: (49)

I persoanlly wouldnt go with anything smaller than a 3 inch.What is the size of the opening in cowl.Thats what i go by.I put a spinner on that covers the hole by at least a 1/4 to 1/2 inch around.

Bratpak

Thanks Buck. I don't have a plane for this yet but I was thinking of an RC Guys Treehopper or a Hanger 9 Ultra Stik Lite 120.

Mark

Bratpak

I am done my engine test stand and bought some 2 stroke low ash oil and am just waiting on my prop hub to get here. I know this engine fuel was mixed 40:1 when it was in the weed eater. So I will just mix it the same for now.
There was quite a bit of buildup in the muffler and I figure the manufacturer is always going to lean toward a rich mix when fuel/oil mixing is concerned.
I have read about guys going to a 50:1 or even 100:1 mix when running these engines.
Thoughts ???????

Mark

Bratpak

I put some fuel in the tank and tried to prime the carb( I won't start it until I get the proper propeller hub).
I was having no luck priming until I plugged the tube that is next to the adjustment needles. Then it primed right away.
What is that tube for and will it need to stay plugged all the time??

Mark