Elect. ignition for Poulan 25cc?
 

Yesterday I was tinkering at my bench with several engines that I have. My goal is to make a conversion to go in my GP Tiger Moth. I had already converted a Ryobi but with the rear carb and exhaust it is too long and I dont want to hack up the firewall. I had been tinkering with a Poulan 18cc but it is too small and the timing is too tame. I have several other Poulan motors laying around and I started looking at them. First I noticed that the 25cc that I had used the exact same crankcase as the 18cc and that the head is almost the exact same size. So I slapped it on my 18cc crankcase and checked the timing on it.

Exhaust 135
Transfer 95
Intake 122

Much more aggressive than the 18cc. And compression seemed pretty good. It has 4 transfer ports but they seem pretty narrow but fairly deep. The piston ring is pinned.

My conclusion was that the 25cc egine may be what I am looking for. I can get an egine mount, prop hub, and velocity stack from wackerengines. What would you all recommend to convert it to electronic ignition?



Thanks
Jim

RE: Elect. ignition for Poulan 25cc?
 

I have the CH_ignition's CHXL unit on my 25cc Toro. It runs very well.

I also purchased the XYZ unit from www.hobbycity.com.
$25.00 plus $8 for the pickup.
I haven't installed it on anything yet but it does throw a real nice spark.
http://www.hobbycity.com/hobbycity/s...idProduct=6292

There is not suppose to be a need for spark advance on these small engines.
When I set the CG to spec. I had to add a 3 ounce heavy spinner.
And my Tiger Moth needed 4 degrees of down thrust to fly right with the Toro on it.
That's in instead of the 2 1/2 degrees called for.

I don't remember the weight of my Toro Be 2 1/2 pounds comes to mind.

RE: Elect. ignition for Poulan 25cc?
 

I have a Super Tiger G90 on it now. No weights added and it balances perfect and flies with authority. It does have onboard glow as well. I might just try it with the mag first to see how it goes.

Jim

RE: Elect. ignition for Poulan 25cc?
 

I moved as much as I could behind the cockpit.
I added a 4 cell 3500ma battery for a flight pack.
Mine balanced perfect according to the book.

I'm re-doing the the muffler.
Extending the stinger, slanting it back at a 45 degree angle and increasing the diameter 1/8th of an inch.

Perhaps this will help keep the plane a little cleaner and build some low end tork.
The stinger didn't extend far enough past the firewall.
I ended up with a lot of black goop on the bottom wing.

This the before picture.

RE: Elect. ignition for Poulan 25cc?
 

What size tiger moths do you guys have? mine is 1/4 scale 88" ws I'm putting a 28cc weedwacker/poulan on it and it has the rear carb and exhaust it is alittle to long but not to bad. I'll try to post a picture of it.

RE: Elect. ignition for Poulan 25cc?
 

I forgot this picture.I made my prob hup and threaded the crank shaft and then I cut all the extra shaft off.

RE: Elect. ignition for Poulan 25cc?
 

Mine is a Great Planes 60 size.

Length: 60" [1,524mm]
Weight: 10.25 lbs [4,592g]
Wingspan: 71" [1,803.4mm]
Wing Area: 1360 sq in [8,840 sq cm]
Wing Loading: 17.35 oz/sq ft [485.5 g/sq cm]
Radio: 4-ch (5 servos)
Engine: .61 two-stroke, .91 four-stroke [10cc 2-stroke, 15cc 4-stroke]

The basic rule is 1200 sq. in. for a weed eater motor and mine flys great with the Toro.

A friend is building the SE5a kit from Dyna Flight and were planing on using the 25cc poulan in it.
It actually has shorter wings than my Tiger Moth.
The Cowl is very narrow so the rear Carb and Exhaust is a perfect fit.

I hope the Poulan performs as well as my Toro does.

RE: Elect. ignition for Poulan 25cc?
 

I really wanted at least a 31cc for it but until something else comes along I'm going to try the28cc.My wing area is 2,247 sq.in and it calls for a 120 4stroke.I'm still working on the build of mine.I bought it at a auction and all the turn buckels and fixing plates are gone so I have been making all this and as you know it takes alot of time and the plans don't show good pictures of them.
clocknut

RE: Elect. ignition for Poulan 25cc?
 

I ordered the XYZ CDI ignition from Hobby City yesterday and a prop hub and mouting plate from Wackerengines. The CDI and the Hall sensor shipped was only 39 dollars. Until all the stuff comes in, I'll be waiting for parts.

I also have a Zenoah G20 that I am going to mount in my GP Tiger Moth.

I too have the Dyna flite SE5 about half built. I had a Ryobi that I was going to put in it but I think it is too big. Considering putting the Poulan 25cc in it. Been thinking about making a custom muffler for it from copper water pipe and using a pipe clamp to strap it to the head. Does this sound like a doable idea? That way I'll only have the carb sticking out the side on the SE5 and I'll pipe the exhaust out the bottom.


Jim

RE: Elect. ignition for Poulan 25cc?
 

Here's a muffler I made for my Katana out of copper pipe, etc. It sounds great and the engine turns over 9000 rpms.

Remember though that it has to be brazed or silver soldered with real silver solder. The Sta-brite silver solder that most people use when they think of silver solder will quickly melt. (Ask me how I know...)

AV8TOR

RE: Elect. ignition for Poulan 25cc?
 

Guess I am ignorant about the solder. What is the solder that plumbers use to install copper pipe? I did not know there were different kinds. But I can see that you would have to use a solder that could handle some heat.

Jim


BTW, Great looking muffler.

RE: Elect. ignition for Poulan 25cc?
 

Check with a welding shop and ask for true silver solder or silver braze. Or you can braze the parts with bronze welding rod. The solders used for plumbing, electrical, etc. are low melting temp and won't last 2 minutes on an exhaust system. There is also a silver solder called "Sta-Brite" that has a small percentage of silver in it, but it is also low melting temp and won't work either.

The brazing will require a hotter torch than the common plumbers propane torch as well...

AV8TOR

RE: Elect. ignition for Poulan 25cc?
 

We have an acetylene torch here in the shop. Will that be hot enough?
I have never used it.
We also have a mig welder too.


Jim

RE: Elect. ignition for Poulan 25cc?
 

Another question. Does anyone have a suggestion on how to make a spacer for the CDI magnet without a lathe? I do have a drill press and extra flywheels. Could I cut out the center of a flywheel and use it?

Jim

RE: Elect. ignition for Poulan 25cc?
 

I use a hole saw and cut the center out of the flywheel. It is a little tough to dress it perfectly round with a drill press, but it can be done. Make sure you make it big enough around that it won't split when the prop hub is tightened down against it.

Yes, an acetylene torch will work fine for silver soldering and/or brazing.

AV8TOR

RE: Elect. ignition for Poulan 25cc?
 

I finally got a message today from United Hobbies that they have shipped the ignition I ordered. Now I need to figure out how to mount it.

I figure the best way to mount the sensor is going to be with a pipe clamp.

Couple of questions.

What size magnet do I need to get? Does it matter which pole is up and how do you tell which pole is which?

Where on the hub do you mount the magnet? It would seem to me that you mount it on the hub at a point that is accessable to the sensor at around 28 degrees BTC. Is this correct?

Thanks
Jim

RE: Elect. ignition for Poulan 25cc?
 

Jim,
I have a couple of those ignitions on Ryobis, you'll be pleased. I use the 1/8th inch rare earth magnets from Radio Shack. It does matter which way the magnet is mounted. Just hook up your ignition and pass the magnet over the sensor to figure out which way. I mounted the sensor on a hose clamp with some small counter sunk machine screws and self locking nuts. It makes for unlimited adjustments (at least on the Ryobi). As a note the ignition fires just as about half of the magnet has exited from under the sensor. That might help in where you do the final installation. You are correct, just find your TDC and your 28 degrees BTDC and mount the magnet wherever it fits best. Im not sure on the Poulan but on a Ryobi, using a hose clamp it really doesnt matter, you can mount the magnet anywhere and just move your sensor. Just depends on where you can mount the sensor on that Poulan. Hope that helps...............mark

RE: Elect. ignition for Poulan 25cc?
 

Thanks Mark.

Exactly what I needed to know.

Now if I can just get the ignition here. After I started having trouble with Hobby City not shipping it, I found a US distributor for this ignition and the XYZ engine brand. http://southeastengines.com/ At $55.00 it is still an inexpensive option. That is if it works well. From all I have heard so far, it should.

Jim

RE: Elect. ignition for Poulan 25cc?
 

Forgot to ask Mark,

What size battery are you using on your XYZ ignitions? Can you post some pictures of your installations?

Jim

RE: Elect. ignition for Poulan 25cc?
 

Jim,
Im using a 5 cell 2100 mah. There are no instructions with the unit. On the actual ignition box it just says 6 volts. I know alot of the units use 4.8-6V but i didnt try a 4 cell. I'll try to remember to take a picture tonight and post it.

RE: Elect. ignition for Poulan 25cc?
 

Thanks.

Jim

RE: Elect. ignition for Poulan 25cc?
 

Can any of you guys tell me if that United Hobbies ignition unit is auto advancing??

Thanks,
AV8TOR

RE: Elect. ignition for Poulan 25cc?
 

That is a good question. I noticed that the US distributor has been answering posts on the gas engine forum. Lets aske him.

Jim

RE: Elect. ignition for Poulan 25cc?
 

I wanted the answer to that also so I brought my timing light to the field yesterday but it got too windy so I gave up. I planned on trying the light tonight after work. Hopefully I'll be able to post my results tomorrow.

RE: Elect. ignition for Poulan 25cc?
 

I posted the question to Ron the US distributor of XYZ engines on the gas forum. In was in a thread labeled XYZ engines.

Jim

RE: Elect. ignition for Poulan 25cc?
 

The answer is in. The XYZ ignition is an auto advancing ignition but you have to use their sensor for it.

Jim

RE: Elect. ignition for Poulan 25cc?
 

I also picked one up for an upcoming project.
Hooked up to only a 4.8vdc ,it throws a very
nice spark, with aloud "snap/snap" sitting here at the desk.

RE: Elect. ignition for Poulan 25cc?
 

Nitro Joe
I've been running mine on 6V, the owners manual (term manual used very loosely here) states to make sure the voltage isn't below 5.5V. It doesnt state what will happen if it falls below 5.5V however it says it will destroy the ignition above 7V and explode above 10V. (which might be interesting)...........mark

RE: Elect. ignition for Poulan 25cc?
 

hackinboy,
My bad. It was running on 4 AA’s at my desk.
The plan is to run it with a 1200ma.7.4v. Lipo through
A 6v. regulator that was bought along with the ign.unit.

As far as low voltage go’s,I sure hope that’s not a problem.
Maybe someone here has an idea on that?

RE: Elect. ignition for Poulan 25cc?
 

Finally got my XYZ ignition from Hobby City. Just took a month to get here. I think next time I will order from the US Distributor. http://southeastrcengines.com/

Anyway. Need to finish up a couple of projects before I can try it out. Maybe this weekend. Still need to make me a hub with the magnet. Bought me a holesaw last weekend to cut out the center of one of the multitude of flywheels I have.

Jim

RE: Elect. ignition for Poulan 25cc?
 

Hope to start working on installing the EI on the Poulan 25cc this weekend. However, not sure how to procede. Advice needed. How do you set the timing on this unit? At what postion is the best place to mount the magnet? How many degrees before top dead center do you mount the sensor? Lots of questions. I do have a timing wheel.

Thanks
Jim

RE: Elect. ignition for Poulan 25cc?
 

http://www.hobbycity.com/hobbycity/s...idProduct=6292

I can not find on this page were to get the sensor. Do you have a link for the sensor?
Paul

RE: Elect. ignition for Poulan 25cc?
 

This mite sound bad but what is a xyz engine?

lol

RE: Elect. ignition for Poulan 25cc?
 

XYZ is a brand name.

http://www.hobbycity.com/hobbycity/s...idProduct=6291

RE: Elect. ignition for Poulan 25cc?
 

Although I bought mine from Hobby City, I would not do it again. Here is where I would get the next one. http://southeastrcengines.com/see_008.htm This is the US Dist. For a few extra dollars you can get service on it. The owner hangs around the gas engine forum regularly.

The sensor is on the same page.

Jim

RE: Elect. ignition for Poulan 25cc?
 

Why would you not do it agian? What prob did you have with hobby city? I have never did any thing with them before.

RE: Elect. ignition for Poulan 25cc?
 

After I paid for the transaction, it took over a week before they shipped it. After they shipped it, it took over a month to arrive. I shudder to think what would happen if I needed some warranty work.

Jim

RE: Elect. ignition for Poulan 25cc?
 

If you choose the cheapest shipping they are in no hurry.

If you upgrade your shipping, you can have it in a week.

RE: Elect. ignition for Poulan 25cc?
 

Success!!

After much frustration and bad luck, I finally got it to run. And run it did. After adjusted, it idled smoothly, trasitioned great, and had a really good top end. Have run a 10 oz tank of fuel through it now and I am very happy so far. I took pictures during the process.

Let me tell ya all about it.

I had already done all the cutting on the crank case and mounted a 11mm carb. Also, I already had the wackerengines conversion kit installed.

First I removed the magneto and the flywheel. Need to make a hub for the magnet for the XYZ ignition. I decided to make my own using a hole saw on my drill press. I tried to eyeball getting the hole centered on the drill press. First attempt came out off center and unusable. That was ok. I didn't expect it to go perfect the first time. Luckily the flywheels are interchangable from all the Poulan weedeaters and I have a ton of cast offs. Second attempt came out pretty well. I chucked it up in the drill press and cleaned it up using a file and some 320 sand paper.

Second is the critical step and I was concentrating so hard, I forgot to take pixs. This step is to figure where you want to mount the sensor and to mount the magnet on the hub to match with the correct timing. The best place to mount the magnet on this engine is on the bottom. To set the timing, I took the back cover off the engine and set the crank to TDC. Then mounted a timing wheel on the front of the crank. Still making sure the crank is on TDC, I made a mark on the engine where 0 degrees is on the timing wheel. I then rotated the crank clockwise from the front to 28 degrees and made a mark on the bottom of the engine and on the hub at the same spot. This is where the sensor will go and where the magnet will go.

I then removed the hub and made a shallow 1/8 inch hole and CAed in a 1/8 inch rare earth magnet. Making sure I have the right pole facing the sensor. To find the correct pole, I hooked up the ignition to a spark plug and battery and waved the sensor over the magnet until I had the right side up to get a spark. I took a permanent marker and put a mark on the magnet for reference.

I then put the hub back on the engine and mounted the sensor. I used a hose clamp to hold it on. When using the XYZ sensor, you have to cut out the center of the clamp to give room for the wire coming out of the sensor or you will crush the wire. Ask me how I know. Put the sensor on the mark where you marked the 28 degree mark. This should give 28 degrees before top dead center BTDC. Now to mount it up and run it.

Ok now it is mounted up on the test stand and ready to fire it up. I set my needles to 1 1/2 turns to start out. After quite a few flips on choke, it fired. Turned the choke off and a couple more flips and it was running. Ran a little rough at first but I expected that. Ran for a minute or two then quit and would not restart. After a couple dozen prop flips, I noticed as my arm was getting tired that the cylinder moved. Found that the cylinder bolts had come loose. Tighted those back down and off we go again. Choked and fired right up again. Ran for a few minutes and quit abruptly with a loud bang. Tried to flip the prop and felt something broken inside. Darn![:@]

Pulled it off the stand and pulled the back cover off. Found a small brass screw laying in the crank case. Also found a broken piston. The throttle plate screw had come off my carb and got sucked into the engine. Luckily the cylinder was ok. Grabbed another engine I had a pulled the piston and rod out of it. While installing it, I stripped out one of the rear cover threads. Darn and double darn. Pulled out that other engine again. The crank on this engine is bad but the crankcase and bearings are good. So out came my grinding tool and I proceeded to cut off all the unneeded parts of the case. Pulled the cranks out of both crankcases and swapped them. Put everyting back together and I'll be darned if I didn't strip out the threads on the last bolt on the new crankcase. [:@] [:@] By this time I decided to call it a night.

Today, I got the original crank case back out and examined it closely. I came to the conclusion that the crankcase does not have enough threads in it to start with to handle the loads that will be needed for this application. So I took the crank case with me to the auto parts store this morning and purchased a 1/4 by 28 tap and some 1/4 size bolts. The original bolts were 8-32. I decided to practice on the first crankcase first. Drilled out all 4 bolt holes with a #3 drill bit mounted in my drill press. Tapped all 4 holes all the way through. BTW the new bolts I bought were 1 inch long. This worked out really well so I decided to swap the crank back to this case and rebuild the engine again. After all was done, getting it running smoothly was done in less than a few minutes.

I learned a lot about what works and what doesn't so I guess the experience was worth it. The XYZ ignition has worked flawlessly so far. It says it takes a 6 volt battery but I have been running it with a 4.8 volt with not problems.

Looks like my Dynaflite SE5a will have an engine after all.

Jim













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RE: Elect. ignition for Poulan 25cc?
 

More pix