My saw just arrived. I cranked it to be sure that if it doesn't run that it is my fault. I have my test stand ready, and will begin disassembly tonight. Thanks in advance to everyone for all the questions you'll be answering. I promise to do a search first though. I think I've read every 46 thread I could find, and the echo, and scratch built ignition. Wish me luck.[sm=spinnyeyes.gif]

fwman1

How about posting a few pictures of the process as you go along?

Jim

For your excitement:

Here is the result of my first conversion:

Poulan 46cc from 2750 chainsaw - Brand new from Home Depot. The saw was a display demo with alot of parts missing. $30!
Conversion kit from Scott Baldridge
CH Ignition with Synchro Spark, Bosch Cap
Bennet G38 muffler
Mounted on GP Wagstaff.

The engine runs great. I have yet to fly the plane but the weather is getting warmer.

Well, I got it stripped down in about an hour. Pretty easy. Sorry, but I don't have a camera that works well enough to post pictures here, but I will keep a log of activity. I've got to get some Garolite to make the carb stand off and get a coil to go with the ignition board that Ralph sold me. I think I'll have Ken Lamber turn down the mag to make my prop hub attachment including the magnet pickup for the Hall sensor. I'm having fun so far.

You won't be disappointed.....
Here's one with CH ignition and BCM wraparound muffler...

Well, I thought I'd research my Carb. It is a WT-657. I checked Walbro's site and cannot find reference to it. It has a 16mm venturi. I'm removing the choke apparatus and cleaning up the passages that these used. Anyone have any ideas about this carb? It works, so I guess it is curiousity kind of thing. Thanks.

Roger

Ultra Copper seems popular for attaching carbs, but I can't find where anyone tells about which type to use reassembling case halves after cutting the bonus crankshaft end off. When I look at pictures, the ones I see don't look copper colored. What do ya'll use to remove the old gasket silicone? I've been using elbow grease with a little Goof Off. Is there a better choice? I have another question about reassembly. Do ya'll use the red Loctite for bolts, or the blue? I usually use the blue. Thanks for the help.

So far....

I disassembled the case to remove the crankshaft. This allowed me to remove the bearings and clean them in my ultrasonic cleaner while cutting off the rear part of the crankshaft. I had to first cut off the threaded part the clutch mounted to from the rear of the crankshaft before I could remove the rear bearing. It was keyed in, and a tight fit. I used my old Foredam jewelers flexshaft and a dremel cutoff wheel for all grinding. This enabled me to work carefully, and stop if things started to warm up.


I found the piston had a massive carbon deposit on the top, and the ring and its groove was covered with it too. I removed the ring, and carefully cleaned off as much of the carbon as I could from the piston top, without touching the metal on the top or edge of the piston.

I gave the internal parts a light touch of Marvel Mystery oil prior to reassembly. I had cleaned off the old gasket material and degreased the case parts with acetone. Using the THREE BOND 1104 (motorcycle case sealant), reapplied gasket sealant to the case halves and reassembled it.

I'm just waiting for my conversion parts to arrive, so I can solder up the componets and get the mechanicals ready. I have already gotten my Carb cleaned up, but will wait to do linkage work on it until after I decide on the mounting details. This way I can get the best alignment with the throttle pushrod, etc

Still having fun.[8D]

Update, in case anyone is interested. I got the conversion parts and have installed pretty much everything. The carb mount is a bit tall, but hopefully will work out ok. I am using an ignition board that Ralph @ RCignitions was kind enough to blue light for me. The coil and metal bits and pieces came from CH. I have the engine timed and am ready to run it..................except! The metal parts I got from CH didn't include the prop bolt. I used one from my G-38 to set the timing, but I don't think it is really an exact fit. The nice folks at CH are supposed to send out the bolt and prop washer tomorrow. I'll attempt to crank her up when the right parts get here. About a week, judging from the original order.

Keep us posted. Good thread !

Thanks to Ralph, Bill, Dave, and Terry for the help getting to this point.

I went to the hardware store(s) and found the 8mmX1mm bolt I needed to attach the prop. I had requested an engine with good compression when I ordered this Poulan 295. I got what I asked for! To start it without the engine trying to bite me I had to reduce the timing to just a little before TDC . I put on a Zinger Pro 18-8 and got 7500 rpms. This is low, but the engine was cutting out past this point; probably because the timing was retarded so much. I need a 20-8 prop. Once I get used to this particular engine's starting characteristics, I think I will be able to move the timing back towards 28 degrees BTDC as Ralph has suggested. It's on a mobile test stand right now and I am trying to pay it the respect a big engine deserves. I am using the Poulan chainsaw muffler at this stage. The engine is markedly quieter than when I ran it as a chainsaw. I guess all that machinery whirling around makes a lot of racket. I will update the thread as events occur. Now I need a plane for this thing! Funny, my wife told me I'd say that.

I need to make an update to give a heads up to others who may try this. I got my carb mount from CH ignitions. The folks there are very pleasant, and easy to deal with. There is a characteristic of their carb mount and the Poulan carb mounting flange that was not in the directions I received. It would have helped me to do a better job mounting the carb.

The base of the carb mounting flange on the Poulan 46 has a small radius at it's base. The mounting block CH supplies does not have this radius. You need to relieve the plastic around the carb mounting block base so that the carb mounting block rests SOLIDLY on the base of the Poulan carb mount BEFORE you mark for the 6-32 set screws. This will reduce the tendency for the carb and block to rock at certain rpms. Eventually this will work loose. While I tried to press the mounting block down as far as possible when tightening the set screws, my need for and lack of bifocals caused me to miss that the block was slightly raised off the seat. I found it later, but the set screw holes had already been drilled and tapped.

Just a little heads up for those trying this.

I have a carb mount from Baldridge conversions. It is a well made adapter but it came loose after a couple of flights last weekend.
I have drilled & tapped holes on either side of the mount. I then installed screws and a hose clamp to hold it all down. This is in addition to the original set screws and adhesive. I hope this works. It is really tight!

Get a 2" square of G10, 3/8 thick..Drill a 3/8 hole in the middle..Put a 3/8 bolt in a lathe chuck, bolt the G10 to it..Turn it to about 2'' round..Take out of the lathe, drill the hole to 3/4''. Trace the outline of the oval stub onto the 3/4 hole, it will be almost big enough at the center, but too small to fit the oval..Drill out the brass pulse pressure fitting that sticks out of the flat surface by the oval, tap to 10-32 or 5mm...Enlarge the hole in the G10 slowly to the oval shape, fitting it on the oval and looking for small black marks where the G10 does not fit..Remove the small black marks a little at a time until the G10 fits snugly over the stub..Take the small numbers cast into the flat surface of the cylinder at the base of the oval off until it's completely flat.Take a 10-32 or 5mm short screw and grind a point on the end..Screw the pointed screw into the 10-32 or 5mm hole until only about 1/8 sticks out..Put the G10 on the stub and hit with a hammer to make an imprint with the point into the G10..Drill the G10 with a bit just large enough to clear a 10-32 or 5mm flathead allen screw..Countersink the G10 so the flathead screw is flush..You will have noticed by now that the G10 hits the cylinder fins before it can go all the way down on the stub..Grind off the fin...
Put the carb over the G10 so that the throttle shaft is vertical, that way the throttle servo will not need a bell crank..Mark the position of the bolt holes on the G10 and drill and tap it for 10-32 carb hold down screws...Put Permatex Ultra Copper or 5 minute JB Weld on the stub and flat surface and press the G10 down all the way, securing it with the flathead 10-32..Drill a hole sideways all the way through the stub and tap for
10-32 screws..Put short 10-32 screws through the G10 and into the stub..Grind off flush with the inside the stub..This mount will NOT come off or leak, unless broken completely off in a crash....You will have to tap the case somewhere for the pulse..The transfer port at the rear of the cylinder is a good place, a Du Bro 8-32 brass pressure tap works well..The back cover of the carb has a cast boss not drilled through...Drill it with a #23 drill and press a Walbro fuel fitting in it..Grind the excess brass off on the inside of the cover..Connect the pressure fitting to the Walbro fitting with a short Tygon or seamless black neoprene hose...You can make a throttle arm for the carb shaft from a piece of 1/16 brass flat stock, drilled to fit the carb shaft and soldered on with Sta-Brite...There was a picture of this on the old RCFAQ site,probably lost forever..

RCIGN1,
Thanks for taking the time to put that down. I'll let you know how mine turns out. fwman1

vxoa203,
That looks like it will do the job. Good thinking.

There was supposed to be a very thin o-ring on the factory intake. It was to be reused with the CH intake. It serves to lock the intake so it won't rock.
If its not we will have to change the instructions.
In the mean time just remove the CH intake and put a bead of J B Weld on the flange and reinstall the intake. Once the JB Weld set the intake won't wiggle anymore, but can still be removed caus the JB Weld won't stick to the intake.

Terry, I saw that reference to an O ring in my instructions when mounting my carb. I checked carefully and found no O ring around my carb mounting on the saw. There were two flat gaskets. I placed one between the carb and CH block. I don't see how an O ring could make the base of the mount more stable. A gasket could have helped cover the flange at the base of the carb mount on the engine casting. Were you referring to this gasket in your instructions? Sorry, but I was looking for an O ring, not a gasket. This is probably one of those things that a bit of common sense or experience would have helped with. I know Ralph will get a kick out of this but I ASSUMED that I had another version of the saw without an O ring. They seem to change these tools more often than some folks change their socks. It does have a late model Walbro carb. I have not disposed of any saw parts, so I'll check the parts box again tomorrow for the O ring, and let you know if I find one.

Rest assured, I'm not trying to flame your products or company. I just am trying to help others avoid the mistakes I've made. How well the participants of this forum help one another is what makes this one of my favorite forums. Thanks for your contribution to the thread to spread useful information.

Roger

Nice plane vxoa203.
Hows the vertical on it with that motor?

We have had this sort of problem before, get an engine and develope a conversion kit. Then the engine maker makes a running production change and something doesn't fit. Any way we will put a bevel in the backside of the intake so it fits both engine styles.
Thanks for the heads up.

Antslake-

It flies very well. In my humble opinion, the Poulan has plenty of power for the Wagstaff. Vertical performance is suprisingly good. It will be even better once the engine is broken in and I put a 20X10 on it! You will see the plane at the field soon - as we are in the same club!!

Roger, why not use a mechanical advance on the ignition? just mount the sensor to a ball bearing locktitened (?) to the crankshaft right behind the prop hub. hook it to the throttle arm with a pushrod and ball links. you'll have to mess around with the linkage a bit to get the ratio right but it should be worth it.

another trick is to mount two sensors, one for starting and one with full advance, and a switch to choose between them. you could even operate the switch with a cam on the throttle arm and set it to go to the advanced sensor at 1/3 throttle.


dave

Dave, I like the two sensor idea. Have you actually done it on an engine? It would be easy to set up. I'd put the switch in front of the firewall as I am deathly afeared (hillbilly talk) of radio interference. Which muffler do you like for the engine? I was thinking of using an old G-38 Bennett style. I've read where it is supposed to fit right on this engine. I'm a bit low on rpm now, and I think some of it has to do with the stock muffler I'm running. Most guys quoting rpm seem to refer to the square tip Zinger 20-10 (6600-6800 range), so I guess I'll get one to see how things stack up. This is so entertaining, I'll have to tear myself away to begin building the plane soon. Thanks for the tips.

yes, i've done the switch trick on a couple engines...works like a charm. the idle won't be as smooth as the mechanical advance but you'll never get a prop bite no matter where you set the throttle for start-up. i wire the sensors in parallel and switch only the output lead that goes to the SCR.

no noise issues where i fly so i don't use mufflers, only short headers. sounds really cool[8D]


dave

I made the first ball bearing advance I ever saw, Loctited to the crank and connected to the carb with links, SEVENTEEN years ago, still doing it on the larger engines..I found out early on that the Loctite sometimes fails..All subsequent hubs have the ball bearing mounted on the HUB on a short extension, .669 diameter for a light press fit with Loctite...Tried the 2 sensor setup, decided it was not needed on smaller engines...Or ANY type of advance/retard at all.....
If you're timing an ignition, measure the diameter of the hub that the magnet is mounted in, multiply by .244 for 28 degrees..Works with any size...
Diameter x 3.14, divided by 360, x 28....Works out to .244...
2" x 3.124 = 6.28
divided by 360 for 1 degree = .0174444.. X 28 = .48832
Not at all critical, a few degrees one way or the other makes no measureable difference..
If you go too far on the advance the engine will miss and cut out at WOT, not far enough and the engines slows down and loses power..Best setting is JUST above the point where the engine starts to slow down...

Mine didnt have the O ring either. Th e rubber boot was all. Ran fine as a saw so I guess there are some that dont have the O ring