RE: Who is converting Toro trimmers?
 

Hi Rollmyown,
It ought to be very interesting to see what happens. It will be a lot easier to tell how it works after a actual test.

Dave

RE: Who is converting Toro trimmers?
 

As they say a picture tells a thousand words, so 3 pictures should tell all! Here are 3 images taken from the engine tech data which explain the fresh air lead charging via the reeds as I tried (maybe not very well) to descibe above.

Cheers,
Rich

RE: Who is converting Toro trimmers?
 

Hi Dave, Today was test day. The 2bbl engine with the adapter to fit the Walbro WT324 carb on the cut down and modified Toro intake was run today. The Reed intake tubes are now getting an air and fuel mixture. It runs pretty decent and is flyable. The RPMs were 8200. Maybe a larger carburetor still would raise the RPMs a bit more. 8200 is about 500 more than I got before. Scott is getting these RPMs without all the extra work. I think I will leave this engine as it is and convert one of the other 2 bbl engines I have, the way Scott does them, and use a bigger carb than the Zama carbs I tried before. One drawback to making an adapter plate to fit on a modified Toro intake is that you still have the carb sticking way out to the side. I am going to try a closer-in mounting for the carb. The muffler I came up with sounds much better than the original, but I don't see much of an RPM difference. My muffler mounts a lot closer to the engine so I am going to see if I can find some more of the 1"x2" "Aluminum Railing" stock to make more with the stacks on the end this time. With a close mounted carb and muffler, the total width is easier to fit to an airplane and will look a lot better. I fussed with a single barrel engine also, the results were weird, so I think I might have messed up the carb spacer that I made, it was a preliminary design and I tried something different. I junked it and will try a new one. You CAN spend time on these. I don't have the Laser Tach under control yet, I only attached one reflective spot but it must be counting both blades anyhow because I was getting 16K readings. The Laser also does the autoranging bit like VOMs do and that is distracting when you are operating the throttle and watching to keep your hand out of the prop.

RE: Who is converting Toro trimmers?
 

Hi Rich, The photos don't come up large enough, but it doesn't really matter. After I first took a 2 bbl engine apart, I could see how it worked, and as Dave Wallace pointed out Reeds work usually in one direction only and some engines use them for timing the fuel charge into the crankcase etc. I knew about these "Reed" engines, but was never really fond of them, and then I ended up with some Toros. What really got me is that the top surface of the piston bisects the directional ports and the piston does not go down any lower than 1/2 of the port diameters. I looked at that and thought, the fuel charge from the main port in the crankcase area is also flowing through these ports, which are never more than I/2 open!, and then at some point the Reeds must only open for an extremely short period of time, so That is why I increased the diameter of the ports. I then wondered if I went too far, but after all the tinkering it still runs and I gained about 500 RPMs. The velocity of the fuel charge through these 2 bbl engine ports must be pretty high. I made them about 20 to 25 percent larger I would guess, I wonder how far you could go, but I am not curious enough to try it at this point.

RE: Who is converting Toro trimmers?
 

its to auto resize thing the forum does that messes up the pic size. Just click to open it full size, right click and save the pic to your local drive, then open it at actual size (100% zoom) in any photo software.

Sometimes with transfer ports the manuafcturer has the port only half open (actually the port is twice the height) as it stops the ring riding over the lower edge of the port so extends ring life. I don't know if thats the case with the toro.

Cheers,
Rich

RE: Who is converting Toro trimmers?
 

Hi Rich, I will try saving the photos and looking at them in my Camera software just for the fun of it and to see if it will work. Several posts back I give the diameter of a drill bit that I used as a gage to check the diameter and match up the port sizes and this drill bit is quite a bit larger than the original ports were. The original ports are susprisingly small and I don't think it is to prevent the rings from snaging the ports in this case.

Rich, I checked and printed the photos you supplied. I now see what you were talking about. How it works is different than I thought. It looks to me like the "lead Air" term they are using, as we might see it, is to finish purging the exhaust gases from the previous exhaust stroke and to prevent any of the incoming air/fuel charge from exiting the exhaust port before it closes. I would have thought that the emission design part of this engine would have had more to do with the burnt gases and now I wonder, Did this idea really work as they expected? Because of how these engines are designed, the Reeds are probably of no use to us?, but it is midnight, time to forget it and sleep. Maybe the rest of you will check these photos and come up with something.

RE: Who is converting Toro trimmers?
 

Hi Rollmyown,
A lot of good info has been presented in the last few posts on the 2bbl Toro. The top carb barrel and the reeds act like the air injection pumps used for auto emmissions in the 1970's. They lower the combustion temp and NOX output. Later they went to the EGR exhust gas recirulation valve to do this.Many of the Homelite 25 and 30cc trimmers have the port above the exhust into the muffler. Maybe it is a California model.

Dave

RE: Who is converting Toro trimmers?
 

Hi Dave, I have no doubt that California requirements have everything to do with the design of the two bbl Toro. Maybe it was also an attempt to get a 2 cycle engine to meet emission specifications and not have to go to a more expensive 4 cycle design. Some/many? of the manufacturers of small 2 cycle engines either have or are working on 4 cycle designs. Subaru and Tecumseh come to mind. Honda has one also as you know, but these 4 cycles are heavy.

The 2 bbl Toro might not have made the grade to meet stricter requirements?, and maybe that is why they are surplus? All that is of no real interest for us now. We only need to figure out if it is worth using or eliminating the Reeds? I am close to just following what Scott does and be done with it. I got 8200 RPM which is OK but this Toro could very well do that with the Reeds eliminated. I am going to do another 2 bbl like Scott does next.

RE: Who is converting Toro trimmers?
 

Hi Rollmyown,
I think thats a good idea. It will make an interseting comparison.

Dave

RE: Who is converting Toro trimmers?
 

You got 8200 on with the reed valves in place? That is very good. What prop did you use?

RE: Who is converting Toro trimmers?
 

Hi Scott, I got 8200 RPMs with my 16x8 M/A classic propeller, which is the one I used for the other tests. This was with the modified Toro 2 bbl intake and a WT 324 carb sitting on top. The installation is the same height as with a Toro 2 bbl carb sitting on it. It is a bit of work to make the transitional 1/4" thick plate match the modified Toro intake and the 5/8" throttle plate bore of the Walbro. I might get aroungd to trying a bit larger Walbro. (I cut 1/4" from the top of the Toro intake, of course.) The reason I wanted to try this is because of the relatively small size of the main intake port of the 2 bbl engine, as you well know. Making a carb spacer for the 1 bbl engine is easy compared to the 2 bbl engine as you have also no doubt found out. It did seem to run pretty well, but I haven't run it since.

RE: Who is converting Toro trimmers?
 

this reply to my post is to add photos to the thread because we have discussed the differences between a 1 bbl carb and a 2 bbl carb Toro engine but have not supplied side by side photos. The exhaust ports are identical on both engines. The 2 bbl engine which you can identify by the Reed inlet tubes also shown in the photo has a very different intake port than the 1 bbl Toro.

RE: Who is converting Toro trimmers?
 

I just spent most of the day messing with the single and two barrel versions, with some interesting results.
First, the single barrel:

Exhaust timing duration- 130
Intake timing duration- 130

Completely stock-
Easy hand starts
7300 on APC 16x10
2000 idle

APC 16x8-
7300 (?)
2000 idle

MA 13x6
9200
2200 idle

Echo GT carb block and WA-167 carb-
Starting ok
7400 on APC 16x8
2200 idle
Poor transition

Stock + widen exhaust port
No change

Stock+ exhaust to 140
No change

Stock+ .005 cylinder gasket replaced original .020 (exhaust back to 130)
7500 (16x8)
6200 on Pro Zinger 20x6 (!)
Starts excellent
1800 idle

Two barrel:

Completely stock-
Easy hand starts
7600 on APC 16x8
1900 idle
Great transition

This engine seems to be (port) timed to make power around 7000. My plans include trying to find the bottleneck...



I checked the ignition timing, as the magnet position indicated it should be firing about 30 degrees after TDC!

WE HAVE AN AUTO ADVANCE MAGNETO!
Apparently, the coil picks up the impulse very early, like 330 degrees early.
It then delays the spark, depending on engine speed. Awesome!
Here's what I got:
At 2000 RPM, it fires at 20 BTDC.
As RPM increases the timing advances smoothly and proportionally, to 30 BTDC at 7400!!!

The stock carb is amazing too. Although there are no means to adjust mixture, it did well with 13x6 thru 20x6 props!

More to come...


Joe Petro

RE: Who is converting Toro trimmers?
 

Hi Joe, Welcome to "Tinkering with Toros". Dave Wallace and myself have been talking about modifying the timing on a Toro. Last week I used a timing light on one, but I wasn't running it, I was spinning it with a Sullivan 24 volt starter, in the basement, and I really couldn't tell what was going on. I actually have two timing lights and they were not responding the same, so I gave up. I suppose you were running yours for your test? From emailing this subject with Dave and from a couple of things he mentioned and looking at how the engine is set up, I was wondering how it runs in the first place. If they have something extra built into the magneto, that would explain a lot. I have had a suspicion about that possibility since last year when I used an ohmmeter to compare a few Magnetos and could not tell much, I would have thought they were junk, but the engines for them run. I was getting ready to test run the 2 bbl engine with the Walbro and conversion plate on it tomorrow with the flywheel advanced a bit more than the width of the keyway and now you have me thinking this over. Now I am also wondering if a search on Magneto design will turn up anything.

RE: Who is converting Toro trimmers?
 

One other thing..
It always starts on the second flip, never the first.
This may indicate a CDI unit with logic.


Joe Petro

RE: Who is converting Toro trimmers?
 

Actually most of the newer magnetos on trimmers and saws change the timing. A poulan 46cc does the same. If you look at Walbro.com it will explain that all thier magnetos retard timing at idle and advance up to 15 deg or so at high rpm. That is why I do not understand why people are so concerned with electronic ignition like C&H. The magneto does the same thing and is more bulletproof than C&H ignition will ever be. Weight savings is minimal because a mag requires no battery or extra ignition box.

Joe. I noticed the same thing about 2 flips to start them. Never just one.

I will post some pics of my latest 1bbl model engine. I have a great intake for them now that runs remote pulse and turns the carb. I stopped porting on the 2bbls for a little while. One engine I sold lost compression so I want to get it back and make sure the chrome didn't peel due to the porting. It is a possibility. Hopfully it is just a cracked ring or somthing.

I also did a compression check on the 1bbl Toro. I got from 145-160 PSI on the 6 I tested. Very high. All the Poulan 46cc engines I have checked are around 125. Also some Poulan 25cc's were 125.

RE: Who is converting Toro trimmers?
 

Removing the magneto also changes and upsets the dynamic balance. I will look up and attempt to post the engineering analysis for use as reference material. Electronic ignition adds complexity with a net weight saving of only 6 to 8oz.

Stihl also retards the timing for starting on some engines.


Bill

RE: Who is converting Toro trimmers?
 

I gave up on messing with the timing on a Toro. If you can get 8k+ on essentially new, not broken in, engines, what more can we realistically ask for? As far as removing the flywheel and using a CDI unit to save weight, I agree wholeheartily with what you and Bills are saying. The engine is designed with the flywheel for more reasons than the ignition and its built in fan to cool itself in the original plastic housing as a trimmer, chainsaw, or whatever. The dynamic balance of the engine as Bills put it is an important part of it. The single cylinder flywheel is also an absorber of the harmonics produced by the power pulses of the engine firing. I am trying to say this in a way so every reader can get some idea of the actual complexities of the total design of engines that appear on the surface to be simpler than they are. I am not an engine engineer but I have enough interest to have researched the subject some. The torque output of a piston being driven by the burning and expansion of the air/fuel mixture is not linear, it has a rise and fall curve to it. Multi-cylinder car engine cylinders can balance each other out as far as some of this is concerned. A single cylinder "gasser" has a huge flywheel, compared to the Damper/Harmonic balancer on a multi-cylinder auto engine because there are no other cylinders to help out with balancing. With our single cylinder "gasser" conversions we can get away with "trimming" the flywheels and then we add some "flywheel mass" back to the engine by using a prop hub and the propeller itself. Removing the flywheel and turning the "harmonics" loose can possibly result in shortened crankshaft life and even breakage from what I have read, so I have no intention of removing a flywheel. If an ignition system could be designed to use the flywheel magnets, I would consider that a possibility to improve performance, but I strongly suspect that many others would not look past the weight of the flywheel. Does my reasoning make sense to you two, Scott and Bills?

RE: Who is converting Toro trimmers?
 

rollmyown,

Makes good sense. Most of the time when weight is discussed the weight of the battery and coil and ignition box added back is omitted. As stated we will be in the minority. Having a magneto flywheel is not considered cool. Although I have two ignition units on the shelf my engines have magneto ignition.

Bill

RE: Who is converting Toro trimmers?
 

It makes perfect sense to me also. These engines are not DA 50's designed from the start to be run on CDI ignition. Just look at any ad for a CDI ignition engine. They give the weight and a picture of the engine. It almost never includes the ignition unit in the pic or in the weight. They just show a sleek engine with no mag, flywheel or anything. They have everyone thinking that an engine with magneto ignition is not worth putting on a plane. Most people do not know a magneto is able to retard and advance the timing as much as a CDI setup. Plus I hate waiting for batteries to charge. The last thing I want is another battery to go dead. Also from what I have been reading. Magneto ignition with a resistor plug causes far less raido interference than a CDI setup. I know the Futaba 127DF has trouble with CDI ignition and interference. Magneto ignition keeps everything up front on the engine where it belongs, away from the radio gear. Plus how many times have you heard of a magneto going bad. Not often. Look here on RCU and you will find tons of posts about CDI ignition problems. Simpler is always more reliable. My computer screws up constantly. My calculator never does :)

RE: Who is converting Toro trimmers?
 

Incidentally a Stihl blower engine has a magneto without fins that is only 3 1/2” diameter.

Bill

RE: Who is converting Toro trimmers?
 

Hi Bill, I think that 3.5 inches in diameter is close for a lot of 2 cycle engines. That is what a Toro is and my McCulloch engines are. After all, Walbro and Phelon make a lot of these as suppliers. While we are on the subject of a flywheel helping to smooth out the non-linear power pulses of a single cylinder engine, I happen to remember where you can actually see the power pulses of an engine. I have seen this at an airport and most recently on Wings on HBO, where they have shown a big Radial engine idling. Ever notice that the blades of the prop on a big recip seem to play with the Sunlight? If you look closely, at the slow idling speed, you can actually see the varying acceleration of the propeller tips as the cylinders fire. I had noticed this many many years ago and then later after I had learned how an engine ran, I became more observant. It is noticeable with the big recips and their 3 or 4 bladed props and about the only place to see them now is on Wings. I bet the mechanics on these engines noticed it and just took it for granted. Another thing I remembered was in an RC magazine about a year ago where a big twin gasser sheared the engine hub off behind the prop at full throttle on a ground run up. No one was in front of the engine and the prop stuck a blade in the ground breaking one blade of the Polycarbonite prop off. I would suspect a harmonic problem of some kind here. This was a 30" prop as I remember. I have propped full scale airplanes a few times and I make it a point to respect all props.

RE: Who is converting Toro trimmers?
 

Many years ago while testing props I observed quite by mistake that the tail feathers shake differently at idle depending on the prop location relative to top dead center.

At some prop locations the tail feathers shake like a streetwalker looking for her next job. Rotate the prop 90 degrees and she looks like church lady all prim and proper. Didn’t understand at the time but rotating the prop simply changed the dynamic balance.

Bill

RE: Who is converting Toro trimmers?
 

Hi Bill
Now that you mention this, I saw this happen yesterday while running a Mac 32cc, I just converted and was testing. The first thing you think of is if you machined the flywheel off center or something. When I increased the RPMs a bit the prop tracked true, but I could still see what you described along with the prop tips reacting to the load and RPm of the engine. I will have to try a different position. I more or less have it lined up with the magnet and counterweight for ease of propping, but maybe that is not the best position.
John

RE: Who is converting Toro trimmers?
 

Hey. I had a guy who bought a 25cc Toro from me. He put C&H fixed timing ignition on it. He set it at 30 deg I think and gained 500 rpm on an APC 16x8. He is up to 8950. He only lost about 5oz in weight and the hand starting suffered but he did get more power.

RE: Who is converting Toro trimmers?
 

Hi Scott,
What version was it, a 1bbl or a 2bbl? Did you ever figure out what caused the loss of copression on one of your motors? It sounds like the stock mag timing can gain from a slight advance, right?

Dave

RE: Who is converting Toro trimmers?
 

It was a 2bbl model. I did the usual enlarging of the intake and exahust and cut the transfer ports deeper. I think the 2bbl has more potential than the 1bbl because of the larger transfer ports. I didn't get the bad engine back yet. I hope it wasn't chrome peel or that will put a halt to the 2bbl engine for me. Hopefully it was a ring that broke. I could have cracked it putting it together. My fingers are crossed :)
I do think we could get a little more out of these engines by rotating the flywheel a little bit clockwise. Just enlarge the groove for the key and putting some locktite sleeve retainer on when putting it together. Just a few degrees to advance the timing some more. It can't hurt and using the standard mag it will still retard the timing at low RPM. I want to try it as soon as I get time. It seems like when I think I have a chance to do it 2 more engines sell. It is hard to keep up but there is going to be alot of Toro weedeaters flying around the country :)

RE: Who is converting Toro trimmers?
 

Re post 137
My Futaba 127DF is 8 inches from my firewall. Both batteries are between the receiver and firewall...Rubber boot on the spark plug, no shield on the wire....NO interference....CDI is no worse than a mag, if the circuit is INSIDE the mount;)

RE: Who is converting Toro trimmers?
 

Hi Ralph,
I havn't figured out how to put the CDI inside those flat plate mounts that I have been using.:D

Dave

RE: Who is converting Toro trimmers?
 

Let me know if you figure it out :D

RE: Who is converting Toro trimmers?
 

OK I answered the question of what engine is better. 2bbl or 1bb. (in my mind anyway) The 2bbl is a far better engine. I just ran one tonight I built for a guy that needed one ASAP. It turned an APC 16x8 prop at 8320 rpm. That is amazing for a new engine. The 1bbl models are doing around 7800+ when new. The 2bbl models seem to be consistantly higher. Usually over 8000. Keeping in mind they will pick up 600+ rpm as they break in. I think the reason is the transfer ports. I mill them deeper on the 2bbl engine. The 1bbl has a huge intake port but very small transfer ports. A poulan 25cc has larger ones. That is the only reason I can come up with for the increased power. I open up the intake, exahust, and transfer ports on the 2bbl. Just the exahust on the 1bbl. No real way to safley open the transfer ports on the 1bbl. I still didn't get the bad engine back so I am taking a chance with the milling. The worst that will happen is I will have to build another one.
So to sum up, the 2bbl, even with the smaller intake, even after milling it open, still has more power than the 1bbl. That is what i am finding and I have converted 27 of them so far. About half 2bbl and half 1bbl.

RE: Who is converting Toro trimmers?
 

Hi Scott,
The smaller 2bbl intake must compensate through higher volocity. That small transfers were the first thing that I noticed when I diassembled my first 1bbl. After converting so many engines with great success, that one engine problem may be something unrelated to your mods. Thanks for sharing your experience.

Dave

RE: Who is converting Toro trimmers?
 

Hello Dave, Forgive for jumping in here, I have a Mac' 22 (10-12 years old)and have it installed in an NOS RC boat.(Found in freinds attic!) How do I break-in this type of engine? I have Nitro engines that have lasted for years with proper break-in, do these act the same? Can I make a type of custom exhaust to vent the exhaust out of the boat hull?(instead of pointing down inside hull) Also I have read that I should use "Camp Fuel" ie. White Gas mixed with Amsoil, 4-6oz./1 Gal of fuel. Any help would be appreciated

RE: Who is converting Toro trimmers?
 

Hi Ritz,
You would get more responses with a new thread,but here goes. If the engine isn't broken, you can run it on 32 to 1 mix (4oz. per gal) for the first couple gallons then switch to 40 to 1 mix. If it has a water jacket break it in in the water, moving. You can find mufflers and other parts at Wackerengines.com. Pete does have boat mufflers. Anyway, don't let it over heat. Good luck.

Dave

RE: Who is converting Toro trimmers?
 

Where has everyone been? I soo look forward to getting an email that someone responded to this post :) Just wondering if any of you have actually flown a Toro. They do very well in the air. I have one on a 14lb Sig Rascal 110". It flies like a dream. My buddy has one on a 1/4 scale Space Walker. It is amazing on that plane. Many of the engines I have sold are now flying with happy pilots. Just wondering about all of you.

RE: Who is converting Toro trimmers?
 

Hi Scott,
I am still here. Rollmyown is alive and well in PA. That is good to here that you have had such sucess. I havn't flown one yet. Working getting a big mule airborn. Flying season is year round here in south Texas since we are on the same latatude as south Florida. I bought a poulan 46cc off RCU and it has a bore and stroke of 40x31.5mm. This works out to 40cc for me. What is the bore of one of your 46cc Poulans? This one came from a Craftsman saw which was labled 46cc. It has the coil mounted on the cylinder like the 46cc, but has a flat on top with no vertical fins like 46cc I have seen. Nice motor with a chrome bore and CH adapter. I havn't been able to track it down by part number. I am glad that your E-mail notification works, as mine don't. I seen you mention the Sig Rascal a couple times and thought that the 110" was a typo, but I gusee it is correct. This must be a big floater at 110inches. Stay warm.

Dave

RE: Who is converting Toro trimmers?
 

Hi Scott,
I have some airplanes but they are not suitable for a Toro, so I haven't flown one. They are also not powerful enough to get my 4 ft tree stump off the ground. The building season is here in PA now, but I keep getting sidetracked with other stuff. Too much tinkering with engines also. I am planning on an airplane that I can try more than one engine on. The other thing is that airplanes are getting bigger and I am running out of room. This has to a common thing with us modelers. Time is going by too fast also. I also wonder when you get time to fly with all the engines you build up.
John

RE: Who is converting Toro trimmers?
 

Dave, I did some checking and your engine is indeed a 40cc. It is the same basic engine as a 42cc like in a Wild Thing saw but for some reason just the 40cc has the coil mounted to the engine. That is nice to know. I was looking for a 38cc class engine to convert. I think you helped me find one ;) Thank You!

RE: Who is converting Toro trimmers?
 

Time to fly has been limited latley. I have been selling a ton of engines in the past few weeks. Everyone is buing stuff for thier winter projects. It should slow down soon. I have a few planes to get done too. Too many projects and too little time.

RE: Who is converting Toro trimmers?
 

OK, My last Toro, with some new mods, 2bbl model, spun an APC 16x8 at 8500. That is just amazing for these little trimmer engines. Look out Zenoah G26, 8900 is getting closer :)