davewallace

My Feedback: (29)

Hi,
I think 14mm is way to much carb. This the size used on 45-50cc motors. Scott E. has gotten great results with a 11mm walbro, which is the size that almost everyone uses on a 25cc. You may have an air leak in the cylinder base gasket or somrting causing uneven RPM. Mine is almost ready to run with an 11mm carb. I just need to get a small diameter hub with 8x1.0mm thread for the shaft. I think that the port timing is limiting your Rpm. Good job so far.

Dave

rollmyown

davewallace, your reference to 14mm probably being too much carb is only because you haven't seen my 25cc Weedeater run with a duplicate carb. The weedeater runs as good as you can get one of these things to run, very smooth, good idle, and good throttle response, and it seems to running clean enough that carbon should not be a problem.
I think we are really talking about 14mm being too much carb for the Toro, but the engine ran the same way with the original carb, then I suspected the carb, now I am going to try a different magneto. After the running session was over and I thought it over, it sounded like it could be an electrical problem, and there is only one electrical part. (By the way a good tool for setting magneto gaps is a piece of Aluminum flashing, flashing is usually around 12 to 15 thousands thick.) The Toro has higher compression than the weedeater and I will probably open the ports on the Toro like I did the weedeater. By looking at some of the good references for Walbro and Zama that were posted by other here, you can see that most of these carbs have a pretty wide cc range. I sure am going to try again with this carb. It was not running any worse than the original carb and if carburization was the original problem with this particular engine, I would expect a bigger carb to aggravate the problem further. Did you get the 3 photos I sent you?

One last point, it is hard most of the time to get the intake big enough to fully use the capability of a larger carb as I am doing. This carb has a 9/16" bore but I was only able to open the carb spacer on the Weedeater, for example, to 1/2" diameter. This is one of those things I think we can "get away with".

davewallace

My Feedback: (29)

Hi,
I haven't recieved any pictures. How did you send them? I check my e-mail frequently and my private messages. If you look at some of my earlier posts in this thread you will find Toro carb insulator bored to 5/8" and modified for standard carb pulse port. I up loaded one.

Dave

rollmyown

I did some work on engines I am testing, a single bbl and a 2 bbl. The 2 bbl intriqued me some so I studied it. The primary bore and secondary bores, in nominal sizes, are 3/8" and 9/32" diameters, respectively. In total they are pretty large as far as area is concerned, but the secondary only feeds the small Reed ports. Now the Reed ports also feed the directional ports ("directional" porting using the same ideas used in model aircraft engines), but these directional ports also are the main and only ports so the Reed ports are piggy backed into the main ports and mounted into the covers for the main ports. These are the covers that Scott removes to mill out the port transfer areas. (A mill is great for this and I don't have one.) That is some background info for what I did. I enlarged the main port as much as it can be enlarged and still use the original carb spacer which I retained and modified. I enlarged the main port through the carb spacer. Then to a depth of 250", I cut through the web seperating the two bores in the carb spacer, alowing both bores to feed both the main porting and the Reed ports. So far I left the Reed Ports in place. I opened up the ports into the cylinders somewhat, maybe 10 to 20 percent and opened the transfer passages from the crancase to the cylinder as much as I could with a file. This altogether gave me 8000 RPMs, which I didn't think was too shabby with the original 2 bbl carband the idle is still very good at 2100 to 2500. This engine is still not broken in. Maybe I should remove the Reed ports alltogether? The single bbl engine with a Zama carb only gave me 7500 RPMs. I runs nice and idles well, but it needs more work. Need to work on posting pictures now. A safety note: The carb spacer smeels like bakelite, asbestos, when working on one don't breath the dust, wear a mask, and wash away the dust with water occasionally.

rollmyown

davewallace, I used my digital camera software to email photos to your email address. I thought they went out, but now that I know you didn't get them, I will check in to what I am doing. I remember the picture of the carb spacer you show here, but it didn't register, I guess it looked too big to be a Toro spacer. I am going to look at mine again to see if it looks like yours. The intake port on a 1 bbl Toro is huge, I don't think it needs to be enlarged at all, but the exhaust port seems as though it can use a bit of help, so I worked the exhaust over on the one I am testing. I checked the gaskets as you reminded me of, I had looked at them before, they wern't leaking, but I noticed that the cylinder base gasket could ft better so I made a new one. After I put the cylinder back on, I wondered if I shouldn't have put some Form a Gasket at the "T" of the base and case gaskets. Anyhow it wasn't leaking and the magneto seemed to be giving me trouble. After a while, it quit, I changed it and ran again. It only gives me 7500 RPMs but idles well and transitions well with the Zama carb that you thought could be too big, but the same carburetor works great on two 21cc and one 25cc Weeedeaters and they run great. This particular engine seems to have too much end play on the crank, I need to look at that. I have a couple of 5/8" Walbros, maybe I will try one to see what the results are. These engines have the porting and the compression is high, maybe they can handle more carburetation?? I have been using Poulan oil at 32:1 so far. Have you seen any recommendations on the ratio of oil for these Toros? By the way, the 2 bbl engine has a domed piston, not real high, but still not flat.

Scott Ellingson

My Feedback: (146)

The mix ratio for the Toro is 50:1. Try that oil mix. You should get better numbers. 32:1 is way too much oil.

Ralphbf

My Feedback: (27)

I have motorcycle and chainsaw experence and was told years ago, about 20, that 50 to 1 was a smog thing,
and that 32 to 1 was the wise mixtute.

I run oil that is rated at 100 to 1, but I run it at 75 to 1.

Am I out of touch.

Scott Ellingson

My Feedback: (146)

On the Toro the tolorences are close. Thus 50:1 is all the oil that is needed. On a cheeper engine like a Weedeater they are not as close, so therefore 40:1 and on alot of the cheeply made pocket bikes and chineese chainsaws the ration is 25:1. They also meet EPA standards but the tolorences are not as close so they need more oil to run well. Just like in the 70's 100,000 miles was alot on a car engine. Moset didn't make it that long. Now with closer tolerences in machining they go much longer on avarage. If you run an engine that should have 50:1 at a higher oil content all you will do is cause excess carbon to build up which will lead to premature wear and overheating.

rollmyown

I had not seen any recommended info on the oil ratio for Toros. I suspected maybe 40:1, but I already had some 32:1 so I tried it. I also guessed a bit more oil wouldn't hurt for break-in. I am surprised a bit at 50:1 because 32:1 runs pretty clean. I did some more work on both engines, the single bbl and the two bbl. The 7500 RPM number for the single bbl is probably not valid and I was surprised that it was not higher. While preparing a larger carb yet to try, I discovered that I had the 14MM carb on wrong, the pump was not working. It was one of those " how in the world did I do that?" deals. I noticed that the needles were not reacting normally, but it did run. Probably because the carb has a 14mm throttle bore and a 3/4" top opening but the venturi is about 3/8" in diameter, so I guess it pulled the fuel in. I will retest that carb and the 5/8" bore carb, I have, which has the same kind of relationship between the bore and venturi. There is a lot to these 2 cycle carbs. I worked over the exhaust opening on the single bbl and reworked all the ports again on the two bbl, now that I found out my idea of opening up the intake manifold for the 2 barrel carb worked out. The throttle response was good, the idle was good, and I now think it will go over 8000 RPMs. 50:1 oil and some break in time will also help. Now I think(?) I can post some photos in another post, so this one doesn't time out.

rollmyown

Here is a photo, it shows a 21/64" drill bit, as a gauge, in an intake port on the 2 bbl to show direction also. A 13/32" drill was used the same way on the intake manifold. You really couldn't drill the intake without ruining it. It has a countoured passage. The other photos should match the text in previous posts. Photos didn't upload. Will try again.

Important note: This drill size gauge idea turned out to probably be too large. When you look at the port with the top surface of the piston bisecting the diameter of the port, the top uncoverd half of the port looks really small and my drill gauge idea looks reasonable, but it seems that by me reffectively raising the intake ports, about .040" to maybe .060" (this is difficult to measure), I went to far and you can here this difference when you flip the prop. If you want to work a bit on these ports, I would suggest increasing the width a bit, but remember it is easy to go too far.
I am going to lower the cylinder around .020" of an inch to correct a bit of my excessiveness. The engine still runs well enough as it is, it idles well at 2k and has a top around 7500 plus. The next thing I am going to do with it is change the carb to a 2 needle Zama and forget the rotary Walbro, even though my "slotted" intake manifold did show some promise. We do need the reliability and adjustability of a 2 needle carb. A hint for working on ports with a file: fashion a piece of aluminum flashing 2" wide and about 3/4 of the cylinder diameter, to insert into the cylinder to protect the cylinder wall from the tip of the file. Clean up the edges of the flashing guard also. Without protection, you will probably scratch the cylinder wall.

rollmyown

Photos uploaded, but I don't know to where? Computer said they were uploaded successfully? The second photo shows the bottom of a 2 bbl cylinder. The two openings on the sides are the transfers from the crankcase to the directional ports where the Reeds are also located. I see now that I can upload a few pictures at a time. the 2 bbl engine is verysuprising because the piston only uncovers 1/2 of the intake ports to take in the fuel charge. Now that I knew my modification of the 2 bbl intake worked, I went ahead and opened up the intake ports some more and I concentrated on the top side of the port that the piston uncovers. To look at these engines you would think the single bbl has more potential because of port sizes. I also guessed that the 2 bbl carb had more potential because the second barrel was only feeding the Reeds and probably had enough flow to add some to the primary port to the crankcase, it looks as though it does. There is no Sun out today for my Tack and I have to run some errands, but I am ready to test again. I will post the intake manifold photo etc. next.

davewallace

My Feedback: (29)

Hi Rollmyown,
You done good. I can see where these 2bbl engines have potential. I would like to get one to play with.

Dave

rollmyown

hi davewallace,
The 2bbl carb is what is working for me so far. I figured that the way it is designed, there is no adjusting of it except for idle, could be put to use. The secondary bore doesn't open until the primary is pretty far off the idle so I guessed it wouldn't flood and stumble and was worth trying. You don't know if something like this will work at all unless you try it. The carb is a Walbro and is not junky, so I wasn't going to just discard it. My original idea was a plate on top of a cut down intake, cut down 1/4", so I made a 1/4" cut down into the dividing web and could cut down the rest of it if it didn't work. This two barrel carb is fairly large, but it works well, and I am going to stick with it. I will post the photo of the modified carb intake /spacer for everyone to see, but I got to run now. I sent you the first photo by email as a test, did you get it? Added photo, 8-31-05

Note: This slotted intake idea did show some promise, until I went a bit further on opening up the intake ports. (I think that is what happened, but if you change a couple of things at a time as I probably did, even small changes, this can happen.) Sometimes it doesn't take much to skew your experimentation off the course you think you are on. I just want to point out that this has possibilities, but it is not 100% perfectly perfected.

rollmyown

To continue with photos, here is a side by side of a stock 2 bbl manifold system and my modified intake spacer alongside an unmodified one. There is more of an increase in the bore size of my modified one than is apparent in the photo. the hole of the modified port is perpindicular wheras the unmodified one has a contoured bend shape to its bore. The size of the modified bore in the intake manifold limits how big you can go with the matching port in the engine. You can only go so big in the carb spacer and still get a gasket to work. The directional ports and the transfer passages need worked on also. I am ready to test the second enlarging of them. I now have them as large as they probably can go. I will get some photos of them also.

rollmyown

To continue with photos. Reed valves this time.

rollmyown

More photos. 2 bbl rotary barrel. I included my prop hub for size comparison. The hub is 1.5" long. The smaller section of the carb barrel is the primary and the larger diameter is the secondary. The needle going through it is not removable to modify this item and now I don't think it is necessary. I made the Prob Hub from Fortal, it is harder than 6061, which I wanted for the same reasons Rhysium stated. The rear of the hub has 8mm x1mm threads, 1/2" of them and the front of the hub, 1" long, has 5/16"x24TPI threads. These two thread are familiar enough looking that i didn't want to have prop bolts of both types and risk mixing them up. I use the 5/16x24 bolts on other engines also. This will keep it simpler at the field during a flying session. (I can screw up enough without adding possibilities, excuse the pun.)

rollmyown

More photos. Square exhaust port and one of the directional intake ports.

Scott Ellingson

My Feedback: (146)

If you look on the top of the carb. In the center you will see a small white plastic plug set inside the hole. Remove that plug and you can adjust the low end needle for a good low idle. I had one idleing very slow and reliably by doing that. The high speed on the other hand is a fixed jet. No way to adjust it. You can only drill it or change it. This will also work on the 1bbl models with the walbro WYJ carbs. Some have them instead of Zama carbs.

rollmyown

More photos. Cylinder with piston at BDC (bottom dead center) and you can see that it does not fully open the intake ports. Originally the top of the piston cut the port in about half, I now have enlarged the upper half. The second photo is the carb body, fingers for comparison. I have actually enlarged the upper half of the ports more than is shown here.

rollmyown

More photos. Intake port (with flashlight lighting) which can go larger than this if intake manifold was not a limit to it. Look familiar, Scott. The second shows opening to crankcase, that is all there is, two, and I worked these over as I am sure Scott does. This is what made me think about getting more use out of the intake tubing to the upper ports and the 2 bbl carb.

Scott Ellingson

My Feedback: (146)

Here are a couple pis of what I did to the intake and boost ports. I close off the reed valve ports and make an intake to fit. I use 11mm carbs and run remote pulse. I deepen the boost ports and clean up the hole on the bottom like you did. I just mill the whole port almost 1/8" deeper. There is plenty of aluminum to work with there.

Scott Ellingson

My Feedback: (146)

Actually the pictures I showed are of the first one I did. I now go larger on the intake port and deeper on the boost ports. The pictures shown are not the same as I do now. Just an idea of how i do them. I think the 1 bbl models may be easier to work with. I have 20 of them now i just bought so I will find out. The intake port is already massive so just the exahust will need some work. Also the bottom of the boost ports will bet some milling and the deck of the case to match the boost ports. I am also going to run a 12.7mm carb on them to see what a difference that makes.

Scott Ellingson

My Feedback: (146)

I copied your picture of the bottom of the cylinder. I marked in yellow another thing you can do to make a little better flow. It is what i do. Cut the hole open right up to the cylinder wall. It will hurt nothing. I just use a dremel.

davewallace

My Feedback: (29)

Hi,
Great pictures. Making thr transfers deeper was the first thing that I thought of when I seen the picture of the 2bbl cylinder.

Dave

rollmyown

Thanks for the info Scott, but I'll pass on drilling jets. I know from automobiles that it is tricky. I think the 2bbl carb has more potential for us than the 1bb. Now I think it might be of use on other engines with custom intake spacers. As you no doubt haver found out, you can easily change these carbs from "push" operation to "pull" operation for a servo, but the spring pressure is fairly stout. I correct this by moving the anchor point for the coil return spring. I will try to photograph this.