I HAVE SPENT A LOT OF HRS ON ONE OF THESE SINGLE BARREL MODEL TOROS. IT WONT GO OVER 6500 RPM WITH OR WITHOUT A STOCK MUFFLER. IVE DONE EVERYHTING THAT I CAN THINK OF BUT NO GOOD. THERE NOT ENOUGH MATERIAL OVER THE EXHAUST PORT TO RAISE IT THE .140 TO GET THE TIMING RITE AFTER I LOWER THE JUG .040. I CUT OUT THE FIN OVER THER PORT AND MADE AN ALUMINUM FILLER BLOCK SO THAT WHEN I RAISED THE PORT THERE WOULD BE ENOUGH MATERIAL SO IT DIDINT COME THROUGH. I NOW HAVE .O25 HEADSPACE BETWEEN THE PISTON AND THE HEAD, EX TIMING IS 98 ATDC. I MACHINED THE BOTTOM OF THE PISTON SHIRT TO GET 108 ABDC ON THE INTAKE PORT. I HAVE TRIED 4 DIFFENT CARBS 8MM, 2-9MM, 11MM. ALL HAVE THE SAME PROBLEM. I HAVE TO GET UP HIGH RPM BY HOLDING MY FINGER IN THE VENRURI TO CHOKE IT THROUGH THE LEAN SPOT. TWO OF THESE CARBS ON MY ECHO 23.6 CONVERSION TURN 7600 AND 7800RPM'S. SAME 16-6 PROP ON BOTH ENGINES. IVE CHANGED PLUGS WITH DIFFERENT GAPS, CHANGED MAG COILS. I DONT KNOW IF OF YOU HAVE PUT A TIMING LITE ON ANY OF YOUR ENGINES BUT THESE 2 COILS HAVE TIMING ADVANCE BUILT INTO THEM SOMEHOW. AT LOW SPEED I HAVE 21 DEGREES AND AT HIGH I HAVE 31 DEGREES. I HAVE NO IDEA HOW THIS WORKS IT MUST BE SOME KIND OF MAGIC. IF IVE MISSED THE BOAT HERE SOMEWHERE GIVE ME SOME IDEAS. THIS THING SHOULD BE PERFECT BUT ITS REAL TERD ,[&o]THE SMALLER ECHO THAT I HAVENT DONT THE COMPRESSION OR THE PISTON INTAKE MACHINE WORK YET PUTS IT TO SHAME. THIS TORO TURNED 6500RPM STOCK AND ITS STILL TURNS 6500 WITH ALL THE HI TECH MODS. ONLY THING I HAVENT CHANGED IS THE FLYWHEEL, MAYBE WEAK MAGNETS?? I GOT 800 TO 1000RPM WITH ONLY A CARB CHANGE AND RAISING THE EXAUST PORT .100 ON MY ECHO! THE OTHER TORO THREAD HAS GOTTEN TO LONG SO I THOUGHT IT WAS TIME TO START A NEW ONE

The last time I had this happen to me, it turned out that after all my high-tech trickery, I had neglected to check the piston ring gap. Embarrassing but true. A new ring from Frank Bowman brought the engine right into the power I had expected. Ring gap should be approximately .003". (That's a really tiny gap!!)

I'm assuming you've provided plently of exhaust exit to compliment your other changes that allow the engine to breathe better. I completely gut the stock muffler, then add two 1/2" i.d. exit tubes.

As a reference, my highly modified Echo 23.6cc turns an APC 16 x 8 prop at 9000, and my souped up Homelite 30cc turns the same prop at 9400 or so. My modified Homelite 25cc turns that prop at about 8500.

Good luck,
AV8TOR

Hi teddy,
When you lowered the cylinder, you also lowered the transfer ports as well as the exhust. I beleive that the small transfers are the weak link in the 1bbl engine. Also the piston skirt blocks the transfer passages at the bottom of the stroke. If you havn't raised the transfer ports, the their timing is very retarded now, as it was only 51 degrees BBDC stock. You could have a rpm limiter circuit in your coils, but it doesn't sound likely, since you tried several. Have you ever got over 6500 rpm with any Toro? Here is a G23/26 piston pic.

Dave

THIS IS MY FIRST TORO SO I HAVE NOTHING TO COMPARE IT TO EXCEPT WHAT IVE READ THAT ALL YOU GUYS ARE GETING FROM YOUR TORO'S. RING END GAP IS GOOD. TRANSFERRES ARE STILL STOCK AND I DIDNT CHANGE THE BOTTOM OF THE TRANSFER OPENINGS. THATS A GOOD POINT! TRANSFERES SHOULD BE IN THE MID 60 DEGREE MARK?? ARE YOU SAYING THAT THE BOTTOM OF THE TRANSFERES ARE SHIELDED BY THE PISTON SKIRTS? DO YOU MAKE THE TRANSFERS ANY WIDER OR DEEPER OR JUST HIGHER?
FARMER TED

Hello Ted,
I don't have a lath so I didn't shave the bottom of the cylinder. They have great compression any way. When you pull the cylinder and put the piston at the bottom of the stroke it is obvious that the skirt is blocking the transfer. Major modifications can decrease performance. All of the related variables must be considered. The cylinder doesn't have much meat around the ports to allow enlargement. Here is a picture of the piston at BDC.

Dave

I CHECKED THE TRANSFER TIMING AND IT WAS 41 DEGREES SO I PULLED IT APART AND PUT IT BACK IN THE MILL TO RAISE THEM. I NOW HAVE 58 DEGREES. I ALSO CUT THE WHOLE PISTON SHRIT UP TO ALMOST THE LEVEL OF THE INTAKE SKIRT FELIEF I CUT INTO THE PISTON SKIRT. IM GOIN AWAY FOR A FEW DAYS NOW SO I WONT GET A CHANCE TO TEST IT TILL NEXT WEEK. IM VERY INTERESTED TO SEE HOW IT WORKS THIS TIME. DOES ANYONE KNOW ANYTHING ABOUT THIS TIMING ADVANCE BUILT INTO THESE MAGS AND IS THERE A REV LIMITING SYSTEM BUILT IN TOO? I WONT GIVE UP ON THIS THING.
FARMER TED

Wish I had a mill and a lathe.

I'd be a hub turnin', mag shavin' cylinder portin', cylinder shaving, piston notchin' FOOOOOOOOLL!![:-]

Your a lucky man to have that stuff.

Hi Teddy,
Once you get the engine to run cosistantly, you can run it with a smaller prop and if the rpm doesn't go up you are rev limited. Make sense? You don't even need an accurate tach since you are comparing numbers from the same tach.

Dave

I RAN MY TORO I BBL TODAY WITH THE TRANSFER PORT MACHINE WORK DONE AND I THINK ITS GOT IT NOW. IM TESTING WITHOUT ANY MUFFLER. WITH A 20/64 CARB IT NOW TURNS 7850RPM AND WITH A 24/64 CARB I GET 8350RPM. THAT A GOOD RESULT FROM RAISING THE PORTS UP TO 58 DEGREES. WITH EITHER CARB IT ONLY TURNED 6500RPM BEFORE THE MACHINE WORK. ID LIKE TO TRY A 4/64 BIGGER CARB TO SEE IF THERE IS MORE IN THERE BUT I DONT HAVE ANYTHING IN THAT SIZE YET. SO ILL MAKE ANOTHER POST WHEN I FIND A CARB. IM OPEN FOR ANY OTHER SUGGESTIONS FROM YOU GUYS FOR ME TO TRY ON THIS BABY. I WAS WORRIED WHEN I STARTED OUT THAT THIS THING WAS A TERD BUT I THINK IT HAS EVEN MORE POTENTIAL.
FARMER TED

Ted,
Remember that the porting didn't work until you cut down the skirt. More of that weakest link thing.

Dave

CAPS LOCK is hard to read mate!!
It is the internet equivalent of shouting, so please turn it off.
Nice thread though.
Cam

sorry bout the caps BUT IM NOT AN OFFICE WORKER IM AN OLD FARMER THAT IS HARD OF HEARING FROM SITTIN ON A TRACTOR FOR 45YRS AND EVEN WHEN I PRINT BY HAND ITS ALL CAPS. TO EACH HIS OWN. IM NOT SHOUTIN IM JUST BEING MYSELF.
TORO TECH:
THERE ARE STILL A FEW THINGS THAT THE COMUNITY CAN HELP WITH.
WHAT MM CARB THROAT IS WORKIN FOR YOU?
ANYONE ELSE FIND THESE MAGS HAVE 10 DEGREES OF TIMING BUILT IN?
HOW MUCH MORE CAN WE GO ON THE PORT TIMING?
.025 COMPRESSION HEADSPACE
98 ATC EX PORT
108 IN. PISTON SKIRT
58 TRANSFER PORTS ALL 4 SAME TIMING
PISTON SKIRT ON TRANSFER SIDE RAISED .100 FOR A RPM INCREASE OF ONLY 400RPM. THE BIG RPM CHANGE WAS THE TRANSFER PORT CHANGE FROM 41 TO 58 DEGREES.
I DONT WANT TO BORE YOU GUYS THAT ARE HIGH TECH INTO ENGINES NUTS AND BOLTS BUT LET ME TECH SOME OF YOU ON HOW TO CHECK THE IGNITION TIMING WHILE RUNNING!?
FIRST YOU NEED TO FIND TDC
USE A PIECE OF 1/8 SOLDIER WIRE BENT 90 DEGEREES AND INSERTED INTO THE SPARK PLUG HOLE.
TURN THE ENGINE C.W UNTIL IT STOPS, PUT A PIECE OF TAPE ON THE FLYWHEEL UNDER THE COIL MAGNET PICKUP ABOUT 2 INCHES LONG WITH THE 2IN. PART HANGIN OUT TO THE LEFT OR CCW DIRECTION. (OR JUST MAGIC MARKER THE FLYWHEEL ITS EASIER)
NOW HOLD THE SOLDIER IN THE SAME PLACE IN THE PLUG HOLE AS BEST YOU CAN AND TURN THE FLYWHEEL CCW UNTIL IT STOPS AND MAKE ANOTHER MARK UNDER THE COIL ON FLYWHEEEL OR TAPE.
NOW PUT A MARK IN THE CENTER OF THOSE 2 MARKS A CLOSE AS YOU CAN AND THIS IS TDC.
NOW FROM THE TDC MARK WHICH SHOULD BE RITE UNDER THE STATIONARY COIL PICKUP WHICH WILL BE YOUR TIMING MARK POINTER, MEASURE 5/16 TO THE LEFT OR CCW. DIRECTION AND MARK THE FLYWHEEL THERE. THIS IS 10 DEGREES ADVANCED
NOW DO THE SAME THING 2 MORE TIMES WHICH WILL BE 20 AND 30 DEGREES ADVANCED.
NOW GET ANY OLD KIND OF STROBE TIMING LITE (WE ALL HAVE 1 FROM OUR HOTRODING DAYS) OR BUY 1 AT A GARAGE SALE FOR CHEAP BECAUSE NOBODY USES THEM ANYMORE.
IM OUT OF SPACE ILL DO ANOTHER POST TO FINISH

TIMING YOUR TORO 101 CONTINUED

NOW HOOK THE 2 POWER LEADS OF THE TIMING LITE TO YOUR 12V. STARTER BATTERY AND THE LARGE SPARK SENCING LEAD IN BETWEEN THE PLUG AND THE COIL WIRE.
NOW START THE ENGINE (BE CAREFUL OF ALL THOSE WIRES HANGIN AROUND THE PROP) AND IF YOURS ARE THE SAME AS MINE IT WILL RUN ON THE 20 DEGREE MARK AT LOW SPEED AND THE 30 MARK AT HIGH SPEED. MAGICAL BUILT IN TIMING!!! I HOPE SOMEONE CAN EXPLAIN HOW THEY DO THAT TO THIS OLD FARMER. I HOPE I GOT ALL THE DIRECTIONS CORRECT ON THE MARK PLACEMENT. RITE AND LEFT AND CW AND CCW GETS CONFUSING.
LETS HEAR FROM YOU GUYS AND SEE IF I HAVE THE ONLY 2 THAT DO THIS ADVANCE THING. MY 23.6 ECHO DOESNT DO THIS, IT EVEN RETARDS 3 DEGREES AT HIGH RPM
SOMEONE POST WHAT THE EXTREME PORT TIMING WOULD BE BEFORE THE ENGINE ONLY SCREAMS AND WONT IDLE, MINE DOESNT IDLE AS GOOD AS IT DID BEFORE I STARTED (2300RPM) SO THERE IS A POINT AT WHICH YOU MAKE JUNK!!
SOMEONE SAID IN ANOTHER POST THAT THIS ENGINE MODIFICATION IS A HOBBY IN ITSELF AND I AGREE. I USED TO WORK WITH SB CHEVY RACING ENGINES BUT WHEN THE COST GOT TO $30,000 I GOT LEFT BEHIND SO NOW IM HAPPY AGAIN. I HAVE A $30 MOTOR TO PLAY WITH WHICH IS JUST WHAT I SPENT ON MY FIRST 283 SHEVY ENGINE BACK IN 65
FARMER TED

Ted,
Careful inspection of the one barrel engine transfer ports will show that the back two ports open slightly sooner the the front ports. This gets the upward flow started earlier in the rear of the chamber helping to scavage the burnt gases to promote a stronger recharge. The 11mm Walbro works well although the 12.7mm works as well. These are the same sizes used by the highly sucessful Zenoah G23 and G26 engines.

Dave