Hello all. I remember seeing an ad somewhere for keyway keys that are offset to advance the timing in small engines. Does anybody know where to get theese or have you even heard of theese? The only other way i can think of to change the timing would be to file the flywheel keyway slot and that seems kinda rinky dink. any help would be appreciated. thanks ..jonnybiker
Advance keys
- Thread starter jonnybiker
- Start date
Ok let me clarify myself a bit. I guess i need to buy theese keys mailorder as noone around here has heard of them. Also how many degrees advance do you use , i know it depends on fuel used and other engine mods but as a guide line how many degrees on a fairly stock motor? thanks for your help. Ive been a motorcycle mechanic all my life , but making theese little mini bike motors run hard is pretty new to me. Can anyone recomend any good small engine hop up guides or books? thanks much guys. p.s. seems to be alot of michiganders on this sight , your welcome to contact me im in hopkins just south of grand rapids and north of kalamazoo. jonnybiker
I don't even use a key in any of my engines. Simply use some valve lapping compound and lap the flywheel to the taper on the crank. Clean the compound off thourghly and put the crank where you want it. If using a starter clutch first find a nut that fits your crank and tighten Flywheel with an impact gun or break over bar if you can find a way to hold it.Then remove the nut and re-intsall the starter clutch. The key is only for locating the flywheel,the taper is what holds it in place.
I have been hearing that for years and it's total BS
The Honda and most all of the small engines have the correct taper in the flywheel that is cut perfect to fit the crank. Lapping the flywheel ONLY helps when the flywheel doesn't match the crank properly. When they both fit properly the only thing that holds the flywheel on, and stops it from spinning is 100+ lbs of torque. But it might spin before the flywheel is even tighten. It will usually turn on the first spin of the impact gun. If it doesn't thats good, but you will have to stop right there and check your timing. If it's out of time then you have to start over again.
The flywheel key holds it in place and keeps it from spinning out of time. Which is what you want in the first place.
To not use a offset flywheel key you would need to use a Degree Wheel, Pointer, Crank Holder, etc. Then if you get a good back fire when pull starting it. It will MAYBE twist out of time???????
Remember these flywheels are supposed to be torque down to 60 lbs with a key. To go way beyond that with a stock flywheel your asking for it. To get it off, is why a lot of karting companies need flywheel pullers.(100+lbs with billet flywheels)
The Honda and most all of the small engines have the correct taper in the flywheel that is cut perfect to fit the crank. Lapping the flywheel ONLY helps when the flywheel doesn't match the crank properly. When they both fit properly the only thing that holds the flywheel on, and stops it from spinning is 100+ lbs of torque. But it might spin before the flywheel is even tighten. It will usually turn on the first spin of the impact gun. If it doesn't thats good, but you will have to stop right there and check your timing. If it's out of time then you have to start over again.
The flywheel key holds it in place and keeps it from spinning out of time. Which is what you want in the first place.
To not use a offset flywheel key you would need to use a Degree Wheel, Pointer, Crank Holder, etc. Then if you get a good back fire when pull starting it. It will MAYBE twist out of time???????
Remember these flywheels are supposed to be torque down to 60 lbs with a key. To go way beyond that with a stock flywheel your asking for it. To get it off, is why a lot of karting companies need flywheel pullers.(100+lbs with billet flywheels)
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you never said what engine you have . . .
I wuld advise you to use an advance key and retighten the flywheel nut to factory spec.s
http://www.foxvalleykart.com/timing2.html
I will see if I can find a link for you to buy the keys
I wuld advise you to use an advance key and retighten the flywheel nut to factory spec.s
http://www.foxvalleykart.com/timing2.html
I will see if I can find a link for you to buy the keys
If you guys want to use advance keys be my quest. I won't waste any time on them. I check my timing by using a dial indicator on the piston. I never have any problem with the flywheel moving. I can promise you that the key don't hold anything. The taper is what holds the flywheel in place. Do what you want don't care.
I would like to qualify my suggestion
1.he said he was new to this so timing a engine with a deg. wheel and dail guage timing light or what ever seems to be a bit much
2.he never said what engine he had so its hard to point him in the right direction as to what and where for buying a key just call a kart shop and ask Im sure they can get you what you need
3.torque this is simple torque it to factory spec.s most flywheels are mounted on a tappered shaft over torqueing will have the same effect as a log splitter to your flywheel
4.lapping compound . . . its true it will help match your wheel to your shaft and this is good for two reasons the first and most important is it will remove the high spots and increase surface contact and relieve stress points. also depending on what grit you choose you may change the surface finish a slightly rougher finish tends to resist slipping more ...
make sure you remove all the laping compound
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Or you can throw in an advance key of your choice and torque it back up and be done
1.he said he was new to this so timing a engine with a deg. wheel and dail guage timing light or what ever seems to be a bit much
2.he never said what engine he had so its hard to point him in the right direction as to what and where for buying a key just call a kart shop and ask Im sure they can get you what you need
3.torque this is simple torque it to factory spec.s most flywheels are mounted on a tappered shaft over torqueing will have the same effect as a log splitter to your flywheel
4.lapping compound . . . its true it will help match your wheel to your shaft and this is good for two reasons the first and most important is it will remove the high spots and increase surface contact and relieve stress points. also depending on what grit you choose you may change the surface finish a slightly rougher finish tends to resist slipping more ...
make sure you remove all the laping compound
.
.
Or you can throw in an advance key of your choice and torque it back up and be done
Let me expound on this topic, since it has come up, and happens to be my area of expertise...
Tapered shafts/bores are designed to mount components like flywheels with precise depth location and zero clearance to prevent wobble...
A flywheel mounted on a straight shaft would need to be clearance-bored, meaning the ID of the flywheel bore would need to be larger than the OD of the shaft...
This would produce wobble...
To eliminate this wobble, the ID and OD would need to be the same, and the flywheel would have to be press-fitted onto the shaft...never to be removed without damage...
A tapered bore provides precise depth location, allowing the flywheel to be positioned precisely onto the shaft, as well as a zero-clearance, non-wobbling fit between flywheel and shaft without press-fitting...
This zero-clearance tapered bore is not designed to retain the flywheel on the shaft during rotation...over-tightening of the retaining nut can actually deform (crush) the taper bore, creating wobble...
Retaining nuts should never be over-torqued past the manufacturer's specifications for the material used to make the flywheel...
The most efficient method to keep the flywheel from spinning on the crankshaft is to use a keyway machined into the shaft and flywheel, and a key made of a material meant to shear if the engine RPM is suddenly stopped...
This allows the inertia of the flywheel to shear the key and dissipate without damaging the internal components of the engine...
Tapered shafts/bores are designed to mount components like flywheels with precise depth location and zero clearance to prevent wobble...
A flywheel mounted on a straight shaft would need to be clearance-bored, meaning the ID of the flywheel bore would need to be larger than the OD of the shaft...
This would produce wobble...
To eliminate this wobble, the ID and OD would need to be the same, and the flywheel would have to be press-fitted onto the shaft...never to be removed without damage...
A tapered bore provides precise depth location, allowing the flywheel to be positioned precisely onto the shaft, as well as a zero-clearance, non-wobbling fit between flywheel and shaft without press-fitting...
This zero-clearance tapered bore is not designed to retain the flywheel on the shaft during rotation...over-tightening of the retaining nut can actually deform (crush) the taper bore, creating wobble...
Retaining nuts should never be over-torqued past the manufacturer's specifications for the material used to make the flywheel...
The most efficient method to keep the flywheel from spinning on the crankshaft is to use a keyway machined into the shaft and flywheel, and a key made of a material meant to shear if the engine RPM is suddenly stopped...
This allows the inertia of the flywheel to shear the key and dissipate without damaging the internal components of the engine...
agreed this is why most briggs engines use aluminum keys
they tend to shear half way and ruin spark timing but it helps save the rest of the rotating assy.
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remember most of these engines were intended for home and garden & construction equipment where the drivetrain could encounter a stump or sprinkler head or something else that could instantly stop everything (thats a lot of energy)
they tend to shear half way and ruin spark timing but it helps save the rest of the rotating assy.
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remember most of these engines were intended for home and garden & construction equipment where the drivetrain could encounter a stump or sprinkler head or something else that could instantly stop everything (thats a lot of energy)
I have ran 5 hp Briggs 8700 rpm on an oval track without any flywheel keys. None of the modified motors I have built have I used a key. I have been doing this for 20 years. Funny how all of sudden it won't work according to you folks. As you said the flywheel needs to seat in order to stay in place. The key is only a means to locate the flywheel. Not hold it. I'm a machinist by trade. Many of the machines I have ran use nothing other than the taper to hold the adapter in place. Same thing applys to a flywheel.
The moderators and supporting members of this site have a responsibility to point out tips and techniques described in posts that are potentially harmful to persons and equipment...
As you said, you may do as you like...but those of us with mechanical engineering backgrounds will point out that this may be unsafe, and incorrect according to established engineering principles...
As you said, you may do as you like...but those of us with mechanical engineering backgrounds will point out that this may be unsafe, and incorrect according to established engineering principles...
Your way isn't wrong. But it's just to difficult for a novice builder just trying to learn simple how-to-do's.
Below is a flywheel I had cut the taper to match the Honda crank taper. Then I took a few steps like cut a new key way broach to have the timing at 28 degrees BTDC with a stock key and the coil at the stock location. I also wanted the flywheel to set slightly farther away from the block. That way the magneto will line up correctly with the adapter behind it.
Sure I could have told him in exact detail how-I-did-it. But it's something he has no use for.
BTW those modified engines you said you have built doesn't count. The reason why is because those are started by a electric starter. Hey, I know you think it doesn't matter but it does. The electric starter will only spin one-way. It doesn't have any weak point, so it won't allow the motor to snap back and recoil. Pull starting is a different story. If you were to pull start a modified flathead briggs and it snap back. It will most likely snap back on the weak point of your pull. Normally as your rope is completely unwind. Then it snaps right out of your hand, because it doesn't have enough pulling force to make it pass the power spark/powerstroke. The snap-back causes the motor to turn backwards instantaneously. Usually snapping the flywheel key, or turning the lapped on flywheel.
And this is why lapped on flywheels have over 100+++ lbs of torque on them. And a billet flywheel is needed to keep the stock flywheel from cracking from heavy impact guns or high torque settings. Even with all that torque on the flywheel it will still jump out of time pull starting:sadcrying4:
Get mad all you like. This is not an opinion, this is a fact!
Below is a flywheel I had cut the taper to match the Honda crank taper. Then I took a few steps like cut a new key way broach to have the timing at 28 degrees BTDC with a stock key and the coil at the stock location. I also wanted the flywheel to set slightly farther away from the block. That way the magneto will line up correctly with the adapter behind it.
Sure I could have told him in exact detail how-I-did-it. But it's something he has no use for.
BTW those modified engines you said you have built doesn't count. The reason why is because those are started by a electric starter. Hey, I know you think it doesn't matter but it does. The electric starter will only spin one-way. It doesn't have any weak point, so it won't allow the motor to snap back and recoil. Pull starting is a different story. If you were to pull start a modified flathead briggs and it snap back. It will most likely snap back on the weak point of your pull. Normally as your rope is completely unwind. Then it snaps right out of your hand, because it doesn't have enough pulling force to make it pass the power spark/powerstroke. The snap-back causes the motor to turn backwards instantaneously. Usually snapping the flywheel key, or turning the lapped on flywheel.
And this is why lapped on flywheels have over 100+++ lbs of torque on them. And a billet flywheel is needed to keep the stock flywheel from cracking from heavy impact guns or high torque settings. Even with all that torque on the flywheel it will still jump out of time pull starting:sadcrying4:
Get mad all you like. This is not an opinion, this is a fact!
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with a key and and factory torque works
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lapped and without a key and factory torque works also. but skill and understanding are required
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never over torque
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also it is best to buy a billet flywheel if you plan on reving the engine past 5000 rpm this is a consservitive figure but it may prevent broken flywheel parts from installing them selfs in your crotch
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lapped and without a key and factory torque works also. but skill and understanding are required
.
never over torque
.
also it is best to buy a billet flywheel if you plan on reving the engine past 5000 rpm this is a consservitive figure but it may prevent broken flywheel parts from installing them selfs in your crotch
KB2Rocket we are currently running this "King Of The Alley" trophy race every weekend. The main rule is the engine must be pull start. Any engine size is allowed, and you are allowed to run any fuel you like.
So far there is nothing bigger then a 206cc OHV. But there are 2 bored and stroked flathead 5hp briggs running in this class.(approx 280cc) The flatheads are still hard to start, but not as hard as a large OHV motor. The flatheads just don't have the static compression like the OHV's do.
The stroker Animals, and 305 briggs can't be pull started because of there aftermarket cams, and higher compression. The flathead briggs flywheels have offset keys and are torque to factory spec's. But they are still carefully pull started right at the compression stroke to stop the snap back. The OHV's usually breaks the pull start right off the motor. Billet flywheels are worse because the stronger magnet makes for a harder snap back. Running alky also makes for a harder snap back too.
So far there is nothing bigger then a 206cc OHV. But there are 2 bored and stroked flathead 5hp briggs running in this class.(approx 280cc) The flatheads are still hard to start, but not as hard as a large OHV motor. The flatheads just don't have the static compression like the OHV's do.
The stroker Animals, and 305 briggs can't be pull started because of there aftermarket cams, and higher compression. The flathead briggs flywheels have offset keys and are torque to factory spec's. But they are still carefully pull started right at the compression stroke to stop the snap back. The OHV's usually breaks the pull start right off the motor. Billet flywheels are worse because the stronger magnet makes for a harder snap back. Running alky also makes for a harder snap back too.
All my comments are in reference to Jonnybiker's post
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its actualy quite funny that this thread has become another one of those Im right and your wrong theads
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meanwhile Jonnybiker just wants some offset keys for his motor and he isnt even posting anymore
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MiniBikes are Toys and Toys are fun but they really are not very important so lets not argue over our toys lets get back to enjoying them
happy holidays
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its actualy quite funny that this thread has become another one of those Im right and your wrong theads
.
meanwhile Jonnybiker just wants some offset keys for his motor and he isnt even posting anymore
.
MiniBikes are Toys and Toys are fun but they really are not very important so lets not argue over our toys lets get back to enjoying them
happy holidays
Now in reference to your King of the alley race I have a 440cc snowmobile engine that pull starts Im guessing if some one showed up with a old 2 cylinder pull start snowmobile bike with a torque converter set up they would do quite well ... but with the money it would take to build one you could buy a really nice trophy