Input needed on flywheel damage.

[DangerBoy]

There is no way I would run that flywheel

It already slipped once and sheared the key ,

thats the problem about a taper lock system between dis-similar metals.
as the alum flywheel gets warm it expands away from the taper at a greater rate than the steel crank nose . its actually a self losening system and Unless heavy pressure (not a bolt) is constantly applied seating the taper this happens


hope this helps with your decision

Db

 

[yamanube]

There is no way I would run that flywheel

It already slipped once and sheared the key ,

thats the problem about a taper lock system between dis-similar metals.
as the alum flywheel gets warm it expands away from the taper at a greater rate than the steel crank nose . its actually a self losening system and Unless heavy pressure (not a bolt) is constantly applied seating the taper this happens


hope this helps with your decision

Db

Very much, thank you.

 

[WFO Speedracer]

By 100% reliability I was referring to 100% reliability of the wheel before the damage.

One more time if it was 100% reliable there would be no damage.:1zhelp:

 

[yamanube]

One more time if it was 100% reliable there would be no damage.:1zhelp:

Unless it was not properly installed :twak:

 

[Millertime]

I would lap it, I have seen much worse be fixed by lapping. I would suggest lapping all flywheels even if just a bit with fine compound.

 

[WFO Speedracer]

Unless it was not properly installed :twak:

Wouldn't that one be on you ,just saying :spankme:

 

[yamanube]

Wouldn't that one be on you ,just saying :spankme:

Negative, I purchased the wheel in this condition.

 

[the WaTeRhAwK]

Okay here is the deal,the key does nothing except locate the flywheel in position while you tighten it down,the taper on the other hand is what holds the flywheel on ,not the flywheel bolt,that looks usable but you need to lap the flywheel onto the taper with lapping compound ,that can be done in the boat but would be easier if you just removed the engine.

actually terry, that keyway is more than just locating system. the keyway and key is to keep the flywheel from spinning once it's tightened down, while a lapped and smooth contact surface ensures a balanced and reinforced holding of the flywheel in place. tightening the wheel only keeps it from moving forward on the shaft, and only reinforces the keys' ability to keep it from spinning. the only way that flywheel could be useable is if he lapped it enough to move the key farther forward on the shaft, unfortunately, that will bring it too close to the stator plate, and the key too far towards the end of the wheel, and the pickup coil will probably rub the wheel.
the problem with that flywheel is a direct result of not lapping and tightening it correctly to begin with, and I agree with the "paperweight" statement.

get another flywheel, and install it correctly by lapping with medium grade lapping compound to a pre steel wheel-lapped and clean shaft.

that wheel was probably installed with the boiling method with no lapping prior to install.

 

[#ZERO]

Negative, I purchased the wheel in this condition.

Send it back!... those aluminum flywheels are know for coming loose and with the taper/keyway screwed up you can pretty much guarantee it will happen again.

 

[the WaTeRhAwK]

There is no way I would run that flywheel

It already slipped once and sheared the key ,

thats the problem about a taper lock system between dis-similar metals.
as the alum flywheel gets warm it expands away from the taper at a greater rate than the steel crank nose . its actually a self losening system and Unless heavy pressure (not a bolt) is constantly applied seating the taper this happens


hope this helps with your decision

Db

there are a lot of people that will disagree with that statement based on the idea that a water-cooled engine will not produce enough heat in that area for that to occur, however, you are correct. with as much heat that is generated through combustion, friction between the pistons and cylinder walls, and bearings, even with good lubrication, there is no possible way that the heat is not transferred through the shaft to that area. plain and simple.

an engines' "core" running temperature has very little to do (if much at all) with the water-cooled areas of it. most people think that because it's not cooking the seals or burning grease that it doesn't get hot enough, because of airflow through that part of the engine. the heat produced still transfers to somewhere, and there is no airflow around that part of the motor.

 

[WFO Speedracer]

actually terry, that keyway is more than just locating system. the keyway and key is to keep the flywheel from spinning once it's tightened down, while a lapped and smooth contact surface ensures a balanced and reinforced holding of the flywheel in place. tightening the wheel only keeps it from moving forward on the shaft, and only reinforces the keys' ability to keep it from spinning. the only way that flywheel could be useable is if he lapped it enough to move the key farther forward on the shaft, unfortunately, that will bring it too close to the stator plate, and the key too far towards the end of the wheel, and the pickup coil will probably rub the wheel.
the problem with that flywheel is a direct result of not lapping and tightening it correctly to begin with, and I agree with the "paperweight" statement.

get another flywheel, and install it correctly by lapping with medium grade lapping compound to a pre steel wheel-lapped and clean shaft.

that wheel was probably installed with the boiling method with no lapping prior to install.

You are wrong on that one,the flywheel is a press fit onto the crankshaft,that is why you must use a puller to remove it ,the bolt only pulls the flywheel onto the taper and the keyway only locates the flywheel while you tighten it down.A good friend of mine who builds golf cart engines and sells them all over the US does not use flywheel keys on the engines he sells.He discovered variations in the timing on the flywheels when supposedly they were all the same,he times the flywheel up where he wants it and tightens it down with no key.Now before you get all into the fact that those engines don't turn any RPM I will go ahead and say you are correct but the flywheels weigh a ton compared to what we are running,more weight means more inertia,which would make the heavier flywheel more apt to spin on the crankshaft,so far he has never had a problem with his engines getting out of time.

 

[the WaTeRhAwK]

You are wrong on that one,the flywheel is a press fit onto the crankshaft,that is why you must use a puller to remove it ,the bolt only pulls the flywheel onto the taper and the keyway only locates the flywheel while you tighten it down.A good friend of mine who builds golf cart engines and sells them all over the US dose not use flywheel keys on the engines he sells.He discovered variations in the timing on the flywheels when supposedly they were all the same,he times the flywheel up where he wants it and tightens it down with no key.Now before you gt all into the fact that those engines don't turn any RPM I will go ahead and say you are correct but the flywheels weigh a ton compared to what we are running,more weight means more inertia,which would make the heavier flywheel more apt to spin on the crankshaft,so far he has never had a problem with his engines getting out of time.

I understand what you mean terry, the thing is, the "press-fit" of the wheel is only to reinforce the keys ability to keep it from spinning. if you were to remove that key and visually line up the keyways and press fit the wheel without the key installed, regardless of how tight you get that wheel pressed onto the shaft, (especially with an aluminum wheel) you will get contrary centrifugal movement between the shaft and the wheel. simply due to the weight of the flywheel, added with what little contact surface there is between the two, vs. the outer leaverage the weight of the wheel has over the centrifuge at the conjoining of the two parts during high and continual fluctuations in rpms.

not to mention, a golf cart engine wouldn't exhibit nearly the amount of stress in that area as these engines do.

 

[DangerBoy]

Guys
look up the difference between a locking taper 2-3 deg (Golf Cart)
and a releasing taper 16 deg (superjet)

than compare the Yamaha flywheel

701 needs a keyway
Golf cart doesnt

 

[the WaTeRhAwK]

Guys
look up the difference between a locking taper 2-3 deg (Golf Cart)
and a releasing taper 16 deg (superjet)

than compare the Yamaha flywheel

701 needs a keyway
Golf cart doesnt

this is why there is no woody key on the old 400 and 440 cranks, holding the press-fit pto couplers in place.
and even those will spin on you from time to time.

 

[WFO Speedracer]

I am telling you the flywheels on those are huge compared to what we are running,I can pretty much bet you if you tightened down the flywheel with no key and ran it it will not move unless something locked up the impeller suddenly or you jumed the boat and never let off the gas.

 

[the WaTeRhAwK]

I am telling you the flywheels on those are huge compared to what we are running,

I believe you, the thing is, even with the extra weight of those wheels compared to ours, those engines don't stress that area as much as our engines do. also, I bet there's a lot more contact surface between the wheel and the crank on those engines.

 

[WFO Speedracer]

this should answer a few of your questions about lapping a flywheel,straight from Jetinetics website:
Charging Flywheel Technical Tips.

As is suggested in our assembly instructions, torque is the most important factor in maintaining your flywheel. It is suggested that you re-torque your newly installed flywheel after an hour of conservative riding, and after about 2-3 hours. Regular inspection should take place after each session of riding and should include inspection of the ring gear, bore, keyway and woodruff key. Any unusual conditions should prompt a call to our technical department for an evaluation or suggestions on repairs.
A foul rumor was started sometime in 1994 that "boiling" the flywheel before installation was beneficial, this could not be further from the truth. Boiling the flywheel can damage the magnets and cause the flywheel to fail during operation. Do not boil the flywheel! It is designed to be installed cold, run until warm and then re-torqued to final specifications. Please follow these directions.

It has been suggested by top engine builders like Harry Klemm of Group K and Bill O’Neal of Watercraft Magic, that lapping the flywheel to the crankshaft surface to better seat the flywheel mating surfaces can increase the life expectancy of the flywheel. We agree that this is a good practice, and due to the difficult nature of the process we have not recommended it to the general public. The process requires the use of 320 grit lapping compound spread between the flywheel and crankshaft surfaces (in the bore) and a gentle rotating motion applied to "grind" the inside surface of the flywheel so it matches the surface of the crankshaft. The compound can be obtained at a tooling supply house or automotive parts supply house. Once the anodized surface has disappeared, the compound should be removed and all surfaces cleaned thoroughly. The flywheel can now be torqued using the normal instructions.

650 Kawasaki and 650/701 Yamaha charging flywheels which have the new steel hubs have been engineered to take advantage of a new type of magnet which is extremely powerful. The magnets have an intense magnetic field which causes a slight retardation of the timing. It is recommended that the installer advance the timing on the stator plate approximately 5 degrees to offset this condition. The engine will appear sluggish otherwise. The timing should be set to factory recommendations using factory procedures or using a timing light. We also suggest checking the condition of the spark plugs for indications of detonation.

 

[the WaTeRhAwK]

yeah, I always thought the idea of boiling them was completely stupid. I understand why someone would say that it expands the metal, but the thing is, by the time you get it out of the boiling water and onto the ski, it will have already shrunk back to it normal position, before you get it tightened.

I've always lapped flywheels.