micky Posted March 12, 2008 Report Share Posted March 12, 2008 Feetup, Sorry for the delay in replying. My Maj is an over bored 320. I was not suggesting extra flywheel weight was a good idea but......I think lightening quick throttle response (like the first 240 Fantics and some of the rotax, enduro based motors that required two head gaskets etc.) is not always beneficial if the classic sections match the vintage of the Bikes (and riders in my case!) Plus, I did used to ride in Cumbria, North Yorks and North Lancs where annual rainfall is at a premium. Quote Link to comment Share on other sites More sharing options...
michaelmoore Posted March 13, 2008 Report Share Posted March 13, 2008 Old trials fanatic both the KT flywheel and one out of a TT500 Yamaha shoulr appear to have a steel outer casing. They definitely aren't brass (I can remember having a brass mag flywheel on a Ducati single, but it has been too many years for me to remember what my 1974 Sherpa T had) and someone who turned a TT flywheel to lighten if for a racer told me it was a steel that wouldn't chip, just make long strings of razor-sharp swarf so that he'd have to stop pretty frequently to break it off with some pliers. If you want to maximize the weight within a given diameter than brass is certainly what you'd use instead of steel, but it isn't a lot heavier. I just looked at prices at an online metal merchant and the prices for the same size (3" x .250" wall tube) in steel vs brass are $1.53 vs $12.06 per inch, so brass is almost 8X as expensive. They also don't go big enough in the brass tube they stock to make a ring for the flywheel. cheers, Michael Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 13, 2008 Report Share Posted March 13, 2008 Some people make it sound like they are using weights that bolt on to the outer face of the flywheel and others like they are referring to a ring shrunk on to the periphery of the flywheel. Did Yamaha use both methods? The Yamaha TY250 twinshock has a steel band fitted to the OD of a cup shaped steel magneto flywheel. The Yamaha TY175 motor has a flat steel plate fitted to the outside face of a cup shaped steel magneto flywheel. Quote Link to comment Share on other sites More sharing options...
michaelmoore Posted March 13, 2008 Report Share Posted March 13, 2008 Thanks for the clarification. cheers, Michael Quote Link to comment Share on other sites More sharing options...
matty Posted March 13, 2008 Report Share Posted March 13, 2008 How would you go about removing some or all of the weight of the flywheel on a ty 175 ? If removing some how much? or is it a suck it and see job. Thanks Matt.. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 14, 2008 Report Share Posted March 14, 2008 Yes just machine a bit off at a time, testing between cuts. It doesn't take much change in the size of the weight to make a noticable difference to the engine pickup. In the case of the TY175, I would make the weight thinner rather than reduce the OD (the metal at the OD of the weight provides the most flywheel effect for the least mass). Quote Link to comment Share on other sites More sharing options...
michaelmoore Posted March 14, 2008 Report Share Posted March 14, 2008 It varies as the square of the radius, so the material right next to the crankshaft isn't doing much. Experimenting does require that you have ready access to a lathe or mill and you'll probably want to make up a faux crankshaft arbor to mount the flywheel to so you can run it between centers on a lathe and reduce the likelihood of machining it eccentrically. And if you take too much off you've got to figure out how to put it back. It wouldn't hurt to do a static balance test after you have done a bit of shaving away at the flywheel. cheers, Michael Quote Link to comment Share on other sites More sharing options...
Guest majestyman340 Posted March 14, 2008 Report Share Posted March 14, 2008 It varies as the square of the radius, so the material right next to the crankshaft isn't doing much.Experimenting does require that you have ready access to a lathe or mill and you'll probably want to make up a faux crankshaft arbor to mount the flywheel to so you can run it between centers on a lathe and reduce the likelihood of machining it eccentrically. And if you take too much off you've got to figure out how to put it back. It wouldn't hurt to do a static balance test after you have done a bit of shaving away at the flywheel. cheers, Michael Whats a static balance test Mike, and would this be worth doing on any older bike? Quote Link to comment Share on other sites More sharing options...
michaelmoore Posted March 14, 2008 Report Share Posted March 14, 2008 It is the same thing you do when balancing a wheel. Put it on an arbor/axle on a stand with rollers for the axle to ride on and see if there is an obvious heavy spot. You've probably seen different flywheels (both mag and crankshaft) on bikes that have little drilled dimples on them where a small amount of metal has been removed to bring them into balance. If you've got a wheel balancing stand handy you are probably set once you make an arbor to hold the flywheel. Instead of going straight for the drill try sticking small lumps of clay on the side opposite the heavy spot until you get it to remain stationary in any position. You can get an idea from the clay of how much weight needs to be removed from the heavy spot. And of course, take a little less than you think is needed to start, and keep checking as you go along. The factories that make the flywheels probably have a dynamic balancing machine that spins the flywheels up and detects the out of balance spots, but that would be mainly to speed up the process. A static balance should be fine and you can do it at home. I'd presume that any factory part is probably OK and I wouldn't routinely check an OEM flywheel, especially if it looks like it has already been balanced. But I've taken apart some Japanese forks that came from the factory with the wrong bottoming cone on the damper rod that blocked off the bottom orifice on the rod, and I remember a /5 or /6 BMW that came into the dealership I worked at in the early 1970s that had the rear hub only partially machined, so even factories can screw up. That's why race tuners check everything in an engine, make sure all the rods are balanced and weigh the same, combustion chambers all match, brake pistons are retracting properly so the pads don't drag, etc. If you've got an aftermarket weight that bolts on to the face of the flywheel that weight might be perfectly made and perfectly in balance. But if the holes on the flywheel that it bolts on with or registers to are a bit off then the assembly is going to be out of balance. Or what if one of the three bolts that hold it on came from a different fastener manufacturer and is 1 or 2 mm longer or shorter than the others or has a little longer or shorter threads? 1mm off the bolt might not be much, but if it is out near the rim of the flywheel and you spin it up to 6000 rpm it might cause enough imblance to be significant. Might not too. A lot of the checking is done just so you know. A problem is that if you do find something out that you think should be fixed you then get stuck having to decide if you are going to do anything about it. Ignorance can bring bliss. BTW, if we're going to be discussing things would you do me a small favor and call me Michael? I've not had people (except elderly relatives) call me "Mike" for most of my life and if someone calls out "Mike!" or addresses a "Mike" in a post it doesn't normally occur to me to look around to see if they are talking to me. Thanks. cheers, Michael Quote Link to comment Share on other sites More sharing options...
subanator Posted March 15, 2008 Report Share Posted March 15, 2008 How would you go about removing some or all of the weight of the flywheel on a ty 175 ?If removing some how much? or is it a suck it and see job. Thanks Matt.. I had mine machined a little, metal taken off the side (as in thinner), but only went as far as the head of the rivet heads. Then if you went further the outside diameter would need further machining, not recommended as per Feetupfun's post. Does pick up revs a bit better for it off idle now. Quote Link to comment Share on other sites More sharing options...
Guest majestyman340 Posted March 15, 2008 Report Share Posted March 15, 2008 It is the same thing you do when balancing a wheel. Put it on an arbor/axle on a stand with rollers for the axle to ride on and see if there is an obvious heavy spot. You've probably seen different flywheels (both mag and crankshaft) on bikes that have little drilled dimples on them where a small amount of metal has been removed to bring them into balance. If you've got a wheel balancing stand handy you are probably set once you make an arbor to hold the flywheel.Instead of going straight for the drill try sticking small lumps of clay on the side opposite the heavy spot until you get it to remain stationary in any position. You can get an idea from the clay of how much weight needs to be removed from the heavy spot. And of course, take a little less than you think is needed to start, and keep checking as you go along. The factories that make the flywheels probably have a dynamic balancing machine that spins the flywheels up and detects the out of balance spots, but that would be mainly to speed up the process. A static balance should be fine and you can do it at home. I'd presume that any factory part is probably OK and I wouldn't routinely check an OEM flywheel, especially if it looks like it has already been balanced. But I've taken apart some Japanese forks that came from the factory with the wrong bottoming cone on the damper rod that blocked off the bottom orifice on the rod, and I remember a /5 or /6 BMW that came into the dealership I worked at in the early 1970s that had the rear hub only partially machined, so even factories can screw up. That's why race tuners check everything in an engine, make sure all the rods are balanced and weigh the same, combustion chambers all match, brake pistons are retracting properly so the pads don't drag, etc. If you've got an aftermarket weight that bolts on to the face of the flywheel that weight might be perfectly made and perfectly in balance. But if the holes on the flywheel that it bolts on with or registers to are a bit off then the assembly is going to be out of balance. Or what if one of the three bolts that hold it on came from a different fastener manufacturer and is 1 or 2 mm longer or shorter than the others or has a little longer or shorter threads? 1mm off the bolt might not be much, but if it is out near the rim of the flywheel and you spin it up to 6000 rpm it might cause enough imblance to be significant. Might not too. A lot of the checking is done just so you know. A problem is that if you do find something out that you think should be fixed you then get stuck having to decide if you are going to do anything about it. Ignorance can bring bliss. BTW, if we're going to be discussing things would you do me a small favor and call me Michael? I've not had people (except elderly relatives) call me "Mike" for most of my life and if someone calls out "Mike!" or addresses a "Mike" in a post it doesn't normally occur to me to look around to see if they are talking to me. Thanks. cheers, Michael Sorry Michael.............most people in the uk and europe dont have a problem with the shortened version of your name. I am very interested in balancing my std Majesty Yam crank, but not very well up on anything technical, so wonder if you could detail what I would need to ask my local engeering shop? Quote Link to comment Share on other sites More sharing options...
michaelmoore Posted March 16, 2008 Report Share Posted March 16, 2008 You'd need some sort of arbor made with a taper to match that in the flywheel. Have the same diameter at the points of the shaft that will be running on the balancer rollers. Your friendly neighborhood model engineer could probably turn that up for you. Then look at a wheel balancing stand, the kind that has four discs mounted to bearings that the axle sets on. You can make your own like these: http://www.nomartirechanger.com/ProductHer...iumBalancer.gif http://www.roadstarclinic.com/TechTips/Whe...ages/standf.JPG If you aren't noticing a lot more vibration than would seem appropriate you probably don't have a problem. cheers, Michael Quote Link to comment Share on other sites More sharing options...
pat Posted September 6, 2008 Report Share Posted September 6, 2008 Does any of you know if a flywheel from IT250-83 fits bolt on TY250R? Quote Link to comment Share on other sites More sharing options...
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