I am using a 3.5 hp B&S lawn mower motor that i had recently converted from a vertical shaft to a horizontal shaft. (which was not too bad) but i am now stuck on adding a clutch to the crank shaft so that the bike will b able to idle once i start it. Or maybe there in another way to make it idle ether way could any one help me with this problem. Thanks
Need some help with clutch
- Thread starter air250
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The crankshaft should be 7/8" You can use a centrifugal clutch, but you will have to use a 1" clutch and a sleeve or bushing to make it fit. You havent indicated what kind of drive you are using.
Check ebay for a pulley sleeve, Grainger also had them. I sometimes use 2 bronze bushings from ACE trimmed to fit.
air250. Do you have a Princess Auto near you? If so that's the place to find what you need.
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Princess Auto carries both things yes and so much more. if you need a gear box they carry them as well, They have a wide selection of sprockets in just about any configuration possible. It's a strange name because they don't carry too much dealing with automotive at all. Prices are usually very good as well. Where are you putting the engine? Inframe, rear rack, front rack. That has a factor of what else you need.
I wouldn't worry about an extra gearbox. You can probably get by with doing what i did. And setting up pegs or something somewhere else. It being a four stroke it will have more torque available and won't rev as high, so you probably won't need the magic 20:1 ratio. Play with the ratio calculator until you find the max speed you would like to have.
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I might be stating the obvious here, but have you fitted a heaver flywheel when you did your conversion? Those things are meant to run with the mass of a blade helping them over the compression stroke...failure to do this can have very painful results!
What part is painful? The harder starting, Loopy idle, quicker revs, or just plain shaking itself to death? You don't think the added weight of a 1" centrifugal clutch, clutch drum and bushing would make up the difference?
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The painful part is when the engine tries to rip the pull cord out of your hand when you try to start it. No, I doubt very much that the small mass of a clutch drum rotating so near the center of mass of the crankshaft would help much. I speak from personal experience; tore the skin off two of my fingers, put a heck of a bruise on my right thigh, very close to my precious dingleberrys and left me with memories I wouldn't want anybody else to have to re-live. Been there, done that and I ain't a' goin' back!
As I'm sure you know, a flywheel is all about storing kinetic energy, something of a high mass and a small diameter can work, but if the diameter is larger, the circumference of the flywheel travels at a higher feet per second rate, storing much more kinetic energy than something of the same mass traveling closer to the center on a smaller diameter flywheel. If a large portion of the mass is located near the outer circumference, the effect is amplified. In other words, yes, a clutch drum is fairly heavy and if it had a diameter of say 6 or seven inches would probably be more than adequate, but I have my doubts if your standard size clutch would provide the necessary rotating mass.
I dunno, it might not be an issue and the only way to know for sure is to try it, but I would recommend when starting the engine for the first time, the user wear a good heavy pair of leather gloves and stand off to one side just in case. I'm sorry for dragging this thread off topic.
As I'm sure you know, a flywheel is all about storing kinetic energy, something of a high mass and a small diameter can work, but if the diameter is larger, the circumference of the flywheel travels at a higher feet per second rate, storing much more kinetic energy than something of the same mass traveling closer to the center on a smaller diameter flywheel. If a large portion of the mass is located near the outer circumference, the effect is amplified. In other words, yes, a clutch drum is fairly heavy and if it had a diameter of say 6 or seven inches would probably be more than adequate, but I have my doubts if your standard size clutch would provide the necessary rotating mass.
I dunno, it might not be an issue and the only way to know for sure is to try it, but I would recommend when starting the engine for the first time, the user wear a good heavy pair of leather gloves and stand off to one side just in case. I'm sorry for dragging this thread off topic.
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No worries i really needed to know that. i was wondering why it was so hard to start and why it kept ripping the cord out of my hand, i even broke a drill trying to start it, do you know how i could get my hands on a bigger / heavier flywheel for minimal costs i don't want to spend too much on the build
Affordable go karts.com, or "AGK"....SHOULD have what you need, or you could try a lawnmower "you-pull-it" yard...if you have one near you...there's one up the street frm me, n I've scavenged many a part from!
Good luck!
Good luck!
You need a cast iron flywheel from a horizontal shaft Briggs. The blade acts as flywheel on a mower.
The clutch doesn't have enough weight or diameter to add much flywheel effect.
The horiz. Briggs were used on many lawn edgers, some tillers and older waterpumps.
The clutch doesn't have enough weight or diameter to add much flywheel effect.
The horiz. Briggs were used on many lawn edgers, some tillers and older waterpumps.
You know it may be possible to just add weight to the existing flywheel. Many B&S flywheels i have seen have two flat spots on them, one on the magnet area and one opposed and two drilled and tapped holes. Don't know if they are still there or not but i'd look. Again check Princess Auto.
Those holes are for the starter sprag. Prolly would work with a solid disc that fit the shaft snugly to keep shear load off bolts. Would block airflow thru the vanes and have to do something about starter. Easy to just stick on a stock ez to find cast iron flywheel.
I apologize. I got the types of engines confused. It's Techumseh that has the flywheel i was thinking of and not B&S.
Np, Ill try adding some wight to the wheel not sure how im going to secure it but ill figure it out. O and If im able to get it started is it bad to run it with the aluminium flywheel by its self or will that wreck something. (because i got it started). Ps have been looking for a fly wheel and for a while now but still nothing so if i dont absolutely NEED one that would b good
