cosworth
Member
Has anyone tried balancing one of these cheap motors?
Smoothing Out The Engine
- Thread starter cosworth
- Start date
Well, the best thing I've done to help, is put a better wrist pin bearing in. The better bearings are lighter, and help quite a bit.
Glen Look here======POCKETBIKEPARTS.COM======Piston Wrist Pin - 10mm x 36mm for 44mm pistons
Glen Look here======POCKETBIKEPARTS.COM======Piston Wrist Pin - 10mm x 36mm for 44mm pistons
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Deleted member 12676
Guest
If you put in a lighter wrist pin and use a Jaguar CDI you will be all set. If you drill some holes in the flywheels to more correctly counterbalance the piston/wrist-pin then it still will vibrate at top rpm because that is mostly caused by the standard ignition firing too early. Click on my signature link and read more on the subject.
cosworth
Member
Wow, what a wealth of information you've provided. Lots of reading to do with much thanks.
Fabian
Well-Known Member
The Jaguar CDI helps to make the engine "run" smoother, but you cannot balance a single cylinder engine unless using a balance shaft.
You can only reduce the level of vibration at a specific rpm zone by altering the balance factor percentage - anything outside of that rpm zone will have the engine vibrate just as bad as before, if not worse than the original balance factor.
You can only reduce the level of vibration at a specific rpm zone by altering the balance factor percentage - anything outside of that rpm zone will have the engine vibrate just as bad as before, if not worse than the original balance factor.
How would you balance the flywheel? They are dynamically balanced (sometimes called spin balanced) at the factory, much like your tires are balanced while they are being spun. I wouldn't touch the factory balancing because it is not a simple hole drilling. Although I don't know if any of these Chinese motors are balanced at the factory at all. I personally wouldn't drill any holes anywhere.
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Deleted member 12676
Guest
Fabian, it might be that the reason balancing is rpm range dependant is that this info is always in reference to race engines with expansion chambers that increase the dynamic cylinder pressure at the top rpm range. That pressure is one of the things that have to be counterbalanced since the piston is basically trying to push the engine "up" when rising and pushing against it. So a downward force from the flywheel is needed, and had by lightening the flywheel close to the connecting rod pivot point.
But most people here use the standard muffler that has no compression increasing effect at top rpm. Therefore these engines should be able to have very good balancing (which was not accomplished at the factory).
But most people here use the standard muffler that has no compression increasing effect at top rpm. Therefore these engines should be able to have very good balancing (which was not accomplished at the factory).
Fabian
Well-Known Member
A single cylinder piston engine cannot be mechanically balanced - altering the balance factor simply shifts the minimum perceived vibration either up or down the rpm range and that can be proven with maths.
Combustion related vibration (sometimes referred to as secondary balance) is minimal compared to mechanical imbalance.
The only way a single cylinder engine can be balanced is with the use of balance shafts.
Unfortunately maths has been said to be the language of God, and no one messes with god when it comes to maths.
and here is the maths, once again:
Combustion related vibration (sometimes referred to as secondary balance) is minimal compared to mechanical imbalance.
The only way a single cylinder engine can be balanced is with the use of balance shafts.
Unfortunately maths has been said to be the language of God, and no one messes with god when it comes to maths.
and here is the maths, once again:
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Deleted member 12676
Guest
These arent spin balanced at the factory, I guarantee you.
The size of the flywheel holes should be a percentage of the weight of the top half of the connecting rod plus piston/rings weight plus wrist pin weight.
You can increase the hole size or you can use a lighter wrist pin. Both affect balancing in a positive way on this engine. But there is no getting around the need for a 2 stroke CDI to replace the 4 stroke one that comes with it because it has too advanced an ignition timing at high rpm.
Fabian, your non-understandable video (because of teachers heavy accent) doesnt prove what you are saying. But anyway your statement of 2 strokes not being able to be balanced is too broad. You need to give details and specify.
My position is that an engine w/o an expansion chamber can be balanced enough so that the handlebars don't vibrate excessively which is tolerable for bike riders seeing how they adjust themselves to so many discomforts anyway. The standard Grubee engine vibrates at an untolerable level. It can be brought closer towards perfection, enough to make it a pleasant experience to ride.
The size of the flywheel holes should be a percentage of the weight of the top half of the connecting rod plus piston/rings weight plus wrist pin weight.
You can increase the hole size or you can use a lighter wrist pin. Both affect balancing in a positive way on this engine. But there is no getting around the need for a 2 stroke CDI to replace the 4 stroke one that comes with it because it has too advanced an ignition timing at high rpm.
Fabian, your non-understandable video (because of teachers heavy accent) doesnt prove what you are saying. But anyway your statement of 2 strokes not being able to be balanced is too broad. You need to give details and specify.
My position is that an engine w/o an expansion chamber can be balanced enough so that the handlebars don't vibrate excessively which is tolerable for bike riders seeing how they adjust themselves to so many discomforts anyway. The standard Grubee engine vibrates at an untolerable level. It can be brought closer towards perfection, enough to make it a pleasant experience to ride.
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