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Discussion in 'Motorized Bicycle General Discussion' started by Dan, Feb 3, 2009.
or start your engines. Is an optional thing
Good Morning Guys, Well i guess i will add my 2cents here.... First of all let me just say I love these little chinese engines for what they are and believe that for the money they would be hard to beat... I spent most of my adult life working with industrial and agrigultural equipment, I.E. Pumps,Harvesters, and Wind machines...and relacement engines for industrial applications....over the years(i am 55) i have seen a multitude of engine mounting systems and read factory supplied tech manuals regarding engine mounting and been personally responsible for hundreds...no thousands of instalations ....so i feel somewhat quilified here to give an opinion.... one thing i have noticed in regard to the discusions here is that nobody has addressed the mounting location , probably the most important issue in mounting the engines...without really getting technical i would just suggest that (if you are concerned with vibration) you look at the rotating mass(crank and piston assy.) find the centerline of that mass and and place your mounts as near to that centerline as possible...as to rubber vs solid, well all my bikes will be solid... these little suckers like to jump around and want to do all i can to hold them still. . . i saw one claim here that " eliminates all vibration" well the only way to eliminate the vibration is to turn off the engine....and you might do two "glass of water" tests, one on the bike and one on your engine... if you mount with rubber the engine will move more than if mounted solid. . nothing there to stop it. . for me, well i just bolt em' down and go, a little vibration lets me know what i'm riding and i use the vibration for a tach/speedo back out to the shop now.... love to build...
If your gonna bring logic, experience and good sense into this, well thats just crazy.
Have a great day building. After a cup or 3 of coffee, gonna be right out there with ya a couple-a thousand miles away
Hi,David.Welcome to the funny farm!
I totally agree with you about mounting the motor to the bike as close to the center line of the motor.
May I add that the motor should be mounted as far down in the "V" as possible.
I also agree that the only way to completely stop a 2 cycle motor from vibrating is to shut it off.
"That said" I also think that there is alot of room for improvement in minumimizing the vibrations of these motorized bikes.
I am working on a safe way to isolate the motor from the frame if it works great!!
If not "nothing ventured nothing gained"
I have listened to"experts" all my life and many of them I have whole heartedly agreed with!
I have also listened to "experts" and have had to Bite my tounge till it blead before I could prove them wrong.
The motor isn't the only source of vibrations.
I noticed "that" when I installed a sprocket on my first spring-loaded chain tensioner.
Another source is the exhaust,if you have a stock exhaust rev your engine and look at the end of the muffler!
That is why some kits supply that cheezy muffler to frame bracket!
That is why I build my own exhaust and mount the muffler in the back of the bike with a flex pipe between the header and the muffler some of the "experts" think it's the same as a POO-POO pipe
That just shows that they don't know what they are talking about as the flex pipe minimizes the vibrations in the exhaust,and in my opinion it looks"Cool"
Expansion Chambers increases the vibrations good for performance, bad if you are striving for smooth!
I'm also working on that!
I put the "Pundants" and the "Experts" in the same category as the nay sayers that told the first guy
that put a motor on a bicycle that it wouldn't work.
I can see that guy blowing buy the nay sayers peddeling away giving them a one finger salute as he proved them all wrong,and the motorcycle was invented."CAN I GET AN AMEN" Kip.
I like that "half a bubble off plumb!" Is that like a couple cans shy of a six-pack?To strive for as smooth as possible you have to address the whole package.
Port match intake & exhaust.deburr inside of intake and exhaust
Polish piston and combustion chamber and exhaust port."Tunable exhaust coming"
Higher output mag for better spark.indexed NGK plug, proper gap,better wire and boot.
Adjustable carb.Properly mixed oil/high test fuel.
Vibration "dampner" not "elimination" mounting system.
Vibration dampners inside covers.clutch,mag,clutch arm cover.
Spring-loaded chain tensioner with urathane sprocket! Better quality chain.
Balanced wheels and tires,and much much more!!! Kip.
Kip, love it man! I could not agree more on the expert thing and your approach is brilliant! I mean that. Is not only the mounting, have to address all contributing factors.
As I said, I am looking forward to having lunch with ya and Carol make some real good cheese-burger.
Go fourth and make!
But won't work. nnanananana. lol
Hey Dan.I've got a question for ya! Your Avatar is that a picture of you and do you have M&M tatooed on the back of your head?
I see pictures of you all over Wal-Mart without your hat!Is that you or your twin brother in all those smile Thingies?
Thanks At least I have someone agree with me even though you don't have any confidence in me!!Kip.
lol, yes to all.
Cool video I saw Queen in 74 they were a backup band for Mott the Hoople "All the young dudes" in Portland,Maine at the Expo building.I think it was their first apperance in the states! Kip.
i don't really understand why anyone would prefer a solid mount over a rubber mount on a China Girl. These little engines are perfect for rubber mounting imo because they make so little power it's easy to do.
The hocky puck, muffler clamp method I'm using is working very well in my first 120 miles and showing no signs of trouble at this point. The rear mount is just the stock mount with inner tube wrapped around the frame.
Yea that one looks good, guessing a hockey puck is relativly stiff, but would certainly help isolate the high frequency vibrations.... what do they cost?
The compound that a hockey puck is made from is hard enough to keep things from moving. I use a very hard urethane bushing in my front mounts too. The material composition is so hard that you can't compress it or even make a mark in it with a screwdriver. This is the difference between rubber and pucks or urethane bushings. Rubber, or ANY soft material will cause problems. This has been explored and explained here time after time. The reason is that you CAN NOT eliminate the vibrations produced by the engine. All you can do is distribute it. You CAN NOT isolate it to the engine itself because the mounting fasteners are then the link between bike and engine and they can't take the stress. Either the fasteners will eventually fail or the threads in the case will. My bet is that if the hockey puck or my urethane bushings were replaced with metal that the degree of vibrations felt in the bike would be the same. This myth of soft mounting engines to "eliminate vibrations" is my pet peeve, just as cheap bikes are to Bairdco.
I'm inclined to simply post my opinion once then back away and let people do what makes them happy but the problem with that approach is that newbies then will not have the benefit of the facts and will soft mount their engines because the theory sounds right. Then they'll have failures and problems that can be directly linked to the resiliant mounting of the engine. I really hate to see a new guy have problems that keep him from enjoying the hobby and his bike and therefore I will continue to argue this issue with anyone who says that soft mounting a Chinese 2 stroke is the way to go.
I agree fully with Tom (2door) on this
all broken stud probs I have ever seen/had were due to flex at the mounting points
I'm a big fan of urethane bushings. My Sportster came with soft rubber bushings that mount the handle bars. They make the handle bars flop all around, and are really nasty. I replaced them with hard urethane bushings made for that purpose. Even though they're very hard in comparison, they dampen vibration about as good as the soft stock ones.
If I could find a hockey puck made out of urethane I think it would work even better than the rubber one I'm using.
I've never made a solid mount China Girl, but my Sportster in solid mount. There's no question it vibrates 10x worse than a China Girl. Sportsters are world renown for having parts break off and roll down the street behind them. After 47 years of production the motor company decided to rubber mount Sportster motors. I've ridden both and to tell the truth I didn't feel much difference either.
Rubber mount or solid mount, everything breaks in time. You know what they say, if it's got tits or wheels it'll give you trouble.