Piston rod bearing keeps breaking

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Thank you all for supportive conduct. Now i started thinking worn out cylinder which is causing major compression loss migh be messing with ignition timing. Before doing anything timetaking Rebuilding the top end might be worth a try.
I forgot to say bearing was high quality it cost 30try (3000try is minimum wage here) and i took professional help to disassemble and assemble the crankshaft.
Making a carburetor spacer sounds a brilliant idea I'll note that.

Again thanks for all this support makes things a lot easier to deal with.
 
Was a custom made 5 speed cassette, with a jack shaft double sprocket( one for low end and one for high end, an of course the driving sprocket), bored the nt throat, made my own slide to fit, custom intake, custom exhaust made from a dirt bike, ported all to hell and back for high rpm, used an old dirt bike cdi, all i know is it was honda and older than dirt like me, head had a custom shaped conical flat top chamber, etc, etc. I have since scrapped the jug, didn't like it. was a big turd till around 5-6k rpm, then it jumped on the pipe and scream till gear change. an the gps was spot on ( =/- 1mph), it has been tested with many vehicles speedos. all which happened to read the same thing tested. $80k ford truck speedo, yep read the same, rousch mustang, yep same test, same result, gps was accurate. took me a year of tinkering to make that sucker scream, then again I really don't get a lot of free time. got tired of crap parts and started building my own, then i wanted to see just how fast 66cc could take me. I found a 66cc engine will take me way faster than i care to go not on one of my motorcycles. I'm not worried about if you believe me, I could careless to be part of some " good ol' boy" club. I did it for me, and I happily exceeded my wildest goals.
Dude I've been building engines for over 40 years now and using these bicycle engines since 2002, I'm a authorized service center for many name brand power equipment manufactures as well as servicing all types of motorcycles, boat engines and so on.
None of what you said would lead me to believe your claims as there is no mention of crank balance which is first and foremost for ANY performance build! Then you say ported to hell and back which says nothing really, I bored out a NT speed carb to 16mm which is as large as it can go, and you claim to have made a custom slide, how when the body is only 16mm !
With the NT bored out to 16mm a 40% balance factor crank and a port map that I posted for all here back a few years ago, 11/30 gearing and 27" wheel, toroidal style chambered head with .7 squish which is much more efficient and suited to higher rpm use than conical heads as Jennings stated in the 2 stroke tuners handbook, conical combustion chambers reduce thermal loads and mechanical loads on the rod and bearings but have poor surface/volume characteristics and give a too broad squish to be efficient. I also used a custom built truly tuned pipe with all the port volumes at the windows matched and re timed for the build not just hogged out flange areas that does nothing. All this plus others like correcting the transfers, reducing case volume, shimming the crank and wrist pin for high rpm, still only just got me into the 60's and at that time I was still trying to get 11k and over stable as to not grenade even with all the balance work and corrections! You stated that it came on the pipe at 5-6k and with narrow band dirt bike pipes that means you could only get around 8k topped out so none of this makes any sense.
 
Like i said, dont care what ya believe. I did it. An im happy i did. Ive been building engines for about the same amount of time. Sorry you cant make em do it. But some of us can. An again, not bragging, i made the bike for me, not for bragging rights.
Dude I've been building engines for over 40 years now and using these bicycle engines since 2002, I'm a authorized service center for many name brand power equipment manufactures as well as servicing all types of motorcycles, boat engines and so on.
None of what you said would lead me to believe your claims as there is no mention of crank balance which is first and foremost for ANY performance build! Then you say ported to hell and back which says nothing really, I bored out a NT speed carb to 16mm which is as large as it can go, and you claim to have made a custom slide, how when the body is only 16mm !
With the NT bored out to 16mm a 40% balance factor crank and a port map that I posted for all here back a few years ago, 11/30 gearing and 27" wheel, toroidal style chambered head with .7 squish which is much more efficient and suited to higher rpm use than conical heads as Jennings stated in the 2 stroke tuners handbook, conical combustion chambers reduce thermal loads and mechanical loads on the rod and bearings but have poor surface/volume characteristics and give a too broad squish to be efficient. I also used a custom built truly tuned pipe with all the port volumes at the windows matched and re timed for the build not just hogged out flange areas that does nothing. All this plus others like correcting the transfers, reducing case volume, shimming the crank and wrist pin for high rpm, still only just got me into the 60's and at that time I was still trying to get 11k and over stable as to not grenade even with all the balance work and corrections! You stated that it came on the pipe at 5-6k and with narrow band dirt bike pipes that means you could only get around 8k topped out so none of this makes any sense.
i
 
i made the bike for me, not for bragging rights.
I understand this as well since i make my bikes for my pleasure...i just happen to take delight in keeping the motors stock, (with the exception of the air filters), Tune the carbie to as optimum as possible, throw on the mags, disk brakes, and whatever accessories i need, make it look as decent as possible, (I dont like some of these "ghetto" death traps i see some people riding), Use a decent motor as far as China Girls are concerned anyways, in my case, the Zeda 80, and am more than pleased that i had it at 47 MPH that i refuse to do again remembering how old i am now, plus it is not dignified to be cleaning the racing stripes out of ones underwear when you remember that it is only a bicycle with a motor strapped to it, NOT a motorcycle...lol...Im more than happy cruising around between 30 to 35 MPH and loving it, thats what most of the speed limits are on the roads im on anyways...Just keep enjoying your ride there Karl...For me its "No brag, just fact" my bike is what it is, no more no less...lol...Same for you, im sure...lol...DAMIEN
 
I understand this as well since i make my bikes for my pleasure...i just happen to take delight in keeping the motors stock, (with the exception of the air filters), Tune the carbie to as optimum as possible, throw on the mags, disk brakes, and whatever accessories i need, make it look as decent as possible, (I dont like some of these "ghetto" death traps i see some people riding), Use a decent motor as far as China Girls are concerned anyways, in my case, the Zeda 80, and am more than pleased that i had it at 47 MPH that i refuse to do again remembering how old i am now, plus it is not dignified to be cleaning the racing stripes out of ones underwear when you remember that it is only a bicycle with a motor strapped to it, NOT a motorcycle...lol...Im more than happy cruising around between 30 to 35 MPH and loving it, thats what most of the speed limits are on the roads im on anyways...Just keep enjoying your ride there Karl...For me its "No brag, just fact" my bike is what it is, no more no less...lol...Same for you, im sure...lol...DAMIEN
Yep, no bragging rights with my bikes. Im to old to care what others think, never cared when i was younger either. Ive always be the guy to do exactly what you tell me i cant do. People limit themselves, while i try to find my limits. I only built the one that fast. Took many hours of reading the lords of the smokers books( over again, read then in my youth when i was hard for dort bikes), and trying for myself. Like i said i spent over 400 in just chain before i got the right set up on just the drive train. I would blow chains like crazy. Almost gave up. Kept going with it and finally broke 50. Then i was like, hit 53 and I'll be more than happy. An i hit over 60. Bout sh!t my pants at that speed. Since i have detuned and went back to torque builds. I just wanted to see if i could do what everyone said i couldn't. Build a bike that tops 50mph. Blew one engine reaching that speed. An it was from bad porting and me pushing way past what the porting could safely do. Pretty much melted the exhaust side of the piston. Almost crashed when the motor locked. I had around 20 hours and 400 bucks in that engine. Then i moved on to a new engine and started over. The day i hit 62.9 mph ( i say 63, but reading was 62.9 before i backed off the throttle and checked my drawers) i was highly elated. Even had a few shots to celebrate, and i really dont drink often at all. That bike now weighs like 100lbs. Broke the frame being crazy off road with it, more times than i can count. Its got so much extra metal welded to it, its a scrap yard more than a bike. But it still hauls to over 50 at the top, but only on fresh chain and sprockets. If either is worn it just tears the chain in to pieces and shreds the back cassette. Ive got more money wrapped into that hunk of crap looking bike than most people make in a month.
 
Yep, no bragging rights with my bikes. Im to old to care what others think, never cared when i was younger either.
And that is the best attitude to have and especially in forums where passions can and do run a little high once in a while and skins can get thin...lol...as i always tell myself, "don't take yourself too seriously, no one else does"...lol...DAMIEN
 
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I'll chime in on this thread again... What works for one person may NOT work for another person.....
We are ALL here to give or take ADVICE from each other.... Take it with a gain of salt..... Just saying. :)
 
now if someone said they got one of these to 100, i'd call BS. but there is proof on youtube of guys taking these up to 80-85mph. an the people videoing have nothing to do with the motorized bikes. they just seen them and started recording, and got passed by them on a hyway!! lol. I'm not mad, butt hurt or any of that sh!t for someone saying i'm full of sh!t. Honestly, I was at the time, but I just took a crap. So I'm good there. lol. I even get where streetryder is coming from. Bunh of fuqn morons come here wanting to make some racing 200mph motorized bike. Or guys that have no idea wtf flow dynamics is saying they can make one of these scream. I bleieve they can make them scream, scream right to the grave. An their future posts show exactly that. lol, they burn 'em down before they ever come close to their goals. Some guys just flat out lie, because they need attention. An again, I have no hard feelings towards streetryder, he has no idea who i am. I could be a 12 year old idiot for all he knows. Not that I am, but this is the internet and people say some crazy sh!t here. lol. It takes more than anyone here has to get me offended.
 
Like i said, dont care what ya believe. I did it. An im happy i did. Ive been building engines for about the same amount of time. Sorry you cant make em do it. But some of us can. An again, not bragging, i made the bike for me, not for bragging rights.

i
I thought this thread was about piston rod bearings breaking. Not a argument on who's bike went what speed. Thanks guys
 
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