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Discussion in 'Motorized Bicycle General Discussion' started by scottcason69, Apr 26, 2013.
Can anyone tell me what's.the fastest anyone has gone on a Chinese 80cc motor on a bicycle
There is no Chinese 80cc motor speed record and there never will be.
to elaborate, there's no chinese 80cc motor. it's a 66cc.
officially, there's no land speed record. there's a few videos somewhere of people going fast, but most of it's kinda sketchy.
i've seen bikes radared at the track with the top speed in the straight around 43mph, but those bikes are usually geared lower for better speed out of corners.
mbr and the aleman witnessed me at 54mph with a gps, and i think neil hit 45 on my bike that same day. i'm lighter, and was drafting traffic.
i unofficially hit 62 on the same bike drafting a truck using my phone gps, and then it blew up.
i've seen many riders hitting mid 40's in the street.
one of these days i'd like to issue a speed challenge, using the same gps phone aps, video cameras and witnesses, but haven't got around to it yet.
Bairdco is the man!
....what would it take? 1/2 mile to get up to speed, maybe a 1/4mile for the trap, then another 1/4 mile to get it stopped.
Do it at sea level on a nice level road...
Sounds like a great idea, B !
You blew up the phone or the motor? At that speed, you must have been spinning over 9000 RPM or better, really straining the structural limits of the materials the rod, piston, wrist pin, crank & bearings. If your motor blew, it's probably because something came apart internally.
At 30 MPH, my motor vibrations are so bad it shakes like a titty dancer on meth, everything in my mirrors becomes a blur. (gotta stuff my handlebars with lead shot, I know) At those speeds I'm not so much afraid of wrecking or spilling at speed (although I'm sure it'll hurt if I do), so much as the motor grenading between my knees.
i had mine up to 60 mph,then i took it out of the car,opened the box and installed it on my bike.hasnt gone that fast since.
ha... blew up the engine. phone was fine.
i was riding down the pacific coast highway in newport beach with the wind at my back, and about 5 feet behind a pickup truck.
the speed limit is 55, but everyone does closer to 70, and the stoplights are far apart.
the guy i was drafting knew i was there and kept slowly speeding up to see how fast i could go.
my phone was in the sleeve pocket of my gas station jacket so it picks up the gps satelites for the speedo ap i was using, and it saves the top speed.
my motor made a loud bang, and since i was in a full tuck, i was looking at it. a small fireball came out of the head, it blew my exhaust pipe off, and grenaded inside.
luckily my back wheel didn't seize up. the motor tried to seize, but the momentum just broke apart the piston instead, so i could roll off into the bike lane.
the guy in the truck came back and said his speedo had me at 65, but my phone said 62. he said his neighbor has a bike that's lucky to get up to 30mph.
i collected my pipe off the side of the road and pedaled home.
after i pulled it apart, the top of the head studs were bent and stripped, my piston was pretty much missing except for the part connected to the rod, the exhaust threads were completely stripped in the jug (i was using bolts instead of studs,) the plug gap was smashed closed, and the cylinder lining looked like grey, melted slag, and the head's combustion chamber looked like it was hit with buckshot.
what i think happened was the rod stretched, just enough to slam the piston into the head, and all the other damage followed after.
the head was from a harley aermacchi m50, and i had to modify the squish band so the piston wouldn't hit. it had a buttload of compression but worked great for 8 months of everyday use.
modified, these motors can easily run 9k or more rpms.
the bike is the silver 1940's colson on my profile page. i ended up selling that bike with a stock-ish engine for a bunch of money
i think by the description the rod had it best and the cylinder melted from being at a standstill airpocket while redlining. who knows/ i came to the conclusion in 30 seconds or less. what do i know right.
the story of whaching it grenade was really very good thanks.
what sprocket size do u recomend and rpms for an allaround road runner that will last a whole season with a piston or two? reeded or no reed valve???
I'm curious to what sprocket size and revs you got out of it Bairdco, Not that I want to try it, well sort of.
I'm a bit limited with where I can ride my bike, If I could Streamline Some one at 100 Km/hr, There is a nice 'track' heading north from here.
But Subs right about keeping the poor thing cool.
And maybe wire/chain the head down. Just in case.
And better tyres!
I don't know the record, but there's a 50cc class on the SCTA site. I think an Aprilia has the record.
Budfab had mentioned running 1mph per cc is pretty darned good!
...for naturally aspirated...
here's a link
and a vid
I was there the day when Baird did 54 GPS'd on his. IIRC, he had a 27T and 24" wheels at the time and so that would equate to 8400-8500RPM.
He did this at a time before many of the high-performance parts that are out now existed for the chinagirl 2-strokes, too.
He's not a large man and half his weight likely consists of cojones, so it wouldn't be a stretch to say he's taken one or more over 9K RPM.
He certainly has the know-how and the size to go fast. The bike he did this on is older than the fathers of many members here.
For those that wish to replicate his feat, in all honesty, it's easier now. Not smarter tho, IMHO anyway lol
Your balls will never be as big, either. Baird is a damb _freak of nature_! He's a human flea!
I have been starting to think about doing a water cooled KTM build with a Stingray and scooter tyres and brakes, should get me out on the open road.
I hear...er ah feel ya Dave!! 39 M.P.H. was my top speed going down a hill 32 level
Dave as i bet you already know 90% of the vibe is coming from loose motor mounts, I had one mount vibrate out and the vibration was ten times worse so after I fixed it & I went over the other 3 bolts and glued some rubber tubing inside the mount as well as the saddle clamp.
I got on it , got up to speed and it was sooo smooth hardly any vibration at all . Still feels like its gonna fragment between my legs though at top speed!~
I've hit a gps' d speed of 45.8 mph on my 1963 Western Flyer bike, it has 24" wheels and a 30T sprocket, the engine was new and had just over 10 miles on it and I was on a slight decline when I hit that top speed.
I have seen 9400 rpm on one of my bikes and didnt have a speedometer on it at the time so im not sure what my speed was on it, it has 26" wheels and a 34T rear sprocket, im guessing around 45mph my dadwas cruising with me on his motorcycle and said he registered a little over 45 mph while riding beside me,, but of course those cant be seen as official mph.
Both of these bikes are running the dax GenIV lowers with good port work and piston mods, with current exhaust set up on the Kulana bike I have it cruises nice at 41-42 mph with the 34T
After hitting 45.8 mph on the WF bike I have settled in on feeling plenty comfortable with top speeds 45 mph or less on my bikes.
There have been so crazy claims of people saying they hit 45+ mph running 44T sprockets and such but I dont see that happening, Arrow racing bikes run 24" wheels and 37-38T sprocket and these are very highly moded bikes with direct case induction and well buit and balanced cranks and they hit low to mid 40's on the straight when they reach their rpm plateau.
Bairdco has the highest proven top speeds here as far as Im concerned, he has witnesses that have seen what his bike was able to do and I haven't seen or heard. Of anyone else here that has done that.
And by the way my dax lower builds run comfortably smooth at max rpms and speed..... no harsh vibes with either of these engines at wot.
While using some kind of elastic isolator might sound like a good idea, it has been the experience of many that it will cause more troubles later. By isolating the vibes from the frame, the motor mount studs end up sustaining the majority of abuse, oftentimes resulting in broken studs. Upgrading the factory provided studs with Grade 5 hardware or better will help with this, but it won't prevent the studs from stripping out the threads from the case, another problem that has been reported.
Best suggestion: Remove the studs & make sure the threads are tapped all the way in. The Chinese workers often cut corners here & won't take the extra minute it requires to do it all the way, they are encouraged to crank out as many units as possible, so to save time they only tap the threads 1/2 to 3/4 the depth of the hole. This means less grip of the stud in the case & may result in stripping. Next up, replace the studs with good hardware. Avoid the temptation of using AllThread Rod & cutting it to length, even if it is grade 5, the act of cutting creates friction & heat, weakening the temper & strength. I got my upgraded precut studs from JuiceMoto, but other vendors sell them too. Lastly, use locktight & double nuts, red locktight for the case & blue locktight for the nuts.
There are a few cures for vibration, using a quality CDI such as a Lightning or a Jaguar helps by recurving the timing advance to be more advantagious to our China Girls. It has been said that the factory ignition provided is better suited for 4 stroke equipment that operates at a constant speed, such as rototillers, lawnmowers & sump pumps, there's too much advance built into them. Aftermarket CDIs correct for this. If that is too much for your budget at this time, a Rocket Key can be used to replace the half moon key under the magnet rotor, retarding your ignition in an old school manner(I've done this, because my SuperRat uses a 1Peice magneto, an aftermarket CDI isn't an option for me). Some folks have reported using a Dremil Roto-Tool to wallow out the mounting holes in their magneto in an effort to have some timing adjustability.
There are additional methods available to reduce vibrations in a China Girl, which is one of the biggest limiters of RPM & speed, such as internal balancing. Most of us reading this do not have the equipment, knowledge base or skill set to do this ourselves. You might take your motor to a reputable machine shop with experience in 2 strokes or just purchase a prebalanced assembly from Dax, Arrow or CR Machine. Some have reported varying degrees of success by lightening the piston by drilling holes in it. But unless you have experience in rebuilding motors, I wouldn't recommend it, as it is far too easy to remove too much or cut the wrong location, resulting in a junk engine that will never run again. I tried using a lightweight titanium wrist pin & I can report that while it did ease vibrations, it didn't last, the titanium alloy used turned out to be too soft, it deformed within 10 miles & resulted in internal damage. At present, I'm awaiting FedEx to deliver me a new top end kit that I bought last week.
I know this doesnt go with the thread topic but I wanted to say regarding the titanium wrist pin that my engine that is running one has a little over 30 miles on it now and its holding up so far with the aluminum bushing instead of the needle bearing, I did blow a head gasket the other day so Im thinking when I pull the head I may as well pull the jug and see if I can see or feel any signs of wear between the pin and bushing, if so Im gonna pull it out and consider it a failure, I have been running the engine pretty hard the last few miles just to see how it would hold up under the high rpms and vibes from this engine, I think I blew the gasket because the engine was so hot after running it at wide open for about 3+ miles the other evening, still no knocking or signs of pin and bushing failure so maybe its a good combo... time will tell unless I see wear when I check it out maybe next week.
This bike only tops out at 36mph vibes are better than before but still uncomfortably high at top speed.
I did 53mph on gps with a 24" schwinn on 34T sprocket......this was 2 years ago.....same setup
Wow....! 53 mph with 24" wheel and a 34T sprocket
Was that on flat ground?
Im not sure about how to figure the rpms your engine would have been turning but it would have had to be crazy freaking high rpms, I've had mine at 9400 rpm according to my tach and with a 34T on a 26" wheel and didnt go that fast, that is some serious speed and serious rpms.
calling baird a flea is kinda old. lately he's been working at his friends bar so instead of ''flea'' maybe ''crab'' might be a better term. #a200 dennis
53KPH maybe, that is 33MPH and possible for a direct drive 24" wheel.
I have built and rode many a 66cc that will do 50 MPH but they were all 26" jackshafted shifters like this one...
And this one...
And this one...
But that's too fast for me on a bicycle, even one with dual disc brakes.
Around 35 MPH is my comfort zone, I just like to there in 3 or 4 seconds ;-}