50 mph ?? (Down hill doesn't count)

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BarelyAWake

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Jul 21, 2009
7,194
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Maine
my bike goes... oh, nevermind.............
Good one Baird! laff

I have come to the same realization.

The race bike for Ian in Trinidad is nearly complete...I'll leave it to him to post his thoughts on the fit, finish, speed, and quality of his China engine powered motorbike that I built for him.

Jim


I'm sure you guys know this, but I'm gonna take this as an opportunity to remind ppl anyways...

Obv anyone who straps an engine to a bicycle is - or shortly will be, a motorhead. A commonality shared by most motorheads is a obsessive interest in speed, performance & reliability... not necessarily all three or in that order ofc, but nevertheless that's the trinity of primary concern.

So one would think regaling us with tales of maximum speeds would be welcome - and it is, the ONLY problem is substantiating the speed claimed with evidence, vids of a GPS as you ride or even a chase car's speedometer: YouTube - 2 stroke hybrid puch motorized bicycle (yea, I know, he's not wearin' a bucket - his choice). Bicycle speedometers can be somewhat accurate - but due to the commonality of incorrectly calibrated bicycle speedometers, even those whom would leave them set to KPH and report it as MPH - unfortunately such reports can't be trusted fully.

The reason we shoot down unsubstianted claims is the importance of accuracy and the inevitability of exaggeration, as with most performance modifications so much effort is spent for the most marginal of increases - yet it's almost human nature to round up, to tack on an additional 5 or 10mph, to report a maximum speed (like a downhill grade) as a maximum sustainable speed (on a flat & holding it) - which ofc is not the same thing.

Where this becomes such a problem is it devalues all the efforts of those whom have spent countless hours of research and work, money and time, all the experimenting and blown engines to bring us the performance and modification tips we all love so much. When an experienced builder may have spent years learning to get the utmost out of their engines reports their hard-earned top speed, only to have someone turn around and report jus' a lil more out of their stock JBweld & duct tape bike in the classic "one-upmanship" game - that experienced builder rightfully feels slighted and probably won't bother to continue to share such valuable insights as obviously "anyone" can do better with just a sprocket swap or whatever.

This misinformation is a real problem. When someone throws together a stock kit and happily reports in excess of 35-40mph - all the new guys wonder why their bikes will only do 30 and assume they've done something wrong, or they assume that the report is false and that their 20mph is normal when they could indeed easily get better. We really want to hear of your successes - squeezing the utmost out of these motors is a wonderful and entertaining pastime, those willing to share tips & tricks are the most valued of our members and there are hundreds, no - thousands of members that benefit and greatly appreciate anything that is offered... but we gotta keep it real or none of it means anything.

So... increase that compression, balance that crank, port & polish and beat that poor HT and get back to us, all we ask is that you back up what you say with proof, which in all honesty should be the easiest, simplest thing in the world to do, as all that's gotta be done is hand the cam to a buddy...



...if for some reason that "can't" be done - ya jus' gotta ask yerself why - wouldn't that be something you'd proudly share? ;)







vid link frm foureasy's: http://motorbicycling.com/f13/hybrid-chinese-motors-performance-tuning-14204.html thread :D
 
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andrewflores17

New Member
Jul 12, 2010
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colorado springs, CO
my old dax 2 stroke with a 36 tooth sprocket filed down exhaust could do 46 mph on flat ground if i ducked down (made myself streamlined) and 42 43 ish with my lil headlight on would cruise at 35 just got my 4 stroke gona break in for awhile then start tweaking it up realy good would love to do 50 mph or more think it is atainable

confirmed speeds wtih gps unit and car alongside 46 mph was peak their wasnt anything left in the old girl to give me hey good luck though hope u reach 50 mph dont think id drive anywhere doing that much though (maybe midle o no were brnot
 

BarelyAWake

New Member
Jul 21, 2009
7,194
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Maine
So... you're sayin' that with nothing other than a sprocket swap and yanked baffles you got yer lil 2 smoker to beat foureasy's? http://motorbicycling.com/f13/40mph-speed-secrets-revealed-11141.html I think he'd be seriously disappointed to find that he wasted so much R&D time & money lol

Here's a pic of his setup BTW;


...there's a bit of a difference between saying "confirmed speeds" and showing confirmed speeds BTW ;)
 
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Goat Herder

Gutter Rider
Apr 28, 2008
6,237
20
38
N.M.
Now that's fast!!! I just got two burritos about two and a half miles away and there still warm. I am eating one as I type.:D
 

stuartracing

New Member
Dec 9, 2008
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63
Gainesville FL.
So... you're sayin' that with nothing other than a sprocket swap and yanked baffles you got yer lil 2 smoker to beat foureasy's? http://motorbicycling.com/f13/40mph-speed-secrets-revealed-11141.html I think he'd be seriously disappointed to find that he wasted so much R&D time & money lol

Here's a pic of his setup BTW;


...there's a bit of a difference between saying "confirmed speeds" and showing confirmed speeds BTW ;)
This is ONE BAD ASS MOTOR BIKE.......SWEEEET.....
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
I'm sure you guys know this, but I'm gonna take this as an opportunity to remind ppl anyways...
The reason we shoot down unsubstantiated claims is the importance of accuracy and the inevitability of exaggeration...
So does that mean I shouldn't claim this is me on my new bike that can break the sound barrier?



Or this?

YouTube - Jet rocket bike. Fast as, 236 khm. Cool

Hahaha, of course they are not me, I just thought you guys would smile at the idea ;-}

My 48cc 3-speed cruises comfortably at 30 MPH about half throttle.
I just finished my last tank of break-in gas and got a new 'No Cat' tailpipe in for it.
The pipe needs port matching, but once I get her set I'll push it with a chase car and she what she'll do.

50 is doubtful for me without better motor mods and playing 'spandex rider', but 40 should be obtainable sitting up.
That would be fun on the paved canal trails, but with the legal MB road speed at 20 I am more than happy with 30 without even stressing the motor.

I have said it before and will say it again...
Having a single chain and those 3 gears in the hub completely changed my perception of MB riding enjoyment.
 

PaulFlorida

New Member
Dec 4, 2009
52
0
0
central florida
Yes, I have an unsubstantiated claim of 51mph. This story ends with a warped slant head, a broken frame downtube, and now what sound to me like the little end bearing toasted. It began on my way to work, WOT, tucked in, top gear on flat road. 50mph speed limit. I noticed cars we crawling by me less than ten mph faster, so my est speed was about 47 or 48. Everyone speeds on rt441, 55 mph usually. Ended up at the top of a hill at a red light, pedaled through, ran through the gears, and tucked behind a truck going by after the light changed. I sat upright in 8th gear, motor strung out WFO for nearly a mile like that. At the next red light, he said he was doin "over 50, and where did you buy that bike?" Now, my head is warped, the motor has a death rattle and my frame cracked and separated at the front motor mount. So, it started on a down hill, but went to a slight uphill grade for the majority, and I was drafting a pickup the whole time. Bike runs in to too much wind resistance above 47-48 for the power.
 
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