How Fast are You going? - I wana know

T-lo

T-lo

New Member
Gps says i'm doing 26.4 mph at tops. I think i'm tuned up pretty well with no mods on a mountian bike with 44 tooth sprocket. this is with my 66/80cc (or whatever) skyhawk gt5 and the new pain in the ass cns carb.
So, how fast are you going? please tell me your engine, Mph, sprocket, bicycle type... I wana know! and no guesses please
 
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No guessing.
We got a radar speed sign on the Old King's Highway with level ground.

At 240lbs, stock 48cc china girl w/44t ragjoint, mtb frame, city slick type tires.
Top end is 24mph.
I cruise at abt 17mph.

My 180lb kid ran it through the traps at 29mph.
rc
 
Before we go too far:
Historically this subject has a way of causing arguments. If you disagree with someone's speed claim, ignore it and move on. No arguments, please.
Tom
 
lol

I promise I won't go too far, Tom!

...I don't trust the tensioner on my motorized bicycle very far!
 

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This past Saturday I replaced the original 44-tooth rear sprocket with a 39-toother, to try to improve my speed on level pavement. With a 66cc "China Girl" engine, my new setup cruises at about 19-20 mph, where the old setup gave 16-17 mph cruising speed. It's interesting to note that the top speed remains about the same, at approximately 23 mph. I'm about a 200 pounder, and the bicycle is an old Schwinn Suburban five speed "touring" bike, one with 27" narrow, high pressure tires and upright seating (high wind resistance, no doubt.)

I suspect that if the little China Girl had more high-rev torque then my top speed would have risen along with the cruising speed. Perhaps some engine tuning and tweaking will nudge my top speed up into the 25 - 26 mph range, not that I'm really eager to ride a Schwinn bicycle that fast.
 
I have a Huasheng 49cc with 5:1 4G on a shift kit, 3-speed rear hub, top speed is 39MPH @ 7800RPM.
No real engine mods yet, it's got an SBP airfilter and about 34" of flexpipe with a 5-7 horse Briggs muffler.
My cruise speed can be anywhere from 6MPH to 34MPH, it's a very flexible setup.

Edit: When I had 2-strokes, my top speeds were 28 with 44T, 35 with 39T, and 42 with 34T.
Cruise speed was 15-25 with 44T, 15-30 with 39T and 20-34 with 34T. The smaller gears make for a very quiet bike under 30MPH.
Going any faster and I prolly would be wearing a piece of chinagirl in my lower extremities to this day! :D
 
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snogcel, you said you went down in sprocket size. does a smaller sprocket give more speed? what other sizes of sprockets are there? and Aleman, do you have any idea how many teeth on your gears?
 
Last fall I hit 44 mph with port/polish intake/exhaust Jet 66cc, 40t, NGK plug/wire, modded SBP Xchamber, RT carb with 70 jet and Treatland velocity stack, Puch Hi Hi comp head on 93 octane with 32:1 mix. At the time, I weighed in at 160...not so much after winter months...

That motor is going to be torn down, new bearings installed and some jug work done. Hoping for the magical 50.
 
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25+ mph (sometimes 27 mph with tail wind). This on a 45 lb. bicycle (including engine) & a 185 lb. rider. 25cc Homelite. Flat roads, sea level conditions.
 
oops!

I forgot to include that part...

I'm at 1000ft asl.

It's important, because an ICE loses 10% hp per 1000ft ASL.
(Which is REALLY serious, at the power level we are working at! lol )

Best
rc
 
rustycase said:
oops!

I forgot to include that part...

I'm at 1000ft asl.

It's important, because an ICE loses 10% hp per 1000ft ASL.
(Which is REALLY serious, at the power level we are working at! lol )

Best
rc
Click to expand...
Try 6K, MSL. That's what we here in Denver have to live with. :(
Tom
 
66 cc slant head on my cruiser with a 41 tooth rear sprocket I hit 30.8 mph.....once. Too much vibration for me. I'm 170 pounds. She Loves to cruise at 24 mph and vibration is minimal.
 
66 straight head with a bilet intake and standard 66 speed cab
27" alloy wheels on a Micargi cruiser frame- fairly upright with BMX alloy 8 inch rise bars

I have an alloy 34 sprocket on now

According to my analog speedo- which I think may read a little slow- I get up to between 25 and 30 with no trouble-
A good cruise at 30 feels still comfortable and I'm still not wide open- I move along with most of the traffic then.

I've pushed it up to 35 briefly, with the motor starting to really whine which I don't like, and it starts feeling just a bit fast anyway- beyond that, I guess I've never really opened it up all the way- I suppose in neutral wind, and if I tucked a little- it might approach 40- 37 or 38 certainly
 
I don't have the speedo installed at present, but I know I could hit 30 mph (without waiting too long to get there). I had my bike, Tempus, out on a chilly 40 degree morning one time. Once she warmed up a tad she was really itching to fly. All the power I could want from the thing. And I can tell my throttle's not all the way back when I'm at 25 mph.
 
Schwinn DelMar, 66cc BGF engine, slant head, brass bushing replacing needle-bearing on wrist-pin, Billet intake, SBP Xchamber, Dax carb with #70 jet and 36T alloy sprocket with my 215lb self I hit 38MPH yesterday. I might have been able to go faster but I my tach said 7200 and I figured that was enough for the engine. I wanna try again and gps it to see exactly what I'm doing I don't trust my bikes speedo very much.
 
faster then i can run
Slower then I normally drive a truck
what ever speed you ride at sure beats walking when its 90+ f out
 
T-Lo, a smaller sprocket on the rear wheel (which will have fewer teeth) makes the wheel spin faster as each foot of chain is pulled over it. I've seen sprockets ranging from around 30 teeth up to maybe 48 teeth advertised on E-bay, though I'm sure there are some available outside that range. I just search for "bicycle engine sprocket" and up come many choices.

Rustycase and 2door, I too am in the Denver area and have the added challenge of nearly 6,000 ft elevation to work around. (That may be a big factor which limits my top speed to around 23 mph.) I tend to be a believer in the philosophy of the "20 mph club", and generally keep my speed at or below 20mph. (Easier on the engine, less painful on my body should I have some sort of "incident" while riding.)
 
T-lo said:
and Aleman, do you have any idea how many teeth on your gears?
Click to expand...

Sure, but that information is useless to you because my setup doesn't directly compare. What's more telling is the overall drive ratio.

Here's my ratios:
1st gear = 25.5:1
2nd gear = 20.4:1
3rd gear = 15.3:1

A chinese 2-stroke kit on a bike with 26" wheels and stock 44T sprocket has an overall ratio of 18.04:1. With a 36T it's 14.76:1

Wanna play with gear ratios, too? Get the gear calculator from the "/ratiocalc" link on this post
To set it up for a chinagirl engine, enter 20, 82, 10, 44, 1, 1 and 6000RPM to represent safe redline.
 
Here's what my bike was doing according to my iphone GPS... The bike is a 1950 Excelsior with a full ported engine, stock NT carb (jetted), stock pipe (hollowed out), 40T rear Sportsman sprocket & a NGK B6HS plug (gapped at .025).
I weigh 210lbs & was riding on pretty much all level ground. (There were no big hills to boost the speed).
This will show what is possible without all those fancy parts... (Just a 40T sprocket & a little know how). ;)
VMBgpstrack.png

VMBExcelsior.jpg
 
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2door said:
Before we go too far:
Historically this subject has a way of causing arguments. If you disagree with someone's speed claim, ignore it and move on. No arguments, please.
Tom
Click to expand...

Chins 66cc, cruiser, 44 tooth, ragjoint, Conservative 70MPH....
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In the bed of my truck, I really don't know how fast I go, I just want to get there in one piece, so I by my estimation less then 20MPH. I'll have to take my GPS for a spin next out.
 
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