How fast can your 80cc really go?

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BrettMavriK said:
Hey,
This is not a pissin' match.
Chill out. It's a place to share info and
give input. This thread may lay claim to
some Bull Puckey, but that doesn't mean go
attack someone's every word and chastise them.

Go take your frustrations out elsewhere....
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Your right its not a pissing match, different forum. Seriously you could answer a few points/ question raised like the racing fuel? gear ratio's dont matter? 48.5, 55, or 60mph which is it? honestly it reads like the chineese instructions supplied with the kit.

Some people have posted some funky speeds in this thread i just think its about time people show some factual evidence of it to back it up or expect a responce in disput.
I think the bullies are thoes who pull 10-20mph outta thin air.
 
I can haz 32mph if I whisper sweet nothings to me bike... "yea baby, how u likin' that Amsoil?" "Come on honey please? I got a new tuned pipe inna mail fer u!" "Aw darlin' I swear I'll wash ya when we get home... mebbe tomorrow..."

Perhaps I just need to change that damn sprocket lol

I could provide you with a lil movie clip of my GPS as I'm riding ona rare (around here) flat section, but not only is this a believable speed - but I'm askeered of dying tbh

or just dropping my camera ;)
 
Brett,,,you have a purpose built frame
ie...you designed it to do that :)
most are not capable of the vibes and/or stresses related to that kind of prolonged speed
trying to do 50mph on a 100-200$ bicycle is foolhardy at best and could be life-threatening at worst

I did not mean to sound condescending to your skills or others who have proven they have done their homework 1st
 
Not at all, AZBill,
and I agree with you.
I would never attempt to run over 30mph
on any store bought short wheelbase bike with a high center of gravity,
and without good proper braking. Now there are some well made bikes like
Pipelyne with great brakes and suspension that I would have no problem redlining.
I'm even pushing it with my bike,
as the Achille's Heel is the wheel bearings.
I have mine liberally repacked with grease and carefully tensioned in their races.
Not Tight, but No Slop is the magic setting.
Someday, I will have hubs made with tapered roller bearings and wheels
with 11 ga. spokes. I cruise at 40 mph in 5th gear and have just stopped to
get off and feel the hubs for heat or resistance in the roll of the wheels.
So far they have been cool as a cucumber.
 
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Sweet ride BrettMavrik. I see you have a similar jackshaft set-up as I do with my Stiletto. You might want to consider a Mega-range gear cassette. 1st gear-34t, 2nd gear 24t, 7th-14t. I had to build a chain guide to feed the chain onto the jackshaft drive gear straighter to keep the chain from jumping off when shifting. Works perfect though. Have you had any similar problems?
Anybody trying to go faster than 40 on a Mountain bike is trying to commit suicide in my opinion. A low center of gravity like Bretts' or a Stiletto is a must for those kind of speeds. Also good brgs in the hubs like in the 15mm axles on my bike. Not standard 13mm bike axles.
 
I hit 62kmh/38.5mph today on a slight decline. My best speed so far. I think I could have kept going but I freaked out a bit lol. I have 38x700c tires running a 9 speed deore rear cassette. This is with a skyhawk gt5 66cc, rocksolidengines billet head, SBP shift kit with the 10tooth, SBP expansion chamber and a boost bottle.
 
BrettMavriK said:
Achille's Heel is the wheel bearings. I have mine liberally repacked with grease and carefully tensioned in their races. Not Tight, but No Slop is the magic setting. Someday, I will have hubs made with tapered roller bearings
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Absolutely true. Those bearings are the only thing that will ever strand you (ask me how I know). Anything else and you can pedal or hold together with baling wire.

IMO most of the hop-ups and upgrades talked about here are baloney and for those with more money than brains. But I'd pay a few bucks for hubs like those.
 
I Hope This Is Ok In This Thread!! If Not, Let Me Know, I Will Delete It.last Year We Clocked Friction Drive, 49cc Pocket Bike Engine, No Mods, 1 1/4" Drive Roller At 35 Mph. With 180 Lb Rider. I Feel It Would Do More With The New 1 1/2" Roller From Bmp. It Would Start Out In The Grass With Me (300+ Lbs) 1/2 Turn On The Pedals. My Gps Street Pilot Shows My Speed At 70 Mph On The I System, The Truck Speedo Shows 72. Mph. So The Ht With Mods Should Do Much Better. My 2 Cents. Ron
 
Theoretically a friction should be able to top out much faster than HT. The gears are limiting factor and I gotta laugh at claims of 50mph or even 40mph with a stock kit.

And don't forget a small sprocket or big roller is not magic either. You need BIG hp/torque to take advantage of those. Something stock engines are not famous for.
 
If I can get an HT to rev to 8000, I'll pull 55mph before wind / drag coefficients
with the jackshaft and 5 speed set up on my bobber. I have a gear set for 45mph top end and one for 55mph top end.
 
Just put together my first build. Stock 66cc Grubee with 44t sprocket running on 16:1 fuel. I am 240lbs, using GPS for speed gauge.
On level ground no wind was pulling a steady 29mph, hit slight incline went to 24mph, slight decline got up to 33mph and backed off.
 
BrettMavriK said:
If I can get an HT to rev to 8000, I'll pull 55mph before wind / drag coefficients
with the jackshaft and 5 speed set up on my bobber. I have a gear set for 45mph top end and one for 55mph top end.
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And in theory my car will go a lot faster in 5th gear than it probably would in practice...
 
Since putting on a 34 tooth sprocket, I can easily get 43 mph on a flat. All I have is a single speed with a coaster brake.

I took it to one of the bigger hills this summer and was literally crawling to get to the top of it, but I went down that hill with full throttle all the way and when my speedo hit 60, it quit working and that was even before I hit half way!

Man, that was a scary fast ride, but what a rush!!
 
hiker472 said:
Since putting on a 34 tooth sprocket, I can easily get 43 mph on a flat. All I have is a single speed with a coaster brake.

I took it to one of the bigger hills this summer and was literally crawling to get to the top of it, but I went down that hill with full throttle all the way and when my speedo hit 60, it quit working and that was even before I hit half way!

Man, that was a scary fast ride, but what a rush!!
Click to expand...

60 down hill with a coaster brake??? You obviously have a real good front brake on that bike, because you're still alive to tell about it!!! laff
 
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