Top Speed

JerboaJohn

Active Member
Joined
Jul 29, 2018
Messages
674
I'd like to see peeps filming from in a car pacing speed runs, so you can know better. probably is quite a few passing 50mph...
 


FNTPuck

Active Member
Joined
Jul 2, 2018
Messages
343
My goal is 45 from a stock parts kit/no aftermarket performance parts. That means no jackshaft as well, which would make it easy!

Did 41 on a stock DIY triple40 on a Hyper with just some upped compression, a trimmed base gasket to unblock transfer ports, drilled exhaust baffle, vented clutch cover, and an NGK plug(only part not from the kit is the NGK plug, which I swap to after the first start).

Working on one that will be the same but a fully ported jug, a few other tricks, and more mods to the exhaust. I basically am just curious on how fast you can go on an all stock kit with no aftermarket parts but with any mods allowed. The limiting factor IMO is the stock muffler...with no scavenging effect the top end is really neutered so its hard to rev em enough to go fast.

FWIW my generic motors rarely did over 32mph stock on the same exact route. Most were 28-30 (although that was with 44t vs 36t rear sprocket.)
 

junglepig

Active Member
Joined
Oct 30, 2018
Messages
218
I'm running a totally stock 69cc (47mm X 40mm) generic china girl from an eBay seller, mounted on an old Murray Monterrey cruiser. 10T/44T, 26"x2.125" tires, stock kit exhaust. (EDIT: I believe this is A-80, Long Rod, "B" piston configuration - not confirmed yet.)
I was verifying my speedometer today with GPS and on the flats it will run to 38 mph, at which point the vibration becomes unnerving, and I slow down.
That's just over 8K rpm. At 30 mph (6.5K) it's pretty smooth.
 
Last edited:

HumanPerson

Active Member
Joined
Mar 4, 2017
Messages
782
I'm running a totally stock 69cc (47mm X 40mm) generic china girl from an eBay seller, mounted on an old Murray Monterrey cruiser. 10T/44T, 26"x2.125" tires, stock kit exhaust.
I was verifying my speedometer today with GPS and on the flats it will run to 38 mph, at which point the vibration becomes unnerving, and I slow down.
That's just over 8K rpm. At 30 mph (6.5K) it's pretty smooth.
Nice Speed :)
 

Lukesky36

Active Member
Joined
Oct 3, 2018
Messages
311
on my next bike im going to sell im putting a 36 tooth on it i always wanted to try a 36t on the road
 

junglepig

Active Member
Joined
Oct 30, 2018
Messages
218
Nice Speed :)
Thanks. I've had very little to do with it, other than a reasonably careful installation. I'm very happy with how well it manages the hills in my area of north Georgia. And it's more than fast enough for the frame it's built on.
 

CrazyDan

Well-Known Member
Joined
Jul 9, 2016
Messages
1,576
I'm going 47.4 mph right now on my jackshafted 53cc 4 stroke. 14.69:1 reduction at 9000 rpm in 7th gear. No real vibration with this monster. Pulls wheelies on accident in 1st gear with a 35.61:1 reduction.
 
Top