Go Back   ScootDawg Forums > Performance :: Maintenance :: Technical > 50cc - 124cc
Reply
 
Thread Tools Search this Thread Display Modes
Old 08-08-2015, 02:14 AM   #1
Retro   Retro is offline
 
Join Date: Aug 2015
Posts: 1
just installed a 80cc big bore kit and want more speed

Hey i just a installed a 80 cc airsal big bore kit in my Baotion Retro (BT50QT-11) scooter, it has the 139 qmb engine btw.

Going up hills and acceleration has improved a lot, but i would like to make it go faster i got maybe a 10 km/h speed improvement after i installed the kit.

What should i do buy a new carb or just install new jets if so what what size would you recommend? thinking about buying some roller weights as well but not sure which ones to buy, it got 7g weights stock. i am supremely fat and weigh around 300 lbs btw. any other suggestions to make it go faster?



Login or Register to Remove Ads
  Reply With Quote
Old 08-08-2015, 01:19 PM   #2
rks   rks is offline
 
rks's Avatar
 
Join Date: Dec 2013
Location: Western New York
Posts: 454
Maybe you need to lower your expectation, of what such a tiny engine is capable of doing. You have to know how many rpm's your engine is producing at top speed, before tuning your cvt....so, do you have a tachometer? One would think that if it came stock with 7 gr weights, that after a bbk install, a heavier weight would be ok. But this may not be the case, considering your size.

So is it cranking out 8000 rpm's at top speed.....or unable to reach 6500?
__________________
2011 Jonway 150cc..16,109 breakdown free miles, and counting

  Reply With Quote
Old 08-11-2015, 07:43 AM   #3
cheapeto   cheapeto is offline
 
cheapeto's Avatar
 
Join Date: Jul 2008
Location: York PA
Posts: 339
IMHO, you need to look here:http://www.partsforscooters.com/Stre...gines-Complete
You can get a new 150 cc motor for $415.00 to $425.00 you'll have the power you need.
__________________
Ride For Kids.org



Login or Register to Remove Ads
  Reply With Quote
Old 08-11-2015, 11:34 PM   #4
Dodgeme   Dodgeme is offline
 
Join Date: Jul 2015
Location: schofield, wi
Posts: 23
Quote:
Originally Posted by cheapeto View Post
IMHO, you need to look here:http://www.partsforscooters.com/Stre...gines-Complete
You can get a new 150 cc motor for $415.00 to $425.00 you'll have the power you need.
First a 150cc engine will not bolt into a 50cc chassis. next its actually pretty simple to get more out of those engines.
  Reply With Quote
Old 08-11-2015, 11:50 PM   #5
Dodgeme   Dodgeme is offline
 
Join Date: Jul 2015
Location: schofield, wi
Posts: 23
Quote:
Originally Posted by rks View Post
Maybe you need to lower your expectation, of what such a tiny engine is capable of doing. You have to know how many rpm's your engine is producing at top speed, before tuning your cvt....so, do you have a tachometer? One would think that if it came stock with 7 gr weights, that after a bbk install, a heavier weight would be ok. But this may not be the case, considering your size.

So is it cranking out 8000 rpm's at top speed.....or unable to reach 6500?
Yes knowing the rpms is a good point but you can do a lot with these little engines once you know. The next changes I would make are for airflow efficiency a stock cam is at its limit at 80cc. I would also look into a performance exhaust and into either retuning (rejetting) your carburetor or getting a retuned (rejetted) carburetor. Then I would look into performance variators most performance variators have different ramp profiles from stock and thus change the way it shifts with the same weights. At this point you may wind up hitting redline too easily and if you ride mostly on the FLATS you could look into regearing. If you deem regearing to be the right option regear to a taller gear for flats (numerically lower ratio) it may feel stock again or slightly sluggish off the line but will have a higher top speed (of course it depends upon the engines actual power output).



Login or Register to Remove Ads
  Reply With Quote
Old 08-12-2015, 07:26 AM   #6
blueboy5000   blueboy5000 is offline
 
blueboy5000's Avatar
 
Join Date: Jul 2011
Location: Connecticut
Posts: 493
Having installed literally dozens of bbks on 139, 1p40, 157 and 152 engines, as well as being extensively familiar with all makes of scooters since I built my first Lambretta in 1988, I will now state that achievement of any flat land speed of over 5Omph on a 73cc 139, is pretty good, and about all it will do.

Mods help the 139 gain acceleration, but really don't do anything to the top end. A 73cc engine is approximately 4cid, or 1/3 the displacement of the cheapest lawnmower available at Wal-mart.

To assert the modified 139 is capable of speeds in excess of 55 mph on flat ground, is untrue, and unrealistic.
__________________
2011 Roketa MC-23-150

4T 150cc 157 qmj

24mm carb w 115 main jet and paper cone air filter

Manual petcock w Tygon fuel lines

Scrappy Dog Scooters Retro-slash stainless straight-thru exhaust

RED spring clutch

Adjustable CDI (brand unknown, it's blue and red and works great!)

KOSO high performance variator w 12g sliders

Gates Powerlink 835-20-30 belt

GPS verified 65mph on flats.
  Reply With Quote
Old 08-13-2015, 03:00 AM   #7
Dodgeme   Dodgeme is offline
 
Join Date: Jul 2015
Location: schofield, wi
Posts: 23
Quote:
Originally Posted by blueboy5000 View Post
Having installed literally dozens of bbks on 139, 1p40, 157 and 152 engines, as well as being extensively familiar with all makes of scooters since I built my first Lambretta in 1988, I will now state that achievement of any flat land speed of over 5Omph on a 73cc 139, is pretty good, and about all it will do.

Mods help the 139 gain acceleration, but really don't do anything to the top end. A 73cc engine is approximately 4cid, or 1/3 the displacement of the cheapest lawnmower available at Wal-mart.

To assert the modified 139 is capable of speeds in excess of 55 mph on flat ground, is untrue, and unrealistic.
unfortunately I have to disagree because mine did 50mph clocked by gps, chase cars, and a police radar gun going up a 4% grade and that was only at a 47mm bore with only a 1500 rpm gearbox side cvt spring upgrade, but without improving the cylinder heads flow characteristics, without improving the lean factory a/f ratio (stock carb), without regearing, without a full synthetic motor oil, and without retuning the engine side of the cvt. Now if you had ever tried increasing the engines pumping efficiency you would find that indeed you are wrong and that you really need to learn how to correctly optimize an engine. I trained in college and yes I have a degree in auto, diesel, and industrial applications including high performance and how to maximize any engines overall performance and longevity.
  Reply With Quote
Old 08-13-2015, 06:03 AM   #8
blueboy5000   blueboy5000 is offline
 
blueboy5000's Avatar
 
Join Date: Jul 2011
Location: Connecticut
Posts: 493
You're all kinds of wrong. I really wish the admins would stop letting you post bullshit.
__________________
2011 Roketa MC-23-150

4T 150cc 157 qmj

24mm carb w 115 main jet and paper cone air filter

Manual petcock w Tygon fuel lines

Scrappy Dog Scooters Retro-slash stainless straight-thru exhaust

RED spring clutch

Adjustable CDI (brand unknown, it's blue and red and works great!)

KOSO high performance variator w 12g sliders

Gates Powerlink 835-20-30 belt

GPS verified 65mph on flats.
  Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 03:20 PM.

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.