Motorized Bicycle Engine Kit Forum  


Go Back   Motorized Bicycle Engine Kit Forum > Motorized Bicycle > Motorized Bicycle General Discussion

Motorized Bicycle General Discussion All topics regarding bicycles with engines.

Thread Tools Display Modes
Old 04-08-2012, 10:23 AM
newbybikelover newbybikelover is offline
Motorized Bicycle Newbie
Join Date: Apr 2012
Location: abilene texas
Posts: 11
Question bike is way slow, any ideas?

ok, so, i have built my second engine on a bike, the first one was with a friend on his bike, everything went fine except the carborator filter kept falling off. i built my bike on my own with a little hole drilling help from my girls dad. And my bike is solid no problems at all, everything is very sturdy with a perfect fit. They are both the same engine, a grubee skyhawk GT5 2011, my friends bike is pulling at least 30 mph and faster passing all the trafic (he does have a speedometor), the advertised speed is 30 mph. My bike is only pulling at LEAST 20, working its way up slowly once it reaches 15, any ideas what i did wrong? my own thought would be that i probably over oiled it (which i did at first) but will that effect it that much?

Reply With Quote
Old 04-08-2012, 11:35 AM
Bikeguy Joe Bikeguy Joe is offline
Godfather of Motorized Bicycles
Join Date: Jan 2008
Location: up north now
Posts: 11,531
Default Re: bike is way slow, any ideas?

Well, what is "over oiled"? 40:1 is a good mix, then see how fast it goes.

Also, 20-30 mph is the average speed of these things.
35mph? Maybe....25mph. Yep, all day long.
Reply With Quote
Old 04-08-2012, 12:37 PM
2door's Avatar
2door 2door is offline
Super Moderator
Join Date: Sep 2008
Location: Littleton, Colorado
Posts: 16,224
Default Re: bike is way slow, any ideas?

One big difference might be that your friend's bike engine is broken in and yours is not. These little engines run better and better the more miles they accrue.

Also are the rear sprockets the same size (tooth count). Rider weight? Tire size?
There are many variables to consider when comparing performance. In addition it is a known fact that some engines just simply run better, produce more power, than others. Maybe your friend got a good one.

Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"
Reply With Quote
Old 04-09-2012, 06:37 PM
tooljunkie's Avatar
tooljunkie tooljunkie is offline
Motorized Bicycle Elite Member
Join Date: Apr 2012
Location: Manitoba,Canada
Posts: 659
Default Re: bike is way slow, any ideas?

i put a tach on my grubee,48cc.tops out at 6300 rpm's.i read somewhere 7000 is the peak rpm for these engines.
if you could get your hands on a tach and compare the two,you may at least have an idea what you are revving.
youtube has a great video about four-stroking,the demonstration clarifys things.

Last edited by tooljunkie; 04-09-2012 at 06:39 PM. Reason: added link
Reply With Quote

engine, engine problems, slow, slow engine, speed

Thread Tools
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

All times are GMT -5. The time now is 10:10 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2016, vBulletin Solutions, Inc.