Any suggestions for improvement on my kit??? Pros advise needed!

Tsbrunell

New Member
Apr 22, 2011
13
0
0
Harford County, MD
So I put together my kit over a month ago, and have had a lot of ride time on it already. As far as i and a friend know, everything has been put together right, with all the stock parts (it's a Grubee Skyhawk 2-stroke 66cc). It's on a basic Schwinn cruiser bike, I put a real strong wider wheel on the back and a thinner wheel on the front.

Last night, i had a friend drive his car right beside me on a few long straight-away roads at my bike's full throttle, but according to his speedometer, i was maxing out at around 32mph......

This was kinda disappointing, i thought i've been somewhere 40 and 45mph..

Since the start, i've removed all the fenders and replaced a bunch of minor parts on the bike, so it's already pretty lightweight.

What improvements can I make to get more power/speed? Are there any better parts online i can replace the stock parts with that would improve performance? Any homemade ideas that anyone has?

Thanks!!
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
6,599
403
83
Los Angeles, CA.
Think about getting real good brakes BEFORE thinking about going faster! (That's a pro's advice!) ;)

Also... 32 MPH is pretty good for a new stock engine kit!
 

wheelbender6

Well-Known Member
Sep 4, 2008
3,983
111
63
TX
A shift/jackshaft kit will give you more top speed (and help on climbing hills).
Most people think an expansion chamber exhaust is the best motor mod for the dollar (2 strokes only).
You can also try to adapt a reed valve intake from some other motor (like a chain saw) to boost low and midrange power.
Venice is right about beefing up the brakes. When you watch those car hop up shows on speed channel, most motor hop ups are accompanied by a brake hop up.
 
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Tsbrunell

New Member
Apr 22, 2011
13
0
0
Harford County, MD
Haha yeah, I got an upgrade on my coaster brake hub, also i put on some universal caliper brakes on the rear.

And awesome, still looking into an expansion chamber, looks good but they're a little expensive. I just ordered some Amsoil Intercepter oil, maybe it'll give me a little better performance.

At what point is the motor considered to be broken in? I noticed that most people on here say their motors are kicking out close to 40+mph after 1000 miles or more were put on, I probably have about 30-40 miles at most, i'm guessing that that's not near broken in yet?

Thanks all by the way, this is a good forum! I had no clue how many people were in to building motorized-bicycles!
 

freewheeling frank

New Member
Mar 10, 2009
440
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ridgway colorado
i do alot of playing with the carb jet and it makes a huge difference in power, but i am at 7000ft and its all uphill from here, i have tried expansion chambers but have just as good of results by taking the end cap off the muffler then drilling the inside plate out, like 4 3/8 holes louyd but works good. oh and the jet i just solder shut and drill it out using a small srt of bits i got from hobby lobby
 

Tsbrunell

New Member
Apr 22, 2011
13
0
0
Harford County, MD
Hmm, i'm gonna try that mod on the muffler. What exactly do I do? Do you mean to just drill holes in the muffler cap, or something on the inside?

I took the cap off, looked in and there's just a plate with a few drilled holes in it....
 

Nougat

Active Member
Nov 4, 2009
1,332
2
38
Montgomery, IL
An expansion pipe is a necessity, and it should be paired with a high flow air cleaner. Then port match the intake and exhaust. Once that's done, rejet, and experiment with plug gaps. Beyond that is porting proper, which is over my head, adding a high compression head.

On the other side of the coin is reducing rolling resistance. Run the thinnest, smoothest tires you can. Low handlebars, and tuck down low to reduce wind resistance, although this will feel like you are going to die if something dangerous happens.