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cheap 66cc engine mods

We all want our bicycle engines to push our bikes faster. Get exclusive engine modification tips and suggestions from us. Also check out some of our racing members builds


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  #1  
Old 11-04-2009, 07:51 PM
bradentonmotorbikes bradentonmotorbikes is offline
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Default cheap 66cc engine mods

Okay, so I have just recently (3 months ago) installed a bicycle motor kit,
Its a 66cc and its past its break in, but im only getting about 27mph out of it.
Is there any inexpensive ways (under $75) to get it up to like 40 mph?
Also, do the NOS Kits and boost bottles from Boost Bottle Industries work well

Also, i figured this bit of info might help
I live in florida, my biggest hill is my driveway :P

Last edited by bradentonmotorbikes; 11-05-2009 at 05:36 AM. Reason: Forgot a peice of information.
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  #2  
Old 11-04-2009, 10:37 PM
Reel Adventure Reel Adventure is offline
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Default Re: cheap 66cc engine mods

Boost bottle, nope!

Change down to a 34 tooth sprocket and you should get close to your 40mph or definately 35 mph top with a 38 to 30 cruise speed depending on your set up.
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  #3  
Old 11-04-2009, 11:08 PM
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Default Re: cheap 66cc engine mods

Boost Bottle in my opinion is a joke. There are a few that swear by them, my barometer is to look at the factory engines, they are gone. They made a tiny amount of power but only on reed valve motors and only at a RPM we will never see. NOS would just burn the engine up as fast as you pushed the button. I only have one 66cc engine and I am not fond of it. It is a 48cc with a cylinder kit installed so it uses the small bolt pattern and no other top ends will interchange. I do porting on all my engines and so the 66 got the treatment, it is OK but like I said I am not fond of it. The 36 tooth sprocket might be a bit of a chore for that engine. My sprocket of choice is a 39. I am making them so the only way to get one is from Kings sprockets, they will custom make anything. Have fun, Dave
another Idea. http://motorbicycling.com/f13/stock-carb-mod-1494.html
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Last edited by Egor; 11-04-2009 at 11:13 PM.
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  #4  
Old 11-05-2009, 12:27 AM
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Default Re: cheap 66cc engine mods

porting helps a lot. on the intake, dremel out as much as you can to match the intake port on the engine. be careful not to go overboard. the engine port is bigger than the welds on the intake. while you're grinding away, get up inside of the intake manifold and smooth out the casting burrs.

the exhaust can get the same treatment, but again, there's not enough material to match the port exactly, so just do as much as you can.

pay attention to your spark plug's color till you get that dialed in.

make sure your bike's tuned up. good tires, straight wheels, no loose parts, greased bearings, etc. will help. the less rolling resistance that motor has to push, the faster it'll go.

as far as sprockets go, it depends on your weight and where you ride.

i'm 135 and i've got a 32 sprocket. works great on the flats, but bogs on steep hills. i can get an average of 37mph.

i had a 36 which worked great overall, and it averaged about 34.

nos and boost bottles are just gimmicks, don't waste your money. buy a tuned pipe instead. (haven't tried one myself, but everyone else swears by them.)

whenever you're adding a part, tuning something up, or modifying something, do it one piece at a time. that way you'll know what actually works for you and what doesn't. it'll also help you find problems. if you do ten mods at once and your bike stops running, you've got ten times the problems to figure out why.

despite what people say, don't expect much over 35mph, unless you're willing to spend money and tons of time fine tuning it. everyone likes to believe they're getting more out of their cheap little engine than they really are. (including me)
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Old 11-05-2009, 01:06 AM
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Nashville Kat Nashville Kat is offline
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Default Re: cheap 66cc engine mods

Have done:

36 tooth sprocket- Big increase and still has good accelleration- a light rider may get by with even smaller- 34 or 32

Smoother, more narrow tires- if you're riding on the road and not dirt or gravel, and want some more speed- non-cruiser tires are essential- I got some smooth tread 1.175 blackwall tires for $10 each at a bike shop- not only much less rolling resistence and so more speed than knobby 2.25 beach cruiser tires,

a more confortable ride with less vibration- knobby tires aren't meant to go very fast.

In fact the new tires made such a difference, that I ended up putting an even narrower one- a 27 x 1 1/4 with an alloy rim, on the front end for even BETTER rolling and less weight- and I put a campagnolo road brake on to fit with it- which is really a better and lighter brake than the cruiser's cantilever

Haven't done, but probably will-

new carbs are out- a slick racing carb thats a little expensive, but largelly sold out
and a new stock 66 carb for half as much- see both at spookytooth where both are sold out for now. I think they are supposed to start shipping with kits soon, so double check if you order any more kits.

The carb has been the weak link I think.

Pirate bikes makes a nice looking ported carb billet which is a larger alloy intake pipe- not much money and may try that with a different carb someday.

Good luck

Last edited by Nashville Kat; 11-05-2009 at 01:15 AM.
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  #6  
Old 11-05-2009, 08:58 AM
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Default Re: cheap 66cc engine mods

Dave, I thought I heard you say you were not fond of your 66cc engine, twice.
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Old 11-05-2009, 09:00 AM
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Default Re: cheap 66cc engine mods

I have found speeds up to 35-40 mph attainable by making sure the engine is broken in, properly set up and tuned and then turning the throttle to full and waiting for about a minute to pass.
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Old 11-06-2009, 12:44 AM
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Default Re: cheap 66cc engine mods

Joe I did say that twice! Oh well I have not run that engine in a while. I get it out to ride with my wife walking every night but it has been out of fuel for a long while. I have a 30 tooth sprocket on the thing and it is too small, I just wanted to see how it would do. Actually for just rolling along on the flat it is fine and it would get good fuel mileage. It takes a lot of slipping to get it going, I guess if I raised the compression a little and made the transfer ports larger it might be able to top out with that sprocket, I wonder what the top speed would be? I always take my engines apart before I run them and this one the crank was rusty and dirty inside, looked like the parts lay outside for a while before it was assembled. I guess that turned me off to the little thing. OH well, have fun, Dave

PS: Maybe I am not fond of the rust, Fond (I did it again) LOL
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  #9  
Old 11-06-2009, 12:49 AM
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Default Re: cheap 66cc engine mods

c'mon joe, you just pedal off the line like you're in a race, trying to pull the holeshot. then it cuts down the time it takes to get up to speed to like, uh, 45 seconds...
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  #10  
Old 11-06-2009, 07:53 AM
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Bikeguy Joe Bikeguy Joe is offline
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Default Re: cheap 66cc engine mods

I did bust a crank on a Next bike- I was trying holeshots (pedal only) and I really did break the crank where it was "attached" to the sprocket. I welded it and added a Bike Bug after that.
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