Speed Problem

[BThor99]

So for Christmas I got myself a flying horse 66cc/80cc 2 stroke dragon fire engine kit from bikeberry.com and it said it could do 25-40 but I only can top out at 18 mph. I even got the upgraded carb also from bike berry but it made no difference from the stock NT carb the kit came with. I am a pretty slim guy, only 140, but my bike still isn't fast.

Also, the bike idles only sometimes and I have to have been riding it for about an hour for it to do so.
Any feedback on the matters would be appreciated by this newbie. Thanks.

 

[butre]

there's a load of things could be going wrong, first thing I'd check is for air leaks

 

[crassius]

if it only idles with screw turned all the way in, that usually means you're too rich (on the NT, you would lower the needle a notch ot two)

 

[Purple Haze]

They require a break-in period, after about 2 tanks of fuel, you'll feel it getting more powerful and free-revving. Then dial-in the carb; you'll probably have to re-jet it, they are usually too rich from the factory. If you live close to sea level, a #64 will get you close. (#70 is stock) The higher the altitude, the leaner you need to go. The needle height will only affect part-throttle and idle, but is a good place to start. Try it with the clip in the top notch, if it idles and runs better, you need to lean out the jet for optimum top-end power.

 

[butre]

if it takes you 2 tanks to break in you've glazed the rings. a proper break in takes about 5 miles.

also I find that a 66 or 67 is what you want for sea level. just my experience with my density altitude, might be different in hotter or colder or more or less humid climates.

 

[aquielisunari]

In addition to the other suggestions there are a couple other things to consider. Right now your fuel to oil ratio should be 16:1. You shouldn't expect top speed with so much oil. Less gas=less bang. Everything needs time to settle in. The rings for one. Don't rush it. You should run at least 2 gallons of gas before you switch to 36:1. 3 gallons(not tanks) is safer. After that you should see some speed improvements. Your gas mileage should also improve. When you pass the break-in period you should take that 44 tooth sprocket off your wheel and install a 36 tooth sprocket. . That will give you a speed boost. There is a trade off. A lower tooth sprocket will give you more speed on the flats but you lose torque which means less power to climb hills. Go up to a 50 tooth sprocket and it will climb hills like a champ but your top speed is lower.

 

[Deleted member 12676]

butre is right, the best way to break in an engine is with limited times of full on throttle. by "limited times" I mean don't go full out for prolonged periods of time. Take quick short breaks to let the engine cool down.
anyway your problem isn't because the engine isn't broke-in. something is wrong. most likely you need a different main jet (after putting a good air filter on it and throwing far away the stock trash) or you have the typical head leakage and you need to plane it flat with sandpaper on glass. beyond that I'd look at crank seals (if you're sure there is no intake leak) making sure they aren't leaking.