How To Make ZoomBicycles 66cc 2-Stroke Engine Go Faster?

besides pushing it off a cliff, the simplest way to go faster is to tune the engine.

matching the ports to make it breathe better and upgrading the plug and plug wire to make it fire better are two simple and cheap methods anyone can do.

a finely tuned, bone stock kit and sprocket will easily do 35 mph. add a 36t and you can get 40 out of it.

i run the NT carbs on my street bikes, and have raced with them, too. upgrading to a mikuni or dellorto is nice, but it'll only get you a few more miles per hour. depending on how much you wanna spend, it might not be worth it.

the stock exhausts seem to get worse with every batch. i like gutting them and welding the endcaps back on. makes it a little noiser, but quieter than an expansion chamber.

i've tried a few chambers, from factory to custom made, and have yet to find one that works as well as everyone claims. i've never had that "on the pipe" boost that you're supposed to get.

my daily rider cruises at 45 and tops out around 50 on a good day, and has the NT and a modified stock exhaust. the barrel is reversed so the carb's in front, and a 30t sprocket. it's mostly just tuned correctly. being 135lbs helps, too.



you can bolt on parts all day long, but if you skip the basics, it won't help at all.

i got my sprockets a while back when manic mechanic was still around, before he went crazy. i use the hub adapters he made.

Pirate cycles makes an adapter and sprockets, i think you should be able to get a 30 from them.

Sportscar pat makes an awesome adapter, too. but i think he can only go down to a 34t sprocket. check the "sportsman flyer" ad on the sides of the forum.

epoxy won't hold a sprocket. there's enough torque from the engine to break studs, loosen wheels, and break chains. there's no way JB weld or anything else can hold up to that. your only option is a sprocket adapter if you want to run custom sprockets. pretty sure the smallest kit sprocket is a 36.

porting the intake and exhaust flange can be done with a dremel tool or a drill with a grinding bit on it. really simple. if you buy a new carb, you won't get all the benefits of it if the ports aren't letting it breathe properly.

NGK's will screw right in. thread pitch on spark plugs is pretty universal. their might be some oddball threads for small engines, but ours are the same as any car.

any auto parts store sells a plug gapping tool. they're usually sitting in a jar near the cash register and sell for a buck or so. it's a small round keychain lookin' thing.

it's got a groove on the outer edge of the circle that looks like a little ramp with numbers on it. basic plug gap is .025".

you stick the electrode of the plug (that's the bent-over tip on the bottom of the plug) on the ramp and slowly work it around till the center of it points at .025. if you go to big, lightly tap the plug on a hard surface to close the electrode a bit.

super simple. i'm sure you can google a video of it if my explanation baffles you.

to change the plug wire, you need to unscrew it from the black CDI box. the newer kits are gluing them in now, so it's kinda a pain to get it out. it'll break off when you try to unscrew it and you spend an hour scraping little chunks of wire and glue out.

you'll need a small pick and some patience. you don't want to completely destroy the plastic surrounding the wire.

besides the glue, the only thing holding the wire on is a pointy screw, so you just make a clean cut on your new wire and screw it in till it stops. i use heat shrink tubing over the end to seal it up.

i use 7mm copper core plug wire. it's getting kind of obsolete lately. most good auto parts stores (independent ones, not like autozone or pepboys) will have it by the foot. you'll also need a boot and a crimp for the other end.

you can crimp the other end with some basic tools, a knife and some crimpers, or pliers will work, they just don't work as well. google it, it's easier then me explaining it.

finally, yeah, i rip out all the crap inside the exhaust. this is easier said then done on some of them. if you have the kind with the tiny bolts and the casing slides out, it's simple. if you have the sealed one with just an endcap bolted on, it's a pain, and you might not be able to do it. since i can weld, i just cut them open and weld them back up.

if you can't tear it apart, you can drill a few holes in the end cap.

that should cover it...

Have you tried using higher octane gas? A guy I work with switched and has noticed a difference in speed and mileage. He also uses synthetic oil, as recommended in the manual.

I've been thinking of purchasing from Zoom Bicycle. What's your opinion on the engine kits they have?

The first thing you should do to a new china kit is to take the stock spark plug, spark plug wire, and chain and throw them in the trash. You already have the info on the plug and wire, as to the chain go to your local farm type store(Farm and Home, Tractor Supply Co., Big R, Rural King, ect.) and buy #41 roller chain. It comes in ten foot lengths(will do two bikes) for $10-$20. I bought mine at Farm and Home for $20 but it is name brand D.I.D chain. Well worth the extra money in my opinion. The next thing you are going to want to do is address the stock tensioner. There's a few ways to do this. Search it and find what will work best for you. I used a piece of flat stock drilled some holes to clamp it to the frame and drilled a hole for the idler wheel, and used the stock idler wheel with a longer bolt. The easiest way would probably be to put a few tacks on the stock tensioner. I know you said you have no way to weld but you might try your local muffler shop see if they would be willing to do it for you. It would probably be best to have it prepped and ready to weld when you take it there. Just sand off the paint were they will be welding it. As far as porting unless you have experience I would recommend you only port match it. Port matching is were you make the holes in the exhaust and intake as close to the holes in the engine. If you were to buy an aftermarket intake you would only have to port match the exhaust. As far as sprockets go if you use a 36 tooth sprocket you will have to do alot more peddling on take off. I used a 40 tooth and found this a good compromise between speed and take off. As far as carbs go I would recommend the speed carb it is easy to tune and makes good power. If you are interested I have some used parts for sale that could save ya a few bucks take a look.
http://motorbicycling.com/showthread.php?t=46283
Good luck with your new build if ya have more questions feel free to PM me
Mark

I been glancing at kits for sale on Kijiji. I don't know whether I would trust the sellers on those. I don't recall seeing anything about a warranty either. A 66c kit is $150. Which is the same price other websites are showing that offer a warranty.
I live out near Peterborough, Ont. so would have to order online.
Also, is there a special mounting bracket required for an approx. 2 1/2" -3" frame? Not the seat frame but the other that leads from the handle bars down to the peddles. Whatever it's called. Can a u-bolt be used for that?
If someone could attach some pictures if they had to do something like that, I appreciate it. It would give me an idea of how to assemble it when I get it.
Thanks.

sick bike parts has a u-bolt clamp kit ready to go for larger frames.

Ive just got mine consistently to 42 mph but it took a lot of tuning, testing and trying different parts. I am running a SBP shift kit and the extra friction and rotating mass prolly slows me down by 2-3 mph.

The 2 biggest gains I have seen is the Slick Bike Parts pipe and Jaguar ignition. The Jag ignition was the biggest gain in overall performance and mph. Another big gain was the Puch head. Heres my thread on all the tuning and testing I have gone thru so far..... http://motorbicycling.com/showthread.php?t=45435

Vinoy, I went with your first suggestion of Iponic Zone. I drove out there last Thursday and picked one up. I have it on the bike now and just have to do some fine tuning before I use it steadily or more often. I have to adjust the clutch so the rpm's don't increase when I hold the clutch in. I should also check for air leaks. I had to pick up a larger u-bolt than the one that came with the kit for it to mount on my bike. Plus a piece of metal.
What is the minimum speed they will go without using the throttle and stalling the engine? I live out near Peterborough and I may get my son a smaller engine so he can use it to go beer bottle hunting to make a bit of extra coin.

check my bairdco channel on youtube for "getting beer is uphill all the way."

from a dead stop, running an 85lb cruiser with a 30t and 24" wheels up a 1/4 mile 6% grade at speed, in traffic...

All I can say is, with 44T I can climb some pretty crazy hills, with 14 less I would climb less of those hills and going off-road forget it, I need low gear for that.
My goal is 40 mph and I am almost there.