Racers or race engine specialists, rear sprocket knowledge needed!!!

[Frogslayer]

IKR. Dunno what you guys are doing but I’m topping out at 76mph at about 12k on 30t

We're going to need some video proof on that one mang.

 

[Spare_Parts]

I don't have to pedal to 15mph to let the clutch out. Hell, don't have to pedal unless I'm starting out going uphill.

 

[MotorBicycleRacing]

Hey everybody. I currently have a 30 tooth sprocket on my bike and it still has tons of torque and power left to give. but as is right now it tops out at about 43 Flatlands and 45 or so downhill and the engine is screaming.(too much)* I want to go faster and so does the motor. I was wondering what's the smallest sprocket anyone has used with sucess

Buy a tach so you know your rpms.
You should be over 9000, 43mph is way off for a 30 tooth sprocket.
and learn how to use a gearing, speed, etc calculator.
There is a good calculator here as a sticky thread.

 

[Street Ryderz]

IKR. Dunno what you guys are doing but I’m topping out at 76mph at about 12k on 30t

With what? Funny how you busted my balls saying this couldn't be done, yet now your claiming higher r's and speed than I posted,LOL I've still not got over 73,72.8 to be honest with 11/30 gearing and that's only 10,600 rpm so that the engine stays together, Think we are going to need some proof of that!

 

[Deleted member 26224]

It’s ugly and, scary as hell. not gonna do that again. Pictured with 44t

 

[Deleted member 26224]

Guys it was just bait for Neil Sr to see if he was gonna post it elsewhere to try and smear my name; lo and behold he did. That 2-stroke was a POS I got for free; it topped out at about 35mph, maybe not even that I don’t remember; I sold it after riding it about 10 min for $250 and my 2 stroke adventures ended with that. Was during the time my 4-stroke was stolen and a friend tried to help me out. Jokes on you Neil.

However I think it is ridiculous to be talking high speeds with those. If you are getting 40-50mph out of one of those kits you are doing it right. Enjoy it and don’t break it trying to go faster.

 

[Frogslayer]

I've found the trick is to get a low quality bike so it feels like your going insanely fast. My feel factor for my cruddy Walmart bike is real decent like 100mph. So you drive 22mph it feels like 122mph lol. Way more exciting than my goldwing which feels like 45 at 80.

 

[livingoodnathan]

First let me get this straight,the engine is screaming too much at 3/4 throttle and tops out at 43,but the engine want's to go faster?Do you even realize at what rpm that is? That poor engine LOL,try to reduce the header length first and re tune for that but tbh that's not a good pipe for competition

I know the pipe is garbage I have yet to find a 65 or 80 mx pipe for less than $200. And I justbdont have thebmoney rn. guess I shouldn't have said thevmotor wants to go faster but there is just a lot of power left. After the needle jet kicks in I go from 10 mph to 35 in like 2 seconds. I havent ran in that hard. The two times I did open it up it wasn't for long, and I did a top end tear down afterwards to make sure everything was peachy. It's still in the testing phase. I've only ran about 4 tanks of gas through it I'm currently on 32:1 ratio. I guess I'm just not used to all this power yet this is my first ground up race build. Never dealt with a reed valve or big carb before. I didn't say I knew everything. I think we all can learn something more but I'm going to try a few things tomorrow and test again.

 

[livingoodnathan]

Back in 2010, MotorBicycleRacing and I saw Bairdco go GPS-verified 55MPH using a 28T sprocket, but that bike had 24" tires and he's a compact dude, weighed less than 150lbs. That's an 11.48:1 ratio and works out to a bit under 9K RPM. Last time I talked to Baird, he said he's gone even faster.

A 30T (12.3:1) on 26" at 43MPH is a lil under 7K RPM. Going to a smaller sprocket is gonna hurt the low-end even more, and may actually reduce your top speed. Those highly tuned chinagirls like to rev. I agree with Street's observation about your exhaust. If your engine is having trouble revving over 7K RPM, you may have some kind of exhaust restriction. Even a stock chinagirl will exceed 7K RPM readily if it's not overtaxed. I've gone 42MPH with a 34T with nothing but intake and exhaust port-matching, that's ~7500RPM. I weigh 215lbs.

It doesn't have trouble reving over 7K rpm it feels like it's over reving. I feel like I should be going faster idk. I know for sure I'm restricted by this pipe. I should be running a 115 main jet and my needle should be on 3Rd or 4the hole and thats not thecase. I'mgoing to order a tacometer so i have reliable numbers Anybody know where to find a pipe that's not going to cost $300 and is already modified for a China girl?

 

[livingoodnathan]

That pipe is killing you. I have gone 54mph with 11/36 sprockets and 26" wheels. That was with the MZ65 pipe. Think 47mph was tops with the pipe you have.

Yeah that's about where I am. Know where I can get ab pipe?