chain help

[studysession]

I am not sure what chain I have or need....

I have the 49cc engine pictures with the sprocket shown. I also have the rear of the scooter I want to use on my project mini-bike.

What sprocket and chain do I need to get for the replace the sprocket and chain for the rear of the scooter to match on the engine?

Thanks -

 

[studysession]

Anyone?

 

[Russ2251]

Measure distance between teeth, center to center.
This will determine chain size.
Use a caliper.

 

[studysession]

Am I measuring metric for the size?

 

[Russ2251]

Inches
#25 chain is likely.

 

[Russ2251]

http://www.gizmology.net/sprockets.htm

 

[studysession]

I think I am doing something wrong

 

[studysession]

Thanks for the link!!

 

[The Mechtician]

You're measuring correctly, at least good enough to ballpark a chain size out of an unmarked sprocket It looks like it's closest to a #35 chain, which has a 3/8" pitch. Check the sprocket thickness with your caliper, if it's a #35 sprocket it should measure 0.168" thick.

 

[studysession]

with reaching the caliper into place and measure without taking the small sprocket off - its pretty close to the measurement you posted. Nice!!!!

Thanks

 

[studysession]

Closer inspection as I pulled it out of it's box -
It shouldn't hurt anything, but does bother me since it's new. Emailed the seller and no response on a few items, lets see if they respond to this.

 

[studysession]

Anyone know where I have 2 holes in the carb? I assume I only connect the fuel line to the one with the open and shut valve?

 

[robbie]

Your chain may be 8mm. If it is, #35 will look like it's close, but it won't really fit.

 

[studysession]

I assume I measure the sprocket bolt pattern from the center of the bolts so I can order to correct replacement for the rear?

Thanks

 

[studysession]

The EBay seller just replied about the crack message i sent. Hope we work something out.

 

[robbie]

You can run that engine without even noticing that it's damaged. It's just a cracked cooling fin.

Regarding your rear sprocket, what exactly are you ordering? You have an engine with a reducing transmission, and you have a sprocket and wheel on the scooter. Does the output sprocket on your transmission take the same chain size as the rear wheel sprocket?

 

[studysession]

No they are definitely different chain sizes. The chain on the scooter is small compared to the sprocket on the engine.

I want to make a mini-chopper. Figure would use some parts from the scooter (wheels and stuff) since the scooter doesn't work. Friend gave it to me because he was throwing it out.

 

[The Mechtician]

Anyone know where I have 2 holes in the carb? I assume I only connect the fuel line to the one with the open and shut valve?

The port with the on/off valve is the fuel inlet. The hole with the black rubber boot overtop is the throttle connection. Pop the boot off and you'll see the throttle cable ferrule & slack adjuster.

 

[studysession]

Cool thanks!

This is all new to me and I have no clue what it all means yet.

 

[robbie]

I am seriously doubtful about the size of your chain. That's a Chinese transmission, which means that it has a strong likelihood of being an 8mm sprocket.

Chain measurements are from the center of the roller to the center of the next roller. If you measure your sprocket at the tips of the teeth, the measurement will not be accurate. You'll get a bigger number than what the chain really is, because the chain sits down in the valleys. Measure from the center of one valley to the next and you'll get the correct measurement.

If your caliper reads MM and inches, set it for MM and see what it says when you measure in the valley. 8mm and #35 are almost the same, but not quite. 8mm is .314 inch, #35 is .375 inch.