hi, want to go from stock 45 tooth sprocket to 40 rear sprocket. do i need to get new chain length? does any one know what the stock chain length is? looking for alittle more top end speed on my 78' puch. does that sound like a nice change in size?? thanks
I'm planning on doing the same thing. Haven't gotten around to it though. I'll be reading the responses.
Mine is a '78 Puch (Magnum MK II), also.
Yes, you need a new chain length but not a new chain. Using a chain breaker take as many links out as necessary to make the chain fit, but first, run your rear wheel all the way forward, or as far forward as it will go and still clear the swingarm. Fit the chain and take out the slack. Sorry, but I don't know what the standard length of the chain was. Yes, that size is a good choice, it'll give you a nice balance of speed and power provided your moped is tuned up good.
Just do NOT make the mistake of removing the same number of chain links as teeth. I just doesn't work that way. I went from 46 to 40, then 40 to 36. No way have I removed ten links.
If you are careful you can remove chain links in a bench vise with a hammer and punch.....and a ton of rags. Don't forget to lube the chain again after re-assembly!
If you replace the 45 with a 40 you will engage 2 1/2 fewer teeth with the chain. Therefore you should remove 2 links and make up the half by moving the rear axle. You cannot remove three links unless you have a special link. If you have an odd number of links now you will find the special link on the chain. By link, I mean every space in the chain. You should have 99.
Theoretically, your top speed will increase by the rario of 45/40 or about 12%. If you go 25 now you may go 28 with the sprocket change. Hardly worth it unless you go with a front sprocket of 18 teeth also. I cannot say now how much torque is required to drive the combination of 18 front and 40 rear, but I am going to try it Thursday. I have the present combination of 14 front and 45 rear and a 1.5 hp engine. I will put 18 front and 40 rear Thursday. The advantage of changing both sprockets is that the old chain can be used. If you want, I will let you know how it works out.
thanks all. i would be gratful oldtimer, just to see if its worth it.
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