twistedkeys Posted January 28, 2013 Share Posted January 28, 2013 Just changed the gear ratio on my '81. Thought I'd let everyone know some things about this. 1. DO NOT buy a gear lower than 12 in the front. The locking brace is literally 1-3mm too big and will bump up your chain. I installed a 12 and had to shave that bracket down a bit. 2. For a 12-41 it was a 97 link chain at the shortest adjustment. 3. As far as I know you can't physically buy anything smaller. They do sell 10-11tooth fronts, but as I said, you'll have to do some modifications to the locking bracket to get it to hold the chain right. Or fabricate a new one. 4. I have not tested top speed, although I am cruising at 25mph in the mid 3rd gear, instead of the low 4th gear. Still very peppy. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted January 28, 2013 Moderator Share Posted January 28, 2013 why do you want to lower your gearing? is it bogging down on you? Link to comment Share on other sites More sharing options...
twistedkeys Posted January 28, 2013 Author Share Posted January 28, 2013 why do you want to lower your gearing? is it bogging down on you? Um not really. I'm trying to get it to cruise at 65-75mph for when I take it down to SoCal. I don't think this will go faster than 70ish top speed. Cruising in the powerband for hundreds of miles is the thing that worries me. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted January 28, 2013 Moderator Share Posted January 28, 2013 lowering your gear ratios overall will raise the revs! you want a higher gear on the front sprocket ie 12 up to 13 teeth or lower on the rear ie 33 to 32 teeth that will lower the engine revs for cruising A taller front sprocket is better as the chain will have a longer circumference to go round and have an easier life. 1 tooth on the front also = about 3 teeth on the rear. 1 Link to comment Share on other sites More sharing options...
twistedkeys Posted January 29, 2013 Author Share Posted January 29, 2013 lowering your gear ratios overall will raise the revs! you want a higher gear on the front sprocket ie 12 up to 13 teeth or lower on the rear ie 33 to 32 teeth that will lower the engine revs for cruising A taller front sprocket is better as the chain will have a longer circumference to go round and have an easier life. 1 tooth on the front also = about 3 teeth on the rear. Higher means more teeth right? Too bad I can't really find anything less than a 41 on the rear :/ Link to comment Share on other sites More sharing options...
Moderator drewpy Posted January 29, 2013 Moderator Share Posted January 29, 2013 Higher means more teeth right? Too bad I can't really find anything less than a 41 on the rear :/ so you want to lower the engine revs for the same speed? put a 13 on the front BTW you can get sprockets made, not really a big deal, JT's in Wales do them and I'm sure there's someone stateside Link to comment Share on other sites More sharing options...
twistedkeys Posted February 1, 2013 Author Share Posted February 1, 2013 so you want to lower the engine revs for the same speed? put a 13 on the front BTW you can get sprockets made, not really a big deal, JT's in Wales do them and I'm sure there's someone stateside Yeah there's one down the street, no big deal, but it's over $100 for a custom 45 tooth. UPDATE: took my bike 90 miles to a ski resort yesterday (yes, with skis). There was no other way than the freeway to there so I hopped on and went for it. On the way down I had a head wind and was only reaching 50-60 MPH. On the way back my GPS died, but I was keeping up with cars on a posted 80 MPH, who knows if they were going 90+. But this was with a windshield, completely full throttle, and in the powerband. At that speed the little bike will drastically slow down if there's any hill or head wind. It's really lacking power on the highway (unsurprisingly). This is with a 16-41 ratio, had to add a link in the chain to get it to fit from my 13-41 but everything worked out. Link to comment Share on other sites More sharing options...
twistedkeys Posted February 1, 2013 Author Share Posted February 1, 2013 By the way, after 180 miles at almost 100% throttle I finally had to switch to reserve. Link to comment Share on other sites More sharing options...
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