I need opinions or advice! I need to change the rear wheel sprocket, chain, and transmission sprocket on my 1977 sportster. The stock number of teeth on the rear sprocket is 51 and21 onthe transmission sprocket. My question is: Would you stay with the stock number of teeth or is there a better combination? I do a lot of riding in the mountains and on some pulls it seems like my bike is having a hard time climbing. Thanks!

 

I'd leave the stock sprockets alone and just downshift when it starts lugging.

 

How about the other way? Ever run a 22 or 23 tooth drive sprocket?

I just read that with a 24 tooth sprocket, some clearance issues will need to be dealt with.

 

I put a 23 on mine (but it's a 1983 model), and there were clearance issues with it, too. My rear was a 48, and the bike was geared too high. A 23 might work OK with a 51 rear, but I think a 22 is better for a 48 rear. I ended up installing a 49 rear - I needed a new rear sprocket anyway - and it's geared pretty nice for the highway. Not a good mountain setup for Scarletthehog, though.

 

I belive the bigger trans sprocket will shift your power curve up ward. So you will have lower RPM at high speeds but less power in the low gears. A smaller sprocket in the back will do the opposite.
Pat

 

I have a '77. You change sprockets on the front only on drum brake bikes. The rear is riveted to the drum.

For many years, I ran a 22 instead of the stock 21 to lower the revs on the interstate. When I retired the bike from interstate travel and started riding it mostly around town, I swapped on a 20. This geared the bike lower. Acceleration is awesome, however it is no fun to ride on the interstate due to it being buzzy. However, top gear roll ons are great.

 

Everything you ever wanted to know about power ratios and sprocket math.

http://www.motorcycleanchor.com/moto...ocketmath.html

 

Thanks to all that replied! I've decided to stay with the stock sprockets. If it aint broke, don't fix it!

Xxxflhric, I knew you had a 77 and I hoped you would reply. Thanks!

Hog4u, your artical was very imformative. Thanks!

Does anyone have any thoughts on the type of chain? I'm thinking about using an o-ring type chain.

Thanks again!

[IMG]local://upfiles/27198/440F25F1219541E4B15FA16730B7A41E.jpg[/IMG]

 

If you want to use an O ring chain be sure to check and make sure it is not too wide for the bike. There may be a clearance issue up front around the transmission case area.
51 tooth is standard on a drum brake and that cannot be changed as others have said.
The gearing is changed on the trans sprocket. I think you will find a 23T is going to be the largest you can run with and still have acceptable low end power around town.
But the reality is with the engine. The more horses the engine has, the more (higher) gear it will pull. However, for this discussion I am talking about a standard Sportster, not a ¼ mile drag bike.
I have run a 24T for the highway a number of times and I always put the 23T back on because the big sprocket is just one tooth to much. A 24T is also a very tight fit and is the largest that will go on the bike...........pg

 

Like Pinion said, an o-ring chain is sometimes a tight fit under the sprocket cover.

This is the third time this week, I have recommended this chain. I have been using nickel plated chains for over 10 years. They do not require a heavy lube. You only need to wipe them down with WD-40 to clean them and lube the pins to keep them from rusting.

The current chain I am running can be had for about 30 bucks. You have to order the gold one to get the nickel plated side plates.

http://www.motorcycle-superstore.com...cle-Chain.aspx

[IMG]local://upfiles/17633/BB5816437885481C91F0B48711F88312.jpg[/IMG]