WTB - custom made steel rear sprocket

Hi, folks. I was wondering if anyone has had good results having a steel rear sprocket made. I have waded through dozens of google search results, but I have found most sprocket makers offer only aluminum rear sprockets, or steel sprockets at $175 or more. I need a 42 tooth steel rear sprocket that will mount to a Seca 550 rear rim that is being used on a custom build. Even some type of interchange info would be greatly appreciated.

 

i can probably make one, but it wouldnt be cheap. for a one-off sprocket, you're looking at probably 5+ hours of design, programing, and machining at $65/hr.

 

On second glance, I see that I need a 44 tooth rear sprocket. The current sprocket on the Seca rim is a 45 tooth unit. The stock final gearing on my bike is 16/44. I can purchase a 15 tooth front sprocket to use with the 45 tooth rear, but this will change my final gearing from 2.75 to 3.00. I know very little about gearing, but I was wondering if this would be too drastic of a change for my bike. I think it may be feasable, as the bike is a 500cc single, and should have enough to torque to overcome the gearing change. And oops, I should have posted this in "other motorcycles".

 

Changing to 3.00:1 will give more set-off power, but lower top speed.

 

Thank you for the info. I can also purchase a 17 tooth front sprocket, which would change the gearing from 2.75 to 2.65. I would rather have a little less low end, and a more relaxed engine at road speed. Now I just need to see if I have enough room for a 17 tooth front sprocket on my Yamaha SR500. Thank you again for your help!

 

My experience with the SR500 was that if you over-gear it too much so that it's off the powerband at highway speed it won't hold 65-70 in top gear, you need to keep downshifting. They were like that anyway with the stock gearing if it got windy or you hit a long uphill.

16/45 might actually be an improvement. I'd run it and see.

 

Thanks, bigfitz. Do you have any idea what the top speed for a stocker is? I will most likely be bumping the displacement up tp 540cc, and installing a mild cam. I already have a Thumperstuff header to go along with the other performance upgrades. If the bike could maintain 60-65 mph comfortably, I would be happy.

 

Good luck "hopping up" an SR500. Back in the day, one of the motorcycle magazines started a series on upgunnning one and the series just... died away. They found out it was nearly impossible. But going big-bore and with a cam it should gain you something.

Anyway; stock top end IIRC was around 100-105 wound tight downhill with a tail wind. Hit 95 easy. I used to ride mine with some of my Norton buddies and I had to hammer the snot out of it to keep up, but it did.

They'll run 70 all day as long as it's not too windy, or like I said, you hit a long uphill; then you just have to jump down into 4th.

 

They made sprockets for me. http://www.rebelgears.com/

 

It didn't occur to me to keep the original 16 tooth front sprocket while running a 45 tooth rear. The extra tooth on the rear sprocket will change my final gearing from 2.75 to 2.81, and from the info bigfitz supplied, I think it will work out just fine. One last obstacle is to make sure that the sprocket offset, hub width, and tracking of the Seca 550 rim will be compatible with the SR500 swingarm. I've got my fingers crossed, but I smell trouble. Thanks to all that helped me, I REALLY appreciate it!

 

Doesn't the SR500 have the same sized rear wheel anyway? Why the change to the Seca wheel?

 

I want to swap out the front and rear rims to gain a different style and tubeless tire capability. The Seca 550 wheel design is my favorite style of Yamaha wheel (I have 2 complete sets, with the axels and spacers). Yamaha didn't utilize wheels suitable for tubeless tires until 1979. I also want to dump the troublesome rear disc for a drum brake. This bike is in tough shape, so I don't mind altering it. My other SR is quite nice, so I won't be molesting it.

 

I bet you can get exactly what you want from:

Krause Racing / Custom Sprockets

They have Steel and Titanium Sprockets for a multitude of applications.

The Front Sprocket on some Bikes don't match-up with Yamaha too well.
They'll know that; anyway.

I don't know for sure ... but, the hardened Sprockets of some Yamaha ATV's might substitute for what you want to do.

http://sidewindersprockets.com/conversionkits.html

http://sidewindersprockets.com/yamaha.html

 

I think the Seca 550 rear brake will probably be pretty close to the brake that was fitted to the later SRs. Only the very first year or two had the rear disc; then they went to a drum. My '80 had the drum brake.

You should be able to swap the swingarm for one from the later series SR.