Gear ratio Application

[bietau85]

I found this to be one heck of an awesome tool. Maybe you all know about this maybe not but I found this to be a deadly accurate guideline for playing with sprocket sizes for my bike. I have an 81 550M and threw a 42T sprocket on it because I liked the stats this chart showed and it is to the "T" on what I am seeing with the sprocket. I had a 50T rear 15T front and now after switching to the 42T I have absolutely no bog, and a huge power band. call me stupid if you'd like but I will never change to the 50T again. Even on hills I dont have to dropshift, I still have torque to accel and my. My buddys 2010 Sportster dont have crap on my 30 year old GS550 as we found out today with the gearing swap.:dancing:

http://www.gearingcommander.com/

 

[kcorbin]

I've seen that site before and it really is a fantastic resource. So many calculations in one place...

What did you end up with for your front sprocket?

My bike came with a (thanks, PO) 14T front/43T rear (3.07 ratio) and I hate it! It's most noticeable at take offs from dead stop as I really have to feather the clutch to take off smoothly. I was going to switch to a 13T front to get me to a close-to-stock 3.30 but now *you* got me thinking of going down to a 3.58 or something when I can afford swap them both out (they don't seem to make a 12T front in a 530; probably getting too small).

 

[bietau85]

I've seen that site before and it really is a fantastic resource. So many calculations in one place...

What did you end up with for your front sprocket?

My bike came with a (thanks, PO) 14T front/43T rear (3.07 ratio) and I hate it! It's most noticeable at take offs from dead stop as I really have to feather the clutch to take off smoothly. I was going to switch to a 13T front to get me to a close-to-stock 3.30 but now *you* got me thinking of going down to a 3.58 or something when I can afford swap them both out (they don't seem to make a 12T front in a 530; probably getting too small).

I went with 15 in the front and 42 in the rear as opposed to a 50. The bike is much quicker and holds a larger powerband, higher top end by 30mph. and I still redline the gears. I dont know how fast I am going since the gauge stops at 85mph. But half way through 3rd gear ( I have a 6 gear trans) the needle is already buried and this is in 6 seconds maybe 8 tops.:dancing:

 

[kcorbin]

Interestingly, I figured out that my problem with no take-off power was not my lower gear ratio as I was originally thinking.

As I've been riding it around more and more I finally noticed that once I would open up the throttle about 1/4-1/3 it would really bolt. Then the light bulb turned on: that's when the needle jet starts taking over from the pilot circuit.

I had never noticed it before because the clutch has always been kinda grabby and I figured the jerking was just a result of that as I'm trying to ease off the clutch and open the throttle at the same time to make a smooth start.

So, I opened up my pilot fuel screws (the ones on the bottom of the carb bodies; I have the VM carbs with both the pilot fuel and air screws) about 1/8 turn and then re-adjusted my air screws for best idle again.

I went for a test ride around the block and man, what a difference! Take offs were nice and smooth with very little throttle necessary and no fear of bogging/killing the engine. Eventually I'll take the time to do some low speed plug chops to fine tune each cylinder, but for now I'll just enjoy the improved riding!

Cheers,