Problems with the sprocket of my GS 550 L

[valentin]

Hi there:

Recently I changed to the sprocket of my GS 550 L (1980) and I put one that have a few tooth more. The change became because it was needed, since the piece was spent. The sprocket rear I did not touch it.

The point is that until before that change, my bike arrived at the 95 - 100 miles/h and now with luck - and something of effort - miles/h arrives at the 70s.

I need to know what is the correct (or best) relation between the front and rear sprockets to obtain a good fuel consume and maximum speed.

[DimitriT]

More teeth on the front reduces the drive ratio so you motor will have to run at higher RPM.

[fastpakr]

No, that's incorrect. A higher tooth count front sprocket creates a higher (numerically lower) gearing, reducing engine speed at a given road speed.

[bradleymaynar]

Think of it like a 10 speed bicycle. The larger the sprocket in the front, the lower the RPM for a higher speed and visa versa. With the rear it is the opposite, the larger the sprocket the more RPM.

I changed my 1100 to a 16T front and a 41T rear. It made an improvement on my mileage, and lowered the RPM for cruising at highway speeds. Stock is 15T/42T on a 630 chain.

Brad tt

[ddaum]

Valentin,
I also own a 1980 GS550L. When I got the bike it had 15 teeth on the front sprocket, and 51 teeth on the rear sprocket. I recently changed everything out with a 15T front sprocket from Sunstar, a 50T rear sprocket from JT Sprockets, and a new 530 x-ring chain. I pretty sure the stock sprockets were 15T and 50T, but I may be wrong. My bike runs very good with good gas milage given it's condition (needs carb and petcock work), but I still get about 35-40 mpg. I've never had the bike above 70mph, so I can't tell you where she tops out, but I can say that at 70mph I know she can still get a decent amount of more speed. There is a lot of information on this forum about different sprocket configurations fro different results. Try the search feature. By the way, I got my sprockets from www.denniskirk.com and they list a lot of different sprockets that are compatable with our bikes. You might try calling them and asking what configuration might suit you best. Good luck.

[FTGRET]

You also may be reducing your top speed by the fact that you may have regeared the bike to the point that it no longer has enough power to pull the speed.

[DimitriT]

More teeth on the front reduces the drive ratio so you motor will have to run at higher RPM.

Doh! Ofcourse this is wrong. Thanks for correcting me

[valentin]

I just counted the tooth and here is the result.
Front sprocket: 16 (the new that I put a few months ago)
Rear sprocket: 42 (came with the bike when I bought it 4 years ago)

If the bike came originaly from the factory with 15/50 maybe the bike is not working at his full range.

By the way, if i change to the 15/50 sprockets, do I need a new chain? The chain has only a few months, it's not old and being used only for a few miles.

Need opinions please.

[jimcor]

15/51 is the 1980 factory setup for the 550L.

Much too low for any long distance riding IMHO. I run a 16/48 combination which works good on the highway. You won't win any drag races with it tho'.

With 16/42 you're way on the backside of the power curve. You'll find your bike will go faster in 5th gear than in 6th.

[valentin]

Then I will have to change the rear sprocket, but it will be necesary to change the chain too?, I mean, for the links that probably need with a "larger" sprocket.

[jimcor]

Yes, you will probably need a longer chain.

Original Factory setup for GS550L (US) 15/51 110 link chain.

I run a 16/48 108 link setup on my 550L.

If I were you, I would just get a 15 tooth front sprocket and ride that till the chain wore out. You might have to take a link or two off the present chain, but maybe not. Then replace both sprockets and chain as a set, which is the correct way for maximum life of both sprockets and chain.

[valentin]

OK, thanks for all.