81 GS650E Sprocket sizes

[Guest]

Hi all,

Ive an 81 GS650e with 15 tooth front and 45 rear. RPM seem to be way too high, even when doing 80km/h.

What size are others with this particular bike running? I understand that 15/44 is standard for this although the 45 is an option also. I?m happy to lose low down acceleration etc to be able to cruise a little faster, enabling me to go on longer open road type rides.

I?ve done plenty of searches but would like to hear what other combo?s you?re running on the 650.

Cheers

 

[Nessism]

You might want to try a 16 in front. That will make a noticeable difference and it's a cheap swap.

 

[Guest]

Thanks for the response. I’m thinking i’ll Give something like that a go. I’m amazed that the top end cruising speed is so limited based on factory specs.

cheers

 

[Steve]

One other thing to consider. :-k

What is your engine speed at 80 km/h?

What would you like it to be?

What other engine(s) are you used to?

Many who are 'new' to smaller-engined bikes are not accustomed to the RPM that they need to run properly and want to slow the engine down. One problem is that slowing the engine will bring it down, well out of its power band. When it gets out of the power band, you will have to open the throttle more to compensate, which will really start sucking gas.

My son had a 650L (shaft-driven). If I remember correctly, engine speed was about 6k at 70 MPH (110 KPH). Fuel economy was decent, in spite of the pods and pipe. Can't say that the engine ever sounded like it was running too fast at those speeds.

.

 

[Guest]

Thanks Steve,

I believe mine might be in the order of 5500rpm or so at only 80km/h but i’ll take it for a run soon and confirm the RPM etc.

Mine certainly seems to be excessively high given the low speed.

cheers

 

[Guest]

Ok, took it for a run and it sits on 4050-4100RPM at 80km/h. Seems to cruise along ok. Maybe 1 tooth larger on the front to allow ,e to cruise a little faster at similar RPM?

 

[Himble]

Ok, took it for a run and it sits on 4050-4100RPM at 80km/h. Seems to cruise along ok. Maybe 1 tooth larger on the front to allow ,e to cruise a little faster at similar RPM?

Rev it and love it!

BTW, do the 650s use a 630 chain? If so, downsize to a 530 or 520, along with suitable sprockets.

 

[Baatfam]

Ok, took it for a run and it sits on 4050-4100RPM at 80km/h. Seems to cruise along ok. Maybe 1 tooth larger on the front to allow ,e to cruise a little faster at similar RPM?

I wouldn't....Just run it at a higher rev. You won't hurt nuthin'...

Heck...what's the redline on that thing? 9500 rpm or something? Peak torque around 8K probably?

4K is just loafin'

You can run 7-8K all day on that bike....

 

[Guest]

Hi Andy,

Thats the plan! Haha. Did 100km today and she loved every second of it.

This one has a 530. I’ll do some more research but perhaps one larger on the front.

Cheers

 

[Guest]

Thanks Bob,

I see where you’re coming from but I thought it would be better if I wasn’t riding it too hard all the time.

Cheers

 

[Baatfam]

Thanks Bob,

I see where you’re coming from but I thought it would be better if I wasn’t riding it too hard all the time.

Cheers

Guess that depends on what you mean by "better"

It is probably "better" for the bike to run near peak torque, but others who know more can verify that.

I'd at least try it stock for a while...Easy to change later.

 

[Steve]

... I thought it would be better if I wasn’t riding it too hard all the time.

Actually, running it faster at a lighter throttle setting is better than lower speeds with open throttle. :-k

.

 

[Guest]

I think I get what you mean although it’s not running faster at a lighter throttle setting, I’d be giving it a fist full if I were to be able to cruise at 90-100km/h. Or am I confused? Haha

 

[hannibal]

I think he's saying 3000rpm at 75% throttle with lower gearing is harder on the bike than 6000rpm at 50% throttle with stock gearing.

I agree.

 

[Rijko]

Buddy of mine has a GSX1100F, powerful bike.

He tried going up 2 teeth on the front sprocket and had to cut off a support
off the sprocket cover to make it work.
This powerful bike would not go past 190 km/h. (standard easy over 220)
Guzzling gas too.

So back to 1 tooth over standard. That did lower the revs at cruising speed
between 120-150 km/h, but still using way more gas.

He's back at standard gearing.

The GS650 is not as powerful as that, and will probably suffer more noticable.

 

[Guest]

I’m with you guys now, that makes sense. Thanks for the input. According to everything I can find, standard is 44 on the rear, would 1 tooth on the rear smaller have any real impact?? It has 45 on the rear st the moment.

 

[Rijko]

you may find the Gearing Commander calculator interesting.
Though this site uses theoretical numbers, not taking into account
the bike may not perform the way the numbers would lead to believe,
it is probably pretty good when deviating not too much from standard gearing.

https://www.gearingcommander.com/

It does not have the GS650 in the database but playing with the GS550
gearing may provide answers.

 

[Guest]

Thanks Rijko,

i’ll check It out ��

 

[Rijko]

hint : playing around with the rear sprocket 1 or 2 teeth will make a difference of 150-200 rpm at cruising speed, and make a difference of a few miles at top speed.
Up the drive ratio any more (front or rear sprocket) will take the bike out of its comfort zone and negatively affect gas usage, top speed, performance, etc.

Unlike your cool powerful Holdens, a relatively high-rpm, low-power bike like the GS650 will not be able to cope with big changes to the drive ratio. It needs to rev.

 

[Guest]

Understood, thanks again!