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General Category >> Rubber Side Down! >> Changing gear ratio
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Message started by ericson25 on 04/13/13 at 11:57:41

Title: Changing gear ratio
Post by ericson25 on 04/13/13 at 11:57:41

I find myself looking for the next higher gear when on the highway. My LS 650 is a belt drive has anyone changed either pulley to get more top end ?

Title: Re: Changing gear ratio
Post by paulmarshall on 04/13/13 at 12:01:34

Try swapping belt for a chain conversion.
http://suzukisavage.com/cgi-bin/YaBB.pl?board=tech;action=display;num=1174239333

Title: Re: Changing gear ratio
Post by ericson25 on 04/13/13 at 12:15:49

That is great info and best of all not to expensive. Are you able to put all the guards back on?

Title: Re: Changing gear ratio
Post by Charon on 04/13/13 at 13:08:55

Do not forget that when you change the overall ratio you will change every gear. Low will become higher, which might make it trickier maneuvering around at low speed. And you will not gain anything in top speed, since the stock engine can't redline even in fourth, let alone fifth.

Title: Re: Changing gear ratio
Post by ericson25 on 04/13/13 at 13:13:30

From what I understand it will run at lower RPM at the same speed.

Title: Re: Changing gear ratio
Post by Charon on 04/13/13 at 13:30:32

That is correct. The engine will turn lower rpm at any given road speed, in any gear, than it did before. But that does not give the engine more power to push the motorcycle through the air any faster. As the S40 is presently geared the engine cannot reach top rpm (redline) in either fourth or fifth gear, because it doesn't have the power. If it cannot reach redline in the existing gears it won't in a higher gear, either. So it is extremely unlikely you will get a higher top speed. If you really want higher speed, you need to be looking either at engine modifications or a different bike.

Title: Re: Changing gear ratio
Post by ericson25 on 04/13/13 at 13:36:23

Top speed is not the issue. It's just when at highway speed like around 70 MPH it sounds and feels like it's screaming its little lungs out. LOL

Title: Re: Changing gear ratio
Post by apache snow on 04/13/13 at 13:44:47

What he may be saying is if you get the gear ratio high enough (lower numerically) the bike may not pull 70 mph in fifth gear, especially two up.

Title: Re: Changing gear ratio
Post by ericson25 on 04/13/13 at 13:49:49

So are you saying that instead of changing the ratio maybe I should just get a tach ?

Title: Re: Changing gear ratio
Post by SALB on 04/13/13 at 14:06:37

A cheap way to raise the gear ratio is to upgrade from a 140/80 to a 140/90 rear tire when it's time for replacement. You'll also get the added benefit of correcting the speedometer. ;)

Title: Re: Changing gear ratio
Post by ericson25 on 04/13/13 at 14:12:16

I already have the 140-90.

Title: Re: Changing gear ratio
Post by Dave on 04/13/13 at 18:42:51

You can also use a Kawasaki EN 25 tooth front pulley (stock is 23). The hub needs to be cut narrower and it is really hard material. Acces to a machine shop with carbide cutting tools is necessary. You also need to take a small amount of material off the outer cover and the support for the back screw needs to be trimmed. I will post pictures tomorrow.

This is not a cheap fix unless you get a pulley cheap...new ones are over $ 80 and my machine shop friend said at a normal labor rate it would have been about $ 90 to trim the pulley.

Title: Re: Changing gear ratio
Post by Charon on 04/13/13 at 19:52:04

The stock S40 has the engine turning roughly 4000 at 60 mph. So, at 70 it is turning about 4600. Note that these are not exact numbers, but approximations. Once upon a time I made a table of engine rpm at 65 mph for a number of bikes, as reported by Motorcycle Consumer News. Interestingly enough, the S40 was just about the average of about a hundred reported bikes. I posted that data somewhere on this site, but don't particularly feel like searching for it.

Title: Re: Changing gear ratio
Post by rfw2003 on 04/13/13 at 20:25:40

6E55584F5E52494F545C514E3D0 wrote:

That's something I might be able to do if the inside of the pulley is smooth enough to get it running true on the lathe. But is it really worth while on only a 2 tooth increase?

R.F.

Title: Re: Changing gear ratio
Post by WD on 04/13/13 at 22:18:32

5A4E5F1A18181B280 wrote:

[quote author=6E55584F5E52494F545C514E3D0 link=1365879461/0#11 date=1365903771]You can also use a Kawasaki EN 25 tooth front pulley (stock is 23). The hub needs to be cut narrower and it is really hard material. Acces to a machine shop with carbide cutting tools is necessary. You also need to take a small amount of material off the outer cover and the support for the back screw needs to be trimmed. I will post pictures tomorrow.

This is not a cheap fix unless you get a pulley cheap...new ones are over $ 80 and my machine shop friend said at a normal labor rate it would have been about $ 90 to trim the pulley.

Title: Re: Changing gear ratio
Post by rfw2003 on 04/13/13 at 23:01:40

7A692D0 wrote:

[quote author=5A4E5F1A18181B280 link=1365879461/0#13 date=1365909940][quote author=6E55584F5E52494F545C514E3D0 link=1365879461/0#11 date=1365903771]You can also use a Kawasaki EN 25 tooth front pulley (stock is 23). The hub needs to be cut narrower and it is really hard material. Acces to a machine shop with carbide cutting tools is necessary. You also need to take a small amount of material off the outer cover and the support for the back screw needs to be trimmed. I will post pictures tomorrow.

This is not a cheap fix unless you get a pulley cheap...new ones are over $ 80 and my machine shop friend said at a normal labor rate it would have been about $ 90 to trim the pulley.

That's something I might be able to do if the inside of the pulley is smooth enough to get it running true on the lathe. But is it really worth while on only a 2 tooth increase?

R.F.[/quote]

Probably not. A minor fuel savings, and a slight reduction in internal wear, resulting in a slight increase of engine component life and therefore bike life.

Anybody remember off hand who it was on Bert's forum that got almost 200K miles out of his Savage before it blew up?
[/quote]
Then it wouldn't be worth the time to do it for myself. So I guess chain conversion it is, when I get the time. I'm looking for a gear ratio of around what the 17/43 would give me. I spend alot of time at 70mph and if I have to hit the super slab when going to some of my Dr. appts the speed limit is 75mph so I definitely gotta get the revs down abit to keep it from eating the oil especially during the summer months. Depending on what someone offers I might do the machining for them though, as I do have the carbide cutting tools for my lathe, and I also now have a 4 jaw independent chuck so I should be able to dial it in to run true if the inside of the pulley isn't quite smooth enough for cutting it down. I would just need to know how much to take off is all.

R.F.