Fifth gear mod

[Brasco18]

I have been reading about the final drive modification that can be done in order to reduce the rpms, thus getting better gas mileage. Is there any mod that can be done on just the fifth gear? It seems over kill to reduce the rpms on all the gears when the fifth gear is really the only one that needs it. Is it possible to install a different size fifth gear?

[xschop]

possible

yes, you will need to custom grind or Graft a 5th gear and its counter drive gear......save some cash and do the 750/850 FD mod,it is on the Beta site now I believe....chop..... The reason for doing the 750 FD mod is to get better/lower RPMs in 5th gear on the hiway. On any other bike, this may be a problem starting out in 1st gear, but not for the 11 because it is a torque monster and it will also make your shifting easier between all gears....

[xschop]

forgot

welcome to the jungle

[Brasco18]

The pics for the mod are missing. And the beta site link doesn't seem to work. I would love to look into this mod but would prefer to have as much info as possible as I don't want to start this mod and end of having my bike broken for the rest of the season!

[xschop]

patience is a virtue I don't have either

just wait for the Beta site to kick back in or T.C. to chime in....

[trbig]

One of the things I like about the 750/850 mod IS the way it is in the other gears, but 1st gear especially. The bike still has enough torque to do wheelies off the line if I choose, but feels like it now has a COMPLETE first gear, not a granny gear. Racing guys on other XS bikes, 1st gear is generally where you get them the most. I can rap it up to a much higher speed in 1st than they can. When they go to hit 2nd and shift, it looks like they hit the brakes compared to you. When you finally hit 2nd, they can't make up the ground they lost because they are soon shifting into 3rd.

While cruising around with Hobbyman, our bikes sound almost exactly the same RPM when I'm in 4th and he's in 5th. 5th now is like having an overdrive. Mine sits right at 3900 rpm at 70mph. Although I never noticed a better MPG in fuel like some, the bike just feels so much better to me at highway speeds. I used to be in 5th and always be trying to bump it up another gear.

It's a pretty easy mod to do. Buy some beer and find someone who is somewhat close to you to help you out. Some people will drive a long way for beer and barbecue. I go over 170 miles one way routinely for it!

Tod

[DavesXS]

Do the FD mod and also the 5th gear mod . How nice would 2500 rpm at 65 mph be? 50+ mpg I'm sure. I'd be real nice for those long road trips.
Who would do that kind of work to the gears? Any body in mind?

[HobbyMan]

If I had a set of gears to match, we might still have gear cutting machines here at school. I guess it would be a matter of getting the material and machine time.

[xschop]

Plans

if someone (being me) had a set of spare gear set, a different 5th gear set is highly feasable...... I had it done a few years back to a 944 Turbo. Now I have access to a gear cutting shop that likes to trade work.....

[Brasco18]

won't this cause the bike to always run under the power band? The power band starts at about 4k. Wouldn't that make the bike not happy to always be lugging along? it just seems that even thought this bike is a "torque monster", it would still be hard on the bike to always be lugging.

[DavesXS]

Originally posted by Brasco18
won't this cause the bike to always run under the power band? The power band starts at about 4k. Wouldn't that make the bike not happy to always be lugging along? it just seems that even thought this bike is a "torque monster", it would still be hard on the bike to always be lugging.

The power band is not there for cruzing speed. No motor cruzes in the power band(unless its build for the racing circuit). Thats very hard on a motor. You should cruz under the power band and down shift if you need the band.

[DavesXS]

Re: Plans

Originally posted by xschop
if someone (being me) had a set of spare gear set, a different 5th gear set is highly feasable...... I had it done a few years back to a 944 Turbo. Now I have access to a gear cutting shop that likes to trade work.....

I have a 5th wheel gear. And a fith pinion is only $73.
I'll swing by yamaha today and see if it is available.

Are you going to be able to test fit it? I think for them to match up you have to take away from one gear as much as you add to the other. Do you know how to figure out the # of teeth to add/take away, and witch gears to do it too?
We might want to PM Chop to come in here and lend us some advise.

[xschop]

what a mesh

What is critical is the gear mesh tolerance. To do this mod correctly, you would need to have an XS motor split in half with the clutch shaft and main shaft installed in their places and mic the ridge to valley of the pinion and drive gears.....There is another way by mic'ing the distance between the centers of both shafts, then mic'ing the pinion and drive gear diameters, counting teeth ratios and reconfiguring the new gears......Of course I won't be tearing into my motor to figure it out....

[trbig]

It just so happens.....

I have several extra gears, and a set of cases split on the garage floor. Not quite sure what you're after on the mic' ing, but sure we could figure it out.

Tod

[xschop]

RATIO

Does anyone know the exact ratio of the 5th gear pinion and drive?.....CKTC