6th gear rpm sweet spot...

[ckrockets]

So do you think it's a coincidence that at exactly 4.5K RPM in 6th gear the speedo reads 55 MPH?

I don't think so personally...I believe Yamaha engineers observed that 4.5K was the sweet spot in this motor for minimum vibrations and noise....and they appropriately geared 6th so that it would be at 55 MPH (universal/politically correct/average highway speeds)....I was cruising down the blue ridge parkway yesterday in 6th gear holding 55 MPH and it was shear heaven it was so smooth (engine wise)...now on I-26 doing 70 MPH in 6th it was a bit buzzy and I can see that being a problem on long long interstate halls...

With this in mind I plan on doing a lot of touring with my new FZ6 and I would love to be able to do 70 MPH at 4.5K RPM in 6th gear....here's the thing though...

I don't want to use the sprockets as it will change the drive ratios for all the gears...and i rather like 1-5 the way they are now....

So what I want to look into is solely replacing 6th gear in the transmission so I can obtain the exact result I am looking for....

I'm not sure is I need to increase or decrease the number of teeth on 6th gear (there are two it looks like wheel and pinion) and it's going to be challenging to find a gear from a donor bike that is compatible with the FZ6 transmission (compatible with the existing dogs, shifts forks and such)...

Ronayers.com Microfiche Yamaha>Motorcycle>2009>FZS6YL/FZS6YB/FZS6YCL/FZS6YCB>TRANSMISSION

Another thing to consider is can I get to the transmission in this motor from the bottom....this conversion will not really be worth it if I have to go from the top to the bottom to get to the transmission...

Does anyone have any input?

Thanks,
Mark

 

[ChevyFazer]

I don't think this has ever been done, and don't think it would actually be possible with out lots of other work.

As far as 55 being the sweet spot, I personally like cruising around 6-7k no matter what gear and tend to get better mpg like that to so I think that would be a personal thing.

 

[Marthy]

I experience with different ratio since I got the bike (6R). Here's my recommendation.

The stock ratio (16/46) give some good zip and compensate for the lack of HP. But once on the big slab the engine spin 7K+ on the freeway. I tried +0/-8 (16/38) at first. The engine was revving 5200 @ 70 MPH. It was nice on steady speed on the freeway but on acceleration it totally suck. By the time you're in 3rd gear you hold the clutch and go straight into 6th. LOL

I tried +1 front. One of the most popular mod on the 6R. Speedo get almost spot on accurate and it bring down the RPM on freeway about 300 RPM or so. Then 17/44 was nice (= 1 gear over drive... stock 6th=new 5th) but the alloy rear sprocket didn't last very long with the extra ponies that I have. So now I'm using 17/43, steel sprockets. I have only 100-200 mile son it. But so far it's not too bad. The first gear is very short on the 6R so the acceleration is still ok (and keep the front wheel on the ground) 6K RPM give me 74 MPH.

I think it's ok for now. I need to check the MPG on my next long ride to see if I gain anything. Vibration is not really a big issue for me. Renthal handlebar and heavy bar end kind of fix 90% of the problem.

What you need to keep in mind is what is working well at 55 MPH might not work as good at 70 MPH. If I can remember well, double the speed = 4 X more drag!

Having a real over drive (6th) will be nice like you said... but I don't think there's something available out there. Just need to find a good compromise somewhere. There's some good gear tool out there, if not I have a Excel spreadsheet that I've been using and work well for me. PM me if you want it.

 

[YZF73]

One thing to bear in mind with this is that the distance between the gear shafts is fixed, hence the distance between the gear centres (Centre Distance) must stay the same, whilst you manipulate the Pitch Circle Diameter and Module of the gear pair to achieve the desired ratio (which also needs calculating).

If you can come up with a value for the distance between the gear shaft centres, we could run some calculations and see if it’s actually physically possible.

If it were possible, I would imagine the new gears would have to be custom made, the chance of finding gears of the correct dimensions to fit the FZ6's gearbox is very unlikely.


Yamahaboyz

 

[ChevyFazer]

Gearingcommander.com has a great tool to get ideas on different sprocket sizes

 

[Marthy]

One thing to bear in mind with this is that the distance between the gear shafts is fixed, hence the distance between the gear centres (Centre Distance) must stay the same, whilst you manipulate the Pitch Circle Diameter and Module of the gear pair to achieve the desired ratio (which also needs calculating).

If you can come up with a value for the distance between the gear shaft centres, we could run some calculations and see if it’s actually physically possible.

If it were possible, I would imagine the new gears would have to be custom made, the chance of finding gears of the correct dimensions to fit the FZ6's gearbox is very unlikely.


Yamahaboyz

Nice to see someone knowing what they're talking about! By trade I'm a machinist and use to set up gear hubber and gear shapper.

From what i found stock 6th is 24/26 underdrive. (1.08...) if you go 26/24 overdrive (.9ish) it brings down the RPM about 1K around 65 MPH. A lot of work but doable.

 

[FIZZER6]

I averaged my best every MPGs on the Blue Ridge Parkway at 55 mph in 6th gear...

I got 60 mpgs! It's definitely more efficient at lower rpms and speeds (unless you are trying to save time of course) :thumbup:

 

[YZF73]

Nice to see someone knowing what they're talking about! By trade I'm a machinist and use to set up gear hubber and gear shapper.

From what i found stock 6th is 24/26 underdrive. (1.08...) if you go 26/24 overdrive (.9ish) it brings down the RPM about 1K around 65 MPH. A lot of work but doable.

Cheers Marthy :thumbup:

Don't be fooled though, I'm only a Uni Student studying Automotive Engineering at the moment, you've got far more experience than me.

To be honest, I just find problem solving very rewarding. I must be in the right industry, as all we ever seem to do in Engineering is solve problems!!!


Yamahaboyz

 

[Cali rider]

One thing to bear in mind with this is that the distance between the gear shafts is fixed, hence the distance between the gear centres (Centre Distance) must stay the same, whilst you manipulate the Pitch Circle Diameter and Module of the gear pair to achieve the desired ratio (which also needs calculating).

If you can come up with a value for the distance between the gear shaft centres, we could run some calculations and see if it’s actually physically possible.

If it were possible, I would imagine the new gears would have to be custom made, the chance of finding gears of the correct dimensions to fit the FZ6's gearbox is very unlikely.


Yamahaboyz

+1. New gears would need to be designed and manufactured from scratch. Based on 2 gear vendors I have used for machinery rebuilding in my area, I would say that a matched pair of ANY ratio would run $800-$1200.

Remove existing gear set from bike. Measure all splines and dogs, calculate ratio and load, CAD, CNC programming, material, rough machine, broach splines, mill everything, stress relive, heat treat, finish grind. This is a big task. Not even considering the time/cash required to remove and reinstall in the motor.

If you do it, please document the entire process.

 

[CowtownBiomed]

As has been pointed out buy Cali..I think the whole thing would be cost prohibative for the average Joe..
Now if you had access to a CNC machine and a bunch of time it could be done, but would be hugely time consuming.

That being said...if you do redisign it, yes, please share...

 

[ckrockets]

Not even considering the time/cash required to remove and reinstall in the motor.

That's the easy part of this possible venture...I can have the motor out and on the bench in about 2 hrs....back in and everything hooked up usually is double that...still with all that it's the easiest part for me...even getting to the transmission is not that bad as long as I can get to it from the bottom of the motor...the difficult part is coming up with new gears for 6th...

Two things have to happen for me to even consider doing this...

1) ability to get to the transmission from the bottom

2) can use donor gears from another bike (i am not interested in having gears made)

It's a long shot but worth looking into....

 

[ChevyFazer]

How is the 03 r6 geared? That might be a option if it has a higher 6th gear which it might.

 

[mikw73]

I averaged my best every MPGs on the Blue Ridge Parkway at 55 mph in 6th gear...

I got 60 mpgs! It's definitely more efficient at lower rpms and speeds (unless you are trying to save time of course) :thumbup:

I had a Honda Civic with a 1.6L engine that did a similar thing. It was rated 30mpg city, 36mpg highway, and if I did 68-72mph on summer (ethanol) gas, I'd get 44-45mpg. That car was manufactured in Canada, interestingly. If Canada had a native brand, I might buy one after that experience. I wonder why not? Maybe whatever Detroit's got wrong with it is contagious?

 

[ckrockets]

How is the 03 r6 geared? That might be a option if it has a higher 6th gear which it might.

Good idea! :thumbup: ill look

 

[sloring]

riding in 6th gear is probably not best idea since you won't have the power to pass or perform emergency maneuvers. Go 5.

 

[mikw73]

Since you're going for 70mph and want the same smoothness, do you think you'll have to factor in a few hundred extra RPM to let the motor work at the same level of effort against the significantly increased wind resistance? Or do you think the motor has plenty of pull at 4500 to fight the wind at 70 without any added vibration?

 

[FinalImpact]

That's the easy part of this possible venture...I can have the motor out and on the bench in about 2 hrs....back in and everything hooked up usually is double that...still with all that it's the easiest part for me...even getting to the transmission is not that bad as long as I can get to it from the bottom of the motor...the difficult part is coming up with new gears for 6th...

Two things have to happen for me to even consider doing this...

1) ability to get to the transmission from the bottom

2) can use donor gears from another bike (i am not interested in having gears made)

It's a long shot but worth looking into....

Hmm . . . if getting at it from the bottom is the biggest concern I think you're in over your head! With the engine out and upside down the two pans come off and the gear box is exposed. However, having the gears made (if anyone would even bite), is gonna cost you more than the bike is worth. As John mentioned, there is way more going on to make a gear set than we mentioned here. It'd be easier to buy a different bike!


If the pictures are still up here are some R6 guts!
http://www.600riders.com/forum/gara...ke-guts-heres-bunch-r6-engine-trans-pics.html

EDIT: yep pictures up. Look at #32. Left side is the input shaft right side is the output shaft. 6th gears are those on the right. 1st is on the left and you'll note its a wider gear set for the strength needed to not bust when the clutch gets dumped at 7k and you launch down the drag strip. Also numerically its the lowest gear having the greatest split.

Thanks Mr R6 guy!

 

[Nelly]

55 MPH (universal/politically correct/average highway speeds)....Does anyone have any input?

Thanks,
Mark

Which universe are you talking about? It would seem that 55 mph (89 kph) is not the average universal speed.
Speed limits by country - Wikipedia, the free encyclopedia

Nelly