Final Drive Swap: 6th gear solution?

Yamaha FJR Motorcycle Forum

Help Support Yamaha FJR Motorcycle Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Joined
Nov 15, 2011
Messages
192
Reaction score
71
Location
San Jose, CA
For the small percentage of you out there, like me, that feel the FJR could use 6th gear or at least some taller gearing, this post may interest you. I’ve had my ’05 for only about 2 mos and while I love the bike, the gearing is still my biggest issue (if I can even call it that). Honestly, this really is a non-issue; it affects nothing, the engine is very smooth and there is no shortage of high mileage FJRs happily spinning those “extra” revs with no ill-affect just the way Yamaha intended. And being a shafty, our options are essentially zero for gearing changes and I know that with time I’d simply learn to live with it. However, there IS an alternative.

Many years ago, Yamaha Royal Star Venture (RSV) owners found their gearing to be too tall. They often ride double-up, heavily loaded, even towing trailers occasionally and were having to drop to 4th and even 3rd gear to maintain their speed on the hills. The solution was to put VMax gears in their Venture Final Drive (FD) cases to gain ~500 rpms in top gear which greatly helped their acceleration and getting over those big hills. From what I could gather, the RSV, FJR and VMax FD cases are very similar but not interchangeable but the gears ARE.



Here's my '05 and the FD unit sitting on the lift has RSV gears installed. The RSV gears are 10/33 for a ratio of 3.30 whereas the FJR (and Vmax) gears are 9/33 for a ratio of 3.66, a 10% difference (the later GEN1 Vmax may also have the 3.3 gears but I’m not sure). Here are the numbers for our FJRs with the original FD gears and then the RSV gears. I used a rear tire rolling circumference of 76” giving 834 turns per mile (measured on my bike, with a slightly worn 180/55 x 17 Michelin PR2 which should be fairly typical):

With OE FD gears: Primary x 5th x Secondary Reductions (middle gear x bevel gear x FD) x 834

GEN1: 1.563 x 0.929 x 2.772 (35/36 x 21/27 x 33/9) x 834= 3357 engine revs per mile.

GEN2/3: 1.563 x 0.929 x 2.698 (35/37 x 21/27 x 33/9) x 834= 3267 engine revs per mile (that’s the well-known ~2.7% difference from GEN1).

With the RSV FD gears:

GEN1: 1.563 x 0.929 x 2.495 (35/36 x 21/27 x 33/10) x 834 = 3021 engine RPM @60mph (336 less revs)

GEN2/3: 1.563 x 0.929 x 2.427 (35/37 x 21/27 x 33/10) x 834 = 2939 engine RPM @60mph (328 less revs)

So there you have it…. A few hundred less revs by making this change. I installed my re-geared FD unit about 2 weeks ago and I love it! The change is not huge but it is noticeable as soon as you get rolling. Acceleration and roll-ons seem to have changed very little. Fuel mileage difference? I don’t know yet as I haven’t even burned through a tank. Any downsides to this? The only issue I see is that the rpm drop is not apparent on the gages. The speedo and tach read exactly the same as before (~3400@ indicated 60, ~4000@70 on my bike). And why is that? This is because the FJR’s speedometer sensor gets its signal from the transmission middle shaft and is subject to the same reduction as the engine due to the FD ratio change. I haven’t measured anything yet, but I’d guess that my speedo is now reading about 4-5 mph slower than before at the same actual speed. Example: assuming my tach is correct, at 3000 rpm my speedo indicates about 55 mph when it should be showing ~60 mph based on the above calculation with the new RSV FD unit. Time for a Speedo-healer?

I got my re-geared FD unit from Blue Ridge Mountain SportMax based in Catasauqua, Pennsylvania, and their website is https://rmsportmax.com/gateway.html. I’m sure some of you have heard of them. They’re actually a Vmax specialty shop that also supports the Venture/Royal Star as well. Owner’s name is John Furbur and he’s been doing these FD gear swaps for about 15 years and provides Vmax gears for the Royal Star and Royal Star gears for the Vmax (and now the FJR). Apparently, some Vmax owners also like taller gearing. You can buy a re-geared FD unit outright with the option to send back your old unit for a core exchange credit (which is what I’m doing).

So how did I find this guy? Well, I spent a few hours searching the interwebs, including anything I could find on FDs in the two main FJR forums (FJRforum and FJRowners). What I found was a lot of posts about the GEN2 gearing change with the usual questions, speculation, misinformation, swaps etc., and at least one example of someone buying a VMax FD unit only to find it didn’t fit their FJR and it had the same gearing… lesson learned. My search eventually took me to the Venturerider.org forum where I found details on their FD changes. I figured if the Vmax and RSV gear-sets could be swapped, perhaps it could be done for the FJR? An email to John quickly confirmed that Yes, he could do the swap for the FJR and he had a few FD units already converted and ready to go. So I placed my order and it was delivered in a week. Strangely enough, John and “RMSportmax” have been mentioned in the FJR forums before but I cannot find one single example of anyone actually making this change. Could I be the first?? Nope. John say mine was the first unit he’s shipped out to a Customer but he’s already done a few installs for local customers (where are those guys?). Anyway, John says he’s “just getting started” on these FJR swaps which makes me wonder why the late start since he’s been doing the RSV/Vmax swaps for so long. Lack of interest from the FJR crowd? I don’t know.

Anyway, that’s my story. I love this change… 5th gear now feels like a 5th gear and I’ll never go back!!

Best Regards,

Mr. BR

San Jose, CA

 
Interesting, good write-up.

One minor detail:

... The only issue I see is that the rpm drop is not apparent on the gages. The speedo and tach read exactly the same as before (~3400@ indicated 60, ~4000@70 on my bike). And why is that? This is because the FJR’s speedometer sensor gets its signal from the transmission middle shaft and is subject to the same reduction as the engine due to the FD ratio change.
...
Mr. BR
San Jose, CA
The Gen II and Gen III speedometer will still read "real" road speed as the speed sensor is the ABS sensor on the rear wheel. Only the Gen I used a transmission sensor.

 
Last edited by a moderator:
Yes, this is an interesting option. Thanks for sharing your work.

And please do come back and report on such things as fuel mileage differences when you get enough data to be conclusive. I would expect a measurable improvement in mileage running these taller gears at highway speeds, much as the 2nd gens have better mileage on average than the 1sts even though they also weigh more.

Not sure that I would bother with doing this as I'm perfectly happy with the 1st gen's gearing as is, but if it improved the mileage, and therefore the tank range to empty, by a few percent, I'm sure there are some LD type guys that would be interested.

 
Last edited by a moderator:
cool write up...I used to set up gears for drag cars and changing ratios is the quickest way to performance gains..

Care must be taken not to ruin the driveability tho . Experimenting with my FJ1200 if I went too low the engine was screaming..too high and it was lugging in fifth gear. Personally, I think Momaha hit the sweet spot with the Gen 2. Only change I made was to fit a 190/55 which dropped rpm by @ 100

 
Good stuff and I hope your great work pays off for you. I just don't think the revs on an FJR are excessive at highway speeds. My BMW R1200RT would turn 4000 RPM at 72 miles per hour in 6th gear. The FJR turns 4000 RPM at 75 miles per hour in 5th gear. The RT redline was 8000 RPM; the FJR is 9000. Existing gearing is not an issue in my book. But your ingenuity is to be admired and if it makes you happier with the bike then it was worth doing.

 
My guess is that if the gearing was pushed up that much higher that 5th gear would become much more of an "over-drive" type gear, and you'd only ever shift into 5th when you were north of 70mph and just steady cruising. Passing quickly would require (at least) a downshift into 4th even at interstate speeds.

 
Fred hit it on the head. With just a 190/55 rear tire 5th is tall

enough on my Gen II that the engine simply falls off the

torque mountain below 55 mph requiring 1 or sometimes

2 downshifts especially two-up.

 
My guess is that if the gearing was pushed up that much higher that 5th gear would become much more of an "over-drive" type gear, and you'd only ever shift into 5th when you were north of 70mph and just steady cruising. Passing quickly would require (at least) a downshift into 4th even at interstate speeds.
I think that would be the case based on my experience with my C14. If you compare the overall gear ratios, a GEN1 would be 3.62:1 with the new gearing and a GEN2 would be a 3:52:1. My C14 is 3.40:1 in 6th gear and while 6th is very quiet and smooth, the fuel economy actually goes down (when riding within 5-10 mph of legal highway speeds) in comparison to 5th if I am pushing a head wind or going even slightly uphill (5th gearing is 4.09:1). Fifth gear obviously has much more passing power. I think 6th would be a lot more useful and get better overall fuel economy if the ratio was in the 3.60-3.70 range.....and that would also be true for the FJR. With the current ratios, I prefer the GEN2/3 gear ratios to the C14s because I spend more time in 5th than 6th on the C14.

 
Last edited by a moderator:
I seem to recall a Kevin Cameron column in Cycle World a few years back, relating to MPG and gearing changes. His take on it was the the MPG was more influenced by wind resistance than gearing changes. Something about the same amount of energy is needed to overcome wind resistance regardless of the engine RPM; it's just that at some RPM's the engine is more efficient at that.

 
Yes, that is true, but...

At an identical speed the vehicles will have the same wind resistance, so that is not a factor for or against changing gearing. The bike with higher gearing will get better fuel mileage (as long as the rpm is not so low as to drop off the torque curve) because the engine will be turning slower, swallowing fewer gulps of air and fuel per mile, and doing that with lower pumping losses (intake, exhausting and compression of the fuel air mixture all consume power that comes from the fuel).

 
Last edited by a moderator:
My guess is that if the gearing was pushed up that much higher that 5th gear would become much more of an "over-drive" type gear, and you'd only ever shift into 5th when you were north of 70mph and just steady cruising. Passing quickly would require (at least) a downshift into 4th even at interstate speeds.
That is pretty much how I use 6th on my RT. I don't ever get to it unless I am doing 75+.

 
Yes, that is true, but...
At an identical speed the vehicles will have the same wind resistance, so that is not a factor for or against changing gearing. The bike with higher gearing will get better fuel mileage (as long as the rpm is not so low as to drop off the torque curve) because the engine will be turning slower, swallowing fewer gulps of air and fuel per mile, and doing that with lower pumping losses (intake, exhausting and compression of the fuel air mixture all consume power that comes from the fuel).
It would be interesting to see just how much difference there is in pumping losses. I'm guessing it won't make a big difference in MPG.

 
Nice detailed report. Excellent.
Question: Will the RSV gears be stressed by handling the greater load of the FJR?
Certainly more engine power for the FJR compared to the RSV but I wonder how low-end torque compares? A fully loaded Venture is a pretty porky lady so I doubt the FJR would be any harder on the final drive.

 
Great stuff thanks for posting the information on hte swap. Seems a worthwhile change if a lot of time is spent at freeway speeds.

 
Top