vmax rear= more mpg !!!

[kyle]

well i had the chance to run 3 tanks of gas thru the bike with new vmax rear and my mpg's are up !!! the first tank not so much cause the throttle hand was loving the new found power...hehe I now settled down and the last 2 tanks were 40 and 41 which I have never had with this bike, 38 was the norm and 35 was the low end.

 

anyway the best $$$$ i have ever spent on a bike, kudo's to whoever come up with this.

[MikeWa]

Congrats Kyle

 

Mike

[kkent66]

Where did you get the v-max rear from? Was it new or used. I am taking a trip to the Cabot Trail in NS in 1 month. Considering the upgrade but my bike is running great and a little worried I might take a great running bike and mess it up!

[Wade 2000]

Ok I've been tossing around doing the V-Max upgrade but I figured on loosing a few MPGs because of it being a lower gear. How is it that people are gaining MPGs with this change?? I definitely get the better throttle response and power in top gear but better MPGs?? Somebody smarter than me, explain this. Please:bowdown:

[Rosie1965]

I really enjoy the lower gears on my MKII. One reason people are probably seeing better mpg's is less of a need to downshift. These motors have a sweet spot and I think the VMax or FJR final drive helps get them in that sweet spot. I regularly get 40 mpg two up with mine.

[slowrollwv]

I have been thinking about the upgrade but I am getting 42-45 mpgs now 50 if I keep out of fifth and under 65mph.

[darthandy]

Ok I've been tossing around doing the V-Max upgrade but I figured on loosing a few MPGs because of it being a lower gear. How is it that people are gaining MPGs with this change?? I definitely get the better throttle response and power in top gear but better MPGs?? Somebody smarter than me, explain this. Please:bowdown:

 

There are a number of threads on this including a current one in the 2nd gen section. Baasically, it amounts to this - 4th and 5th are Extremely overdrive on the 2nd gens and if you use those gears at speeds under 100 kph (62 MPH) you are lugging the engine and falling out of the power band. So - when that happens, most people crank on more throttle thereby shoving more gas through the carbs to get going. You wind up running rich which of course wastes gas. The name of te game is to stay in the lower gears and rev the engine - remember, these are 4 cyl. motors not v-twins. They have less torque at lower r.p.m.'s so require more throttle to get moving. The V-Max rear end has lower gears (Higher numerically) which keeps the motor spinning at slightly higher revs at all speeds so that torque is available sooner even in higher gears so you don't have to crank the throttle as hard to get more power to the rear wheel. There are probably better explanations elsewhere in the forum, but this should give you a good idea as to what's happening. If you check out the thread in the 2nd gen section, you'll find that pretty much everyone who did the switch is happy with it and many are getting better gas mileage.

 

Andy

[MikeWa]

There are a number of threads on this including a current one in the 2nd gen section. Baasically, it amounts to this - 4th and 5th are Extremely overdrive on the 2nd gens and if you use those gears at speeds under 100 kph (62 MPH) you are lugging the engine and falling out of the power band. So - when that happens, most people crank on more throttle thereby shoving more gas through the carbs to get going. You wind up running rich which of course wastes gas. The name of te game is to stay in the lower gears and rev the engine - remember, these are 4 cyl. motors not v-twins. They have less torque at lower r.p.m.'s so require more throttle to get moving. The V-Max rear end has lower gears (Higher numerically) which keeps the motor spinning at slightly higher revs at all speeds so that torque is available sooner even in higher gears so you don't have to crank the throttle as hard to get more power to the rear wheel. There are probably better explanations elsewhere in the forum, but this should give you a good idea as to what's happening. If you check out the thread in the 2nd gen section, you'll find that pretty much everyone who did the switch is happy with it and many are getting better gas mileage.

 

Andy

 

 

Well said.

 

Mike

[Venturous Randy]

As I have said before, the position of the throttle pretty much dictates gas mileage. If you are pulling in one gear and downshift and either began to accelerate or let off the throttle to maintain the same speed, you are bogging below the power band.

Getting back in the power band will improve your engine efficiency, therefore improving your gas mileage.

If I am getting less that 45 mpg while running around 2-up, unless running down the interstate at 75 mph+, I am wondering what is wrong. And I don't baby my bike.

RandyA

[Wade 2000]

Thanks for the insight on this. I think I'll be changing out my gears this winter. You Guys Rock!!

[VentureFar]

Yep I am convinced also. Will be the next major upgrade.

Thanks all.

VentureFar...

[pmelah]

well can this mod be done to a mkI

[M61A1MECH]

Where did you get the v-max rear from? Was it new or used. I am taking a trip to the Cabot Trail in NS in 1 month. Considering the upgrade but my bike is running great and a little worried I might take a great running bike and mess it up!

 

Not sure where the original poster got his V-max rear end , but here is the place that I believe most folks go to for the swap.

http://rmsportmax.com/gateway.html

[Venturous Randy]

well can this mod be done to a mkI

 

Sure, I just put a V-Max rear end in my 83. I seriously doubt I will see any gas mileage improvement for awhile as I can't seem to get past the throttle giggles. I do not expect the gas mileage to get any worse for me in my 2up riding around the mountains and I routinely get about 45 mpg. Now, if I am going to make a 75 mph run down the interstate, I may see a little drop.

The reason I went with the V-Max rear is I have another 1200 engine that I installed an 02 Venture transmission that the gears are wider spaced. This way, 5th will be about 5% higher, but 1st will be about 10% lower.

I just need to get my butt in gear and get the engine swapped out.

To use the V-Max rear I had, I had to go to an MKII driveshaft and a different dust cover/shield on the wheel. Other than that, it was a straight swap.

RandyA

[frankd]

well can this mod be done to a mkI

 

 

To a Mk II it can be done, but I'm not sure about a Mk I. However, First Gens are geared more aggressively than 2nd Gens. and 5th gear is not as much of an overdrive. If you're wondering about how much this would help your bike, run a tank on the highway in 4th gear and see what you get. Changing the gearing also would make the bike take off from a stop easier and feel pepy as you shift through the gears. That's why this is so popular with those that pull a trailer.

 

I don't want to open a can of worms about gearing the 2nd gens lower, but I think this really indicates carburetors that are too rich in the mid range. Engine friction goes up with the square of RPM change. That means that if you go down a gear and spin any engine 20% faster, your engine friction goes up 44% (it's still small though). Also the engine will produce a a higher vacuum (at the same bike speed), so that means that the pistons will have to work harder to draw the mixture in, also increasing the loss. Increased engine friction and piston load reduce gas mileage. Then why does the mileage go up? With the lower gear, you will cruise at a lower throttle opening than the stock setup. At light throttle opening the idle circuit has quite a bit of effect. At higher throttle opening, the slides move more, and pull the needles out more, partially opening the main jet and increasing the fuel flow. There have been articles here talking about the fuel level in the 2nd gen carbs all being set too high at the factory, and adjusting them to the right level helped the gas mileage a lot. You can check your fuel levels easily, and if you have a 2nd gen with poor gas mileage, this is probably the first thing to check or fix. I know that nobody wants to work on carbs, and that includes me. However, although I've never pulled a set of 2nd gen carbs. I get the impression that they come out a lot easier than 1st gen bikes. But then the V-max rear gear makes the bike feel so much stronger.....

[Whistler]

From reading this post is it telling me to stay in 3rd gear cause I don't go to over drive until at least 50 . It seems you are at higher revs in a lower gear witch should use more gas I get 37 at the most unless I'm doing 75 or 80 Ron:detective:

[VentureFar]

Please

Someone with a 2nd gen RSV and vmax rear end do a mileage test next time you take a freeway 70mph ride.

Fill up before you get on the road and fill up again 2 hours later.

That should be a good start.

 

This is the season to get out in the hwy so someone be a Venturerider forum hero and report a specific 70mph test for us.

 

I am appreciative and grateful to you all on this terrific forum.

VentureFar...

[RSTDdog]

How does the Vmax rear affect the speedometer error?? Since the pick up is on the gear set at the input end of the diff, the gear is therefore spinning faster at a given speed with the Vmax rear than it is with the stock rear correct? To accurately check for mileage changes between the two, you also need to know the speedo error associated with both. I can't figure out in my head at the momnet if you would log more miles or less with the vmax rear???

 

2nd gen owners can't compare fuel mileage to first gen owners or expect that type of mileage either. The aero dynamics on the first gen appear to be much better to me which has a big effect on mpg.

[dewinks]

This is all rather interesting. I bought a Venture Rear end for my VMax to lose power and gain MPG! hahahaha. Just need to finish fabricating the shock mount................

[VentureFar]

This is all rather interesting. I bought a Venture Rear end for my VMax to lose power and gain MPG! hahahaha. Just need to finish fabricating the shock mount................

 

This reminds me of the old joke about everyone in the French foreign legion getting a change of underwear- "you change with you and you change with him.."..

 

VentureFar...

[MikeWa]

Please

Someone with a 2nd gen RSV and vmax rear end do a mileage test next time you take a freeway 70mph ride.

Fill up before you get on the road and fill up again 2 hours later.

That should be a good start.

 

This is the season to get out in the hwy so someone be a Venturerider forum hero and report a specific 70mph test for us.

 

I am appreciative and grateful to you all on this terrific forum.

VentureFar...

 

I have done that. Picked up about three mpg. (results may vary).

 

Mike

[MikeWa]

How does the Vmax rear affect the speedometer error?? Since the pick up is on the gear set at the input end of the diff, the gear is therefore spinning faster at a given speed with the Vmax rear than it is with the stock rear correct? To accurately check for mileage changes between the two, you also need to know the speedo error associated with both. I can't figure out in my head at the momnet if you would log more miles or less with the vmax rear???

 

2nd gen owners can't compare fuel mileage to first gen owners or expect that type of mileage either. The aero dynamics on the first gen appear to be much better to me which has a big effect on mpg.

 

There is no affect on the speedometer as both gear sets us the same number of teeth on the ring gear.

 

Mike

[MikeWa]

This is all rather interesting. I bought a Venture Rear end for my VMax to lose power and gain MPG! hahahaha. Just need to finish fabricating the shock mount................

 

 

Ha ha ha that's the thing V-Max owners like the Venture gear and Venture owners like the V-Max gear. Are you listening Yamaha? Hello.

 

Mike

[k9cottage]

well after looking all around Australia with no v-max or fjr diffs, i got one in Germany apparently fjr are very common over there got one for 99 euros very handy having a German bike riding buddy so now i sit and wait for it to arrive

[Venturous Randy]

Well, I just filled up after the first tank running with the V-Max rear on my 83. I got right at 44 mpg's, which is a little down, but most of the riding was 1 up, where I usually do get less mpg's. In this case, I expected to be down some as I am still dealing with the throttle giggles and that has been fun.

I also did some riding at 65 mph in 5th and I do have to say that the desire to shift up one more time would not go away.

RandyA