Sprocket Gearing... any good kits?

Hey guys, I have an 85 vf700f. (Yes squirrelman, I know it's antiquated and not worth comparing to the all mighty 86... :thumbsup Last summer when I took it on the highway to go visit my sis. the rpms were running at about 7500 in 5th gear (that's my top gear) at about 75mph. So when I change my sprockets and chain this spring, I want to try and change the gearing to drop the rpms around 1500-2000 rpms or so. My ideal would be around 5500 - 6000 rpms at 75-80mph.

I don't need a ton of acceleration and torque. I don't stunt, and don't need to race anybody off the line. Just would like a little better gas mileage on the open road.

So I was thinking if I went up 1 tooth in the front, and maybe down 1 or two in the back? I looked for kits a little. But so far I've only found something for 86 750's I guess I got the unpopular bike here... lol. And I noticed that most kits seem to change the gearing for more acceleration and torque. Any advice and or information would be very much appreciated. I saw a thread where somebody had posted a link to a site that had a gear calculator but they didn't have my model in their database. They had an 86 750 though...

Thanks guys.

StormHorse

 

Have you looked at SprocketSpecialists? SPROCKET SPECIALISTS-Sprockets for all makes of bikes. They list a wide range of sprockets for the 700.

For what you want to do you shouldn't need an extensive gear calculator, you just want to change the final ratio a certain percentage. Here's a write up on how to do that: Understand Motorcycle Sprocket Math @ MotorCycleAnchor.com

A 1500 rpm decrease would be a 20% decrease, which seems like a lot, but use that and your current sprocket sizes to figure out what new sizes you need.

 

Trying to drop your rpms that much would absolutely kill you accel, It would be like going from a v8 mustang to a geo metro. For illustration purposes, I DROPPED a tooth on my front sprocket and the rpms only went up by 200-300. so if you reverse that and go up a tooth youll only be going down 200-300rpms. In order to get the 1500 rpm drop you would have to at the very least add 2 teeth in the front and drop 2-3 in the rear. Personally I wouldnt recommend that drastic of a change, it would make starting damn near impossible, but hey you could go 200mph. One tooth up on the front probably wont hurt much though and should make a noticeable change in cruising comfort. Try Sprocket specialist or your local dealer for sprockets and Ebay for a good EK chain. Just my 2cents

 

Hey thanks guys. I'll check Sprocket Specialists.

And I was wondering if that much of a change would kill something like that... hmm well it is an old bike and it can probably only do so much. But if I just do an up 1 on the front and let it go at that... maybe it will be fine. thanks

 

Im just curious, Is it the sound of the bike at those Rpms that bother you or is it really shaky, or are you just trying to prolong the life of the engine? Just curious. I regularly cruise at 70mph at 7-8k in fifth. I love the whine of the enigine at those RPMs and my bike has lasted nearly 60k so far. Granted I can drop it down to 6k in sixth for long long hauls.

 

i feel you buddy i had the same thing going on with my bike, so i went 3 down on the rear and kept it stock in the front and ended up using a 104 link chain and no the bike at 85 mph is around 6300 rpms not to bad but im also able to stay in a lower gear when im in the mountains which helps out alot!! when accling out of the corners, good luck RK makes good sprockets :thumbsup:

 

I mostly want to prolong the life of the engine, and get at least a little better gas mileage on the highway. I take trips around 4-5 hours long fairly often. And it kinda makes me nervous having the rpms up that high all the time for that long. Maybe it is nothing to worry about. But at the least, a little better gas mileage would be nice.

Someone was telling me that they thought somebody had probably already changed the gearing on it. And that I should just go back to stock before I play around with it. The problem is that the bike is at my mechanics garage right now, he is on a three week holiday, and I don't know what gearing is on there right now. And also my service manual is there and I don't know what the stock gearing is on an 85 vf700f. So yeah.

Thanks for the helpful input guys,

Question for you matt, you said that when you dropped your rear sprocket down 3, you are now able to go 85mph at about 6300rpms. Was this with your 500? Cuz dang man... it's just not fair. lol

Also, from what I've been reading, it sounds like if you drop or add 1 on the front that is equal to dropping or adding 3 on the rear sprocket?

 

try this site >>>>Gearing Commander: Motorcycle Gearing Ratio Sprocket RPM Speed Chain Calculator<<<<<
will tell you what stock gearing for your bike is and what changes occur to speed -rpm as you change gearing.

 

yup it was the miniceptor that i did it to :thumbsup: i think that is right 1 down in the front equals 3 in the back

 

Except that going down 1 in the front would be like going up 3 in the back, and going up 1 in the front would be like going down 3 in the back... right?

I guess I'm thinking it's not too much different than a bicycle as far as the concept goes.

More teeth in the front means you can go faster but it's harder to pedal to reach that speed. Less teeth in the front means it's easier to pedal but you have to pedal really fast to reach a decent speed.

and the opposite for the rear.

Just wanted to clarify.

Thanks for the link to that sight chomper. But they don't have the 85 vf700f in their database. And I don't know all the specks to enter them.

So far, from what I've been able to find. The stock front sprocket is 16 and the stock rear is 44. Paired with a 530, 110 link chain. Is anybody able to verify this? I would check my manual but like I said it's not available at the moment.