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18 Tooth Front 37 Tooth Rear +2 / -1 Highway Gearing

4K views 14 replies 7 participants last post by  Obo 
#1 ·
Hey guys, this is my first post here.

I picked up my 2001 ZR7s with 15k on it about a month ago.
When I bought it I didn't know it was a 5 speed. Not that it really mattered, I was on a limited budget and got the bike for 1200.

I've put about 300 in it to get it set up to my likings, which includes the highway gearing + Highlighter red chain
55 watt HID and 2x 15 watt LED headlights, Barnett Clutch Springs, Ivan's Carb Kit, and 2 Bros Slip on(included). I will be doing the PVC mod soon.

The previous owner had installed a 17 tooth front. This wasn't enough for me at all. I immediately noticed myself hunting for 6th and I don't like doing 6k+ to keep up with traffic.

I looked online and realized this setup 18/37 was the lowest gearing I could get and probably about the max you should run. Both sprockets are made by Vortex.

The cover needs clearencing as the 18t doesn't even fit in the hole. A die grinder and dremel handles this with ease. (I've read that the 17t front requires clearencing but the previous owner didn't. It didn't seem to make contact but it was damn close) the 18t WILL REQUIRE CLEARENCING.
The rear sprocket uses oringal bolts and holes easy.

I've now been riding with this set up for 2 weeks and I LOVE IT!!

I DONT find myself looking for 6th anymore.

It still has plenty of power in 5th at any speed above 50Mph. I've road 2 up for about 200 miles(1/2 freeway 1/2 city) and it was great no issues or lack of power.
This gearing is 100x better when downshifting before a tight corner. It's not screaming and I can often hold the gear I was in before.

I'm now averaging about 50-52 mpg (upfrom 42-45) when cruising at 75 mph. Now that the engine isn't screaming, she sips fuel.

I'm going to pull my cover off in a few days to inspect the sprocket. I'll take a few pics so if anyone is interested in the swap they can see how much cutting and metal had to be removed(about 3/4 inch X 7 inch round )

Here is some RPM / MPH difference between Stock, the popular 17 tooth front/stock rear and my Highway setup.
70MPH
Stock - 5077 RPM
17t front/38t - 4779
Highway (18t/37t) - 4394
85MPH
Stock - 6165 RPM
17t front/38t - 5803
Highway (18t/37t) - 5336
 
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#4 ·
I see Vortex sells a steel 18T 525 sprocket for $29. They don't carry a steel rear sprocket(s) tho, for our application but, rear sprockets can be purchased plenty of other places... Most of their sprocket choices are for the 520 conversion and mare of T5 aluminum.
 
#5 · (Edited)
The carb kit dropped my Mpg from about 48-50 with the 17tooth front to 42-45. I leaned it out a bit, and now with the highway gearing I'm just above my original Mpg numbers.
I bought the sprockets on eBay.
Carryall found it, that's the front I bought, and I bought an aluminum rear 37. I kept everything 525
With about 800 miles now, the rear sprocket has no wear or issues. I greased everything well for breakin
I didn't forget about the case pics, just haven't taken it off yet. I think at about 1000 I'll do that.
 
#6 ·
I've tried Aluminum rear sprockets in the past and can say that I will only use them on race or track day only. Regardless of who makes them they just won't find a place on my bikes. When you are looking at saving ounces and tenth of a seconds go for it. High mileage on the street hardened steel is the way to go. In my opinion.
 
#7 ·
I agree LPS. For maintenance free riding, ya can't beat steel vs Aluminum over the long haul. I'd try the 18T with the stock rear tho, just to see how it feels. Especially if I commuted on freeways/highways frequently, where my sustained speeds are 70-75mph. 5-6K seems to be the sweet-spot RPM range on mine for cruising with relatively decent mileage and power to still be had.
Look forward to your review and pics of the extent of trimming for the chain clearance prerunning.
 
#8 · (Edited)
Hey guys, so I'm finally back from Montana. Its been really rainy here in Cali so not to much riding but i just got around to pulling the case off and taking some pics. I found that i had to cut about 3/4 inch more than i had originally because it was making slight contact when the suspension compressed hard. When riding 2 up and hitting large holes, the rear swing arm would pivot causing the chain to rub the top of the side cover a bit. The die grinder and 10 mins, problem solved! The gearing is GREAT. I work the clutch a bit more on take offs but its so worth it. No vibrations on the freeway, plenty of power. I raced a 5.0 mustang and smoked him, which is plenty of power for me. Cruising at 80 feels really modern now. My china red chain and aluminum rear sprocket are wearing really nicely, not that I'm really hard on them tho.

I still have a few things i have to fix on the bike.
Its due for a valve adjustment. I would like to replace the valve springs and possibly go with stiffer springs if thats something viable on these bikes. Im not really sure with the talk that these cams eat shims fairly quick. But with the jet kit the bike really loves 7-8k pulls, so maybe stiffer springs could be a good thing if it doesn't eat the shims really quick.
What springs do you guys recommend? Has anyone replaced the main bearings? Thats something i would like to do at some point so i have the confidence to run it hard back it forth to Las Vegas and Arizona often(250 miles)
It also duck dives HARD. One of the fork seals is blown, so i need to fix that and then do the PVC mod. Wish I had more time... But ill get it done!

I installed Amber LED turn signal mirrors. I wired them to be always on as running lights. They look great and increase visibility ALOT.
Heres the pics and idling with the LEDS
Auto part Family car
Auto part Black-and-white Wheel Metal
Auto part Engine Metal
Auto part Engine Automotive engine part Clutch Fuel line
Tire Automotive tire Wheel Rim Auto part
 
#15 ·
Its due for a valve adjustment. I would like to replace the valve springs and possibly go with stiffer springs if thats something viable on these bikes. Im not really sure with the talk that these cams eat shims fairly quick.
The bike doesn't eat shims & the springs shouldn't need anything stiffer. Just check them at the specified intervals and change the shims of it's out of spec.
As for the main bearing, if it's good there's nothing to really do to it. Just change the oil & filter regularly with the specified stuff.
The engines and transmissions are known for being long term reliable.
 
#9 ·
Great looking bike for $1,200! Really sounds good. I'd like to put a jet kit in mine but it runs so well now I'm afraid to fool with it.

Before you go tearing your forks apart, try just cleaning the fork seals with one of these:

Motion Pro Sealmate Fork Seal Cleaner Hyosung GT650R GT250R GV650 Honda Yamaha | eBay

Here's a video showing how to use it:



If you don't want to wait for one to ship to you, you can make one out of an old plastic milk jug.

They're cheap, easy to use and work great.

If you've lost a significant amount of fork oil you may want to add oil to bring the leaky side's level even with the good side. Or if you're feeling motivated, drain, flush and fill with fresh oil.
 
#11 ·
Sounds and looks good, I like the mirror mounted LED lights, please share where you got those from. As far as valve springs don't bother. I have been riding these 750 air (oil) cooled Kawasaki motorcycles since my first one a 1980 KZ750 E1 in 1980 and have never had or heard of valve spring issues of any kind with any of the KZ, ZR, GPZ or any of these bikes. Run them as hard as you want do the preventative maintenance use good stuff and enjoy. They at as reliable and as well made as a Stanley framing hammer. So "Hammer Away" !
 
#14 ·
I really can't comment because I have never "changed" my valve springs (to my knowledge) I had Rob Muzzy's performance shop "do a number" on the engine on my 97" ZX11's engine so it put out a stupid amount of power while being able to idle and run pump gas. I really don't know the complete list of mods and parts it had. But it flat ran away from 99' Busa's and such. On a local mobile dyno it was putting 209 RWHP out. Had to sell it. It was almost worse than being addicted to drugs.
 
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