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Discussion Starter #1
Has anyone tried the old trick of dropping one tooth on the front sprocket of your ZR7 ?

If so, how hard was it to install , and what difference in acceleration did you notice after the swap ?

- Woody
 

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From all previous calculations it'll be about equal to adding 3 to the rear. The big benefit (besides low end) is you won't have to add links to your chain.
 

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Woody,

I'm no expert, but I think it's better to drop teeth on the rear sprocket because dropping teeth on the front leaves the radius of that spocket so small that it gives the chain a noticeably harder life. The acceleration benefits can still be had.

Malc
 

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Discussion Starter #4
Well, I think you are both right. But has anyone at the forum doe this ? That is, either add 3 teeth in back, or gone to a tooth smaller in front ? If so, what does the "seat of the pants", before, and after tell you ? Iss it a big difference ? A noticable difference ?

- Woody
 

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I've been playing with gearing on motorcycles for a few years (all seat of the pants) and it's all pretty predictable. As far as more wear with a smaller diameter, yeah it'll be there, but not so as you'll notice. The stress on the clutch will actually be more noticeable because you'll need more rpm and clutch to get it moving from a dead stop.
 

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Discussion Starter #6
Martin,

My goal here is to gain faster revs, faster acceleration, conseqentaly I'll loose some top end speed - lossing a tooth in front will do this right? Or do I have it backwards - its been awhile since I've thought abut this stuff.

- Woody
 

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No, I had it backwards
 

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No, that's with adding a tooth. There isn't enough room in the case and you have to remove some of the excess casting to get it to fit.
 

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Andy Bajka said:
Isn't there an issue with the chain guide when you drop a tooth on the front sprocket?
I wouldn't think so, just readjust the chain after making the change. Your'e not stretching the chain with a one tooth departure on the front sprocket. More teeth on the rear could be a chain guide problem. IMO, Tom :)
 

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my neighbor dropped 1 tooth on the front. it feels quicker, actually it is quicker we went out and he could pull away from me low down but i caught up but i got the jet kit. you'll gain some rpm in every gear so cruising is slightly buzzy
 

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Discussion Starter #12
How many teeth on the stock front sprocket ?

If its 15, and you drop to 14, I think that is roughtly a 7% increase in faster rev/accelleration - approximately equal to a jet kit. (Of course you loose some top end speed with re-gearing, but I've never gone 120 mph on any bike I've ever had, so I doubt I would miss the 130 mph, vs. 120 mph.)

Also, In general I've heard its better to add teeth in back, than to drop in the front to reduce front sprocket wear. But personally, if I did it, I would swap the front sprocket. We are not talking gobs of hp on the ZR7S, plus I only put about 4,000 miles on my bike a year living in Minnesota. I don't put a lot of wear on my bikes from year to year.

- Woody
 

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Stock is 16 teeth on the front and 38 teeth on the rear...
 

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The chain sort of rides on the chain guide (look at the top of your swing arm). If you go down a tooth on the front it would ride on it even harder. I don't know what effect that would have.

Andy
 

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I went up just 1 on the rear and that equates to 6000rpm @120km/h ( 75mph ), which I guess is 500rpm up on stock.

Definitely improves acceleration, but I think 3 on the rear will have it howling like a banshee on the freeway.

:)
 

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Hey Andy, that's not really a guide. It's more of a guard to keep the swing-arm from getting all beat up from the chain.
 

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A COMMON TRAIT WITH THE SEVEN IS THAT SOME PEOPLE WANT A SIXTH GEAR. WE NOW IT PULLS ALL DAY FROM LOW DOWN BUT LACKS A LITTLE ON THE MOTORWAY{FREEWAY ACROSS THE POND} WHY NOT GO DOWN A TOOTH ON THE REAR! STILL PULLS BUT FEELS A BIT MORE RELAXED AND SLIGHTLY LOWER REVS AT CRUISING SPEEDS. A MOD I FANCY, IF YOU WANT A SCREAMER THERE A RE LOTS OF THINGS WRAPPED IN PLASTIC, BUT I THINK THE SEVEN IS FOR COMFORT NOT FOR SPEED.
 

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Discussion Starter #18
Wayne,

I am looking for a little more pull (torque/hp/accelleration) because I'm more used to true sportbikes, and want a little more umph when riding 2 up. I'm willing to sacrifice top end, and a little higher rev at highway speed. Plus the infamous buzz happens around 60 to 65 mph - by changing the front to 15 teeth, this buzz would happen around 55 to 60. I don't spend much time at 55 to 60 mph - much more either below 50 mph, or on the other end above 65 mph.

- Woody
 

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I think theres nothing to lose in trying. I've often considered dropping a tooth in the front, make sure you get the tooth pitch right though, theres a lot of sprockets out there.
As has been said you'll gain about 7% power at the back wheel but lose the same off the top end. And lets be realistic here in most real driving there is very little chance to reach these speeds on a naked bike, it starts to get hairy at about 110mph.
My bike sits bang on 5000rpm at 70mph which means it will touch 140 (on the clock) at 10000 rpm. I suspect your bike is like mine pulls well to about 110 in 4rth then into top and power delivery is lacking to say the least If I had a long straight and a lot of patience and ducked down it may, in time get to 140 on the clock.
It all depends where you live and what you want.
Sme guys cruise along big straight freeways for hours at a time and high engine revs may be annoying, lower revs may be their choice.
Some guys like me sit on crowded London streets and main roads, my bike rarely sees a freeway or motor way as they are known here, revs are not a problem, driving is very stop start and blasting off the lights against a porsche or subaru turbo is quite normal. I would choose to drop a tooth.
 
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