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Discussion Starter #1
Hi All ,
I have switched to a 36 tooth rear sprocket [from the stock 38 tooth item] . No hassles in actually doing the swap, but the chain adjusters had to be screwed out almost double the original length to get the requiste chain tension........ is this normal and to be expected ?
No, I have not yet taken a ride to check it out [the snow is still melting], but I will post my impressions when I do.
micah
2002 ZR7s/silver/ignition advance rotor/36T rear sprocket/carbs 2.5 turns 'out'/'Bright White' headlamp bulb/gel seat/fibre-glass hugger
 

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Micah,

correct me if I'm wrong, but that will bring the rpm's down at any given speed, right? This is also on my short list of things to do, whose sprocket and where'd you get it?

Adjusters: How many miles on the bike, or, how much chain stretch is being accomodated while tweaking for the new sprocket? Chains stretch and sag over time/miles, a thing to be considered before worrying too much about it. Maybe time for a new chain? But a 2002, probably not. Measure the circumfrance of the sprockets and compare the difference, that should tell you what you need to know.

Now, about the sprocket.......
 

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A smaller rear sprocket will make it harder to take up the slack in the chain later. You may have to remove the chain and cut a link out so you'll have enough adjuster to accomplish this. Adding a tooth to the front sprocket doesn't affect the chain adjuster as much (very little infact!), but you have to remove the web of aluminum to get the chain and sprocket to clear the side cover.

By adding a tooth to the front sprocket or going with a smaller rear sprocket it lowers your cruise rpm. First gear isn't affected very much, but the other gears are "taller". Mine pulls between 4,500 and 5,000 rpm (indicated) at around 75mph (indicated). When you go to pass another vehicle at that speed, you really have to drop a gear but you can pull alot further up in the rpm in 4th to make the pass. I've ran mine up above 95 mph (indicated) in 4th and still had plenty more to go.
 

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The 36 worked out for me, I used a sprocket specialty alum and paid the extra for the hardcoat, worth it IMO. Got 12kmiles on it and it looks perfect. I think the chain would be worn out before you ran out of adjustment. Since I can still touch redline in topgear I think it is about perfect. The other option is adding a tooth to the front, thank Martin for being bold enough to grind on his case, LOL. It would raise the gearing a tad more than the 36. Old rule o thumb is: 1 in the front is = to 3 in the back. I only did the mod to move the "buzz" out of my freeway fast lane pace speed range
 

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I think for all around gearing the 36T is probably the better option. Not that I'm unhappy, but if I were to have a different commute (less freeway), I'd opt for the 36T.
 

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Oh, I checked my speedo/tach coming home from work and at 75mph it's at 5,000 rpm (both indicated) in 5th gear.
 

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Discussion Starter #7
Thanks for all the feed-back.
Concerning the adjusters requiring to be screwed out........makes sense, as now there is "more" chain for "less" sprocket.
The sprocket was sourced from Sprocket Specialists [www.sprocketspecialists.com]. Its aluminium with a hardening process [paid extra for that] applied to the teeth.
Any recommendations for a 'replacement' chain ?
micah
 

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How many miles do you have on the current chain?.... I replaced the original with an RK.
 

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May order one this weekend....

and I'm thinking, since I still do a chunk of hiway commuting, maybe the 35t is the appropriate choice, though I'll be way out it sounds like on the adjusters.

Hey KLRBILL, can you give some numbers comparative to Martins, just to have a little extra info on the difference. I think I remember someone saying 1 up front is egual to 3 in the back. True?

I'm sure the safe bet is the 36, and probably what I'll get, but curious.


Later,
James


PS: Factory Pro did a test on a GSXR with many, many miles on it and found that new chain and sprocket brought the delivery of HP to the rear wheel back up to spec. (I'd have to dig up the article, but I'm fairly sure it was a significant change, neighborhood of 8 hp lost in sloppy chain and worn sprocket)
 

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I think I remember someone saying 1 up front is egual to 3 in the back. True?
Yup!
 

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I'd probably add a tooth to the front before i went down to a 35t on the back. The smallller rear runs the chain closer to the swingarm protector, a concern (wasn't a problem) I had when I put the 36 on. Also not sure if you'd run out of chain adjustment with the stock chain? Maybe someone has tried it. Also wouldn't put a new sprocket on and high mile chain, wait until you need a new chain. The 36 is a about right for my use, wouldn't want to be any taller, mainly because I'm usually loaded up with hard bags and travel gear. Stock gearing is acceleration gearing, typical jap bike formula, gear it 1/2 redline at highway cruise. This makes the roll-on strong and makes the bike feel powerful. Not a bad thing, but in my case it puts it at the buzz rpms, otherwise I'd would just had let her spin. Can't remember what the rpm vs speed are, bike is still in storage. A little math and you can figure it out.
 

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Wheelie for Safety
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Re: May order one this weekend....

Offpeak said:
PS: Factory Pro did a test on a GSXR with many, many miles on it and found that new chain and sprocket brought the delivery of HP to the rear wheel back up to spec. (I'd have to dig up the article, but I'm fairly sure it was a significant change, neighborhood of 8 hp lost in sloppy chain and worn sprocket)
I knew there was a reason I lube the chain before each ride.
 

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Discussion Starter #13
This site "http://dropbears.com/u/utilities/index.htm" has calculators for mo-bike stuff.
micah
 

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Don't be afraid of the 17T front sprocket, y'all. You only have to grind a little notch in the cover, not the engine case itself.

RM <--- has 17T, will travel
 

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Johnny Blue Lightnin'
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Isn't there some sort of sprocket/gearing spread sheet posted on the home page???
 

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Just having spent 1000 miles riding in 2 days I checked my speed/RPM against my GPS.

Top gear only: I can do the whole breakdown if people really want it.

5th:

3000RPM: 40.5mph
5000RPM: 65.8mph (72 indicated = my cruise)
6000RPM: 78.2mph (85 indicated)

I did 8 or 12hr days and really didn't notice vibration. The handlebars had nearly none. My feet could feel the pegs vibrate but I sure didn't mind it.
 

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Discussion Starter #18
Due to the weather conditions, I was able to squeeze in a single day of riding with the 36T rear sprocket [and ignition advance].
Seat-of-the-pants tells me that the motor is 'more willing' throughout the rev range, especially in 3rd, 4th and 5th; the impulse to 'find' a 6th gear is gone and the bike is more smooth.
Question: Given the bikes 'audience', why did Kwack opt for the 38T as an OEM sprocket ?
micah
2002 silver ZR-7S/2.5 turn carb adjustment/ignition advance rotor/mesh baffle removed from stock silencer/gel seat/hugger/PIAA 'white light' headlamp bulb/
 

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People want a rush when they whack the throttle open. An all-purpose bike should have all-purpose gearing, but the buying public doesn't understand that...
 

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36 teeth

Hi,hope your 36t sprocket went well.I was wondering if you could tell me where you got it? I've tried to source one but cannot see one anywhere on the net!

Cheers,Russ.
 
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