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The Garage Motorcycle Related Discussion (Yamaha XS650, other makes and models, and anything else motorcycle related including tools and gear)

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Old 06-19-2010, 06:00 PM   #1
bassgoat1979
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Default Rear sprocket help

I'm sure this is on here somewere. I put the 30t rear and still have my 17t front (don't want to change that) Anyway I like the rpms, but it has no balls at all like it did with the 34t. I can't give it much throttle at all in 2nd and 3rd if you shift standard, it stutters untill you get moving. If I run like a two stroke it's great, but it's all or nothing. Will a 32t rear still have some torque on a stock motor with pipes and pods? I don't want to spend $40 for it to have it be too high as well. I don't care if the rpm are higher on the highway, just lower than stock will work.
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Old 06-19-2010, 06:12 PM   #2
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Default Re: Rear sprocket help

I had the 17 front 30 rear for a while too. People told me it was great, but they were probably running a 16" rear wheel. With my 18" (gearing it up even more), it was pretty anemic. Ran great on the interstate though.

During my recent engine rebuild I added MikesXS internal 5th gear, which gears it up slightly in 5th only. I'm now running 18 tooth front and the stock 34 tooth rear. The compromise is good: it'll still pull away at a stoplight with little throttle and only tachs 3000rpm at 50mph.

I miss the smooth cruising of the higher gearing, but it's much easier to ride. It could still use a true overdrive gear, but that's not really possible.

Pete's spreadsheet has proved almost spot-on for me:
http://xs650temp.proboards.com/index...y&thread=11068
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Old 06-19-2010, 06:24 PM   #3
bassgoat1979
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Default Re: Rear sprocket help

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I had the 17 front 30 rear for a while too. People told me it was great, but they were probably running a 16" rear wheel. With my 18" (gearing it up even more), it was pretty anemic. Ran great on the interstate though.

During my recent engine rebuild I added MikesXS internal 5th gear, which gears it up slightly in 5th only. I'm now running 18 tooth front and the stock 34 tooth rear. The compromise is good: it'll still pull away at a stoplight with little throttle and only tachs 3000rpm at 50mph.

I miss the smooth cruising of the higher gearing, but it's much easier to ride. It could still use a true overdrive gear, but that's not really possible.

Pete's spreadsheet has proved almost spot-on for me:
http://xs650temp.proboards.com/index...y&thread=11068
So your running a stock motor? Your low gears would be the same as me throwing a 32t rear. Did your bike stutter at cruising shift too at the bottom of the gears? I got the vibration at high rpms down pretty good with timing, plus it sounds more wicked at idle.
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Old 06-19-2010, 06:27 PM   #4
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Default Re: Rear sprocket help

A stock 17/34 tooth at 50mph is 3430 rpm.
17/30 at 50mph is 3027rpm
18/34 at 50mph is 3240rpm
17/32 at 50mph is 3229rpm

I can tell you that the 18/34 is fine, so 17/32 should be as well.

------------------------
Yeah, it seemed like I was always lugging the engine with the 30t sprocket...I'm not a fan of two-stroke power bands.
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Old 06-19-2010, 06:36 PM   #5
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Default Re: Rear sprocket help

I was fighting with jetting till I figuerd out it was fine if your run the gears up higher. I know the V-rods run about 5000rpm at 80mph, so I should be close. The cruisers are only running about 3500 at 80mph. That's about how we cruise the expressways here, it should be fine. Hell a crusier Harley red lines about 5500 rpm, so I should be good on the xs running 5000 on the expressways. I know these can turn better rpms than a harley. It definatly sound wicked running like that with straight pipes.
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Old 06-19-2010, 06:43 PM   #6
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Default Re: Rear sprocket help

The timing needs to be retarded a bit for tall gearing to shine......for sure........xsjohn
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Old 06-19-2010, 06:56 PM   #7
bassgoat1979
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Default Re: Rear sprocket help

Yeah this gearing I have now I had to advance the timeing back to normal advance because it was lacking so much in the low end. I am hoping the 17-32 will be a good compromise. I don't mind some vibration from it burn the highways up, just want to be a little nicer to the engine. I like some, it feels more like a machine. Will it hurt these engines to run 80mph with stock gearing if I retard the timing a little? I see the don't even red line till 9,000 rpm on the guages
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Old 06-19-2010, 07:15 PM   #8
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Default Re: Rear sprocket help

i just ordered a 31 tooth sprocket I hope I don't regret it.... i kept going back and forth between different sizes
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Old 06-19-2010, 07:41 PM   #9
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Default Re: Rear sprocket help

I think I'm going to go back to stock and just run her. A extra 450 rpm just isn't that much on the engine anyway.
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Old 06-19-2010, 07:49 PM   #10
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Default Re: Rear sprocket help

Does anybody know the 70 or 80 mph rpm of a stock geared with a 18" rear? (I have the old skool tall 16" tire, same hight as a reg 18" tire) How much would it drop to run the 32t sprocket.
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Old 06-19-2010, 08:33 PM   #11
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Default Re: Rear sprocket help

These are 360 engines.....vibrations and high revs will tear them up .........I suspect all the revs on the tack were just a sales pitch when other makers were selling horse power..........you can set them up to scream or set them up to last .......pick one..............xsjohn
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Old 06-19-2010, 09:31 PM   #12
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Default Re: Rear sprocket help

If it can't handle running about 5000 rpm, I will have to build it to be able to I guess. Hell they don't even hit full horsepower till over 7,000 rpm. I always thought they made these to race brit bikes and win. The brit bikes say they can run the highways. I want it to have balls first and formost, if I get 50,000 per overhaul, I'll be giddy. I'll sythetic 20w50 to get a full 50,000 with my fingers crossed. I dont have any gauges so who know, I guess I'll go by years. 5 years per overhaul. The ones my unlce races tt have 38t or bigger rear and run the s++t outta them and get quite a few races per rebuild.
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Old 06-19-2010, 09:34 PM   #13
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Default Re: Rear sprocket help

My only data point is that I ran stone stock 71 from Wisconsin to Florida and back on spring break in about 1975 I was riding with a KZ900, we didn't dwaddle, got a ticket for 100 in a 55 zone, the cop said because he was being nice.......... After the vibration made the usual parts fall off, no issues.


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Old 06-19-2010, 09:50 PM   #14
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Default Re: Rear sprocket help

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My only data point is that I ran stone stock 71 from Wisconsin to Florida and back on spring break in about 1975 I was riding with a KZ900, we didn't dwaddle, got a ticket for 100 in a 55 zone, the cop said because he was being nice.......... After the vibration made the usual parts fall off, no issues.
Now that sounds like a good ride!!! The good thing is my bike doesn't have many parts anymore to fall off. I made sure I followed Harley and locktited eveything! I just got to get a strap on gel pad for the seat befor I go that far. Great story!
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Old 06-19-2010, 09:54 PM   #15
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Default Re: Rear sprocket help

I put the 17:30 sprockets on and it runs fine. Sure, too accellerate you have to drop a gear. I run down to idle in 2nd gear and it pulls away smoothly. Curise as low as 2500 and pull away smoothly in 5th. Guess my jetting is right and when I checked my timing it was at the sliglty retarded positon the XSjohn recommends.

Just made a 90 mile ride earleir no vibration in the handlebar, but I have a Renthal thickwall aluminum w/barend weights which dampens the vibes. at 75-85 I could feel the vibes in the seat, but not in the grips.


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Old 06-19-2010, 10:16 PM   #16
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Default Re: Rear sprocket help

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Originally Posted by gentlemanjim View Post
I put the 17:30 sprockets on and it runs fine. Sure, too accellerate you have to drop a gear. I run down to idle in 2nd gear and it pulls away smoothly. Curise as low as 2500 and pull away smoothly in 5th. Guess my jetting is right and when I checked my timing it was at the sliglty retarded positon the XSjohn recommends.

Just made a 90 mile ride earleir no vibration in the handlebar, but I have a Renthal thickwall aluminum w/barend weights which dampens the vibes. at 75-85 I could feel the vibes in the seat, but not in the grips.
I can pull away fine. I'm talking about cracking throttle wide open at cruising speed and it kind of stutters (boggs) then clears and climbs okay to good. When I had the stock gearing you could cruise at 3000 rpm and give it full throttle and feel it pull away hard. I was wonder if the 32t had the same thrill. I run will hard asses so I was having trouble keeping up with the 30t when we were around cruising 55mph and they take off in fifth. I had to down shift and by then they were gone. I got the stock back on a little while ago and soon going to go for a ride and see how she acts.

Mine turns the plugs black too, when I had the other sprocket it didn't do that. It's abvious lugging the engine. I think that is worse with my riding style.
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Old 06-19-2010, 10:36 PM   #17
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Default Re: Rear sprocket help

cut a coil on your atu springs. It will ensure that you don't hit full advance until 3500. I'm running 17/30 and it made a huge difference.


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Old 06-19-2010, 10:43 PM   #18
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Default Re: Rear sprocket help

I think I may try a 33t if the stock is unlivable. Just seems these bikes can't handle well the 30t right unless it's for cruisng only. I was thinking of going big bore and a cam this winter, then I could run the 30t. But then I think how fast it would be with stock gearing!

I got my wife's stock XS400 out erlier and tried to shift up to third instead of second (like how the 30t was) And it did the exact same think my 650 was doing. Hit it hard and it would stutter, down shifted to 2nd and it threw me back with that much throttle.
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Old 06-20-2010, 06:47 AM   #19
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Default Re: Rear sprocket help

what are your rpms when you're trying this? Anything from 3k on shouldn't 'shudder', no matter what.


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Old 06-20-2010, 07:50 AM   #20
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Default Re: Rear sprocket help

Like I said, I don't have gauges. Basicly a little over idle it does it ONLY if you hit the throttle hard. If you get into it smooth and don't overdo it it is fine, no fun, but goes smooth. Or I have to run the gears like a 2 stroke (which is what I was always doing) to keep the power up. I know that is probably worse that a little vibration on the highway. If it runs good stock, I know for a fact that's all that is wrong.
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