Rear sprocket change or overdrive 5th

peanut

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Which rear sprocket gives the closest ratio compared to using the overdrive gear in 5th ? 30T 31T 32T ?

I've read lots of threads and none of them seem to answer this question.

I'm trying to decide whether to go for the overdrive 5th gear and retain the standard gear ratios in the other gears or to fit a 30T or 31T rear sprocket instead.

The overdrive gear is going to cost me a kidney to get delivered from Mikesxs to the UK
 
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Read somewhere in this forum that the install and performance of the 5th overdrive wasn't what someone expected. Try the 30 on for size. My experience is that the lower gears will be used more often than just getting to 5th.
Others may vary........
 
Peanut, have you tried Heiden tuning? As they are in Europe my bet would be it MAY be cheaper?? Worth a try IMO....

I'm also in two minds about this, with varying comments/results off members here, but I thought of it as my engine is split in three!:D

:popcorn:
 
Read somewhere in this forum that the install and performance of the 5th overdrive wasn't what someone expected. Try the 30 on for size. My experience is that the lower gears will be used more often than just getting to 5th.
Others may vary........

I think you are dead right on this....
I did some calculations and it seems you can only get a reduction of about 180rpm from the 5th overdrive gear which is equal to reducing your speed from 60mph to 57.5mph !
Thats useless.

30T seems the best way to go as you say.
Tomorrow I'll post the results of what I've found out and we can take a look at it.
Thanks for your imput :thumbsup:

Airwolfie
Peanut, have you tried Heiden tuning? As they are in Europe my bet would be it MAY be cheaper?? Worth a try IMO....

I'm also in two minds about this, with varying comments/results off members here, but I thought of it as my engine is split in three!:D

:popcorn:

thanks for the Heiden suggestion they look to be the best source. About 29euros for a 30T sprocket plus p&p
My calculations would suggest we should be looking for a reduction in revs of about 600rpm at 60mph to have a significant effect on vibration at cruising speeds. I am anticipating riding at around 55-65mph on carriageways so I'd like to see around 3500rpm at 60mph

I believe it is about what johnxs ran his bike at and he sure knew his stuff RIP John
 
Just got back from a loop in the hills, hollers and a bit of straightaway. On the straightaway, I was doing 65MPH at around 4K RPM....just about 4k, not quite, and she wanted to go faster. No problem with vibes. This is the old zero to 140 MPH speedo. Thinking I should take a GPS out and check too. In the hills and hollers a lot of second and third usage....I noted third gear at 30 MPH at 3k rpm at one point. I'd break someones arm if they tried to take me back to the stocksetup. Weighing in at 178 lbs with my boots on......
 
J I'd break someones arm if they tried to take me back to the stocksetup. Weighing in at 178 lbs with my boots on......

this could be a bit of a problem for me because I weigh 240lbs currently. :eek:

I guess it all depends what sort of riding folk want to do.

I don't want to charge about at speed ,if I did I'd get a Triumph speed triple I just want to cruise along some twisty country lanes in good weather taking in the view and enjoying the whole experience without stress. I think a 17T x 30T is likely to be the best option for me.
 
well this is what I have discovered so far

Like many owners I want to reduce the vibration at motorway cruising speeds ie 55-60mph and would like to know what the various options are and which options are the most effective and the best value for money .
I have read everything I can find both on XS650.com and on various other forums and the more I learn the more confusing the whole thing becomes.

This is what I have collated today in an attempt to come to a decision about which option to select. I hope that the following may be of interest to other new or inexperienced xs650 owners like myself who are also considering how best to go about reducing the vibration of their bikes at cruising speeds by reducing the RPM per MPH.

For the purpose of this discussion I am going to ignore chain interference problems as there are already too many variables . I trust that whatever option I choose there will be a solution to any particular interference problems that might arise.

First I considered fitting an overdrive 5th gear as I am fortunate enough to have my engine already stripped.

With a 16” rear wheel and standard 17T primary and 34T secondary sprockets referring to Pamcopete’s chart in 5th gear at 60mph the engine should be turning over at about 4280rpm.

Adding a 5th overdrive gear will reduce the rpm to 4102rpm at 60mph saving a mere 178rpm this is unlikely to make any appreciable difference to vibration levels at 60mph and in fact if you just reduced your speed by 2.5mph you would achieve exactly the same reduction of 178rpm !

It would seem that an overdrive 5th gear is only likely to be effective fitted in conjunction with a change of sprocket/s and not just by itself.?

Changing just the primary sprocket from 17T to 18T should give a reduction at 60mph to 3888rpm a reduction of 392rpm !
To put that in perspective if you changed down from 5th gear to 4th gear at 60mph with the standard 17T x 34T sprockets ,the revs would increase from 4117rpm up to 4712rpm… a difference of 595rpm !

On this basis I would expect the most agreeable reduction in rpm at 60mph would need to be in the order of at least 600rpm so lets look at changing just the rear sprocket.

With a standard 17T primary sprocket, changing the rear 34T sprocket to a 30T at 60mph reduces the revs from 4280rpm to 3632rpm a total reduction of 648rpm !

Thats a significant drop in rpm and will feel about the same as changing up a whole gear to 6th gear

The beauty of just changing the rear sprocket is a, they are cheap (typically £20 ) b, they are very easy to fit and to change back again , typically a 1x hour job or less.

The down side is that a 30T sprocket is bound to have a significant effect on acceleration in lower gears and also pulling away in first but I'll cross that bridge when I come to it so I'm ordering a 30T 530 from Heiden Tuning . Fortunately I already have a new 530 primary sprocket and chain fitted by the po
 
I'm curious to know what happens (the changes in rpm) when you change from a 17T to an 18T primary and from a 34T to 30T rear sprocket WITHOUT 5th gear overdrive? Is anyone out there running this setup?

I need to figure out how to use that excel spreadsheet Pamcopete posted to calculate all this stuff myself... I'm currently planning on using a 20" rear the previous owner had on the bike.
 
Weight of the rider has to be taken into account. 18/30 is equivalent to 17/28 + a 20" rim would be closer to 17/26-27. If you manage to get started without burning out the clutch plates, or blowing up the engine through having to rev it so much or riding the clutch for take off, the bike will probably stall when changing into 5th gear

A lot of guys are happy with 17/32, but on a Standard configured XS650 17/33 is also well received. A 20" rim will also reduce the rear sprocket size by about 1 1/2 teeth or so, making those figures around 17/30-31 and 17/31-32
 
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Other alternatives to "overdrive 5th" or small rear sprocket would be a 19" rear wheel with a 4.00-19 or 120/90 tyre.

Or a higher primary drive ratio (not cheap, but maybe the very best option) See here:

http://xs650.biz/p/28/3237/mo74-cg|29=1/#ht-6584-primary-gear-set-new-heiden-tuning-design

Smaller than stock sprockets can cause chain rubbing on the swing arm, especially when using longer shocks to raise the rear end for better handling. A 19" rear wheel would also raise the rear 1/2" (12.7 mm), reducing the required shock length.

So, with the exception of tyre availability, the best solution is a higher primary drive ratio (low numerically) combined with a 19" rear wheel, and a suitable shock length. Less issues with chain rubbing, more ground clearance, less load on gearbox and clutch and more freedom to play with sprocket sizes. But not cheap.
 
Hi peanut,
I plain ol' don't trust that overdrive 5th gear. Adding another tooth without changing the gear's centre distance has to compromise the geartooth profile enough that it won't last too long or work too well.
Stick to the sprocket shuffle, eh?
Into all this comes the XS650 engine's available horsepower.
Geared too high and 5th gear becomes a mere overdrive, right?
 
If reducing vibration at cruising speed is the primary objective, first ensure that the carbs are carefully synchronized. In my experience, carb synch seems to have a major influence on vibration level in our beloved 650's at cruising speeds & rpm's- much more than sprocket sizes/tooth ratios.
 
I don't even know how you could stand to ride the thing with a 30 rear. I had a 32 and it was pretty awful for stop and go....and I only weigh 158 lb. I have a 33 on the shelf. Just wanna wait till I replace the chain and front too.
 
I don't even know how you could stand to ride the thing with a 30 rear. I had a 32 and it was pretty awful for stop and go....and I only weigh 158 lb. I have a 33 on the shelf. Just wanna wait till I replace the chain and front too.

We have the same problem with the XS1's taller first gear.
It works out to being like having a 31.5 tooth sprocket on the later bikes.
 
I've been running the 18/30 combo with a 16" wheel for quite awhile and it works great for my riding needs. I never felt the need to excessively slip the clutch or rev it more than usual when starting out. Once you have the setup for awhile you don't even notice the lower ratio. I have this combo strictly for comfort. The stock gear ratio makes my hands numb after a short time riding, where the 18/30 allows 60 mph rides for hours. You do lose some performance but the comfort far outweighs that for me. My tach shows 3500-3600 rpms at 60, ride your bike at those revs and see how smooth it is.
 
My Tahoe with its 350 CuIn V8 turns about 1800 @ 60 mph, when in overdrive (0.7 ratio)
How would the numbers compare if I were to cut it up into 8 equal pieces?

Tahoe with driver and gas = 4800 lbs, 350 CuIn V8.
Divided by 8.
600 pound contraption with a single 43.5 CuIn cylinder.
This 1/8 Tahoe is kinda like an overbored Suzuki Savage.

When I look at my ol' XS1B, upped to 750cc (and back to when I was lighter):
Bike with rider and gas = 540 lbs, 750 cc (45 CuIn) engine.
Divided by 1.
540 pound contraption with a 2-cylinder 45 CuIn engine.

The chevy engine, with its 4" bore and 3.5" stroke is similarly oversquared to the 750's 80mm bore 74mm stroke. A close geometric relationship.

This XS1B shows a slight advantage over the 1/8 Tahoe in the weight/power department.

You'd need a vastly different cam for this, but imagine:

1800 rpm @ 60 mph, when in overdrive...
 
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