changing sprockets

[bradshaw106]

Im getting ready to order my chain for my bike. was wondering if someone could explain to me the pros and cons of changing sprockets sizes. it seems that changing the front to a 18t is pretty common. what about changing rear?? my bike is more of a cruiser i have a 30 minute ride to work in the morning where i average 65mph. to give you an idea of type of driving i do.
thanks matt

 

[inxs]

- the larger the front sprocket the faster you go, the smaller the rear sprocket the faster you go...standard is 17T front, 34T rear...if you change the front to 18 and leave the rear you will cruise at a slightly lower rev range...too large a change and you start to affect your 1st gear take off characteristics

 

[bradshaw106]

by changing the front. in your opinion does that make for a better cruising bike?
is the first gear "feel" changed much with the 18t?

 

[Gordon]

I run a 17-31 combo gear set-up, which has brought the RPM down on the freeway to a less vibration 4000 RPM at about 65-70 mph. It's allot more comfortable, and less vibrations on the bars & mirrors.

 

[Sundie]

@Bradshaw - it's pretty easy to figure out. stock rpm x new teeth / original teeth = new rpm. So, if you're 4500 at 70 with the stock setup, 4500 x 30 / 34 = 3970rpm with the new setup.
I find that as long as you're not looking to jackrabbit off the line every time, and your advance is working properly (which is to say, your spark advance doesn't start advancing until after 2k rpm, which means more lower end torque) the 30 tooth rear is fine.

 

[xsjohn]

18/30 if you don't weigh a bunch..........and the TCI is too advanced for taller gears ......shoud be retarded a bit.............I say it but no body believes me......but I have only worked with 100's of these.........and if you are using BS34's they need some attention............max retard on these for a good cruise is .168 thousands.....somewhere in between just causes them to get more cranky for start offs and corners......mine just rolls off like a car.....even with 18/29 and a fat rear tire.........3500rpm at 65mph......and 4th is wonderful when not on the express....and changing the timing is stone easy to do.....the stator case is threaded after grinding off the break of screws that hold the pickup coil on....replace with screws (same as threads as the other screws on the stator) ......mark the pickup coil to the case before moving it counterclockwise so you sill know where it was and the notch in the side cover case lets you adjust it without removing the case......

Think if I show this easy and necessary mod for taller gears again I'm gonna get fired..........

xsjohn

 

[650Skull]

Im getting ready to order my chain for my bike. was wondering if someone could explain to me the pros and cons of changing sprockets sizes. it seems that changing the front to a 18t is pretty common. what about changing rear?? my bike is more of a cruiser i have a 30 minute ride to work in the morning where i average 65mph. to give you an idea of type of driving i do.
thanks matt

Go over to the Garage........
www.amckayltd.com/xs650 revs.xls ........this spread sheet Pamcopete made up gives you different ratio combination's, click onto the front and back sprockets, it has drop downs to change the gearing and shows the revs in relation to sprocket changes

 

[nj1639]

Past three days have been great for my commute. I'm running 17/30 gearing with Johns' 8-1 compression setup and needles. The ride is a combination of hills, hollers, twisties, straightaways and town traffic. I'm weighing in at around 180 lbs. On the straightaways I'm doing around 60 mph @ around +3500 rpm. I still have torque enough in the lower gears and can take slow speed corners in 2nd gear with no grumble. Perfect for me and my conditions.

 

[Bandito]

I was just looking at chains and sprockets since it's about the only thing I haven't
replaced on my rebuild. I was going to get some miles on it as is and see how I
like the feel.

I notice that my gearing is off in the other direction.

This bike I have is setup with a 17/36. I've only ridden it up and down my
street a few times, and it's got very snappy accelleration....

I have a spare set of wheels from another Special, and that ALSO has a 36 on it.

I find it odd that two different owners would have put 36's on...

Not sure about highway... I haven't got it out of 3rd gear yet.. since I don't
have any plates or insurance.

This isn`t a highway bike for me... I have a Bandit 1250 for long journeys,
this is for around town and cruising twisty backroads. I think I`ll keep the snap
and forego the top speed.

Maybe I have a wheelie machine and don`t even know it yet.... LOL.

 

[inxs]

- 17-34 is normal, some have 17-33...104 links

- early models to TX650 with shorter swingarms had 17-34, 98 links

 

[cruza]

nji639,3500rpm at 60 sounds good, do you have an 18 or 16in back wheel.

 

[inxs]

- in truth theres not too much difference between 16 and 18 in wheel tyre height as the tyres balance the sizing pretty much out

 

[nj1639]

cruza,
16" on an '83 Special, but like inxs sez.....

 

[bradshaw106]

I had a conversation with michael morse over at 650central and he recommended that i change booth sprockets 18 front and 32 rear. he said my bike would handle the taller gears after i change the exhaust. sounds kind of tall to me

 

[suiteo]

I'm running the 18/32 combo, and after rebuilding the carbs, I have no issue with the way the bike runs with this combo. Before the swap the vibes at 70 were terrible. Running a solo seat, and a bony a$$ made for some uncomfortable rides. The vibes settled down quite a bit after the swap, and there is still plenty of "snap" for me. I'm not looking for "rice rocket" type speed anyway, but it's got more than enough grunt to get up and down the hills outside of town. Hoping to do a mountain run after I get the top end sorted out and can report more back later on how it does in the grades.

Jay

 

[angus67]

when i got my engine it had a 15 on it. i have17/32 now. i weigh 230. the bike is a stripped chop

 

[nj1639]

According to the ratio chart on Mikesxs, the difference between the 17/30 and the 18/32 gearing setups is .02, 1.76 for the 17/30 and 1.78 for the 18/32. You can keep the shift shaft guard on with the 17 tooth front sprocket. Eh, 6 of one, half dozen of the other.

 

[xsjohn]

Gearing for specific tasks like back roads and the such it would not really have to be very tall............but for sustained expressway speeds requiring reves much over 3800 will greatly reduce the engines longivity............that is about the point when the balance factor falls apart and the destructive vibes begin.....I use the lower gears for the back roads and at 70 I am turning 3750 or so in 5th.........

xsjohn

 

[Bandito]

Hmmm... this is interesting. I've never ridden an XS before my project, and I've only
ever had it around the block so far... so I have no idea what the vibes and buzz
are going to be like.

Given the gearing you guys are running, this thing is geared really short with the
36 on the rear. I'll have to see how tall first gear is... maybe it's not very usefull
for most application being so low geared, we will see.

When not on the freeway, what is the comfortable RPM range for this motor?

 

[Trebor13]

so 18 * 30 will do for a 750??
or should i buy a nem 5th gear since it's still al apart.
in pete's chart the rev drop is only 200 orso revs whit the mike's 5th gear.