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Old 01-05-2011, 09:03 PM   #1
bmwktmbill OP
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KTM 640 Adventure-17/42T gearing question

Hi Everyone,
Busy tonight changing gearing for an upcoming trip.
I have always wanted to try higher gearing but never got around to it.
I am trying to get the RPM's down at cruising speed but still have passing power fully loaded for travel

I have the 17T counter shaft sprocket mounted and I ground the case protector to fit the larger sprocket. Everything went well for the mechanics.

I am wondering if any of you are running the 17/42 gearing for your regular gearing and what you think of it?

What RPM's are you turning at 65 mph.
I won't be able to try the change until I get out of the snow belt so I need your advice.

Thanks,
bill
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Old 01-05-2011, 11:06 PM   #2
Luke
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I have similar gearing (16/40) I tried 17/40 and it was too high. I found it made no difference in the RPM at cruising speed because I increased my cruising speed about 5 mph.

Passing is no big deal, just downshift more as you need to. First gear gets worse of course. There's even more clutch slipping in tight stuff.

You may be happy with the new gearing, but for a long trip I'd hedge my bets and bring a 16t along as well. After you've decided you can mail home the one you like least.
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Old 01-06-2011, 12:15 AM   #3
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Originally Posted by Luke View Post
I have similar gearing (16/40) I tried 17/40 and it was too high. I found it made no difference in the RPM at cruising speed because I increased my cruising speed about 5 mph.

Passing is no big deal, just downshift more as you need to. First gear gets worse of course. There's even more clutch slipping in tight stuff.

You may be happy with the new gearing, but for a long trip I'd hedge my bets and bring a 16t along as well. After you've decided you can mail home the one you like least.
Luke,
That's good advice. One thing I did find out is that with a 110 link chain you can switch contershaft sprockets without modifying the chain length. The adjusters take up the slack and/or allow the wheel to slide forward with the switch from 16-17T and back with the 42T on the rear.

It was really easy to grind the case protector larger to fit the 17T sprocket. I thought the job wold be difficult but it wasn't.

The worst part was unbolting the case protector from the frame because it is tight and backwards but it went OK once I got serious. I used a little propane torch heat to loosen up the countershaft bolt. Jamming the sprocket and chain on by inserting an old chunk of wire brush handle made loosening the bolt easy.
bill
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
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Old 01-06-2011, 05:32 AM   #4
laramie LC4
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Originally Posted by bmwktmbill View Post
The worst part was unbolting the case protector from the frame because it is tight and backwards but it went OK once I got serious.
bill
that little fucker is one of the worst parts of pulling the engine. doesnt seem to matter where you are at, or what angle you try, you just cant get on it. so you end up with an open end wrench and a lesson in patience.

laramie
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Old 01-06-2011, 05:57 AM   #5
makazica
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Are you guys talking about the alu part that's bolted with two 8mm screws through the plastic sprocket guard and with an 10 mm screw to the frame just above the swingarm pivot bolt?

M.
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Old 01-06-2011, 08:34 AM   #6
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Are you guys talking about the alu part that's bolted with two 8mm screws through the plastic sprocket guard and with an 10 mm screw to the frame just above the swingarm pivot bolt?

M.
Yes that's it. I will post some pics of the project I took a little later(gotta get to a faster connection). Everything is in the way of unbolting it. Plus if you forget to use loctite it will vibrate loose and disappear, then the chain will flop cause it holds a roller to stop that.

I had the best luck with a small 10mm box end working into the shock tunnel, I got a pretty good wrench swing that way. The rear brake master cylinder and linkage is in way. Yada, yada.

When I bought my bike used the roller and bolt were missing altogether and it took me awhile to figure out what was going on.
bill
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
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Old 01-06-2011, 09:19 AM   #7
Low594
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When I made my 3500 mile trip I ran the stock 16/42 & stock tires. Bit too low for big freeway. Later changed to a 17/42 and much happier, no dirt yet. Good cruising 70mph @ 5k and 75mph @ 5.5k, but I suspect my tach to be inaccurate. Still have passing power at those speeds!
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Old 01-06-2011, 10:02 AM   #8
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Bill,

I've tried various gearing on my 640 Adventure from the standard (16/42), (17/42) and (16/48).

(16/42) 110mph ish
Pro's - Does everything KTM and the Emissions people need to pass the conformity checks.
Con's - Love it or hate it, its the base.

(17/42) 115mph ish, depending on carburation being setup!!
Pro's - Good for long distance work, Drops a 1000rpm for the same speed, Easy to change front sprocket without modifying chain.
Con's - Engine labours/four strokes a lot easier, Highlights fueling/carb issues, No engine braking.

(16/48) 95mph ish Absolutely in the red zone
Pro's - Great offroad, Lots of engine braking.
Con's - Long distance can be done but its hard on the engine, Fuel consumption.

I would fit the 17 front sprocket to the engine and bolt the 16 sprocket to the frame somewhere, then change as needed for the terrain. Just take a couple of spare lock tabs for the sprocket nut.

L

P.S.
KTM do a different plate for the case saver when fitting the 17 tooth front sprocket, Its in the parts catalogue.
I bought a 118?? link chain for mine with the idea of having a spare section of chain left over (approx 2 inch).
I carry this in my spares bag with a couple of spring links for that type of chain.
Small to carry but could prevent a show stopper.
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Old 01-06-2011, 10:40 AM   #9
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Quote:
Originally Posted by bmwktmbill View Post
Hi Everyone,
Busy tonight changing gearing for an upcoming trip.

Thanks,
bill
Where are you going? Obviously south...

I found that in a lot of the countries I went to, I actually wanted lower gearing. It was very seldom I got over 90 km/h. With myself and all my gear at 145 kg, a 48t rear could of kept me in 5th instead of shifting between 4 and 5.
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Old 01-07-2011, 12:18 AM   #10
bmwktmbill OP
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Originally Posted by dirtydeeds View Post
Where are you going? Obviously south...

I found that in a lot of the countries I went to, I actually wanted lower gearing. It was very seldom I got over 90 km/h. With myself and all my gear at 145 kg, a 48t rear could of kept me in 5th instead of shifting between 4 and 5.
Thanks to everyone for the advice.
I will pack two sprockets and change if necessary.
No lock tabs, a spring washer is used under the countershaft bolt in combination with red locktite on the threads.

Headed to Panama/Costa Rica and all points in between plus some USA, Texas and the west but first cross the border at Brownsville and go for Vera Cruz. I've traveled in CA so I understand that speeds drop further south.

Actually I wanted to try to cut the buzz at cruising speeds. If I could get the worst of it above 65 mph and still have some pulling power that would be a plus on faster roads.

Here are some pics of the changeover including the 'enlarged clearance' case protector and the 17T sprocket fitted and a new chain.





Grind here, the aluminum is very soft.



This is the finished job, 17T sprocket and case protector ground out for clearance.



bill
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
Bill Shockley

bmwktmbill screwed with this post 01-07-2011 at 12:29 AM
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Old 01-07-2011, 02:41 PM   #11
katumo_jtb
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I run 17/42 gearing. I think it's the best ratio for all-purpose use. I used to carry different front sprockets for dirt gearing, but I don't anymore. The 640 does better in the dirt if you lug it anyway. I like being able to cruise at 80mph comfortably, without worrying about buzzing the engine too much.

The only time I have problems are riding 2-up in the dirt or starting on a steep hill. Then I have to slip the clutch a lot to get moving.

Looking forward to reports on your trip

John
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Old 01-08-2011, 12:44 AM   #12
bmwktmbill OP
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kat,
Thanks for the encouragement.
bill
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
Bill Shockley
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Old 02-13-2011, 11:43 AM   #13
slackmeyer
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I just found this thread because I was thinking my 640-e was geared a bit low for the highway- 70 mph feels buzzy, I'm in 5th anytime I'm going over 50 or 55. Come to find that y'all are running 17-42 or similar, and my gearing is 15-46! Well, that should give the old girl some longer legs.

I figure switching to a 16 tooth cs sprocket is a good start, and then I can go 42 on the rear for the street wheels, 46 for the dirt wheels. Will one chain accommodate that range?
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Old 02-13-2011, 06:13 PM   #14
bmwktmbill OP
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Zak,
The 110 link chain will do 16 and 17 and probably 15 (I havent tried it) with a 42 rear...that's all I can vouche for.
bill
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
Bill Shockley
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Old 02-13-2011, 09:12 PM   #15
slackmeyer
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Originally Posted by bmwktmbill View Post
Zak,
The 110 link chain will do 16 and 17 and probably 15 (I havent tried it) with a 42 rear...that's all I can vouche for.
bill
Thanks Bill. I'll order some sprockets and try it out.
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