KTM 640 Adventure Gearing

[Matty-D]

Starting to have way too much fun on my 640 Adventure... but I am finding the gearing isn't where I need it. Right now it is great for gravel and some highway, but if I do anything technical (like the B route at the Dead Zone) it becomes an excercise of clutch fanning, frequent stalls, and not enough jam at the right time to unweight the front end. (I am sure it was entertaining at some points for Dorky, Dirty DR, and KTMKen).

I am running a 15 up front, and I'll have to check what is on the back, but thought I would see what others are riding???

Any suggestions on what the advantages of adjusting front sprocket sizes vs. rear? Is one less work? I am hoping changing the front is straighforward so I can swap depending on intended ride and take up the slack on the rear axle... but have not ventured into trying to take that off yet... tips?

Thanks!

 

[Island Hopper]

Your 15 tooth countershaft is already 1 tooth lower than stock and is roughly equal to 3 teeth on the back {larger} ... You can go to a 14 tooth without delinking the chain because the reverseable axle blocks allow a bigger adjustment range...

I run the stock 16/42 on my 03 and find it the best all around... With this combo I can still run the B events and cruise along nicely on the freeways... In the tight stuff slipping the clutch becomes my low gear...

The 640 is front heavy to begin with and when the big tank is near full lofting the front end requires work.... A lot of it has to to with the BST 40 carb and not the gearing.... When you crack the throttle the vacuum slide has a bit of a pause unlike the pumper carbs... A lot of guys have switched to the FCR 39/41 with very good results... The only downside is your fuel economy suffers....

 

[Island Hopper]

The countershaft sprocket is easiest to change: Pull cover, flip case guard out of the way and step on the brake while loosening the bolt /nut... Slide sprocket/chain off the shaft and then remove sprocket from under the chain {loosening the wheel will buy you some slack}...

I would recommend that at this time you replace the o-ring that is behind the shaft bushing and also the spring washer that bolts against the sprocket..

Place new sprocket under the chain and slide back on the shaft... Apply loctite to the bolt/nut, tighten to 42 ft/lbs and replace the guard/cover... KTM spring washer/ bolt kit comes preloctited if you go that route...

Go to this site to find a wealth of info on the 640:http://www.advrider.com/forums/showthread.php?t=86958

 

[Dorky]

Apply loctite to the bolt/nut, tighten to 42 ft/lbs and replace the guard/cover... [/url]

I happen to have several of the splined lock washers here that I would donate to the cause...

 

[Matty-D]

Thanks for the info Island Hopper. I haven't checked the rear sprocket yet... 1... 2... 3... sh!t... 1... 2... 3...

I bought the bike used and I am not sure how much has been "altered" from stock... So far it is exceeding my expectations though! I am definitely asking a lot of this bike, but I am having fun, so I might as well try and mess around with the gearing a little bit. Thanks for the tips on the swap out... getting to know what is going on behind the scenes on your bike is never a bad thing!

Dorky... thanks for helping a brother out! Once I look into grabbing a new front cog (or two??? ) I will be in touch! I'll have to look at the blow up of the drive train to see the parts Island hopper is referring to...

Thanks!

 

[caribooster]

I run either a 15/45 or a 16/45 sprocket setup on my 640. The 15/45 is great for single track but limits you on the open road. I am back running the 16/45 setup this year and have learned to slip the clutch better in the tight stuff. If you are strickly on the roads the 16/42 setup that Island Hopper suggests is the way to go. Gearing is always a struggle on a dual sport bike because the terrain can change so much in one day. I just returned from doing the Harrison-Lillooet-Harrison loop and my 16/45 setup worked great. We encountered everthng from asphalt slabs to rocky hills.

 

[broxy]

I run either a 15/45 or a 16/45 sprocket setup on my 640. The 15/45 is great for single track but limits you on the open road. I am back running the 16/45 setup this year and have learned to slip the clutch better in the tight stuff. If you are strickly on the roads the 16/42 setup that Island Hopper suggests is the way to go. Gearing is always a struggle on a dual sport bike because the terrain can change so much in one day. I just returned from doing the Harrison-Lillooet-Harrison loop and my 16/45 setup worked great. We encountered everthng from asphalt slabs to rocky hills.

I'm running 16/42, and while good on the road, I personally don't like it off road. First is to high, second too low. 15/ 42 is good for everything I do, and 15/45 is great for strictly off-road, but will tolerate some slab as well. I very rarely find myself above 5000 rpm on slab, and with 15/45 I recall it is about 100 km/h(?). 16/42/ 5000 rpm = 120 km/h or so.

 

[Matty-D]

Hey guys... thanks for your input! I have taken a bit of a hiatus from my bike since the deadzone but need to get my head back into it for the upcoming Loose Screw!!! :clap:

Turns out I have the stock 42 on the back. For $30 each I picked up a 14 and a 16 for the front. Now I have all sorts of gears to try out! I am going to try the 14/42 for the upcoming rally.

It is also getting close to time to change out the rear ring and the chain. i was quoted about $75 for a 42 rear... Is this the right price range???

 

[Island Hopper]

Don't buy the stock alloy sprocket... They're overpriced and wear out way too fast..

For double the service life get the KTM steel sprocket at around $40 Part # for 42 tooth: 582 10 051 042

 

[Hockeygod]

Thought I would restart this thread as it is almost time for a new front sprocket and I have gearing, chain Q's.


Currently running 15t front and 45t rear.
Street: 100kph is 5000 rpm, 120 is 6000 rpm.
Dirt: pretty good in the slow single track. Wouldn't want to go any higher! (See below. Going to avoid tough single track in future!)
Dual sport: gravel, 2track, road... Hmmm... 15/42? Or back to stock 16/42? Opinions?


After an exhausting day skirting puddles and crossing bogs, I came to realize I ain't getting any younger, and manhandling a 400lb beast fully gassed is not as much fun as on my dirt bike! So I will start using the right tool for the job.


Figure I will keep the 640 for more dual sport applications as it is an easy 30-45 mins ride from house to find gravel, FSR's. Would 16/45 be the ticket or go back to stock 16/42? Decisions, decisions...


Also, if I were to try the Continental Divide Trail in the future, what would those in the know suggest as to gearing?


Is the old adage true: when you change a sprocket, you should also change the other sprocket and chain? My rear Supersprox still looks good...


Another Q: aside from the technique quoted in the owners manual (weighting the chain prior to measuring), are there any other quick n dirty techniques to know when to adjust the KTM chain? How much slack is recommended? How can you tell it is time for a new one; other than when you run out of adjustment?


Any cleaning and lubing tips you can share?


When switching from a 15 to a 16 tooth front (maintaining my 45 rear), would my same chain (15/45) work if I flip the adjusters? What if I go to 16 front and 42 rear?


(Island Hopper, are you AKA Gunnerbuck?!) I am looking into the Dirt Tricks dome washer for the front sprocket. Is this the same thing as the spring washer you refer to? http://dirttricks.com/shop/dirt-tricks-ktm-dome-washer
Should I still replace the o-ring?


Thanks guys!


Dean

 

[CamWeiss]

This is about as slow as replies get, but you might still be reading!

As far as gearing goes, only you can figure out what's right. But as for the rest of the stuff...
When you change a sprocket due to wear the chain is usually not far behind, so it's best to change the chain + sprockets as a set. However, if they're all still in good shape then you can just do sprockets. If you look in the owners' manual it does cover chain tension, but the quick + dirty of it is that you should, on the bottom of the chain under the swingarm, be able to push it up to the swingarm about 1" behind where the guard is and have the top of the chain take up all slack.
If you have to adjust your chain very frequently (every tank of gas) then it's a good sign that it's stretching out and toast. An easy test is to try and pull it away from the center of your rear sprocket. If you can get more than about 1/8" of chain slack in the middle of the sprocket, then it's getting worn.
I use Motul Off Road chain lube... Seems to work very well. Resists dirt 'n things, and doesn't fling very much.

If you flip the adjusters you can get a pretty decent range of sprockets on the bike... 1t front or 2t rear should be easy.

 

[Island Hopper]

Thought I would restart this thread as it is almost time for a new front sprocket and I have gearing, chain Q's.


Currently running 15t front and 45t rear.
Street: 100kph is 5000 rpm, 120 is 6000 rpm.
Dirt: pretty good in the slow single track. Wouldn't want to go any higher! (See below. Going to avoid tough single track in future!)
Dual sport: gravel, 2track, road... Hmmm... 15/42? Or back to stock 16/42? Opinions?


After an exhausting day skirting puddles and crossing bogs, I came to realize I ain't getting any younger, and manhandling a 400lb beast fully gassed is not as much fun as on my dirt bike! So I will start using the right tool for the job.


Figure I will keep the 640 for more dual sport applications as it is an easy 30-45 mins ride from house to find gravel, FSR's. Would 16/45 be the ticket or go back to stock 16/42? Decisions, decisions...


Also, if I were to try the Continental Divide Trail in the future, what would those in the know suggest as to gearing?


Is the old adage true: when you change a sprocket, you should also change the other sprocket and chain? My rear Supersprox still looks good...


Another Q: aside from the technique quoted in the owners manual (weighting the chain prior to measuring), are there any other quick n dirty techniques to know when to adjust the KTM chain? How much slack is recommended? How can you tell it is time for a new one; other than when you run out of adjustment?


Any cleaning and lubing tips you can share?


When switching from a 15 to a 16 tooth front (maintaining my 45 rear), would my same chain (15/45) work if I flip the adjusters? What if I go to 16 front and 42 rear?


(Island Hopper, are you AKA Gunnerbuck?!) I am looking into the Dirt Tricks dome washer for the front sprocket. Is this the same thing as the spring washer you refer to? http://dirttricks.com/shop/dirt-tricks-ktm-dome-washer
Should I still replace the o-ring?


Thanks guys!


Dean

Yep, I missed this one...

Yes, I hopp is GNRBuck...

You have a 45 tooth on the rear so stick with that and shuffle your countershaft sprocket... On one of my 640s I run a 45/ 17 combo and find it to work very well for all around riding, it is almost identical to the stock 16/42 with a couple advantages and one disadvantage: One advantage is that a chain with less bend to go around the sprockets runs smoother and should last a little longer.. The second advantage is that with the bigger sprockets the chain rides farther away from the swing arm and will rub less giving longer rub block life... The disadvantage is that in order to fit a 17 tooth, the case guard will have to either be replaced with a Duke guard or ground a bit to clear the chain...

I find 80/90 gear oil as recommended by DID gives the longest chain life, but is a bit messy

Any time you remove the counter sprocket it's a good idea to replace the O-ring to play it safe..