How do I change a front sprocket? - 2001 KTM SX 400 Racing

The front part is a bit tricky to change sprockets. I have a mountain bike with three sprockets, I also have difficulty with changing them. It all depends on the design of the changer. I am able to change from large sprocket all the way to the smaller but from the smaller sprocket to the second is okay but going into the third (large) sprocket is a real problem and no matter how hard an adjustment I've tried, it still doesn't want to go to the far end. Example, if it is in the smaller sprocket, it changes okay to the middle sprocket but it will not fully change in the larger sprocket because the cable doesn't fully push the changing bracket far enough to roll the chain on it. So, as with myself having same problem, I'd say, never buy a bicycle that doesn't change the front sprockets with ease. But while you have one of these three front sprocket bicycle, you have two options. Try and put the bicycle on a stand and adjust the changer's screws so that it can reach the far end where the large sprocket is, or in another case -where the smaller sprocket is, depending where your problem lies, the larger or the smaller sprocket). Remember that the air test is different to the road test. On the air test (bicycle on stand) the changer may be able to change sprockets but on the road the chain is heavily under tension and may not over-jump into the larger sprocket, but down-jumps into a mid or smaller sprocket quite easily. So, the best thing you can do is to not to apply force to the pedals to relieve the chain of any tension so that it can jump over the larger sprocket. But apply tension to the chain, such as 'accelerating', and it will not over-jump the larger sprocket with ease. However, if you change down to a smaller sprocket while 'accelerating', it usually changes without problems. The other option you can use is to sent the bicycle to a store and have it fixed there. Work is guaranteed and you can be sure your worries will be over.

To replace the front sprocket follow the chain to the cover on the left side and remove it, loosen the chain tensioners on the rear axle, slide rear wheel all the way forward and remove chain. Then remove the bolt in the center of the front sprocket, change sprocket and reverse process for assembly. That is the process but if you are going to change the front sprocket you should change both sprockets and chain, as the chain stretches and will cause premature wear of the new sprockets. Complete sets can be found on Ebay for little money, maybe they are not the best but as long as you do not abuse them they will do until you get the money for a good set.

Slacken off chain, remove front sprocket cover (6mm hex keys), Remove centre bolt holding sprocket, and prise off sprocket, it's located on a keyway, fit new one in reverse order making sure the key is in place, replace cover and adjust chain. It is usual to change the rear sprocket and chain at the same time, they all wear together, if you just change one, it will wear quicker.

Top end engine rebuild. Sprocket size depends on the type of riding. Standard should be OK for motocross. If you need more top speed install a larger front sprocket and a smaller rear sprocket. Divide the rear sprocket teeth by the number of teeth on front sprocket e.g 48/14 = 3.43 a lower number means higher top speed 45/15 = 3.0 but compromised performance at lower speed. For tight forest riding and steep hills Rear 48 front 13 = 3.69 etc is preferable.

You can add teeth to the front sprocket or take teeth off of the rear sprocket. In the case of your bike , I do not think there is a 17 tooth front available so your best option would be to shorten your chain and drop from the 44 tooth rear sprocket to 40 tooth or a 36 tooth rear sprocket. That would be like adding one or two teeth to the front sprocket. Your stock is 16/44 so decrease from there. Be sure to ID your chain, get a chain breaker, and a new master link.

You will need either a larger transmission sprocket or a smaller wheel sprocket. The larger percentage change will occur with an increase in the front sprocket number of teeth. The way to mathematically determine that is to consider the present tooth ratio/RPM and relate that to the desired ratio. There are practical limits on how big the front sprocket can get before having interference problems. A 2-tooth increase should come fairly close. It would take about 4 to 6-tooth decrease in the rear sprocket to achieve the same results. Take your pick--the front sprocket should be cheaper and much easier to install. You will need to adjust the chain length accordingly. There will be a minor acceleration decrease due to the change. A fatter rear tire will also increase speed somewhat too. Hope this helps!

Your sportster is actually pretty easy to change the front sprocket on. On the right side of the bike, you'll see the rear brake master cylinder. The master cylinder must come off as well as the plate that the master cylinder sits on. To get this off, you'll have ot remove the brake pedal and the exhaust system.

Once you get the plate off, you'll need some special tools to remove and replace the front sprocket. You'll need a special socket to remove the large nut holding the sprocket on and a special device made to hold the sprocket so you can get the nut off and then back on with the proper torque.

In addition to changing the front sprocket, you'll also have to change the final drive belt to match the size of the rear sprocket and front sprocket combination.

Good Luck
Steve

you can change the sprockets.If you go to a 16 tooth front sprocket. two teeth on a front sprocket is like droping 4 teeth on the rear. You could drop 2 teeth on the rear sprocket but a 43 tooth is probably harder to find. the usual choices for front are 14,15,16 tooth.
For the rear they are 44,45,46 tooth

The way to remeber gearing changes is on REAR sprocket is smaller=faster and larger=slower top end.
the FRONT is OPPOSITE to the rear smaller=slower and bigger=faster.
You may have to lengthen or shorten the chain depending whjch way you go.

Usually, it seems that changing the front sprocket is more cost effective and easier to do. The front sprockets are about $10-$20 and rears are normally around $40-$50. Usually 1T gearing changes made to the front sprocket are the equivilant of a 3T-4T gearing change to the rear. I personally would go up on the front instead of down on the rear. Right now your gear ratio is 3.846 (meaning every 3.846 rotations of the front sprocket, the rear sprocket makes 1 rotation) If you go down 2T in the rear (13/48) your gear ratio would be 3.692 giving you a little less torque and a little more top end. If you go Up 1T in the front (14/50) your gear ratio would be 3.571. This would be about the equivilant of a 46.5T rear sprocket. (If they made it) The nice thing about doing the front sprocket first is the cost. If you decide it's too much difference and you want something in between, you can put the stock 13 back on and then change the rear (and you would only be out the $$ for the front sprocket) If you start with the rear and decide it's not enough then you change the front you're out the $$ for the rear.

Speed sprocket is on leftside of front wheel. Disconnect speedo cable from under speedometer itself and turn front wheel to see if cable turns. If not dis connect at front wheel and try turning cable, it's a squared pieces of cable inside black casing. If you can pull both ends out then it is definetly broken. This is much more likely than breaking the speedo sprocket on front wheel. If it is speedo sprocket, get a new one and remove front wheel , change sprocket and reassemble. If Speedo sprocket is being stubborn coming out use something relatively soft and tap it out. Good Luck.