I've got a new 15t front sprocket waiting for me at the dealership. Now, just out of the blue I happened to mention it to a former bike mechanic and he said it is not a good idea to swap only one sprocket and instead to do the whole shebang at once. Meaning front and rear sprockets and the chain.

Will it affect me too badly? I have 6400 miles on the bike now. 05 Ninja EX250.

The bike rides like a dream but I just want to pull those damned RPMs down from my constant interstate riding.

I keep the chain and sprokets lubed with Dupont with Teflon spray.

I must mention that when I first got the bike, it was slightly abused by the chain and such not being lubricated as well as I keep it now.

If I need to replace them all, what are some suggestions and whaddya think the kawi dealer would charge me for the chain/rear sprocket?

Thanks for the input and sorry for the newb question.

Yes, I did search and I only found one suggestion to do all three at the same time.

I even searched that horrible to navigate ninja250.org and their wiki. I did our wiki here also.

-Brandon

Go ahead and swap the front sprocket. It has been done many times before by many people, myself included.

An argument can be made for swapping the whole shebang at the same time but I really don't think it is worth doing unless your chain and rear sprocket are about ready to be replaced anyway.

I have thought about the 15 tooth front as well. But right now I am running a 130/80 rear and have a 130/90 waiting to go on. I may wait and see if the 90 series drops the rpm enough to avoid changing the front sprocket.

I'd just swap out the front and see how you like the change. If you do, leave it. How many miles were you thinking of getting out of your present chain anyway?

I swapped out my front to a 15 about 700 miles after I bought the bike new. I do love the 15 as most of my riding is cruising and I like the drop in rpms. I have had no issues at all with only swapping out the front and I for one love it. But like Kelly said, if you its not for you, its one of those great mods where you can switch it back.

That being said I have heard that if you are switching one of your sprockets and your chain has a few miles on it than it may be a good idea to swap the chain when doing a sprocket swap (Dont know how many miles has to be on the chain to reach that "point") Ive read this on another one of the many sprocket threads on this board so maybe you should ask/look around and see if this may be something you should do.


Either way....good luck:thumbup:

I have a 15-teeth front sprocket. I did ask the Kawi mechanic why people change the front and not the back. He told me that if you change the rear sprocket, you will likely need a new chain, because you current chain will probably be too long or too short depending on whether you increase or reduce the number of teeth. It is not necessary to change both unless you want to radically change the gear ratios. There is no reason why both MUST be changed. - AM

I appreciate everyones input here.

I feel I may have miscommunicated my question.

Will changing the front sprocket only, with the rear and chain both at 6400 miles cause the wear pattern to drastically change to the point that I will be greatly reducing the life of my chain and rear sprocket.

I'm not looking to change the rear sprocket for my RPMs or the chain either.

Brand new front sprocket + worn in chain + worn in rear sprocket = bad juju?

People only tend to like to do them all at the same time because once it is done, you don't have to worry about them for a long time. Normally people, that I have seen, won't service the driveline until the chain starts to fail. So in this sense, it is best to do it all at once. I replaced the front sprocket (which was worn) and the chain when I picked up my bike. The back sprocket looked almost brand new. So I let it slide.

To answer you new question....

No. It won't make it wear fast. However, once the chain starts to fail (sticking here and there), it will start to wear your sprockets at an accelerated rate. So be on top of the chain and you shouldn't have any issues.

People only tend to like to do them all at the same time because once it is done, you don't have to worry about them for a long time. Normally people, that I have seen, won't service the driveline until the chain starts to fail. So in this sense, it is best to do it all at once. I replaced the front sprocket (which was worn) and the chain when I picked up my bike. The back sprocket looked almost brand new. So I let it slide.

To answer you new question....

No. It won't make it wear fast. However, once the chain starts to fail (sticking here and there), it will start to wear your sprockets at an accelerated rate. So be on top of the chain and you shouldn't have any issues.

10-4 Good buddy! I'll be installing it tomorrow. Hopefully it will just wear into the same pattern that is already established. I'll just keep extra lube on it until then.

I suppose there really isn't any type of break in period for these things is there?

On a side note, for anyone with a future reference, it can be found here. Maybe we should make a typical "newbie questions" thread.

/moving to pregen tech section

Shortly after I got the bike I changed to a 15T and it brought the rpms down to where I am now comfortable going down the FWY at 70 or 80 with no problems.

Wow, that 15t really makes a good difference.

Apparently my rear sprocket is made by JT. I saw their emblem on it today while doing the swap.

I also cleaned the **** out of my chain. Found a few rust spots and killed them with a steel wire brush. Nothing more the surface rust but still, I don't like it.

When I removed my front sprocket, I didn't think too much of it.

Here is a picture of the front.

http://img.photobucket.com/albums/v15/obsidian/SANY0547.jpg

Now, when I turned it over I saw.... this....

http://img.photobucket.com/albums/v15/obsidian/SANY0548.jpg

Holy crap! I'm a learner motorcycle mechanic right now so this is probably due to the fact that I over tightened the chain not too long back and rode on it super tight for a while. When I changed the rear tire, the dealer told me they re adjusted it and now it's in specs.

I still think it's loose....

So, seeing this sprocket, think I need to change out anything else or just start gradually buying the parts.

I figure I'll change everything out around 10k. I'm at 6400 right now.

Whaddya think?

-Brandon

how are you aligning the rear wheel when you do chain adjustments?

I was lining the notches up. 2 to 2.. 3 to 3... so on and so forth.

Today, I had a micrometer and I took the aligning bolts out and checked to make sure they were even, and they were. So this time I checked the distance on the bolts, the remainder left out and aligned it that way.

I can honestly not find a good way to do this. I've heard the aligning marks on the trail arm was not the least bit accurate.

Another thing. I heard these guys had a rubber type insert. I also heard these things were supposed to wobble.

I've not noticed either of these peices. Do I have a factory freak or what? I'm starting to think so.

Brandon... chain/rear wheel alignment thread.
http://www.ninjette.org/forums/showthread.php?t=13833

cush drive check/fix...
http://faq.ninja250.org/wiki/How_to_shim_the_cush_drive

That photo of the sprocket looks like the rear wheel is very miss-aligned. The Motion Pro alignment tool is cool, but I am cheap and accomplish the same thing by laying a straight edge on the sprocket.

The chain should have a little slack. It should move up and down an inch or so without resistance. A little too loose is better than a little too tight. Too tight causes the rear suspension to not work properly, stretches chains and can destroy your output shaft bearing.

Judging by the front sprocket and your description of your chain you may want to replace the chain and possibly the rear sprocket soon.

Thanks for the tips.

You think another 3000 miles could be found in my current set up?

Thanks for the tips.

You think another 3000 miles could be found in my current set up?

Can't tell without seeing it, but doubtful.

Well hell, time to start pricing out stuff.

You you explain to me how YOU do the straight edge? I was going to pick up a chain alignment tool but thanks to work demands, I've not had the chance.

Take a peek through that chain/wheel alignment thread kkim linked before dropping any $ on a chain alignment tool for the ninjette...