Thinking of changing front sprocket - any tips?

[n4mwd]

Looks like my chain will need replacing soon. According to most everyone, its best to change the worn sprockets at the same time. So I have to change the sprockets, but what about the ratio? Should I stick with the OEM 14-45 or go with a 15-45 or other?

I know that changing it like that will make the engine run slower, but does that really increase the MPG that much, or is it just negligible? Factory MPG is 70 mpg. It will definitely cut into my 0-60 runs.

And if I do use a 15 tooth front sprocket, will I need an extra link in the chain? OR is 106 links still close enough? Is there a chart somewhere showing what ratios with how many links?

Anybody been through this before? I mean, I like higher MPG, but I don't want to turn my Ninja into a low powered cruiser.

[choneofakind]

If you change to 15/45, the only thing that's going to change is first gear will feel longer. The rest of the time, you can just ride a gear lower than normal and get the same zippy feeling.

15/45 will be fine with the stock chain. 14/47 is also fine (and highly recommended by me for its grin factor) on the stock chain, but if I do it again, I'll get one with 108 links to make it easier to get the wheel on and off.

The other thing to consider is just keeping the stock 14/45, and getting a rear tire with a 90 profile. That will get the same effect of lowered rpm's (check the speed @ rpm calculator on faq.ninja250 to play with different combos of tires/sprockets)

[n4mwd]

I've already got the 90 profiles on their. I didn't notice much other than the speedometer was a little more accurate. Did you notice any difference in your MPG?

[setasai]

Plenty of threads in the similar threads list on the bottom of this page. Consensus, it's good.

[n4mwd]

Since it looks like the 15T sprocket uses the same size chain, I think it should be possible to get a 15T and then switch back to the 14T if its too big of a performance hit. I weigh over 200# so that is a factor too.

I did search for similar threads before I posted that, but none of those came up.

According to some people in those threads, the 15T sprocket doesn't do much for MPG, but others say it does increase it slightly. So the general concensus as to whether it increases MPG or not is maybe.

[choneofakind]

Originally Posted by n4mwd

Did you notice any difference in your MPG?

nope. no difference in MPG's. Funny thing is, I didn't notice a difference in rpm's either when I switched to 90 profile tires. But I definitely noticed it when I when to 14/47, which is basically the same as switching back to stock size tires.

[Solunatic]

I just changed out my chain and upped my gearing today (as in, just got back from a 100 mile test ride) to the 15/45 and I like it! First gear is actually usable in some situations other than parking, I've dropped about 750-900 RPM's at cruising speed so its less buzzy, and after just a short while got used to the gear ratios being further apart (yeah... i think thats the correct terminology...). If you want the same zippiness, just twist the throttle a little harder and wait a tad longer to drop into the next gear. No problems with hills either.

So far, I'd say if you spend any time cruising at 55+ on a regular basis it's a good option. Based on the reduced RPM's i would imagine mileage will go up, but only time will tell. Also, it's a piece of cake to do, and to reverse if you really don't like it in which case you're only out $20 and you've always got the sprocket if you plan on going on a long trip.

[setasai]

You are correct with your assumption. I personally like it because it smooths out every gear a little and lets me get through a turn in 1st. Everything else after that to me is negligible.

[CalvinAmI]

Speed @ RPM calculator

[Bozley81]

Originally Posted by CalvinAmI

Speed @ RPM calculator

what if you installed a stage 2 dynojet and k&n air filter

[choneofakind]

Originally Posted by Bozley81

what if you installed a stage 2 dynojet and k&n air filter

That would have no effect on the gearing ratios, the rpms of the engine, or the final drive. So it would be the same.

That calculator is only for the pre-2008 ninja 250 though.

[EMSRacer07]

When i first bought the bike i used to have alot of vibration and high rpms on the freeway so i changed it to the 15T in the front. It increased my MPG a bit around 2-3mpg more. Depends how u drive. Then i switched it to 15-42. Not much of a difference but in 6th gear every 1k is 10mph. So much easier to travel on the highway. And i have pods, efi, and muzzy and my bike is still quick . And the set up I am running the 15-42 is what alot of pregen track ppl run so they can maintain their top speed and powerband in the gears.

TO each his own :P. ......... install the efi kit too lol.

quick edit: for the 15T front i had the stock 106 chain. With 15-42 i got a 104 chain and it fit perfectly...... perfectly lol.

[n4mwd]

is there any need to rejet the carburetor if I switch to the 15T sprocket?

[choneofakind]

...no. those are two unrelated things,

[EMSRacer07]

Originally Posted by n4mwd

is there any need to rejet the carburetor if I switch to the 15T sprocket?

nope

[n4mwd]

Originally Posted by choneofakind

...no. those are two unrelated things,

Ok, I just ordered a 15:45 set. I'll let you guys know how it works out.

[EMSRacer07]

Originally Posted by n4mwd

Ok, I just ordered a 15:45 set. I'll let you guys know how it works out.

dont forget to shim the crush drive especially since ur doing the rear sprocket

[AlanDog]

I went to 15-44, and my gas mileage definitely, without a doubt, went up by at least 5 mpg. This is riding at a reasonable speed, and only going 65-70 on the freeway. Street riding is a little more comfortable with less shifting. But I do notice the wider spacing in the twisties, when you upshift there is less overlap in your powerband and it's just harder to find the right gear. Overall, it fits my style of riding.

[AlanDog]

I think people with aggressive throttle control may not see a difference in gas mileage b/c they are constantly pinning it and to accelerate at the same rate still takes the same amount of energy.

[n4mwd]

I ordered the 15-45 sprockets. Still waiting. My goal is to let it run at a lower RPM to hopefully make higher speeds easier on the bike by lowering the RPM. I've got about 18K on the original OEM set so its time to think about new ones. The old one has a tendency to slap around a lot which drives me nuts.

[EMSRacer07]

well with the front being 15T u will drop about 500rpms at every speed. Made 1st gear a bit more usable too,

[n4mwd]

My 45T came in today - still waiting on the the 15T. I compared the 45T to the stock one and I can't tell that there is any wear on it. Maybe I'm not looking at the right thing. The only difference I see is the dirt and grease on the OEM.

[EMSRacer07]

after 10k miles on mine rear it didnt look so much difference either. I think the teeth on the new sprocket were a bit beefier

[choneofakind]

The teeth on mine were a little sharky after 14,500 miles, but not super bad. The chain was what needed changed, so both sprockets went as well.

[n4mwd]

Here is the old and new side by side. I've got about 18K miles on them. I have been told that the front sprocket is the one that gets the most wear because there are fewer teeth. But on the back, I can't tell.

Right now I'm getting a lot of snapping sounds back there when I accelerate. Also an occasional repeating crackle that repeats at the chain rotation frequency.

[EMSRacer07]

Originally Posted by n4mwd

Here is the old and new side by side. I've got about 18K miles on them. I have been told that the front sprocket is the one that gets the most wear because there are fewer teeth. But on the back, I can't tell.

Right now I'm getting a lot of snapping sounds back there when I accelerate. Also an occasional repeating crackle that repeats at the chain rotation frequency.

Hmm make sure the sprockets are align and chain straight when u put the new ones on. And also check the chain slack. i always did mine to spec, about 1 3/4 inch and that was too much, i always go for the tighter side at about 1 1/4 inches and i didnt have that slapping sound anymore.

[n4mwd]

I finally got around to making installing both sprockets plus the new chain. There is a noticeable difference in RPM and not such a big difference in acceleration. In fact, with the 0-60 run, its possible now to do it with only two shifts. This saves a little time which may compensate for the lower gearing.

The front sprocket was in real bad shape. The slots were about double wide and the tips were bent over like little hooks. I wish I had inspected it regularly but its hard with the cover in the way. It should have been replaced at least 5K miles ago. The rear sprocket still looks like new. If I had replaced the front sprocket 5K miles ago, the OEM chain would probably still be good.

The only problem I had/have is the master link. I wasn't able to figure out how to properly rivet the thing together so I went ahead and put the clip link on there for temporary. The clip link looks like it would fling off at any minute so I'm going to get the rivet link on there asap.

[EMSRacer07]

Originally Posted by n4mwd

I finally got around to making installing both sprockets plus the new chain. There is a noticeable difference in RPM and not such a big difference in acceleration. In fact, with the 0-60 run, its possible now to do it with only two shifts. This saves a little time which may compensate for the lower gearing.

The front sprocket was in real bad shape. The slots were about double wide and the tips were bent over like little hooks. I wish I had inspected it regularly but its hard with the cover in the way. It should have been replaced at least 5K miles ago. The rear sprocket still looks like new. If I had replaced the front sprocket 5K miles ago, the OEM chain would probably still be good.

The only problem I had/have is the master link. I wasn't able to figure out how to properly rivet the thing together so I went ahead and put the clip link on there for temporary. The clip link looks like it would fling off at any minute so I'm going to get the rivet link on there asap.

Yea for me 2nd gear redline is 61.5mph so yeah does save time.

And i like the clip type. alot easier to take off and put back on. I just put some silicone, the black stuff they put for oil pans, and it hasnt flung off since. I also put some safety wire too for extra protection.

[n4mwd]

Originally Posted by EMSRacer07

Yea for me 2nd gear redline is 61.5mph so yeah does save time.

And i like the clip type. alot easier to take off and put back on. I just put some silicone, the black stuff they put for oil pans, and it hasnt flung off since. I also put some safety wire too for extra protection.

First I tried the rivet link and I didn't have the right tool. Then I went to the clip link and its downright scary. The retaining clip permanently opened up at the second pin and doesn't actually hold anything. The top pin is on fair and is the only thing actually holding it together. I'm going to try the rivet link again with a better tool.

[EMSRacer07]

Originally Posted by n4mwd

First I tried the rivet link and I didn't have the right tool. Then I went to the clip link and its downright scary. The retaining clip permanently opened up at the second pin and doesn't actually hold anything. The top pin is on fair and is the only thing actually holding it together. I'm going to try the rivet link again with a better tool.

what chain did you get?

My rivit is tight on the first pin and it is ok on the second. Its not loose. Thats why i used the silicon and safety wire.

but yeah the better rivit tools does help.

[n4mwd]

I used the SM o- ring chain from cycle gear it was originally 120 links so I cut it down to 106 links. The regular chain tool worked fine for that. I will try to fix the the rivet link but if I cant Ill try the safety wire for sure.

[n4mwd]

Attaching a few photos of the link and sprocket. The clip link doesn't even look properly seated. I pushed it in as far as it would go. In the sprocket pictures you can clearly see the shark fin look. The sprocket had 19K miles on it when changed.

[davenay67]

Couple of comments....

1) That front sprocket is VERY hooked and totally worn out.

2) That clip on the split link is definitely not seated properly. You can see daylight between the pin and the shoulder of the clip, and on the second pin you can see where the arm of the clip is not seating. This will likely fly off in a hurry..!!

[davenay67]

Just yesterday I changed my sprockets to a 15 / 41 combo, using JT steel sprockets front and rear.

I commute daily and want a bike that has a more relaxed crusing speed. The 15/41 combo lowers revs nicely, about 1K rpm per every 10mph. Doesn't sound much but the bike is a different animal and feels so much more relaxed.

If you want to accelerate, simply drop a gear or two. Like others have said, 1st is actually usable now.

Not sure about the mpg component yet, but I will very soon find out as I begin my commute regime again tomorrow....


Dave.

[n4mwd]

I used JT sprockets as well, but I am not certain about the quality of the front sprocket. The front sprocket that I got looked a lot like it was made by powder metallurgy. I could see absolutely no tool marks on the sprocket whatsoever. The rear sprocket looked more like it was laser cut from flat stock which makes for a much stronger sprocket.

For those reading this that don't know what I'm talking about, powder metallurgy is where metal parts are made by packing iron filings into a shape and then baking them in an oven for a little while. After baking, they stick together in the shape they were made into. The problem is that they aren't all that strong. More info.

Having said that, I have no clue how other manufacturers do it or how they compare. It may be just fine for this application. I'll just have to keep an eye on it.

[EMSRacer07]

yea you need to get some needle nose plyers and if you cant with those something to squeze the link together. But yeah that clip isnt on all the way. And yea with a clip def put safety wire. And if you want some more safety put some silicone it will keep things from moving around like a clip from coming off.

[n4mwd]

After reading all the horror stories about using clip-type master links, I went ahead and put the rivet link back on. This time, I got it mushroomed out fair and will finish it off with a ball peen hammer later. Everyone says to do it that way anyhow. In the mean time, I put about 5 miles on it with no signs of it coming loose. I will feel better once its peened.

[n4mwd]

Originally Posted by n4mwd

I used JT sprockets as well, but I am not certain about the quality of the front sprocket. The front sprocket that I got looked a lot like it was made by powder metallurgy. ....

Interesting discovery. The original rear sprocket that I thought was OEM was labeled "JT sprockets". I discovered that after I cleaned the grease and dirt off. Also, the manufacturer says that the front sprocket is chromoly steel. I have a hard time believing that, but the rear sprocket is definitely chromoly.

Oh, well...