Time for a new Chain and Sprocket?

[condor74]

I was riding last week and coming out of a deep run on the throttle in 2nd gear accelerating for a small step up jump the chain jumped off. I managed to put the bike in neutral and roll the chain back on to the rear sprocket. I put the chain back on and rode with no problems for the next 3 or so hours. The chain did look a bit loose at this point. When I got home I looked at the sprocket and it was a bit worn but not too bad. I tightened the chain to specs and lubed it. I havnt ridden the bike since then yet. This happened one other time about 2 months ago. I did the same thing. The axle looks to be aligned perfectly and nothing came loose.

The next question is if I am to replace these items, what would be a hot set up for gear ratios? Currently it has 13 tooth front with a 49 tooth rear. The bike has lots of power but sometimes it seems to drop to far out of the powerband when I am shifting. On the other hand If I drop a tooth in front or raise a tooth in the rear, the top speed of the bike will be limited. There are times I do find myself on long straightaways on hard packed dirt where I have the bike rapped out for long periods. Anny suggestions? Maybe I should leave it stock?

[KDXGarage]

2,263 posts and no mention of which bike? Come on, now.

[condor74]

Sorry about that. I had typed it once before then my computer back spaced and I retyped it. I must have ommited the year and model on the second draft. It is a 2002 KX250.

[cxcmoto]

13/50 is the hot setup.

Its OMG smoking fast, so good from the bottom to the top. No way possible to find a better gear ratio.....

oh yeah - what sort of riding and terrain do you do ?

?

[condor74]

I do a bit of everything. Most of the time I ride offroad, free ride in the hills, finding jumps, mx style obstacles, hill climbs etc. Occasionally I trail ride or ride some single track. I ride desert often also. And I am looking to ride more MX also. I know I am kinda all over the board.

[cxcmoto]

I was being sarcastic in my previous response.

With the wide variety of riding that you do, I doubt that you will find one gear ratio that is optimized for all of them. It will be a question of the best compromise.

I can suggest a couple of things. -- First, buy at least an X-ring chain. The added costs more than pays off in the long run with increased durability, less adjustments, etc. Z-ring is also ok. I also suggest not using a rear sprocket of entirely aluminim. Steel is the most durable, but also weighs more and costs the least($25-30). They are making some very nice sprockets now, with aluminum centers, and steel teeth.

http://www.supersproxusa.com/

They aint cheap, but they will last and last, I think there is even a guarantee?

To help you pick a new ratio, we need to know what problem you are trying to solve. ie: I need more top-end speed in 5th ? or I need more bottom-end pull coming out of the corner? etc... There will always be a compromise in some other area when you change ratios. Do the math on the gear ratios, especially if you are looking at changing both.

49/13 == 3.77

50/12 == 4.17

Changing to a 50/12 will give you more top-end speed at the sacrifice of low-end cornering pull. If you do much in 1st-2nd gear right now, I doubt that you will be happy with the 50/12 in those situations.