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Which sprockets for more speed?

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Hey, i got an 07 crf250x road legal, inspected and insured. I'm ready to go! But i found that on the highway, going 100km/h is reving the bike pretty bad. All though, i cut her out at 124.7 km/h, i think that if i change the sprockets i could hit that speed without it red-linning at 12,250 rpm. But i might be wrong.

My sprockets now are 14/53.

Anyways, i was wondering what size of sprockets i would have to change for it to go faster? And the bike is mostly seeing the streets, not a big fan of trails and paths.

Thanks.

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A couple of points to note:

CRF X's are not designed for sustained high speeds on a freeway - they are a competition machine - not like the old XR's etc

Unless you have done something fairly radical to your engine they red line at 9,500 RPM

And to answer your question -

Either more teeth on the front or less teeth on the rear sprockets

So try a 50 or 48 tooth rear - 14 is the biggest for the front without risking the chain chewing ya cases.

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sorry about that, i ment to say that it cut-out at 12,250 rpm.

It red lines at 10,500 because on my vapor speedometer i can set when i want the red line light to start blinking, so i set it at 10,500 rpm and it sounds just about right to me and my ears. But i might be wrong :S, i could set it at 10,000 rpm and it would be closer and still do the job.

on another post somewhere on this site, i seen that somebody put a 14 in front and a 45 in back. You guys think it would be alright to do that? or is that too small?

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Hey, i got an 07 crf250x road legal, inspected and insured. I'm ready to go! But i found that on the highway, going 100km/h is reving the bike pretty bad. All though, i cut her out at 124.7 km/h, i think that if i change the sprockets i could hit that speed without it red-linning at 12,250 rpm. But i might be wrong.

My sprockets now are 14/53.

Anyways, i was wondering what size of sprockets i would have to change for it to go faster? And the bike is mostly seeing the streets, not a big fan of trails and paths.

Thanks.

Simple math. If you're hitting the rev limiter at ~80MPH, the question is where do you want to be at 80MPH? If you want to be at 10k RPMs, for example, then you have to change your final drive ratio by 12.25k/10k, or 1.225. Your current drive ratio is 14/53, or o.264. You want 0.264*1.225=0.323. If you go up to a 15 front sprocket, then the rear needs to be 15/0.323=46. If you can get a 16 to fit, then you need 16/0.323=49. So, either 15/46 or 16/49. If you want an even bigger change, either go bigger in the front, or smaller in the back.

Lastly, these engines are known to use oil when running at high RPMs for extended times - tread lightly.

JayC

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Today i got my bike inspected. All i was missing was a chain guard but i knew the mechanic well so he let it pass, cuz it was no biggy anyways. I made them put two knew bridgstone tires, both 50% street and 50% trail. And it increased my speed from 2.3 km/h and it runs a very smooth and low rpm ride. Very impressed and a big difference.

For the sprockets, im gunna leave the 14 in front and i ordered a 48 teeth red special edition renthal sprocket. I keep you guys posted on how that works out.

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49 or 48, you need to take two links out and get a new press on m link, about $6 from honda and they should crimp it on for ya.

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alright, thanks

so how much more speed do you think im going to get with the 48 in back and im already hitting 79 mph?

And will it be a short or big difference?

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Don't expect anymore speed, it'll just make the rpms more tolerable on the road.

I set mine up dualsport for a bit last summer and found it not real roadworthy for anything but connecting trails. I just got the feeling I using up the motor and asking for more frequent rebuilds. My old XR with a 6spd and big lazy thump motor seems a lot happier.

Since the 250x is sold road legal in some countries it'd be interesting to hear from some high mile road users.

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bad news boys.... took her out yesterday, going maybe 50 mph.... then the engine let go and my ''new'' back tire jammed shut... lol, im pretty sure it's the crank case... two days ago i made the dealership change my oil and he said the filter was full of brass, but the retard said ''oh thats always commen with these kinda bikes'' i knew it wasn't, but i've seeing this coming for a while now and waiting for it to happen,

I'm not exacly pissed, but i'd rather have a new rebuilt than and worn out engine...

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sorry, but shame on you for riding again knowing the filter showed bronze. Would have a whole lot cheaper to rebuild before it jammed up.

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So funny when i heard the news, everybody told him tho it was gonna happen, and 250x dualstile knew!

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well i knew it was gunna happen, didn't know when, so i just left it like that because it was gunna cost me all the same things for a crankshaft and such to fix it so i just drove her until it broke down.

But its no biggy, it's fixable. But ima sell her after cus it's just gunna happen again on the roads.

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