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Discussion Starter #1 (Edited)
Some of you who have been following a couple of threads in which I have posted recently, will know that I was looking into the possibility of converting my 2015 XT 250's stock 428 chain and sprockets to a more robust, 520 chain and sprockets. I am pleased to report that (as is very often not the case...) it was a very simple, easy, trouble free, headache free, plug and play, direct bolt on conversion. How often does that happen? Very rarely, in my experience, lol...

I've been running 14/48 gearing on my XT 250 for most of its life. I have a funny little anecdote about that, actually. When I was first thinking about how I might do this conversion, I had figured I'd need to calculate the diameters of the 520 sprockets, so that I could match my current gear ratio. I went online and found various calculators and databases and such. First, I determined the diameter of the stock Raptor 250 front sprocket. My calculation showed that to be the equivalent of a 17.55 tooth 428 sprocket. So I input 17.55 for the front sprocket on Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator (yes, you can input 17.55 :) ). Then it was just a matter of figuring out what 428 rear sprocket, when paired with a 17.55 tooth 428 front, would get me the same gearing as my 14/48 428 setup. It was a 60 tooth. Then I determined the diameter of a 60 tooth 428 sprocket, with the understanding that I would need a sprocket of that diameter in a 520 size. Sure enough, you guessed it, the 60 tooth 428 is the same as a 48 tooth 520...lol. The RATIO is what matters (the difference in size between the front and rear sprockets!), not the actual particular diameter of the sprockets...derp de derp :) Anyway, at least I did all the calculations right, so, had that been necessary, I would have still ended up with the correct gearing, lol. Anyway, below is a quick listing of the 520 sprockets and chain that I'm running now.

***The front sprocket that I am using is an OEM, stock, 14 tooth front sprocket from a 2009 Yamaha Raptor 250 (which has, either exactly or very nearly, the same motor as the XT 250). It bolted right on, fits perfectly, lines up perfectly, and even uses the same retaining system (OEM XT 250 lock washer and countershaft nut). I ordered this from www.bikebandit.com .

***The rear sprocket that I am using is from a 1988 Yamaha FZR 400, in the 520 size (apparently there are two different chain sizes that could be had for that model). I ordered this sprocket in a 48 tooth size, from Motorcycle Sprocket Specialists | Stock & Custom Sprockets. I promised to give a shout out to Sprocket Specialists for having the part available, and to Lance for his great customer service: he confirmed for me, via email, that the 88 FZR 400, 520 rear sprocket had the same bolt pattern as the 2015 XT 250 rear sprocket. I was also able to verify this with this amazing database from JT sprockets, which even shows the spline spacing/patterns of the inner portions of the sprockets (seriously awesome, uber useful bunch of data!): JT Sprockets: Catalogue . As with the front, this rear sprocket bolted right up with no problems at all, fits perfectly, lines up perfectly, and uses the OEM XT 250 retaining system.

***The chain that I am using is an EK 520 MVXZ X-ring chain, cut to 108 links (perfect fit). This chain has a 9,000 pound tensile strength, and is supposedly rated for up to 1,000 CC street bikes. I also used the patented EK screw-type master-link (for the 520 MVXZ chain). I've used these before and absolutely love them - SO much better, IMO, than the POS clip-types that come with 99 percent of 428 chains! They are secure and strong, and easy to install with just a crescent wrench. [EDIT (02/25/2018): it is a good idea to file down the nubs a fair bit after you break the nuts off, after using them to press the side plate on.] I ordered these from ★ Motorcycle Chains at MOTO-CHAINS - Motorcycle and ATV Chains for Racing and Street (I've also had great experience with this retailer a few times in the past - top notch seller!).


I must say, I am quite pleased with the results of this conversion. Oh, that reminds me, there is one little issue - not really a concern to me, but worth mentioning - the OEM XT 250, plastic front sprocket cover will not fit on with the bigger sprocket in there. It is possible (likely) that the Raptor 250 utilizes a different cover, so I may try to order that, or figure something else out, but it's not a big deal at all.

EDIT (04/25/2017): The plastic front sprocket cover for the Raptor 250 does fit. However, the metal sprocket guard...(not sure what it's called...goes between the case and the front sprocket/wraps around the sprocket), while it will technically fit, does not offer enough clearance, so the chain, when in motion, will sometimes very lightly grind on it. Not good...so I took that piece off and just put the plastic cover back on.


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