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Razor RSF650 upgrades

Has anyone upgraded this street bike to an off road bike? I’m currently attempting that and have upgraded the entire electrical system with a 48volt controller, 1600watt motor, new full twist throttle and 4 battery in series setup. I’ve swapped the front fork with the MX650 front fork to get suspension front and back. My only frustration is finding a tire solution to upgrade to slightly wider, larger and knobbier tires. I’m hitting a wall searching online. Any help would be greatly appreciated.

Hi Carl, you are the first person to modify a Razor RSF650 for offroad use that we have run across so far. How well did the MX650 front forks fit onto the RSF650 frame?

We know a lot of electric scooter and bike tire suppliers and could try to find the knobby tires that you need. However, we have not received our first shipment of RSF650 tires yet so we do not know what size they are. If you could read the tire size off of the original tires and let us know, then we could begin searching for a knobby version of them. 

Thanks for replying. The front fork from the MX650 has the same basic geometry/dimensions/application with the exception of the front brake mount...a great fit. I'm expecting to relocate the top mounting hole back towards the fork by about 1/8 inch in the existing mounting plate that's welded on, shaving any excess off by grinding and shaping to fit the caliper...OR....buying a larger disc to accommodate the gap/difference in positioning. It also might fit as-is but I haven't yet tried since I wanted to mount the new tires on the rims before putting things back together. The RSF650 stock-tires, front and back, are 100/80-10. I won't be replacing the front plastic fender so a taller tire will fit, the width is the problem's limited by the space between the posts. I did dry fit and test this suspension without the front brake caliper and it drives much nicer and provides a softer ride. I think a 110/90-10 tire would work but I won't be able to measure for sure until I put it all back together to check the clearance of the rear tire and motor mounting area. I have the bike completely apart to paint the upper trellis framework and the front forks, leaving the swing-arm original. I'm going camo-green (plasti-dip) with camo-pattern wrap on certain areas of the plastic cowlings and "tank". Knobby tires would complete the look nicely. I also replaced the rear sprocket to a 89-tooth (80-tooth is stock) for more torque (off-road terrain) and don't know how many links to add to the #25 chain. Do you have a chain already mocked up for that configuration? The motor and wheel distance did not change, just the added teeth on the rear sprocket. I'm completely new to this entire hobby (obsession now) and it's been a lot of fun and a lot of learning about electric mobility....the ideas for future projects are flowing...but keeping them at this scale. I'm limited by time and space only....

Thanks for sharing that information about switching RSF650 to have MX650 forks. That is great to know.

Also thanks for letting us know that the RSF650 tire size is 100/50-10. We checked with all of our tire suppliers and could not find a knobby or turf tread 110/90-10 tire. We did find 120/90-10 and 130/90-10 knobby and turf tread tires, however, I am sure that you were able to also. How about a 4.00-10 tire? They are available with knobby treads and are supposed to be equivalent to 100/100-10 and 110/90-10 tires although 4" is 101mm so it should be closest to a 100/100-10 metric size. 

We have an online calculator that can be used to determine the new chain size when installing a larger sprocket. It is available at this link: 

Here is a quick guide showing how to use this calculator to determine the new chain size when installing a different size sprocket.

Please let us know if you have any questions. 

Great info, thanks. I’ll be sure to use this calculator when I get the bike back together for accurate measurements. Do you offer the chains as a complete setup or will I have to order a length and add a master link myself. I’d order a backup chain as well if I can keep from building the chain myself. I think I’m going to stay with the stock tires for now, they are still too new to replace anyways and I don’t plan to ride across too rugged a terrain to need knobbies at this point. I will most likely move on to another build once I decide what that is after I’m done with this one. This has been fun, even though nothing is getting done quickly. Another question is: do you have a fast charger available to suggest for 48v with the 1600w motor? I really want fast charging since I’m the only one that will have this type of bike at our camp this year (many test rides). I suspect I’ll encourage a few to build their own too after they ride it around. Thanks again for all your help and input. Carl
Also see the front wheel from Sx500 (McGrath edition!) it’s shorter than the MX 650 that you have but it’s a much wider and stronger rim and lined up to the brake caliper without modification (on the mx650 forks) it gives the bike a supermoto look, very trick!

Great suggestion, I might use that setup in the end. Are the brake discs larger than on the RSF630 stock tires? I like the RSF650 rims and want to keep that look consistent with the rear. 

Not sure on that part

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