A while ago I noticed that the front suspension was feeling more like pogo sticks and less like shocks. I drained the factory fork oil in by '13 BV350 which has almost 15,000 miles. The old oil came out black - extremely dirty. Here is a link to a quick video of what the oil looked like coming out. Note that the new fork oil was almost clear! I used Maxima fork oil.

https://drive.google.com/file/d/1CRFC5aMVlMTt7mQEECmxaSHGntLZbJ-5/view?usp=sharing

I decided to replace it with 10w fork oil instead of the 7.5w that is spec. This change stiffened the feeling that the front suspension provides and make for better feedback from the front tire, especially around corners. I did not replace the fork seals and dust boots because the old ones were not leaking and I wanted to see if they would leak if I just replaced the oil. I can confirm that I've ridden it about 20 miles and they are not leaking at all. I have new ones coming just in case.

I may do the Bitubo progressive spring upgrade later on but I wanted to see how just increasing the weight of the fork oil would do first. For me it made the front end feel more planted around corners which is what I wanted. For some, the feeling might be a bit stiff so just replacing with 7.5w oil might be better for those that want the factory front suspension feeling restored.

I also increased the compression by one position on the rear shocks, up from the softest setting. In combination with the heavier fork oil, that made a positive difference in stiffening up the feel of the scooter, especially around corners and on the highway.

If you do this yourself a couple pointers:
-I used a screwdriver handled pick to get the circlips at the top of the fork legs out. Each one took me 15 minutes of picking and prying to get them out
-be patient and don't poke your fingers with your pick.
-after you remove the allen bolt at the bottom and the cap cover at the top, pull the springs / washers, fork valve out and clean everything. I used brake cleaner but not on the fork legs themselves at I wasn't sure if the brake cleaner would damage the rubber seals. I cycled the chrome folk tubes in and out of the legs several times and let the old oil drain out for a while.
-since I did not remove the dust cover and fork seals, cleaning the inside of the fork legs was not possible.
-when filling with oil, fill up to 7.99" from the top of the tube, with the tube fully extended in the fork leg.
-the cap cover at the top of the tube will be under tension from the springs beneath it, so it is best to have a vice to put the fork leg into. I held the fork tube with one hand with the fork leg resting on the floor and then using a torx socket and impact screwdriver pushed down on the cap and screwed it in. Be careful there as it does require some force.

These small changes, in my opinion, made a noticeable improvement in how the scooter rides. Your experience may vary.

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