Effects of leaking fork seal

[Twisthem488]

Not to long ago I noticed that my left fork was leaking oil. Not much seemed to have come out and I didn't notice any performance changes so I wasn't overly concerned. In the recent spirit of trying to not be afraid of doing my own maintenance I order new seals and bushings (now I need a triple stand too if anyone has good suggestions). I'm still waiting on the seals to arrive but more oil has leaked out, and while riding had previously seemed unaffected I did notice that the bike will just slightly pull to the left without my hands on the bars. I assume this is from the lower amount of oil in the left fork?

Today though, a week later, the bike felt quite different. The front almost feel squirrely and like I could really slide it around if I tried. It was enough of a change that I pulled over to make sure my tire was properly inflated and to check for anything else obvious. The bike felt under control, just that it could weave and bank with less intention. It felt unfamiliar, but not necessarily bad, and I have to wonder if I could flick the bike around even more once I got used to it. Would this be because of the lower amount of oil? I weight 205lbs and would have assumed the bike would be less versatile with a leak like this.

I also washed the bike today after changing my oil and went to a nearby parking lot clean the tires by doing slow circles. While I've never had an issue doing tight turns at low speed (thanks MSF) today I could lock the steering all the way right or left with the same level of effort. That's something I practice at least monthly and it definitely seemed easier to turn tighter today.

While I fully intend to replace the seals, I'm wondering if what I've been noticing is in fact from the fork leak, or if there is something else I need to be cognizant off. If it is because of the oil, then I'm also wondering if OEM specs might not be what I want to refill to. I have 10w oil already, but would lighter or heavier oil be better, or perhaps filling to a different level? What do you guys think? Maybe I'm just going crazy and its all in my head.

[Twisthem488]

I took the bike to the gym today to focus on how its handling. It does feel more sensitive overall when I'm really trying to be discerning, but mainly just turning left, especially if I'm using the front brake. This makes sense to me because thats when the forks are compressing, one with more resistance than the other. I notice no difference when cruising in a straight line. I no longer wonder if it might something I want and will return the forks to a stock condition; 10W at 12.2 oz.

I also think that I'm going to keep the bike parked until I get the seals changed, because even though the handling seems manageable, I would severely disappointed in myself if I wrecked a bike I want to fix up because of my impatience. I'm still curious about triple head stands and wonder if anyone has experience to share.

I'm looking at this Venom stand. It comes with 13,15,16.5,17,18mm pins, but I'm not sure what our bikes use.

[Hoons54]

Did you ever get it fixed? How was the process?

[Ghostt]

Originally Posted by Hoons54

Did you ever get it fixed? How was the process?

I'm assuming your in need of a how-to guide on replacement of the seals, here you go.

http://faq.ninja250.org/wiki/How_do_..._fork_seals%3F

Also this would be good time to cut the front springs, and dial in the suspension.

Here is an excellent write-up on the Ninjette suspension by @InvisiBill hopefully he'll stop in, as he's much better at explaining suspension, than me. I have done suspension upgrades/modifications to my own EX500 & Ninjette, and it's the best thing you can do for the Ninjette along with upgrading the tires, it will amaze you, and anyone else..

I've done quite a bit of research and played around with a few different options on my 500, but definitely listen to the guys here who actually have real-world experience on these bikes.

Getting the spring right for your weight will allow the bike to bounce the proper amount. That allows the damping to have the best control over that movement. If your spring is too soft, it will bounce around too much and your damping system will have to work harder to try to constrain that extra movement. If the spring is too stiff, it won't compress enough to absorb bumps, and the wheel will skip. http://www.ex-500.com/wiki/index.php...ension_Preload is a long read, but it has tons of info, and I think it does a good job explaining everything with examples.

According to RT's calculator, the rear spring is ideal for someone who weighs 220lb (100kg). People here have said that may not be exactly right, but the spring is definitely quite stiff compared to the other little Ninjas (it's 73% stiffer than the 500 spring). I'm assuming you're lighter than that, so going to a softer spring should make the rear work better for you. The PreGen's spring is good for about 140lb on a NewGen, but the shock is a little shorter so it would lower the rear and make the handling a bit slower (plus it lacks any preload adjustment). If you can find a decent one cheap on eBay, it might be worth tossing one in just to try it out though (they're usually ~$20 here).

The stock shocks are simple, non-adjustable, non-rebuildable, lowest-bidder units. Aftermarket shocks give you more adjustment options for tweaking the damping system (usually separate for compression and rebound) and are built with higher quality, replaceable parts (so when something wears out on it, you just replace that one part instead of buying a whole new shock). £395 is US$615 which seems somewhat expensive to me. A new Penske is about $800 here, and used ones can be half that. The nice thing about buying a new shock is that they generally include a spring and calibration to match your weight. It should be basically a perfect drop-in upgrade.

If you can do a bit of mod work, the GSX-R shock swap is a pretty cheap way to get a decent shock, and there are a variety of spring rates used on the various models (there's a chart of different rates/weights toward the end of the thread). It's not made specifically for the Ninja's suspension, and requires a bit of work to make it fit, but they're usually on eBay for about 1/10 the cost of that Brook shock. The SV650 shock doesn't have all the adjustments (it's comparable to our stock shock) but should require less work to install, as another cheap DIY option that's probably more suited to your weight.


NewGen Fork Spring Rate Chart
Again, the NewGen has the stiffest fork springs of the little Ninjas. It's still a tad low, but should be acceptable if you're smaller. If you're a fatty like me, it's still quite a ways off, but it is possible for it to match up fairly well to the weight of a smaller adult (unlike the PreGen and 500, which have essentially useless fork springs).

The stock front and rear are pretty mismatched, so if you're smaller and go with a lighter rear spring, you're actually reducing that mismatch and making it less-bad than stock. On the PreGen and 500, replacing a soft rear spring with something appropriate can exacerbate the problems of the super-soft fork springs (because you're increasing the mismatch).

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*** Ghostt, I'm not your mom and I'm not paying for your parts, so do whatever you want with your own bike. ***




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Any other questions please feel free to contact me.

[Ghostt]

Also here's the link for probably the best wiki on the Ninjette, from our friends at ninja 250 riders club, although some of the information is dated, it's still the best resource to start

http://faq.ninja250.org/wiki/Ninja250_Howto

[Hoons54]

Sweet! Thanks for the link

[1ER6F]

Originally Posted by Twisthem488

I took the bike to the gym today to focus on how its handling. It does feel more sensitive overall when I'm really trying to be discerning, but mainly just turning left, especially if I'm using the front brake. This makes sense to me because thats when the forks are compressing, one with more resistance than the other. I notice no difference when cruising in a straight line. I no longer wonder if it might something I want and will return the forks to a stock condition; 10W at 12.2 oz.

I also think that I'm going to keep the bike parked until I get the seals changed, because even though the handling seems manageable, I would severely disappointed in myself if I wrecked a bike I want to fix up because of my impatience. I'm still curious about triple head stands and wonder if anyone has experience to share.

I'm looking at this Venom stand. It comes with 13,15,16.5,17,18mm pins, but I'm not sure what our bikes use.

The PitBull triple tree pin I have is marked with a 20. I measured it to confirm and it does measure 20mm. That is not a bad price on the Venom stand, and you will definitely need this if you're going to be working on the forks. I recommend picking up some springs from SonicSprings.com. The have a spring rate calculator that is very helpful. The OEM springs are horrible and upgrading to a heavier spring is one of the best mods you can start out with. As for the fork seals, buy OEM! I have heard many riders experience leaks shortly after when using the aftermarket ones. Here is the how-to link-> https://www.ninjette.org/forums/show...dust+fork+seal. Also, I would recommend picking up a fork oil level gauge. It makes measuring the oil level super easy and you can pick one up at CycleGear for $20. http://www.cyclegear.com/STOCKTON-TO...il-Level-Gauge. I believe the manual has the oil level listed at 108mm from the top of the fork fully compressed without the spring. Measure the fork that is not leaking prior to draining the fluid and that will give you an indication where you're at. Once you reinstall the forks, make sure you re-align them correctly. Here is a good video on how to do that -> https://www.youtube.com/watch?v=vSunBRB6-r8. It is really not a hard job, it just takes a little time and patience.

[Ghostt]

Cutting and adjusting the OEM fork springs are free and easy enough to do.