Bottoming out everywhere...Stiffer front forks, and oil weight recommendations?

[DieselKilgore]

Hey all, just bought a 2005 Ninja 250 for commuting to work. 15,000 miles and in pretty decent shape. Going over and correcting some of the poor maintenance done to this bike. Replaced an original looking air filter with a giant hole in it and who knows when the last time it was cleaned and oiled, maybe never. Ditched the Autolite!!! plugs for NGKs and just cut off the original chain. Bike leaks from the valve cover, but i've got some new gaskets coming and plan a valve adjustment which i'm sure it desperately needs. Other than that it runs pretty darned good and the engine and gearbox feel strong.

Now onto my next maintenance/upgrade task. First of all i'm 6'2 280lbs. So the bike sinks pretty low beneath me and I had already had in mind to do some suspension upgrades for my weight. But all in all everything has been ok, but just in the last day or so the front forks bottom out over the littlest bump. So it's definitely time for me to address this.

I did a bit of research and RaceTech seems to be the way to go for stiffer springs. But I am at a loss in which of the three flavors they offer to choose from. 80KG, 85KG or 90KG? Also, will any difference in fork oil weight help my issue? Fork seals are good, no leaks, but should I replace them while i'm at it?

Appreciate any opinions and thoughts.

Thanks.

[Ghostt]

You definitely need some upgrades in the suspension department. The OEM set-up is good for people whom weigh about 100 lbs.

New fork springs, go to Sonic Springs calculator

http://sonicsprings.com/catalog/calc...pring_rate.php

Put in your info, and see what springs you need.

90kg/mm is what I've come up with.

As far as fork oil, I'd personally go with 15w. Oil controls the damping, does nothing for spring rate.

And might as well do the fork seals, and dust caps while your in there maybe, your call.

Rear is easier, just get a rear shock from a NewGen Ninjette 08&up it's a straight replacement, and does raise the back up a little bit.

And see how it is after all that

Here's some reading for you, and other options as well.

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

Optional is a set of BCB BIG BOY LINKS, help raise the rear up about an inch and a half.


SERENITY has a cut down set of EX500 springs about .80kg/mm and 15w fork oil. The rear has a ZX600 shock.

I added the BCB BIG BOY LINKS this season not because I needed the clearance, but to help with better handling, quicker turn in, and it gives the bike a slightly more aggressive look.

I'm about 220~230 with gear, and 6'3"

Hope this helps, if not let me know.

[DieselKilgore]

Hey Ghostt, thanks a bunch. Just the info I was looking for. I'll definitely go with your recommendations and order me some parts. Thanks also about rear shock setups for the 250. Honestly the rear seems fine and i've not messed with preload at all. But if I go digging around in the front I should do something with the rear. At least i'll try adjusting preload on it and go from there.

[Ghostt]

No problem, but there is no pre-load for the PreGen shock, and the spring is crap, basically it's crap all around.

The NewGen has a preload adjustment to set the sag, and it has a lot spring for your weight. You can usually find them on eBay for cheap, or the parts for sale section here.

I went with the ZX600 for two major reasons, first is you can change the oil in it, so you can change the weight of said oil, I went with 15w. Second is it's air adjustable, so when I ride two up, I just add some more air.

http://faq.ninja250.org/wiki/Installing_a_ZX600_shock

http://faq.ninja250.org/wiki/ZX600_shock_oil_change


@InvisiBill is better at explaining this suspension stuff, and he has more information about it, hopefully he'll show up. He's a solid member, and I've known him for many years from the EX-500.com forum.

[DieselKilgore]

Ok awesome. Thanks again. I don't know why but I just assumed it had a preload adjustment. I'll poke around for 08 or zx600 rears and see what sticks. I might shoot my budget with the front forks and see if I can score whatever is cheaper.

[Ghostt]

Originally Posted by DieselKilgore

Ok awesome. Thanks again. I don't know why but I just assumed it had a preload adjustment. I'll poke around for 08 or zx600 rears and see what sticks. I might shoot my budget with the front forks and see if I can score whatever is cheaper.

The NewGen shock seems to popular choice around here for bang for bucks, and it's a direct replacement, no fuss.

I would have gone that route, but I wasn't aware of the NewGen set-up. If you look on eBay, and watch it, you'll get the deal.

[InvisiBill]

PreGen Fork Spring Rate Chart has some numbers for the front. I haven't seen much info on the rear, but the PreGen's spring rate is good for about 140lb using the NewGen's calculator (the NewGen rate is good for about 215lb).

To oversimplify it, spring rate determines how far the suspension moves (a spring of a certain rate will always compress down to the same length under a certain load) while the damping (oil weight, etc.) determines how fast it moves.

I'd say spend $100 on .85kg/mm-ish fork springs and ~$40 on a NewGen/300 shock from eBay. After installing, adjust your preload to give you good sag numbers. That'll do wonders for how the bike feels, for relatively cheap. You might want to refresh the forks too while you're in there (seals, oil, etc.). I switched to Intiminators so I can't give you any advice on oil weights.

[DieselKilgore]

Hey guys, thanks for all of your help. No, you aren't my mom or paying for my parts! Haha. But you are giving me all the expertise that I need. I just wanted a parts list of something I can drop in and be happy with by someone who has done it before. You guys have given me exactly that and i'm very thankful.

I ordered the .90kg race tech fronts (found out factory are .44kg!) and found a new gen rear for $45. Got some oil seals also, I figure the dust seals should be ok, they look good at least.

I'm excited, this bike already handles great, compared to old kz's and enduros i'm used to. But now we'll see some big improvements, can't wait. And no more knocking my fender and fairing plastics together.

[kxpower?]

Originally Posted by DieselKilgore

Hey guys, thanks for all of your help. No, you aren't my mom or paying for my parts! Haha. But you are giving me all the expertise that I need. I just wanted a parts list of something I can drop in and be happy with by someone who has done it before. You guys have given me exactly that and i'm very thankful.

I ordered the .90kg race tech fronts (found out factory are .44kg!) and found a new gen rear for $45. Got some oil seals also, I figure the dust seals should be ok, they look good at least.

I'm excited, this bike already handles great, compared to old kz's and enduros i'm used to. But now we'll see some big improvements, can't wait. And no more knocking my fender and fairing plastics together.

I had the newgen rear shock mod for years, then came across some 0.75 racetech fork springs for a song a few months ago. That and fresh 15wt oil, along with properly setting the sag made mine a whole new bike. I'm 200 so probably should have gone up to 0.85 but hey they're night and day better than stock.

One word of advice, take your time and get the preload set right. My springs came with spacers, which uncut left me with a negative static preload (about 1/4"). I've since read that you should have a half-inch static preload (meaning with the bike supported and the front wheel hanging in the air, you should have to compress the springs a half-inch in order to put the fork cap back on). So I need to add a 3/4" spacer (in addition to the spacer already in there) to get that just right.

Here's a link to progressive suspension's fork spring installation instructions. They recommend more static preload, but I suspect that's because their springs are progressive rate, unlike the straight rate in Sonic Springs or RaceTech.

http://www.progressivesuspension.com...rings/3055.pdf

[DieselKilgore]

Thanks for that info. How much needs to be cut from the spacers to get the 1/2" preload. Or do I neec to add another spacer?

[Ghostt]

Cutting spacers depends on the preload need/ sag height, it's a something you'll have to dial in yourself.

Some use 3/4" pvc pipe, because it's cheap, and easy enough to cut. I personally use 3/4 steel pipe afterwards to replace the pvc, once I know the length needed.

[DieselKilgore]

Ok. I'm starting to get it. The spacer at the top of the fork is the one.

[kxpower?]

Originally Posted by DieselKilgore

Ok. I'm starting to get it. The spacer at the top of the fork is the one.

Yup. The aftermarket springs will be shorter than the stock ones, so it will need a longer spacer. Drop the new spring in, measure how far down the tube it is, then cut the spacer to give you the desired static preload.

[DieselKilgore]

This is much simpler than I originally thought.

My front springs are on order and my rear should arrive this week. I'll let you guys know how it goes.

[Ghostt]

As a rough figure, I use the spacer needed and add 1", and see where that leaves the sag at.

Setting sag is crucial in getting the suspension dialed in, so take your time, in the end it will pay off in a positive way.

[InvisiBill]

The new spring/spacer should be about the same length as the old spring/spacer. The exact length will vary a bit, as that's how you adjust preload, which determines how much sag you have. http://www.ex-500.com/wiki/index.php...ension_Preload is a good guide that explains what to do, as well as why you're doing it.

[DieselKilgore]

This page http://faq.ninja250.org/wiki/How_do_...he_fork_oil%3F has left me with another question. With the setup I am going with, what oil level would you guys recommend? Factory 205mm or more oil?

[juliusmichaelhonrada]

Originally Posted by DieselKilgore

This page http://faq.ninja250.org/wiki/How_do_...he_fork_oil%3F has left me with another question. With the setup I am going with, what oil level would you guys recommend? Factory 205mm or more oil?

here in my country i dont know if its right btw but it make sense.

they assemble the fork without the oil seal , and push it down at its maximum length ,the excess oil will usually leak outside and the remaining oil is the proper oil level

[Ghostt]

Originally Posted by DieselKilgore

This page http://faq.ninja250.org/wiki/How_do_...he_fork_oil%3F has left me with another question. With the setup I am going with, what oil level would you guys recommend? Factory 205mm or more oil?

I would keep to the OEM levels.

[InvisiBill]

Oil height is another thing you can tweak. Oil isn't compressible, air is. This will affect how progressive the action of the fork is. With more oil, it's more even throughout the stroke. With more air, it compresses more as the fork moves, ramping up the pressure and making it more progressive.


Also, http://faq.ninja250.org/wiki/How_do_...Fork_oil_level:

The Kawasaki Service Manual has, from time immemoriam, recommended a fork oil level of 226mm for the 86-87 and 205mm for the 88-07, but we're here to say that that number is not correct. Rich Desmond of Sonic Springs, who works with this stuff every day, says that there should be more oil in your forks (remember that, since you are measuring down from the top, a smaller number means there is more oil/less air space). He recommends a level of 115mm, and several of the guys in the club have done so and report no ill effects. Instructions for Race Tech GVEs specify 130mm. Others have gone with 200mm and say that that level works fine. The FAQ recommendation is to choose one of these figures and then do some tuning if you have any doubt.

Note from Payne: I've historically (60,000 miles) run a fork oil level of 205mm per my manual, but based upon the FAQ I raised it today to 160mm and I've got to say, Wow! I could tell an improvement as soon as I left my driveway. Rode for 60 miles, and I definitely prefer this feel. The front feels "happier" and not quite so "nervous" and harsh. Seems to give a better feel for what's going on up there. This is with 15 weight oil and no modifications.

For whatever it's worth, I'm running around 130mm on my 500, which has 37mm forks similar to the 250's. I was surprised to see 200mm+ mentioned, so I looked it up, and found this. I'd probably start at 130-160mm, but it's easy to change.

[Ghostt]

Very interesting, I've run 5 1/8" which is roughly 130mm for awhile now in both my EX500 and Ninjette. With 15w synthetic fork oil.

I don't know where I got this figure from, but it's been many years, and it seems to work just fine.

[DieselKilgore]

Good stuff. I'll definitely tune it and see how it feels. Haven't gotten the fronts yet, but the rear shock came and I'll bolt it up tomorrow. I just ordered the hook wrench adjuster so I won't be able to mess with it til then.

[Ghostt]

Originally Posted by DieselKilgore

Good stuff. I'll definitely tune it and see how it feels. Haven't gotten the fronts yet, but the rear shock came and I'll bolt it up tomorrow. I just ordered the hook wrench adjuster so I won't be able to mess with it til then.

A big ass pair of channel locks works just fine

[DieselKilgore]

Installed the NewGen rear shock, it was great at the first setting. Bike sat up higher and didn't sag under it's own weight like the old shock. Gave me a good reason to do the fender delete i've wanted. I ended up setting it to 3 and it's a bit firm. I'll need to take it for a ride with my gear and backpack for work to see if it's still too firm. But it's a world of difference already and i'm happy that I have the adjustability. It's like a whole new bike, i'm having to re learn how to corner because I have been so used to the sloppy and wallowing rear end. So now that the rear is set I'll get to work on the front maybe this weekend. Report to come.

[Ghostt]

Awesome, wait til you get the front done, you'll be amazed by Tue difference between the two.

Doing suspension is the best modification you can do for the PreGen, and the cost is reasonable.

Personally I also recommend changing out the clutch springs, as they are weak. I consider these as preventive maintenance.

[InvisiBill]

Originally Posted by DieselKilgore

Installed the NewGen rear shock, it was great at the first setting. Bike sat up higher and didn't sag under it's own weight like the old shock. Gave me a good reason to do the fender delete i've wanted. I ended up setting it to 3 and it's a bit firm. I'll need to take it for a ride with my gear and backpack for work to see if it's still too firm. But it's a world of difference already and i'm happy that I have the adjustability. It's like a whole new bike, i'm having to re learn how to corner because I have been so used to the sloppy and wallowing rear end. So now that the rear is set I'll get to work on the front maybe this weekend. Report to come.

Switching to the NewGen shock is an 18% stiffer spring. Your new fork springs are 105% stiffer. If you think the back was an upgrade, just wait until you get the front done. The front may actually seem worse now, since there's an even larger imbalance front to rear.