Fork fix - Wrist Twisters
 
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post #1 of 12 Old 07-01-2019, 10:31 PM Thread Starter
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Fork fix

So a while back I was hit by a falling rock riding in the mountains. I managed to stay upright and avoid getting my body hit at all, but it pretty much destroyed my front fender and headlight and bent my handlebars. I replaced the light/handlebars and have been running sans-fender, but I noticed recently that my left fork was leaking. Removing the plastic guard and dust cap revealed that the fork has a nice dent in it.



The inner tube appears to be unscathed so do you all think I'd be safe to just replace the lower part with this for $40? I'll probably get new Racetech springs and do the seals/oil on both at the same time too. The seals appear to be held in with some sort of spring no? I think that probably should be replaced as well since that is right where the fork is deformed. What is that part and is there anything else I should replace while I do all this?


I plan to rent a bench at a local shop and have 1-on-1 instruction on hand for the process since this is new territory for me, but want to make sure I order everything I'll need in advance.


The other option is to scrap the bike and shop for a new one, but $$$$ . Plus so many people say they regret replacing the 919. Thanks in advance!

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post #2 of 12 Old 07-02-2019, 01:18 AM
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For $40 and some labour, I'd give it a shot. If it doesn't work out, ie your fork leg still leaks fluid, you could maybe look at replacing the whole fork. Seems a shame to consider scrapping the bike..

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post #3 of 12 Old 07-02-2019, 01:21 AM
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PS There was a change in fork spec around the '05 model - might be worth making sure you are getting absolutely the right part for your bike. It's possible to use bikebandit part numbers [or equivalent] to check.

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post #4 of 12 Old 07-02-2019, 09:37 AM
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Quote:
Originally Posted by K1w1Boy View Post
PS There was a change in fork spec around the '05 model - might be worth making sure you are getting absolutely the right part for your bike. It's possible to use bikebandit part numbers [or equivalent] to check.
The change was at model year 2004.

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post #5 of 12 Old 07-02-2019, 01:25 PM Thread Starter
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Thanks for that info. The Ebay part is from a 2002 and bikebandit does show different part #s for 2002 vs 2005 (which mine is).

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post #6 of 12 Old 07-02-2019, 01:43 PM
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The fork lowers remain the same. 2002 are the same as 2005.

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post #7 of 12 Old 07-03-2019, 01:32 PM
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All good, then!

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post #8 of 12 Old 07-03-2019, 01:43 PM Thread Starter
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The fork lowers remain the same. 2002 are the same as 2005.

OK, well that would be good, thanks. I ordered it, along with seals and some other internals that appear from the parts diagram to be in the general area of the dent (bush guide, backup ring, etc.). Now I just need to order springs and oil and hope there aren't any surprises along the way.

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post #9 of 12 Old 07-04-2019, 11:43 AM Thread Starter
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Another quick question... RT's calculator recommends a .87 spring (142lbs). Obviously .85 is closer than .90, but I often ride 2-up and I'm more likely to gain weight than lose any so I thought I should go for the .90. Is that sound logic?

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post #10 of 12 Old 07-04-2019, 01:18 PM
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Quote:
Originally Posted by bacis View Post
Another quick question... RT's calculator recommends a .87 spring (142lbs). Obviously .85 is closer than .90, but I often ride 2-up and I'm more likely to gain weight than lose any so I thought I should go for the .90. Is that sound logic?
A 0.875 is derived by using one 0.85 and one 0.90.
This is a very common practice and A OK to do.
At least some suppliers, chassis tuners in particular, will sell you such a pair, and not force you to buy two pairs and be stuck with 2 springs.

I suggest no less than 0.875 and no more than 0.90.
No more than 15 mm of installed preload, no less than 10.
Remember that Installed Preload is determined with the Preload Adjusters fully backed out so that all the indicator rings are showing topside.
Suggest you begin with 10 mm of Installed Preload then set your Preload Adjusters inwards by 2 indicator rings, regardless of which spring rate you decide upon, then go from there based on road rides.

Suggest you use no higher than 140 mm of oil level instead of the stock setting.

Keep in mind that your 05 was a terribly weak rear spring in comparison to the pre 04s.

Keep in mind that 919 forks are harsh on bump, with that harshness manifesting itself like a stiffer spring.
Make sure there is some grease between the lips of the actual hydraulic seal that is below the dust seal.

If you ride two up, your issue will not the front springs, it will be the rear spring, and you'll have to dial in lots of preload by the adjustment collar.

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post #11 of 12 Old 07-04-2019, 03:04 PM Thread Starter
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Thanks for all that great info! I really am hoping to gain some weight from working out (I’ve been up to 175lbs) so I’ll probably go with the .90.

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post #12 of 12 Old 07-04-2019, 04:10 PM
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Quote:
Originally Posted by bacis View Post
Thanks for all that great info! I really am hoping to gain some weight from working out (Iíve been up to 175lbs) so Iíll probably go with the .90.

The difference in rider on front end height will be no more than 1.5 mm, a number that your preload adjusters can easily account for.
I'd still be saying .90 max even if you weighed 180 # before riding gear.
Proper spring selection is nuanced.

If upon any further pondering, you want to explore getting a set of 0.90/.85 to net a 0.875, suggest you check with Kyle Racing, where our member LDH works.
Kyle Racing carries Ohlins, and I am pretty sure they have a spring that is rated to a 0.88 kg/mm equivalent.
In fact, I think that's LDH starting point selection for 919s and that there's a decent fleet of WristTwister 919s with them, the 88s that is, and some of them are with riders far heavier than you are, or hope to be.

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