Interchange Fork Tubes - Wrist Twisters
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post #1 of 11 Old 05-16-2018, 06:39 AM Thread Starter
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Interchange Fork Tubes

Hey guys,

I bent my fork tubes awhile ago and sent them out to someone who thought they could straighten them. It didn't work out, so they were going to replace them with f4i fork tubes. He says he did it, but not sure if that's true or not.

I wanted to make sure this was kosher and tried digging around here. I found one thread that mentioned they were not interchangeable because of a different bushing location. Does anyone have any supporting info on this, or any other reasons this won't work?

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post #2 of 11 Old 05-16-2018, 11:21 AM
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Partsfish.com has Honda parts fiche. Look up the 919 and F4i part numbers. Best way I know to compare if they are identical or not.

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post #3 of 11 Old 05-16-2018, 01:46 PM
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Quote:
Originally Posted by HondaJim View Post
Partsfish.com has Honda parts fiche. Look up the 919 and F4i part numbers. Best way I know to compare if they are identical or not.

Honda uses different part#'s for all their parts even the ones that are 100% identical and used on more than one model. They want to be able to track unique model sales.
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post #4 of 11 Old 05-16-2018, 05:03 PM Thread Starter
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I did check bike bandit prior to posting. Hoping someone that has done the f4i swap or something can say.. or someone can find the thread where this was discussed in more detail. I tried for awhile and gave up.

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post #5 of 11 Old 05-16-2018, 09:30 PM
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At that point, you've done 1/2 a swap... why not just do a full swap?

I guess the brakes and fender are maybe different, but it's just outside housing that's the same, so take the whole f4i forks?

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post #6 of 11 Old 05-17-2018, 12:04 AM
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Quote:
Originally Posted by LDH View Post
Quote:
Originally Posted by HondaJim View Post
Partsfish.com has Honda parts fiche. Look up the 919 and F4i part numbers. Best way I know to compare if they are identical or not.

Honda uses different part#'s for all their parts even the ones that are 100% identical and used on more than one model. They want to be able to track unique model sales.
That's very interesting and makes perfect sense. I had noticed this and wondered why. Thanks for the education.

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post #7 of 11 Old 05-17-2018, 06:11 AM Thread Starter
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Quote:
Originally Posted by KarlJay View Post
At that point, you've done 1/2 a swap... why not just do a full swap?

I guess the brakes and fender are maybe different, but it's just outside housing that's the same, so take the whole f4i forks?
well, it's a long story. I didn't want to have to worry about fitting the f4i fender for one, or the cost of f4i forks. I heard of Will's Rim Repair straightening forks and thought I'd give it a go. He couldn't save the one but thought a 2002 f4i tube could be used. then he dissappeared for almost 2 months.. had flooding issues at the shop and family stuff. now he says I have 2 straight legs with new seals, but never responded to say he shipped them so who knows.

but you're right, if this doesn't work i should just buy a set of f4i forks off him and have him send back the racetech springs from my set up so i can pass them on to one of you guys.
i think with the f4i forks spacers and everything transfer over from the 919 just need to make a bracket for the fender.

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post #8 of 11 Old 05-17-2018, 06:44 AM
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As long as both were changed to f4i tubes it _might_ be okay. I looked at replacement tubes from tnk, and found the lengths of the tubes are indeed different. F4i is 587mm, and 919 is 615mm. Bushing placement may further impact how far they can extend.

They other concern I would have with a shorter tube is having the damper rod bottom out on the compression valve. Maybe check with the shop to ensure they check the forks through their full travel to ensure there is no interference.

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post #9 of 11 Old 05-21-2018, 10:25 AM Thread Starter
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He said they were 1" shorter now. I didn't want to mess with the geometry like that, so he's sending me some f4i forks. Guess i'll have to come up with some kind of bracket.

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post #10 of 11 Old 05-21-2018, 11:52 AM
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Quote:
Originally Posted by CKutz_GO View Post
He said they were 1" shorter now. I didn't want to mess with the geometry like that, so he's sending me some f4i forks. Guess i'll have to come up with some kind of bracket.
For sure, 919 tubes can not be grafted into F4i fork legs.
Due to bushing zone mismatch to start with.
I assume the reverse also holds true.

Further.
If the above respective F4i and 919 fork tube lengths are correct, or even in the zone of reasonable accuracy, then ponder the fact that both bikes have fork legs of very similar length, and the free length of a stock F4i is only about 5 mm shorter than that of a 919.

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post #11 of 11 Old 06-13-2018, 06:05 PM Thread Starter
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hey guys,
i've got my f4i forks and have .95 springs for them. The invoice from traxxion dynamics mentions 140mm oil height and 11 mm preload. I think they precut the spacers for the preload. In my searches here i see 125 mm oil height recommended but wasn't sure if what traxxion gave me is the height for f4i forks on an f4i or a special height for f4i on 919 as i told them i was doing. what are you guys setting f4i forks oil level at? Or doesn't the bike matter and just set it to the f4i recomended level?
Also, 7 weight oil?

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post #12 of 11 Old 06-13-2018, 06:14 PM Thread Starter
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so i've got the f4i forks and was just trying to see how you guys were setting them up. Got my springs from Traxxion dynamics and their invoice says 140 mm oil height and 11 mm preload. i think the spacers are precut. With the oil height i wasn't sure if they were basing that on f4i forks on an f4i or for my application on a 919. maybe it doesn't matter. What oil level did you f4i guys go with? and 7 weight oil? i saw 125mm mentioned here and there but i think that was for the 919 forks.

also, is it normal for the f4i fork caps to not really fit through the triple clamps? I went to slide these in and it was a pretty snug fit. didn't see that mentioned anywhere so it concerned me a little.

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