NX250 fork spring mods

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scrambler
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NX250 fork spring mods

Beitrag von scrambler »

Unlike the rear shock, the front fork isn’t too bad – at least with an rider of average weight. The main downsize is too much negative suspension travel (or "sag") with the side effect that the NX is pretty unstable on the kickstand and easily tips over. The sag is measured with the rider sitting on the bike – in my case with a stock fork its 7cm or 34% of the total way of travel. Too much – usually something between 20 and 30 % is recommended.

The fork of the NX250 sags so deeply because the short top springs are so soft. These are very unusual for Honda forks, otherwise rigid spacers are used. My guess is that the only purpose of the top springs is to lower the fork.

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So I tried a couple of aftermarket fork springs. Remarkable: none of them have the same length as the stock springs. It looks like that, even though the manufactors claim that the springs were specifically made for the NX250, they were taken from some other bike.
Negative consequences: the aftermarket springs are either too long or too short, so you have to either made some spacers or use massive force to screw in the fork plugs.

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No wonder that almost all of the (expensive) aftermarket springs are not really much of an improvement – White Power and Promoto are still too soft and Wirths are way too hard. Maybe the Wirths work better with a riders weight of more than 100kg – but I haven’t tried that.
The best of the bunch i.m.o are the Hyperpro https://www.ebay.de/itm/KIT-MOLLE-FORCE ... SwPAlcnOBU, but they are also the most expensive. They work pretty well even at higher off-road speed. The hyperpros came with 25 grade fork oil, the others with 15 oil, if I remember correctly.

Since I was pretty disappointed with the aftermarket parts I was looking for an affordable alternative and stumbled over these adjustable fork plugs https://www.ebay.de/itm/1-Pair-37mm-CNC ... Swj61cg3c7 . With those the sag can be adjusted between 19 and 29%. It works even (with 15 grade fork oil) better when the short top springs are replaced with 8.5cm (~ 3.5'') long spacers (thickwalled aluminium, outside diameter of 1 1/4''
or 32mm). A length of 70mm is sufficient for lighter riders

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jonathan
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Re: NX250 fork spring mods

Beitrag von jonathan »

I fitted a pair of preload adjusters to my AX1 but haven't set anything up yet as the bike is still in bits. Only had a relatively short ride (50Km) on the road after buying the bike, before I decided to strip it down, but in that short time I figured the front end was soft, but really compliant. The previous owner had fitted a hagon shock and the preload was way too much, so the bike felt like it was pitched forward....in his defense, he said he'd only just installed it and hadn't played around with the settings.
Zigomatix
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Re: NX250 fork spring mods

Beitrag von Zigomatix »

Hi Michael,
I would like to enhard the NX250 fork spring and plan to add spacers into my fork but, I assume that the 8.5 cm are for the AX1, it has short top spring that the NX doesn't.
On the picture I measure that the top springs are 7 cm long. That would mean 1.5 cm spacers (to reach the 8.5 total).
On the orther side I doubt 1.5 spacers would change anything.
I think I will try 5 cm at first and see how it goes ...
What do you think ?
Thanks.
Patrick
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scrambler
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Re: NX250 fork spring mods

Beitrag von scrambler »

Zigomatix hat geschrieben: Mo Sep 28, 2020 4:31 pm I would like to enhard the NX250 fork spring and plan to add spacers into my fork but, I assume that the 8.5 cm are for the AX1, it has short top spring that the NX doesn't.
The NX250 has also these little springs on top - otherwise you alread have aftermarket springs in your fork.
Zigomatix hat geschrieben: Mo Sep 28, 2020 4:31 pm On the picture I measure that the top springs are 7 cm long. That would mean 1.5 cm spacers (to reach the 8.5 total).
On the orther side I doubt 1.5 spacers would change anything.
I think I will try 5 cm at first and see how it goes ...
What do you think ?
Thanks.
Patrick
That depends on your weight and whether you like a soft or a firm suspension. You have to try - but 1,5cm is not much if you feel that the suspension is way too soft. By the way I I could offer you adjustable fork plugs plus 8,5cm spacers for 20€ ;)
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Zigomatix
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Re: NX250 fork spring mods

Beitrag von Zigomatix »

scrambler hat geschrieben: Di Sep 29, 2020 7:44 am The NX250 has also these little springs on top - otherwise you alread have aftermarket springs in your fork.
Well, I did change fork oil last spring and did not find those litle springs in my fork. So I hope you are right because the orther solution is that those springs were lost !
Do you remember how long are the original long springs ? (So I can identify if they are Honda's or not)
scrambler hat geschrieben: Di Sep 29, 2020 7:44 am That depends on your weight and whether you like a soft or a firm suspension. You have to try - but 1,5cm is not much if you feel that the suspension is way too soft. By the way I I could offer you adjustable fork plugs plus 8,5cm spacers for 20€ ;)
I like firm suspension. And I will use it mostly on road. I weight 74 kg (good days :D ).
I am interested in your offer, how much would be shipping to France ?

By the way I don't have the plate, spring joint 51403-463-003 neither.
But, with the spacer, they might not be needed.

Thanks
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scrambler
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Re: NX250 fork spring mods

Beitrag von scrambler »

Zigomatix hat geschrieben: Di Sep 29, 2020 10:57 am Well, I did change fork oil last spring and did not find those litle springs in my fork. So I hope you are right because the orther solution is that those springs were lost !
Do you remember how long are the original long springs ? (So I can identify if they are Honda's or not)
maybe a former owner placed them on the bottom? usually they are on top and 7.5cm long
Zigomatix hat geschrieben: Di Sep 29, 2020 10:57 am By the way I don't have the plate, spring joint 51403-463-003 neither.
But, with the spacer, they might not be needed.
right, with the spacers those spacers are not necessary, the spacers are thick enough.
Shipping to france would be 9€
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Zigomatix
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Re: NX250 fork spring mods

Beitrag von Zigomatix »

scrambler hat geschrieben: Di Sep 29, 2020 2:32 pm maybe a former owner placed them on the bottom? usually they are on top and 7.5cm long
I hope that the long springs are longer than 7,5 cm :D
That was my question Michael, how long are the long springs ? (do you remember that ?)

I will look at the bottom of my fork see if I find the short ones but I doubt.

29 €, that would be OK for me. I will contact you PM
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scrambler
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Re: NX250 fork spring mods

Beitrag von scrambler »

sorry, my mistake. I don't have the length of the long springs, but with stock springs it should look like this - the top end of the spring about 1cm below the top of the thread. The 8,5cm spacers make only sense with the origional springs - with aftermarket springs the spacers are way too long.
NX250_fork_springs.jpg
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Zigomatix
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Re: NX250 fork spring mods

Beitrag von Zigomatix »

Ok then I think (and hope) you are right, short springs must have been inserted first, because I rememeber it looks like that.
I will check this out this week end.

Thanks, Patrick
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scrambler
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Re: NX250 fork spring mods

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Zigomatix hat geschrieben: Mi Sep 30, 2020 8:35 am
If I put spacers I have to remove the short springs, right ?
right - otherwise the 8,5cm spacers are way too long. At most you get 2-3cm spacers (with longer spaces its easy to ruin the threads of the fork plugs) with the short springs - which is also ok for a better suspension
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