track bike build log - Vitpilen 401, 2017-2023 R1 shock swap

Your spring will be binding up as it is too short there is not enough space between the coils for 147mm of travel.
I went with 180mm air gap for oil as 440ml was very stiff causing hydraulic lock up at 3/4 travel.
 
Jester1971 said:
Your spring will be binding up as it is too short there is not enough space between the coils for 147mm of travel.
I went with 180mm air gap for oil as 440ml was very stiff causing hydraulic lock up at 3/4 travel.
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So i was worried about this to, but the napkin math said it was okay

Spring Stroke = Free Length of Spring -(Number of Spiral x Wire Diameter)
Spring Stroke = 300mm - (25 spirals * 4.72) = 182

182-20mm preload = 162mm available stroke?

i was under the impression the stroke was 142mm
1731953673063.jpg


??????
 
In the UK, Brooksuspension.co.uk. I do not know if you can get YSS stuff in US but the part number is shown on the box in the second pic. Yes sorry 142mm of travel. It’s been a long day…..
 
Jester1971 said:
In the UK, Brooksuspension.co.uk. I do not know if you can get YSS stuff in US but the part number is shown on the box in the second pic. Yes sorry 142mm of travel. It’s been a long day…..
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:( no luck from the official us importer. I emailed Brooks today; I couldn't find the fork springs (L0365A0755350X) on the website anymore.

1731962373427.jpg
 
If I were you I would try dropping the oil to say, 160 or 170mm and see if you gain some travel, if you have measured the coil gap and you think it has the room for the 142mm travel the answer could be in the oil volume.
I think Hyperpro springs are progressive not linear. There is a couple of threads on here where others have changed fork springs, one was using Hyperpro. The results vary for these members as they use different approaches and are very different weights, one guy uses cut down springs with spacer like yourself. He reports riding over a log? And does not use all his travel. You could search in the 401 forum, I would post a link but I don’t know how! Not tech savvy.
I am happy with my fork set up even though on paper a 8.5Nm would seem more suitable, my static and rider sag are spot on.
 
Jester1971 said:
If I were you I would try dropping the oil to say, 160 or 170mm and see if you gain some travel, if you have measured the coil gap and you think it has the room for the 142mm travel the answer could be in the oil volume.
I think Hyperpro springs are progressive not linear. There is a couple of threads on here where others have changed fork springs, one was using Hyperpro. The results vary for these members as they use different approaches and are very different weights, one guy uses cut down springs with spacer like yourself. He reports riding over a log? And does not use all his travel. You could search in the 401 forum, I would post a link but I don’t know how! Not tech savvy.
I am happy with my fork set up even though on paper a 8.5Nm would seem more suitable, my static and rider sag are spot on.
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thanks for the input!

- il try 160mm for the oil height and see where that gets me
- I didn't get the hyperpro springs because they were progressive
- I saw the thread with the cut down race tech springs, cutting springs increases the rate, which I didn't want to do, also you lose the ground end. I ended up machining down the diameter of the spring guide and nut assembly
- I think that 7.5 might be perfect, 8.5 is pretty hela stiff

il play with the oil level this weekend and see where I get,
 
boooobc said:
Engine:
- aux air intake sucked, bike ran way to lean, and the FuelX didn't seem to be able to compensate
- revs would hang at 3-3.5k before settling to idle
- need to get a wide band and some data logging to figure out what is happening
- on the plus side, with the mid-pipe delete and fuelX, bike wants to power wheelie in 1st, which is nice
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What do you mean by aux air intake?
 
GeoKrpan said:
What do you mean by aux air intake?
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Ahh okay, maybe you can help, im pretty new to messing with fuel-injected stuff.
After I installed the intake, the bike took a bit to start, but once it started and ran for a while, it seemed auto-tuning. After it got to temperature, the idle would hang like crazy. After you revved and let off the throttle, it would take forever to fall from 3.5k to idle; it also just sounded and felt lean.

is there something I need to be doing with the fuelX,also I've got a mid resonator delete
 
boooobc said:
Ahh okay, maybe you can help, im pretty new to messing with fuel-injected stuff.
After I installed the intake, the bike took a bit to start, but once it started and ran for a while, it seemed auto-tuning. After it got to temperature, the idle would hang like crazy. After you revved and let off the throttle, it would take forever to fall from 3.5k to idle; it also just sounded and felt lean.

is there something I need to be doing with the fuelX,also I've got a mid resonator delete
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You could try an idle ecu reset. Just start your bike but do NOT touch the throttle, let it idle for OVER 15minutes without touching the throttle but NOT MORE than 16 minutes.
This should allow the ecu to self adjust to the fuels.
I did mine for 15.30 on the stopwatch and could hear the rpm rise and fall slightly whilst it had a think.
 
Also maybe if you are going to keep the modded air box lid you could print another lid with just 2 x 25mm small holes instead of the 6 in your design. I know the coober - k&n type open lids are popular mods but I think they allow too much air in. My lid mod has just 2 small holes, just enough to add a small supplement of air to the standard filter. The intake is a 50mm (158 area) round hole yet the end of the snorkel is a 25mm x 35mm (87area) square. The snorkel is restricting the intake air but the standard filter works really well, it just needs a little extra air.
Most people say the bike runs better with the centre muffler left standard. You may need a full ecu if you wish to continue using the mid pipe delete. There are multiple threads on here and KTM forums regarding this.
 
Jester1971 said:
Also maybe if you are going to keep the modded air box lid you could print another lid with just 2 x 25mm small holes instead of the 6 in your design. I know the coober - k&n type open lids are popular mods but I think they allow too much air in. My lid mod has just 2 small holes, just enough to add a small supplement of air to the standard filter. The intake is a 50mm (158 area) round hole yet the end of the snorkel is a 25mm x 35mm (87area) square. The snorkel is restricting the intake air but the standard filter works really well, it just needs a little extra air.
Most people say the bike runs better with the centre muffler left standard. You may need a full ecu if you wish to continue using the mid pipe delete. There are multiple threads on here and KTM forums regarding this
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ahh, okay, I tried the idle reset, I was just curious: what happens if it idles for over 16 minutes?
and for the mid resonator, il try re-installing it, waiting for a dry day were I can play around with all these parts and use a racebox to log acceleration.
 
boooobc said:
View attachment 6261. this thing
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Ahh....your home made aux intake. I think most ppl here have some sort of modded air box intake on their 401,701....to some degree.
I use a DNA filter on my 401 and a grill with a very fine stainless steel mesh behind it on my 701.
Also...would it hurt to bring your 401 back to standard (no fuel controller,etc) for a few days and ride it around then connect your FuelX again and proceed one step at a time........FuelX was working fine originally.
To me it's like PC's.....don't do mass changes then get confused with the funny results.
 
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