2008 CRF250R - QS138v3 70H - ANT - Sanyo UR18650-RX 20s20p - Votol EM260

[bananu7]

Shock has been serviced and is back on the bike. It's a Frankenstein made from two shocks I gave out for service. I've put the 450cc spring on it which should be about for a 85-95kg rider. I'm lighter but was feeling the rear too soft and the bike constantly felt unbalanced, also partially because of the stiffer front. Now the rear is indeed quite stiff, but the overall balance seems better.



I've also put handlebar extenders on to see how I like the bars being a bit more to the front. They're a bit too long at 55mm, but that's much cheaper than finding a new triple clamp with adjustable clamp locations, though that would be ideal. The current location feels good for standing, there's a lot of space, but the steering feels weird and the increased leverage made it twitchy. Maybe some of that could be remedied by more steering head preload.

 

[bananu7]

Did a small test ride - amazing how much change can be felt from a spring stiffer just by one "size". It definitely sits higher now, definitely puts more weight on the front, which is also helped by the new handlebar location. The handlebar feels weird at slow speeds but it's kinda okay when riding; I think a compromise +30mm location would be ideal; I'll make a set in CAD and get them made, that's still much cheaper than a new triple clamp with offset locations.

Overall the bike feels about even and balanced between front and back now. I did effectively all easy possible changes to make the front softer and the rear firmer and higher, and they all compound together. While I'm glad that I got to this point, I feel that the next step would be to make the front even softer - get 3.8N/mm front springs (or ideally even softer, maybe 3.6, but those are very rare in this size), get softer cartridge springs in (already arrived from the US), and maybe work on the valving even more. The current setup would work great on an MX track, but since I use the bike mostly in enduro, I feel it might be a tad stiff.


Ironically, I'd love to swap the suspension between my rally KTM and the CRF right now. The KTM is exactly plush and comfy for woods riding, but I'm starting to push its limits when I go faster in races. I already run settings at or past "sport" there. The CRF's suspension is definitely a different beast, I wouldn't say it's particularly worse (even though it's 15 years older) but the entire chassis definitely was built with another purpose in mind.

 

[bananu7]

Yesterday I had my first breakdown failure that required a tow home (fortunately, not very far). I was out riding during the weekend, and was doing the usual - mix of fast and technical enduro, some sand riding etc. In a middle of a not particularly steep but quite loose hill climb, my power suddenly cut out. I had similar things happen before, very briefly and intermittently, but a reset always fixed them. Well, not this time. I pushed myself to the top, pressed all the buttons, nothing. Took the phone out, BMS is reporting 10V on cell 19 and 5.5V on cell 20.

Uh oh.

It did also say "severed series connection" though, which i understood as "one of the balance wires broke". I tried to override it in the menu, but no high-level passwords worked and there didn't seem any way to bypass it. The battery was perfectly fine, but the BMS couldn't see that, so he cut the power. I guess, fair, but I'd love to be able to bypass the protection in such a case and treat it as a warning rather than an error.

Back home, we disassembled the pack, which required unglueing the lid. This was mildly annoying but doable with some prying and some knife work. At the very least it confirmed that my choice of polymer adhesive sealer was spot on; it's flexible and sticky enough to keep everything tightly sealed and firmly attached, but soft enough to open out in case the battery needs service.

I didn't take many pics of the repair, my assistant did and I might get them later, since i was fixed on the repair, but the cause of the problem was that the balance wire was attached to a nickel strip that bent over the corner of the battery. This corner, together with the other wires, was rubbing on the enclosure, ripped through the layer of tape I put there for protection, and broke off. We routed the cable through the cell spaces and soldered it to a cell terminal strip directly. Hopefully the other tabs will stay attached for a while longer - I'd love to get rid of this battery (likely together with the rest of the bike minus my suspension) and build a new build with a new battery, likely larger.

The battery ran fine after the fix, although it's only held close by duct tape right now.

 

[harrisonpatm]

This happened to me once as well (loose balance connector), and it's a scary thing to open your BMS app and see a cell voltage reading 10V. Obviously an error, but when you see it in the heat of the moment, you're sure the pack is about to catch fire

 

[bananu7]

Yeah, my first instinct was "oh shit" especially when it happened when i was pulling max power (around 20kW at the time). But once I looked at the temps which were all below 30C and saw the warning text I figured that would totally fit something silly like that. I had the advantage of seeing this before because two wires were broken when i received the package with the battery internals.

Edit: Oh, and I completely forgot to mention, I finally got my "bike programming laptop" and took it with me. Just before the trip, i disabled soft start on the regular mode. This made it absolutely miles ahead better in lifting the front, but suddenly i wasn't getting any traction. All the nice crawl-ability i had mostly disappeared.

As a fix, I tried a different approach. Instead of turning the slow start back again, I reduced the power on both modes, to 120A on regular and either 150 or 200A in sport (can't remember now). This still kept the bike quick to accelerate and much more responsive, but dialed the torque back to reasonable levels. What I really need is a phase-current-per-level or even more complex torque curves, but I know that I won't get this with this controller. It's really a freaking shame they won't just release the firmware source code. We'd have a custom build and a full ecosystem of tunes, tools and tutorials in a matter of days, probably tripling their sales... For now, I guess I'll just plan the next build with a 96V fardriver.

 

[bananu7]

I decided to tackle the traction issues:



The same shop that I got the front wheel from suddenly had the 18" rear in stock. Score! Later on I've realized that this particular wheelset was put in Chinese Barton NXT300. They copied the CRF's dimensions 1:1, but laced 18" rear by default, which I'm very happy about. The wheels are dirt cheap and the front has been holding up fine, so I decided to give the rear a try. I wanted more rubber for more grip, softer compound for more stickiness and more balloon to absorb hits (I'm sure @neptronix will love this sizing). This is a 120/100-18, which comes out slightly larger than my 110/100-19 in overall dimensions, but with radically different rubber-to-rim ratio. I checked with my spare swingarm and it should fit just fine. It's a MH tyre (medium-hard surfaces) but with soft rubber and light carcass, so it should be perfect for the local singletracks with a lot of roots, as well as climbs over leaves and the like.

Weight wise the entire wheel is 10.5kg, the tyre is about 5.6, the wheel about 4kg. The entire tubliss system is surprisingly heavy and it might save weight but only compared to an UHD 4mm+ tube.

I decided to take another experiment and put a Tubliss inside. I actually did that on a live stream, but I talked in Polish, so probably not as interesting for most folks here. Long story short, it took me about 1h40m to get the tubliss on the rim with prep, about 10 minutes to mount the tyre and about 5 to pump everything together and do a check. I assembled it dry and predictably it started to leak, so I just added some latex sealant. After 5 minutes it seemed fine, so I left it overnight. In the morning didn't seem to lose any pressure, so I'm calling it good. I plan to start using it at about 0.8 bar (11 psi) which is at the upper end of the recommended pressures, and see at which point I'll start to notice problems in cornering.

Now fingers crossed for chain clearance

 

[j bjork]

In the tubeliss instructions I have it says that you should spray on lots of soapwater between the tire and rim before pumping air in it.
That is what I have done, it has never leaked for me. Well, it has leaked several times, but trough the tire every time.
Nice with new wheels, your old ones didn't seem great
Hope the quality is decent, but I guess time will tell.

 

[bananu7]

In the tubeliss instructions I have it says that you should spray on lots of soapwater between the tire and rim before pumping air in it.
That is what I have done, it has never leaked for me. Well, it has leaked several times, but trough the tire every time.
Nice with new wheels, your old ones didn't seem great
Hope the quality is decent, but I guess time will tell.

Tubliss has an alternate set of instructions if you plan to use sealant. In that case, you don't use soapy water as that apparently causes problems for the sealant. Instead, the sealant is spread over sealing surfaces and added into the tyre just like with MTB. I did that after initial leak was discovered and it seems solid since.

As for the wheels, I know it's a gamble; worst case if they start bending I'll just reuse the hubs (which are pretty nice) and relace real rims on them, but so far the front has shown no signs of problems.

 

[Balgaroth]

Unless you plan on riding fast paced enduro or MX don't bother at 0.8bar, got for 0.6 and below. If you low hill climbs, getting stuck and all that good stuff you will love tubliss. On my 125exc I ride with 3psi of pressure, grip for days !

 

[bananu7]

I ended up going down to about 0.5-0.6 and the traction is indeed fantastic. The added rubber also massively improves suspension performance.

In the 2nd ride of this season, I had a very nasty accident. We ride a lot through the trees, and there's a lot of loose branches. As you know, I still use a cable throttle. So, what I think happened, on a downhill a branch snatched on my cable and pulled it out of the housing. I closed it on the bar but the cable was still pulled (and i only have one cable, not two), which launched me up in the air and back. I fell on my butt, the bike fell on its tail and collapsed to the side on my foot.

I managed to get the mudguard back (not broken thanks to being held by zipties only!), but the subframe is severely bent. Back home I also noticed this:




That's certainly an easy way to spend 600 eur right at the start of the season... The boot did its job though; my foot had just a bruise on a toe and I was fine otherwise. I also immediately ordered a new subframe, but there's way more subframes for 06-07 bikes which had dual rear pipes, and supposedly the subframe has a slightly different shape. Normally I wouldn't care, but I'm a bit concerned that my airbox mould won't fit it. I should have it here soon so I'll be able to check and make decisions. A new subframe is like 40 eur, while my airbox mould costs ... a lot ... in time and materials. So another option might be to make a different design for the other subframe and buy another one for bike two. Yet another is to try to straighten my original one.

 

[adsc]

Makes me wonder if I should utilise my second throttle cable.

But then again, I'm not going to ride through the woods with a Kawasaki VN 800 Classic.

 

[bananu7]

if I should utilise my second throttle cable.

For what it's worth, I've been riding for a good while and it's the first time this happened. I'm still tempted to try an electronic throttle though, if only to see if I like the feel.

I received my subframe already and while the frame mounting points seem identical, it has a completely different shape and lacks the airbox mounting tabs. No go

And after scouring local postings, seems everyone is only selling 2006+ (dual exhaust) subframes. Not a single one of 03-05. I knew I should've bought one when they were for sale. I guess straightening it is my only option.

Well, actually, there's one more option that I've been pondering. Since i'm already planning for a dedicated custom airbox mount, why not go to the next step and just make a monocoque subframe/box? That's a solid $4000 part in the aftermarket...

I think it'd be too hard of a project for now though. I'll reserve this option for later, once I can prove i can actually manufacture simpler parts, and in the meantime I'll try my new torch on the subframe and see if heating it up a bit makes it a bit easier to straighten...

 

[AdamNoel]

On my electric dirt bike, I have a domino potentiometer throttle and it feels amazing! It's a bit expensive but, it's worth it.

 

[Dui ni shuo de dui]

Makes me wonder if I should utilise my second throttle cable.

But then again, I'm not going to ride through the woods with a Kawasaki VN 800 Classic.

You're way more likely to have issues with any other kind of throttle setup, it's by far the safest.
No system is 100% reliable in every circumstances.

 

[bananu7]

So, I did some thinking.
* The old subframe is really strong, and i can't imagine bending it back myself. Even aimed with a MAP torch, i couldn't get it to anything close to bendable. I might give it out to a metalworking shop to let someone else try, but for now that's unusable.
* The new subframe design is honestly much better. It's symmetrical, smaller profile, simpler shape. And that gave me an idea:



I already had a 2008 fender i bought as a mistake when i thought my bike was 2008MY. It fits the new subframe perfectly, and the subframe fits the main frame. The seat doesn't exactly rest on the reinforcement but it stays on the side rails with enough area to not make me concerned; worst case I can get a newer seat pan.

I scanned both parts and put it all in a Blender mockup. I think this sort of design is much more workable than a dedicated "box" shape. The yellow part in this screenshot is just two flat planes bent in an L shape. All that would need would be some side skirts to hold on to the subframe and extension to the fender. The sides can stay open, as I wanted side fairings anyway. Speaking of...



A rought draft confirms that this would be quite a simple, flat-ish shape. Yes, it would be large, but I'm less afraid of the size and more of the complex curves and multipart molds - this would effectively be a 2.5D relief. And I could add the top middle part over the battery to be joined to the sides, which would give me wiggle room if the battery ever changes shape.

I still want to do the airbox and finish the #2 first, but unfortunately right now I have two half-complete bikes. I might put the straight subframe from #2 on the #1 just to get some training practice before the upcoming rally, but the current plan is to put the #2 with the airbox and OEM fairings, and make an entirely new design for the #1. I already started looking for another 2008 subframe to have a spare for when i bend this one. I kinda like it at least in the sense that now if/when I decide to buy another conversion base, I'll have CAD files for year ranges spanning 2004-2008, which makes it easier to find donor bikes.

For the final shape of this fairing, I want to use Plasticity, as that software is really much better suited for such organic shapes. I want to make most of the pattern by 2d-printing sections, cutting them from PVC sheets, glueing my PUR foam blocks in the middle and shaping by hand to match the curve. For the most crucial mounting points I'll 3D-print sections I'll embed and blend in with the foam, then cover everything with PCP and use uni-mould again to get the mould from it all. And of course I'll need to do it twice, for quite a large shape. I'm not counting materials cost here because I still consider this a learning opportunity...

Any and all tips and suggestions welcome as always.

 

[bananu7]

I did some more doodling, and finally bought Plasticity. This software is such a joy to use, but the further i got the more i realized i need more reference features. Having the old fairing at hand helped a lot (I don't have 2008 fairings though) to understand how it should fit, but i still need a seat scan to confirm the line underneath the seat that will make sure it won't flop around.



The part that looked very hard, i.e. interfacing the mudguard, was actually really easy:



I'm still focused on getting the #2 running first (and actually this one running as well) but since this i can do in the comfort of my PC, i just sneak in a couple minutes whenever i can.