KTM 250SX conversion

[Thumper]

I am finally getting serious about the dual purpose conversion of my 2020 2 stroke motocross KTM 250.

I am converting this into a light and agile single track bike. It was set up really stiff for MX racing. I already softened the suspension, retuned the powervalve and carb for a more linear power and, comfortable midrange and low end performance.

Now I added a keyed ignition switch, patched it into the kill switch circuit (off position). In the on position, it powers the DRL, turn signals, brake lights, horn, and a headlight relay (switched).

I got a Polisport headlight with excellent colormatch, orange/white. It has DRL, and I replaced the Halogen bulb with an led high/lo bulb. I found a turn signal/Hi/Lo beam, horn button control set, included in a kit with horn, adjustable delay turn signal flasher. I added the SPST switch by the mirror mount to turn on the headlight relay. I have sequential front turn signals (led), not mounted yet.




The teeny button rear turn signals have running lights, brake lights too.



I did add a Warp 9 adjustable kickstand, rear shock lowering link (about 1 inch), and dropped the front forks to lowest position (maybe a half inch). OK, so the kickstand adds a pound or 2. Gotta have a kickstand!





It's a work in progress, but I need to get this out of the garage to help my son build his new Templar X in a week or so

[Megadan]

Nice work so far. Wiring a bike like that is time consuming and tedious, so I give you some credit. That SPST switch you chose is the exact same switch I used to activate the relay for my spot lights I mounted to my Hawk, and it is a very good switch.

[Thumper]

Originally Posted by Megadan

Nice work so far. Wiring a bike like that is time consuming and tedious, so I give you some credit. That SPST switch you chose is the exact same switch I used to activate the relay for my spot lights I mounted to my Hawk, and it is a very good switch.

Now that I am getting through this project, I can tell that wiring harnesses are built on benchtops where you can pull wire, the right gauge and color(s) and length, and assemble them with all of the tools, fittings, insulation, heat shrink sleeves, and a soldering gun based on known lengths.

Making one on the bike adds some real challenges! Add to that adapting new mounting places for things like non-OEM relays, horn and flasher and you have a lot of slow work. Yes, time consuming and tedious nails it. Working upside down over the rear tire was no fun, fortunatley not much wiring to do there!

If you do this on the bike, take this advice- Don't actually try to connect things while you are doing it. It stresses your fitting connections. Crimp the fittings and label them. Get it all ready, then when everything is ready, connect and assemble

[Megadan]

Originally Posted by Thumper

Now that I am getting through this project, I can tell that wiring harnesses are built on benchtops where you can pull wire, the right gauge and color(s) and length, and assemble them with all of the tools, fittings, insulation, heat shrink sleeves, and a soldering gun based on known lengths.

Making one on the bike adds some real challenges! Add to that adapting new mounting places for things like non-OEM relays, horn and flasher and you have a lot of slow work. Yes, time consuming and tedious nails it. Working upside down over the rear tire was no fun, fortunatley not much wiring to do there!

If you do this on the bike, take this advice- Don't actually try to connect things while you are doing it. It stresses your fitting connections. Crimp the fittings and label them. Get it all ready, then when everything is ready, connect and assemble

I have only built one harness from scratch, and I used the bike to make all of my wiring runs in a rough manner to plan a layout and get my lengths right. I then took it to my work bench and did all of the time consuming parts. The real trick is to make lots of notes for every little thing you think about while doing that initial layout.

Even with doing that, I left a couple of wire ends blank because I wasn't completely sure where I needed to trim due to how the wiring may interfere with other sections once installed.

[Thumper]

Well I got the wiring done and tested. All good, but I need to install a battery. I ordered a battery tray from ebay vendor, and the battery retaining bracket was in 4 photos. I don't need the tray, just the bracket to hold the battery down, but it was included for a low price so I ordered it.

So I received it today, the tray that is, but no bracket.

Gee.

I got a response from the vendor. He said he will "look around". I just asked him to send it. Cripes.

The battery will arrive tomorrow

[Thumper]

Thanks! After making many decisions, and mounting lots of components, I still had to make a blueprint/plan. The controls set has hi/low beam selector, but no on/off switch, so I am using a relay with fused power directly from the battery. But these relays have one channel, so the power still goes back to the switch. It connects relay output to either hi or lo output. I couldn't figure out a way to go straight to the led bulb since this is only one channel. Well, it is at least a relatively low amp led bulb. My small 4.2 amp PS is enough to light both beams, so I decided it will be OK.

The horn button uses no relay, but it also sounds off fully with the low powered PS, and it's not like I will lean on it for more than a split second. The horn works with either polarity-doesnt seem to have a preferred ground.

Dealing with the ground lead for all of the devices was interesting. I am using a 10 gauge wire from the battery, and there is a similar wire to the frame by the cradle. No starter, but the engine has continuity with the frame.

I decided not to add a reg/rec at present, but rather, a tender lead for charging in the garage. I am not sure the stator has sufficient output to handle a charging system. There are aftermarket stators, so I may eventually go there.

I had to buy a battery retainer bracket since this model has the same tray, but comes with no battery, or charging system for that matter! It's an OEM battery retainer, but from eBay (system pull). Fortunately, the tray/cradle is identical to many sub-400cc models. I haven't selected a battery yet. Need to measure the cradle once I get the retainer. Haven't decided whether to go Lead/acid or Lithium. I am pretty sure Lithium is the way to go. I think the OEM battery is Lithium on those other models.

[Aussie_in_MO]

I run that same switch to power my Hella 500's on my Bonneville.
Thumper, would be interested to see your wiring diag for your mods. I have an old DT175 I'm needing to build a minimal harness for at some point in the future. Have some ideas already pulled together but am always looking for more!

[Thumper]

This bike came with no key. It is "on", and will start when you kick start it. It has a kill button that grounds out the "magneto".

I don't have a charging system. What I've built is a standalone/isolated battery operated lighting system. It is grounded to the frame/engine, but I have no regulator/rectifier.

I did install an ignition switch. In the off position, it closes the kill switch circuit. All I had to do there was patch into the exiting kill button wiring. So I can kill it with the button or the ignition switch. I mounted the switch left of carb under the seat. It is close to the kill switch wiring, and on the way between the battery and headset. Made sense:


In the on position, the kill circuit is opened, and 12V goes to the tail light, turn signals, DRL in the headlight ass'y, horn, tail lights, brake light switch (front lever-hydraulic compression switch), the headlight relay, and the headlight switch gets power. When I switch on the headlight switch, the headlight relay is triggered and the headlight turns on, selectable hi/lo beam on the handlebar switch cluster. This way, I get center tail light and DRL draining the battery unless I use the turn signals and when I hit the brake. Activating the headlight relay with the handlebar switch also turns on the running lights (led) in the turn signals. Brake switch lights up the center AND the two turn signal brake lights, even without the headlights turned on. These little button led turn signal lights have running lights (red), brake lights (red), and turn signals (amber), and a ground wire, so there are four wires coming from each one.

If you have a basically intact wiring harness that you can clone, that would definitely be the best way to go about designing a new harness. As you remove it, you can even label each terminal so you know what it connects to while you are building it on the benchtop. My design won't really work.

I might eventually add a reg/rec, but it may need a higher output stator and the ignition module may not be compatible. I don't know how it is wired in a standard harness with a charging system. My battery tray is identical with the models that HAVE a charging system, so I have mounting positions for a reg/rec and whatnot. I am hoping that my isolated battery powered led lighting system is durable enough to keep me legal and safe when I have to be on a (forest) road

I will make a wiring diagram though I don't know the proper way to indicate standard features. It will be interpretable and anyone that wants to add an isolated lighting system will be able to use part, or all of it for their conversion.

[Aussie_in_MO]

Cool. I've got a background in electrical systems and can turn a napkin sketch into something pretty if you'd like!

[Thumper]

Originally Posted by Aussie_in_MO

Cool. I've got a background in electrical systems and can turn a napkin sketch into something pretty if you'd like!

Thanks. I don't have a diagram yet. It is a list of named connections. I'll be able to make a diagram in Powerpoint and PDF it.

[Aussie_in_MO]

Sounds familiar. When I JDM swapped my Impreza the eBay pics showed all the intake system in place but the engine showed up missing a couple of intake pieces which strangely were available from a different seller in the same zip code as the importer I got my engine from.
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