2003ish F650CS Custom Build


I’m in the process of rebuilding a F650CS/GS. I priced it all out and it seems like it’ll be cheaper than just buying a BMW F650GS Dakar (I used to own one). They’ve shot up in price, sometimes over $4,000+ in my area. Which sucks, I bought mine fully decked out in Touratech gear for $3,000 back in 2016.

Anyway I got a F650CS frame and F650GS sub frame for $200. Slowly collecting parts to make it a rolling chassis. I’m planning on using the F650CS swing arm since I don’t want to weld too much. I’m wanting to run a custom ECU to have more control over this single cylinder engine. I stumbled across NanoEFI, which sounds amazing and perfect for my application. Trying to find a motorsports ECU that supports a single cylinder is such a pain in the ass. I know that no one has done something like this with the F650CS/GS.

But I hate when people tell me, “its not cost effective” or “Get another motorcycle” or “Lol noob”.
Well I’ll be documenting the build in different places but I’m going to be watching this project like a hawk.

Thanks guys!

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I hear ya Squishy. It seems like during the pandemic, or maybe because summer or maybe both, bike prices are going up pretty fast for lots of different bikes.

You’re in good company and I wouldn’t expect anyone to try to dissuade you from your project here. Given Travis’s goals, I think you’ll be pleasantly surprised at the output cost!

At any rate, welcome to the forum. I think we’d all love to see some pictures of your progress, feel free to post 'em in here, or at least link us to your work.

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I sure will post the progress here. It seems like people will be more open to it than lets say the advrider forums.

Oh for sure. This community is here because they are tired of carbs or they are at least interested in EFI. I wouldn’t expect anyone to try to shout down your aspirations.

Since I don’t want to start another topic (someone can move this into the correct category), I’ll just do my build progress here since apparently this “isn’t cost effective” or “Lol, just buy one” on other forums. Which literally isn’t the point.

Well the F650CS frame came in. I’m gonna see if the F650GS sub frame fits. Might as well try. The Subframe was only $50 so it won’t be a total loss. Still trying to find a F650CS engine that won’t cost me and arm and a leg.

Alas, it looks like I’ll have to buy a F650CS subframe:

Actually this is the exact right thread to post your build progress.

You’re really starting from scratch on this eh? Looking forward to seeing it come together!

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Hell yeah from scratch! I really want to customize this bike. I want the frame and fairings to be stock but I’ll be putting in a LCD display and want full control over the engine and sensors on everything. Hence why I’m glad I found NanoEFI.
I’d love to turbo this thing. I know people say not to turbo motorcycles but ehhhh, why not? We’ll see if I get that far, for now it’s working on getting a rolling chassis.

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I don’t see why not to turbo the bike. If the engine can handle it and you have room for it, i think it makes sense as a power adder.

I think if your internals are strong enough (forged crank, forged rods, sufficient oil pressure, sufficient oil supply to feed the turbo additionally, piston cooling, ring lands, etc, etc, etc. Much of this could be bought or made), it’s largely a matter of boost vs chamber compression ratio.

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Well its been awhile but I’ve officially confirmed that a F650GS subframe only fits on a F650GS Frame and the F650CS Subframe only fits on a F650CS Frame. Now I have two frames I need to get titled in my state. This wasn’t too bad I only paid $120ish shipped for the F650GS Dakar frame and its even straight! Still working on getting a rolling frame at least. Money is tight right now so I’m not progressing as fast as I would like.


Nothing wrong with starting from scratch.
Knowing the ins and outs of the bike, and also the satisfaction of building it how you want it.

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Thank you! Yeah people on other forums would scoff at the idea but I also really want more control over the tuning. Would love to use the NanoEFI for tuning the engine and planning on using a MotoGadget for the lights and stuff.
I used to have a 2003 BMW F650GS Dakar but it ended up getting squished up against a garage door and a vehicle and being totaled.

That’s a bummer mate.
I have the same plan too, only mine is a Honda XR400.

Welcome @SquishyMoto! :wave:

Wow, username checks out for sure.

Built, not bought! Right on :metal:

If you have a few minutes to track down any technical documents for your engine, post links and I’ll take a look.

As usual the first thing we’re looking for is electrical/charging capacity at idle, to see what kind of power is available for the fuel pump.

Then we want to find a good source of trigger with (or without) a sensor.

Free thinkers with the talent to back it up are welcome here, we’re glad to have you.

I can find out exactly. I’ll see if the repair manual (its on a DVD) from BMW has any information about that. It should, its very comprehensive.

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If you can, post the relevant manual pages (or a link to some collection of them) here in your thread.

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