Skorpion 660 Lightweight Build

[breakwellmz]

Talking of weight reduction, i took the standard Mastiff exhaust off today.... What a lump! 14 pounds! What will replace it is 6 pounds, and that is still a stainless system.

[jpmsteadi]

The above strange spam sneaker posts are strange, but here is a little update.


I went through some doubting times of what to do bodywork wise on the skorpion. I have decided for the time being to just keep the stock side panels on and work around them in the design. the last couple of days i have done a talilight that used my lighter LED tail light and looks fairly good. there will be another revision at some point, but I'm happy enough to ride around with it for now.

after riding a couple hundred miles the RSC clutch lever is fantastic and will stay. It will be de-anodized and silver when the solution comes in to do so. But, with the changes leverage ratio the clutch pull is so light and nice. Still can get full engagement and disengagement.

Some of the titanium is starting to drift in as well: some brake bolts, a steering stem nut, etc.

I have ordered a CDI conversion box to get a hotter spark and an adjustable spark advance, as well as a slightly higher redline than the stock box.

The thing I am most excited about is the FCR I ordered last night. To those unaware, the Kleihn FCR is the pinnacle of carb development before everything started going FI. Incredible adjustable, so smooth, and light pull. It is a flat slide carb with an accelerator pump. I have one on my DR650 and it completely transformed the bike: super smooth roll on throttle, extremely responsive, and just the feeling of more power everywhere. Honestly it feels better than most of the FI bikes I've ridden with the exception of some of the newer triumphs. I ordered one that was on a WR450 from 2003-2006. It has a 39mm throat, swivel fuel input, and throttle position sensor (TPS). With the CDI box I am getting I should be able to take in the TPS reading and add additional spark advance in part load scenarios, giving better fuel economy and smoother, crisper part throttle response. In addition the FCR39 off o the WR450 has an air cut valve that adds a tiny bit of fuel during overrun situations to reduce the popping in the exhaust. A very nice feature.

Ideally I would have gotten the FCR 41 I think, as the skorpion motor can flow a lot of air at higher RPMs, but the 39s are much much cheaper and easier to come by and should do the job just fine. If I were to do a big bore or high comp piston with hot cams it might start not flowing enough, but that isn't in the plan..... yet....

[jpmsteadi]

A couple more pictures:

[DAVID THOMPSON]

need a device to make the cable pull further your not getting a full pull on the cable..

that lever needs to be straight so it can pull more cable

[jpmsteadi]

need a device to make the cable pull further your not getting a full pull on the cable..

that lever needs to be straight so it can pull more cable

David, which cable are you referencing?

[DAVID THOMPSON]

the clutch cable attached to that lever with the bend in it that hits the handle bar before
the clutch releases

[Puffs]

That bend probably fits the rest of that outfit & is not likely a problem. Levers bent like that are quite common, as are shortened levers in offroad.

It's unlikely, but any chance on a quickshifter for the 660?

[jpmsteadi]

the clutch cable attached to that lever with the bend in it that hits the handle bar before
the clutch releases

David,

The clutch releases perfectly. No issues with anything hitting.

[jpmsteadi]

That bend probably fits the rest of that outfit & is not likely a problem. Levers bent like that are quite common, as are shortened levers in offroad.

It's unlikely, but any chance on a quickshifter for the 660?

It seems like a quickshifter is very possible with the CDI. I plan to play around with it, though it is not on the high priority list.

[Puffs]

Thanks, then UP should be doable, but DOWN might remain a problem (need an ECU?). Of course UP is most desirable, yet I understand it's not on your high priority list.

The question on the clutch handle reminded me of the Svartpilen I rode a few weeks back, which has the KTM 690 engine and a quickshifter.

[jpmsteadi]

Thanks, then UP should be doable, but DOWN might remain a problem (need an ECU?). Of course UP is most desirable, yet I understand it's not on your high priority list.

The question on the clutch handle reminded me of the Svartpilen I rode a few weeks back, which has the KTM 690 engine and a quickshifter.

The svartpilen is a strange looking bike. Doesn't seem like it would be particularly comfortable. I sat on one at a dealer at one point and was kinda cramped and hunched over. What did you think of it?

And I think you are right. I would imagine you would need some sort of ecu and electronically controlled throttle to blip the engine for downshifts? but maybe not. It will certainly be something to play with.

[jpmsteadi]

I got in the FCR carb on monday. Unfortunately it was in much worse shape that I had anticipated, so I have ordered some replacement seals and parts. Thankfully a friend of mine has an ultrasonic cleaner that I was able to dunk it in for a couple of hours.

I started the process of test fitting and designing an intake manifold in cad. The second one fit pretty well and the carb fits well in the space. I think I can keep the stock airbox too!

This is a view into the intake. Forgive the strings and the steps in the curves; this was printed in the fast settings just as a test.

[Puffs]

On the Svartpilen, I didn't feel cramped, but seating-wise I'd prefer the Vitpilen, with the lower bars. And also the white colour scheme looks better, though of course for both bikes the style remains an acquired taste (which I have yet to acquire). Riding-wise it's OK, though your feet are a bit low & maybe it's a bit heavy its power (161kg dry, 75HP, 72Nm). It that sense the 690 was better (148.5kg dry, 147 for the SM).

On your intake manifold: I should consider to get myself a 3d printer - that looks very desirable! (Is that plastic strong enough to carry the carb & can it withstand the temperature?)
But there is a choice to be made on the design of the manifold. Yes, if you keep the length low enough, you can use the original air box, un-modified (and that is desirable). But it seems that the price you pay is that the gas flow has to make rather sudden changes of direction. Yes you will round that off nicely, but still: that will cost power.
If you were to make the manifold longer, the flow should be better - but then the air box needs to be modified (and probably become smaller). That too is less desirable.
Anyway, that's the choice, IMO. And to test the impact of the different manifold designs is not so easy either, at least not with an air box.

[jpmsteadi]

On the Svartpilen, I didn't feel cramped, but seating-wise I'd prefer the Vitpilen, with the lower bars. And also the white colour scheme looks better, though of course for both bikes the style remains an acquired taste (which I have yet to acquire). Riding-wise it's OK, though your feet are a bit low & maybe it's a bit heavy its power (161kg dry, 75HP, 72Nm). It that sense the 690 was better (148.5kg dry, 147 for the SM).

On your intake manifold: I should consider to get myself a 3d printer - that looks very desirable! (Is that plastic strong enough to carry the carb & can it withstand the temperature?)
But there is a choice to be made on the design of the manifold. Yes, if you keep the length low enough, you can use the original air box, un-modified (and that is desirable). But it seems that the price you pay is that the gas flow has to make rather sudden changes of direction. Yes you will round that off nicely, but still: that will cost power.
If you were to make the manifold longer, the flow should be better - but then the air box needs to be modified (and probably become smaller). That too is less desirable.
Anyway, that's the choice, IMO. And to test the impact of the different manifold designs is not so easy either, at least not with an air box.

I also have not acquired the taste to enjoy those bikes.

I completely agree on the longer manifold with longer runners. One of the fun parts about 3d printing is being able to make new parts and change them so easily. My goal right now is to see how little stock things I can change, but once I see how it runs I am very tempted to throw out the airbox and make one of those as well, allowing for longer runners. There will be a point at which the runner length is optimal. I agree that currently it seems that the runners are too short and too oblique of an angle for optimized airflow at higher RPMs. That beings said, I may have less airflow anyway at higher RPM full throttle by going to a single carb; I am almost certain that the two smaller carbs have a larger overall opening than one carb. So, if I gain some low end power through intake velocity with the new carb and slightly restrictive intake, I might be willing to make that trade. But honestly in this situation I only know enough to be dangerous.

As for the plastic, these test fit pieces are being printed in PLA which absolutely does not have the strength or temp resistance, but for the final (ish) print I am going to be using Nylon, which should do nicely in this application. if the part works really well and there are other people who are interested in doing this conversion I may do a CNC run of the part. Not really cost effective for a one off, but if you get 5-10 parts made its not too bad really. A friend of mine is doing a similar lightweight street bike build but with a late 80s honda hawk and has used a machine shop to do some adapter brackets for a different front brake caliper (ironically basically the same caliper that comes stock on the MZ, just the slightly later brembo model)

[breakwellmz]

Love your 3D manifold jpmsteadi brilliant! What does the engine side look like?
You can get 3D printing done in metals as you probably know, check this out -
https://www.3d-alchemy.co.uk/3d-printing-metals.html