Skorpion 660 Lightweight Build

[breakwellmz]

Turning some spacers today. Started with replacing the 3d printed rear upper shock mount spacers out of some 6061 aluminum. Still very light, but no longer quite a limited lifespan.

Before (with one spacer in):

IMG_20200817_085528.jpg

The spacers:

IMG_20200817_085518.jpg

With spacers installed:

IMG_20200817_090820.jpg

All going well then.
I`d have gone for brass spacers myself.
Loads of adjust-ability in the new fork setup but well over-sprung i assume?

[jpmsteadi]

I assume it is oversrpung as well, but I am going to ride it before ordering new springs. I was also thinking about the rake angle of the two bikes, the R6 is much closer to vertical, so perhaps the addition of rake angle will make the fork springs closer to right (given that a smaller proportion of the spring is acting against gravity? I am no suspension expert, but I am going to ride it some before shooting wildly into the dark at a spring rate guess.

[breakwellmz]

Your head angle hasn`t changed on the MZ unless the forks are a lot shorter making it steeper. Will the MZ springs fit, can you compare the spring rates?

[Puffs]

This link might be useful: https://www.thespringstore.com/spring-r ... lator.html

[jpmsteadi]

Right, the head angle hasn't changed for the MZ, but the head angle is certainly more than the R6 is, which is what the springs in the r6 forks are sprung from.

[jpmsteadi]

Just got back from the first ride! the front suspension feels good. Much more compliment and great handling. Still getting the fueling dialed in, but the wideband O2 sensor helps a ton. its very strange that it seems to be wanting a much larger pilot jet than I thought it would and a smaller main jet.

I am at a 45 (4 turns out on the mixture screw!) and a 150 main now. I am going to try a 145 tomorrow.

My thought is that with the larger more open manifold the air is moving slower into the piston and therefor making a smaller venturi effect over the jet, pulling less fuel up at idle. I am going to do some more research and see if I can't get it dialed in more.

[Puffs]

I'd think the size of the carb + the throttle position determine the venturi effect in the carb, not so much what was done elsewhere...

[jpmsteadi]

well, the intake manifold is substantially different. not blockig off half of the smaller port.

it is odd that it wants that much of a bigger pilot. I put a 50 in there and it was a little happier, but still 3.5 turns out.

[jpmsteadi]

Took the carb out this morning and took it apart to check all the seals against the parts breakout online. Found one missing oring on the throttle shaft, a washer an o-ring flipped on the mixture screw, and I replaced an old looking gasket on the top cover. A mixture of all that and it seems to have worked! running real nice now. I went to a 145 main this morning, then went to a 140. Hitting high 11s to high 12s AFR reading on full throttle runs, depending on where in the rev range. And it pulls so nicely. Still pretty rich in the crusing range, so I think I am going to play with the needle now. At some point when the new spark box comes in (it is still stuck at US customs) I may have to alter the jetting and do this again if I want to really dial it in, but the bike is running super nice now.

The forks are a big upgrade, feels very planted, but also quite comfy over bumps. It seems the stock springs are going to work well.

The brake seals were supposed to come in on tuesday of next week and I wanted to ride, so I made an adaptor bracket for the stock caliper yesterday morning. Works great, but of course the seals were delivered three days early yesterday!

PS: it does have fenders on it now! just took the picture before putting them on.

[jpmsteadi]

Got the R6 caliper on. For sure lighter, but not by a ton.

I also scored an OEM titanium slip on muffler from a 2012 GSXR750 that I am going to try and fit. Try and quiet the bike without adding much weight.

[Puffs]

Found one missing oring on the throttle shaft, a washer an o-ring flipped on the mixture screw

That absent 'O'-ring will cause 'false' (unmetered) air to enter the stream, particularly when the throttle is throttling the flow (higher ΔP). That will dilute the mixture, necessitating richer jetting to compensate. But of course the proper solution is to prevent 'false' air, as you did.

Btw, the optimal jetting will also depend on the exhaust, so you may have to re-visit when another muffler is fitted.

[jpmsteadi]

Found one missing oring on the throttle shaft, a washer an o-ring flipped on the mixture screw

That absent 'O'-ring will cause 'false' (unmetered) air to enter the stream, particularly when the throttle is throttling the flow (higher ΔP). That will dilute the mixture, necessitating richer jetting to compensate. But of course the proper solution is to prevent 'false' air, as you did.

Btw, the optimal jetting will also depend on the exhaust, so you may have to re-visit when another muffler is fitted.

Totally, the oring makes perfect sense.

I figure I will have to fine tune the jetting at least two more times: when fitting the other muffler (though I am just going to test fit it first to see if the sound is better) and when I installed the (currently held up in customs) better spark pack from bill. A different ignition curve and a hotter spark will change the jetting some as well.

Alas, its raining here today, so no jetting adjustments to be played with.

[jpmsteadi]

Been doing a decent amount of work on the skorpion, its getting really nice. Getting the jetting dialed in, just got some more main jets and needles in yesterday. Currently I have:

140 main
EMR needle middle clip position
40 pilot

Still a bit rich kinda everywhere, going to try a 138 main today and I have two needles coming to play with, an EMS (one step leaner on the straight diameter for very low throttle openings) and a FMR (one step richer on the taper, I have noticed that at 1/4 throttle its a bit richer than it is at 3/4, so hypothetically I can go to a richer taper, then lean the whole needle out)

I got the GSXR muffler on last night. I just made a mid-pipe to attach it temporarily for now to see how I liked the noise. SO much quieter, really quite nice. still some nice burble of deep noise without having the same bite.

Because of the way the pipe comes out of the can, I had to extended the muffler out from the car. Now that I have it mounted and like it I am going to try to get it back closer to the bike. The muffler is about the same weight, but a slightly larger package.

[Puffs]

It seems nicely made, but indeed maybe a bit big for the bike. And yes, maybe try to get it a bit closer to the wheel.
Will you ever consider rear-set footpegs?

[jpmsteadi]

It is a bit big, but thankfully no heavier than the one that came on it. The joys of titanium. And having a quieter bike I am okay with making that trade off. I just got it closer to the bike. The angle is still a bit odd, but it doesn't feel like it is protruding as much.

I just went through the main jets I got in the mail and have settled on a 135 main. I have been running the carb without the accelerator pump to as to not screw around with the AFR readings. With the 135 I am hitting low 13:1s at lower RPM WOT and getting into the low 12:1s at higher RPM throttle. I might be able to get by on the 130, but I think I would rather have a bit of room for bad gas or a real hot day or something. The bike is very happy and revs through super smoothly. Now moving onto the needle. At the higher end of the throttle range is a tad rich, but in the low openings and cruise zones are very rich still. In the 12:1 range. WAY too rich for that area. I have a zoom meeting in a few, but after I am going to try raising the needle a clip and see if its happy. Another thing to do is to increase the slide cutaway. That has the greatest effect on the 1/8-1/4 throttle range, right in that very rich cruise zone. But, given that being a semi destructive mod, I think I am going to hold off and adjust everything else first.

I don't think I want rearsets, seems like itd be uncomfortable. But, perhaps it would be fun to play with. I was debating getting some clip ons and being able to convert it to be a bit more aggressive at times. Never had a bike with clip ons.