Single carb mod for skorpion

[Srinath]

That goes on top of the diaphragm on the right carb right ?

How thick is it approximately ? what it would do is life up that much more and hence let it rev on through the limit of the carb while still being a CV carb.
Interesting solution to the problem. It is the opposite of how they restrict bikes in some countries but installing a stopper rod to prevent the slide from lifting more than a certain limit.

Cool.
Srinath.

[basser23]

sam,
That is for the right cv carb right? What size drill bits are included..? thinking of making one from 3mm ally

[samandkimberly]

The spacer is about 3mm thick. These diaphragms swell over a very short time; I believe the primary purpose of the spacer is to give more room for the diaphragm as opposed to making more travel. The kit also comes with a little extension for the low pressure hole in the slide. The kit instructions also recommend raising the needle on the left carb a notch.

With these two mods my stock motor seemed to pull a bit harder and run a bit better wide open. The progressive nature of the two carbs became a lot more noticeable, you can really feel when the CV carb comes in to play', sort of like a poor man's turbo. I'm sure I could tune this out with some effort but it doesn't bother me.

The kit also comes with a 1,7mm and 1.8mm jet to enlarge the mains if necessary but the bike feels like the mixture is about right now.

Sam

[Srinath]

Thanks good to know that its purpose it to correct the thing and not to increase its lift.
I guess I am going to have to get one of these things now.
Thanks.
Srinath.

[basser23]

Seeing as how you're in NASCAR country,you may want to contact morbidelli17 and see if he'll supply the cad drawings for the adapter plate he had made to run the single
carb,,,,,using a variety of carbs would then be possible....

[Srinath]

We dont need a cad drawing, it will just turn a 20 buck project into a 20,000 project.
Get a aluminum plate. Get a cardboard to match the bolt holes and the ports on the engine. Cut, drill etc.
Get the manifold off a grizzly. Fit it to the other side. Drill and tap the bolt holes etc.
Bolt to the engine with flat head bolts and screw in grizzly manifold.
Head to carb is the hard part, the manifold to motor part is easier, atleast as I see it. 2 dimension is easier than 3d.
Anyway My carb is doing much better now, the stock skorpion carbs aren't too bad for my street needs. I'll probably do the mod bill Jurgenson has for making the main jet work better. That should do it.
Cool.
Srinath.

[Srinath]

The grizzly manifold bolts on the right side carb are opposite to the skorpion. Like if you see from the back of the bike, the skorpion has them like 2 \\, but the grizzly is like \/. That I am thinking is definetly adapter plate or maybe even a litte clip that screws into the head, and clamps the manifold on can be hand ground out of steel I thinnk.
Cool.
Srinath.

[hb7]

The spacer is about 3mm thick. These diaphragms swell over a very short time; I believe the primary purpose of the spacer is to give more room for the diaphragm as opposed to making more travel. The kit also comes with a little extension for the low pressure hole in the slide. The kit instructions also recommend raising the needle on the left carb a notch.

With these two mods my stock motor seemed to pull a bit harder and run a bit better wide open. The progressive nature of the two carbs became a lot more noticeable, you can really feel when the CV carb comes in to play', sort of like a poor man's turbo. I'm sure I could tune this out with some effort but it doesn't bother me.

The kit also comes with a 1,7mm and 1.8mm jet to enlarge the mains if necessary but the bike feels like the mixture is about right now.

Sam

Once the slide is full open, what good is more room for the diaphram ? See if your 2nd slide is opening all the way or only opening ~90 %.
I wouldn't drill the mains out using the stock exhaust. I suspect top speed is still the same with the spacer kit....

[Srinath]

I got mine to idle, but its doing that @ under 1000 rpm. I got the air screw ~3-4 now, I am thinki gn of turning it further in. Everywhere else it runs like a top.
Cool.
Srinath.

[Linegeist]

I worked hard to get my Skorpion idling nicely at 900rpm - there's no reason why it shouldn't - a well set up stock motor should be able to idle at less than 1000.

I have mine set like that because the sound it makes reminds of the bikes of my youth ..............

[hb7]

900 rpm on the stock tach ? surely you jest.
the stock tach is not accurate and singles don't idle at 900 rpm from what I have seen.
More like 1200-1350 rpm idle.

900 rpm would stall once you applied the clutch.

[Linegeist]

900 rpm on the stock tach ? surely you jest.
the stock tach is not accurate and singles don't idle at 900 rpm from what I have seen.
More like 1200-1350 rpm idle.

900 rpm would stall once you applied the clutch.

I jest not. I don't have a stock tach. I run a cable-driven Suzuki instrument with its drive taken off the camshaft via an XT bevel gear. The reading of the cable tach's been verified by use of my Crypton engine tuner being hooked up to the bike - and it's accurate enough to warrant swapping out the MZ dream-meter.

Low speed idle with a single is a product, among other things, of the flywheel's ability to store enough energy until the next power stroke. The Stock Yamaha flywheel has enough mass to allow a 900rpm idle - my bike is proof of that.

As for the clutch stalling the engine ............... I'm not completely sure why on earth anyone would want to try and pull away from a 900rpm idle? Given the 660 motor's power band, trying to pull away from 1300rpm wouldn't exactly cover anyone in glory ...... I suspect I might be missing your point - whatever it was - but I rather suspect I'm not alone in regularly feeding the bike plenty of throttle on takeoff, if only to experience that awesome Yamaha torque.

[Bill Jurgenson]

For what it's worth, I could turn the idle down to 800 on my blue bike with the Bikeworx kit. It did not have a balancer, tho. The balancer with its cushdrive is the main reason for the rough idle. And the monster jump of the ignition advance curve at 800. With a Sparker, it is much smoother if the curve is set for that and does not emulate the DENSO box.
There is abslolutely no virtue in such a low idle. There are no advantages but many disadvantages starting with oil pressure.
I keep mine at 1800.
The flywheel is not heavy enough really. Compare it to a SRX (kickstarter) flywheel for instance. Let alone just about any 4-stroke flywheel from the good old days. BSA=12lbs and that was a twin. Guzzi flat single 15lbs. Even the little Mondial weighs in around 8lbs. And these single (and many BSAs) had manual advance for the ignition with the ability to set it at BTDC to kick. Add very under square to that and low compression. No wonder a real thumper will sit there and idle at 500rpm all day long.

[hb7]

If I set it lower than the stock ~1300-1350, too much stalling,
here in Los Angeles stalling = possibly getting run over in the intersection.
I don't like to burn clutch. I use an Autometer tach...

[Srinath]

Hehehe - In most of the US stalling = getting run over.

The rpm determines oil pressure, and heck vehicles that idle a lot suffer cam damage as a result, taxi cabs and cop cars have that happen a lot.

I'd shoot for a higher idle just for that reason. I set them to ~1500 on my GS and would think ~1350 is decent for the single in the MZ.

Cool.
Srinath.