carburetors

[brianb]

can someone tell me what size carbs came stock on the 660cc scorpion and help me understand why the one cylinder has two carbs ? different throttle levels kicks in secondary? anyway tring to find best carbs bike is basically stock except muffler off 2000 yamaha 450cc quad please help thx
Brian Burns

[brianb]

1996 scorpion

[Guesi]

These carburetors are called "Register-Carburetors". Up to a certain throttle leverage, only one carburetor is working. If you open the throttle more, the second one is added.

This gives you less fuel consumption on lower revs and more power on higher revs...

[breakwellmz]

can someone tell me what size carbs came stock on the 660cc scorpion and help me understand why the one cylinder has two carbs ? different throttle levels kicks in secondary? anyway tring to find best carbs bike is basically stock except muffler off 2000 yamaha 450cc quad please help thx
Brian Burns

The smaller (LH) carb is a 28mm round slide feeding a single port (three inlet valves) and the RH carb is a 38mm butterfly/CV supplying the other two.
As Guesi says, a (adjustable) linkage bring the second carb into play past a certain throttle position.
I used to think the theory and practice of it was pretty fair until i replaced mine with a single CVK40 (40mm CV pumper carb) but i`m much happier with what i have.
If interested, do a search on here for more detail.

Cheers.

[ralf]

I think the Skorpion carburettor is called YDIS, Yamaha Dual Intake System. I thought it troublesome until I got the primary carb jetted right. Try a 55 pilot jet and 21/2 turns open on the mixture screw, it worked for me! Use an appropriate size (check the maintenance manual but maybe 6mm?) drill shank under the primary carb throttle body to set the critical opening position of the secondary carburettor.
Mine now works beautifully, no hesitation, smooth performance throughout the range. My 500R has a Dellorto pumper carburettor, yes it's much simpler but my Skorpion is much smoother. Persevere with the YDIS before you bin it.

[breakwellmz]

I`ve done all of those things in the past and having the advantage of having tried both i know which setup i prefer.

[burnsy2067]

I think the Skorpion carburettor is called YDIS, Yamaha Dual Intake System. I thought it troublesome until I got the primary carb jetted right. Try a 55 pilot jet and 21/2 turns open on the mixture screw, it worked for me! Use an appropriate size (check the maintenance manual but maybe 6mm?) drill shank under the primary carb throttle body to set the critical opening position of the secondary carburettor.
Mine now works beautifully, no hesitation, smooth performance throughout the range. My 500R has a Dellorto pumper carburettor, yes it's much simpler but my Skorpion is much smoother. Persevere with the YDIS before you bin it.

thank you very much im sorry for being green but what controls the secondary carb how are they i dont understand drill shank under throttle body does fuel amount in primary control second? how does second open thank you again for your knowledge


Brian T. Buirns

[burnsy2067]

i want to put a sing;e 40mm cv/pumper carb on 660 scorpion {1996} i was thinking mikuni and not sure what to do for manifold boot can someone help por is there another route i can take....... thx BB

[DAVID THOMPSON]

the drill is to measure the setting of the slide
to time it where it needs to start moving

[Ashtabula63]

Brian,

Did you get your carb changed out? And if so, what did you end up buying? I think I need to do something similar and need all the advice I can get.

thanks,
Wes

[buckscreek]

Brian,

Did you get your carb changed out? And if so, what did you end up buying? I think I need to do something similar and need all the advice I can get.

thanks,
Wes

Hi Wes,

I'm in NSW and doing a carb conversion on a Skorpion Tour right now. I have selected a Keihin FCR-MX 40 carby off a Honda CRF450X which is being stripped, cleaned, reassembled with new seals, etc and rejetted to suit the 660 engine. I've provided materials (aluminium plate and an intake manifold from a Yamaha Grizzly 660 quad bike) to a machinist to make an adaptor to mate the single carb to the dual inlet ports. I will also be fabricating a new battery box (the original airbox needs to be removed) from sheet steel. I have ordered a Unifilter foam air filter for the setup. Once I've got all the components back with me on the bench, I'll take photos and post them here.

Others have done this, there is much knowledge out there if you search thoroughly. Most have been done with Mikuni BST carby's I believe. And there appears no simple way to do the adaptor, other than to have one made as I am. I'm yet to see the results from the machinist, we may decide to mill the adaptor out of a single block of aluminium if the current job doesn't work out as well as I'd like.

Regards,

joe

[breakwellmz]

You may well have seen this -

[buckscreek]

You may well have seen this -

I've seen and am using a similar drawing, sourced from another MuZ owner here is Australia, who probably received it from someone in Europe. My machinist called last night, he has completed the work on the main flat plate (as shown on your drawing), he's going to mill the face off a Grizzly 660 intake manifold today, ready for welding to the plate. We'll have some further internal machining/cleaning up to do to ensure we get as smooth a flow of fuel/air mix as we can from the end product. I'll post some photos when I have all the bits together, ready to install.

[droy]

The US firm Edelbrock made a a 2 to 1 intake for the Raptor 660 quad. I actually put one up for sale on FB (International MuZ Skorpion Group) if u want to see what they look like.

[breakwellmz]

You may well have seen this -

I've seen and am using a similar drawing, sourced from another MuZ owner here is Australia, who probably received it from someone in Europe. My machinist called last night, he has completed the work on the main flat plate (as shown on your drawing), he's going to mill the face off a Grizzly 660 intake manifold today, ready for welding to the plate. We'll have some further internal machining/cleaning up to do to ensure we get as smooth a flow of fuel/air mix as we can from the end product. I'll post some photos when I have all the bits together, ready to install.

I started going down that route at one point, but thought the hole centre distance difference between the Grizzly manifold and the MZ head to be too much for the (10mm plate in my case) to accommodate. I also found i didn`t have the space within the frame (Mastiff) for it all to fit.
Keen to see how yours pans out.