Carburetor throttle slides - change a 60 into a 40
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
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This is the best 60 to 40 throttle slide modification that I have seen. The only other method of modifying a Dellorto 7454-60 throttle slide into a Dellorto 7454-40 throttle slide involves filing away 2 mm from the front face of the throttle side. While this achieves the 40 relationship between the front face and the back side of the throttle slide, it introduces the permanent problem of the needle being in the incorrect location (and is an irreversible modification). Tatsu Okamoto's method is well conceived, nicely executed, and easily reversible. Very nice work.
Why would you want to change a Dellorto 7454-60 throttle slide into a Dellorto 7454-40 throttle slide for use on your Dellorto VHB carburetor?
Let me be very clear: this is not a required nor even a recommended modification. This is simply a description of how this modification might be made.
The 7454 series of throttle slides are no longer produced by Dellorto and new/used replacements can be tough to find. Changing one into another is may be a good alternative to sourcing a suitable new/used throttle slide.
Before making this modification, you should be absolutely certain that you understand the consequences of bits coming loose and being injested by your cylinder head/valves/piston/cylinder.
That being said, you may wish to try this modification if:
Your engine does not like to idle, especially when hot.
Your engine has a hesitation off idle that you cannot cure with jetting/needle changes.
Your engine is soft at lower engine speeds.
The 7454-40 slide is not a substitute for:
Worn chrome plated cylinders and piston.
Worn valve guides.
Improper valve timing or valve lash clearances.
Incorrect ignition timing.
Faulty coil or condensor.
Dirty carburetors.
Carburetors that are not jetted and set up properly.
Carburetors that are not balanced and synchronized.
Jetting changes will almost certainly be necessary after you have modified the throttle slide.
In other words, you had better know what you are doing before you dive into this.
Thanks to Tatsu Okamoto from Japan for posting this information on his Deer Ducati page. In Tatsu's own words and photos:
I had made custom Dellorto VHB carburetor slide 7454-40 from slide 7454-60. The left slide is my custom one. I put on the hand-made 2 mm duralumin plate to slide 7454-60. I will try test driving with my custom slide 7454-40.
Photo courtesy of Tatsu Okamoto.
I had concluded the hand-made duralumin plate on Dellorto 7454-60 slide by the silicon bond with 2 mm screw.
Photo courtesy of Tatsu Okamoto.
I had tested my hand-made custom Dellorto 7454-40. This custom-slide improve around accelerator position 1⁄8, so accele response is much better than before. This custum-slide successed. I had felt that the fuel is not enough around accelerator position 1⁄2~full power. I think this main jet 118 is not enough, still. So I must ascertain accelerator position with main jet 120~125, again. I tell you that it is going to be more more powerful.
