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Hot!Yamaha R1 carbs on a Pinto.

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nortonnut
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2020/01/05 06:08:29 (permalink)
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Yamaha R1 carbs on a Pinto.

Someone on this forum has done an excellent article on the above (sorry that I can't name you but if I go out to look it up I shall probably not get back in). I have bought a set of carbs off a R1. They are Mikuni 40mm CV stamped 4XV. There are several attachment points for tubing but no tubing. From the article I found the Yamaha R1 Workshop Manual and by using that I have identified Petrol inlet (1 point), Float chamber vent outlets (2 points) Vac Chamber vent outlets (2 points). I am still left with 1 pipe on carb 1 and 1 pipe on carb 4 that look as though they should have tubes attached. They are connected through all 4 carbs so if I blow into 1 pipe I can feel the air coming out the other end. The pipes are different diameters, 1 small (about 3mm) and the other about 10mm. If I was working with a carb on a classic car then I would say that the small pipe is a vacuum takeoff for a tube to go to the Distributor to operate the Vacuum Advance and Retard.
 
I will attempt to attached 2 photos showing the unidentified pipes. Can someone tell me what the pipes are for, do they need tubes attached, where should the tubes go to?
 
If I can't attached the photos could someone answer this to tell me how to do it.
Thanks. Mick.

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    martymexico
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    Re: Yamaha R1 carbs on a Pinto. 2020/01/05 22:31:32 (permalink)
    +1 (1)
    I'll do my best to answer this as I've installed R1 carbs on a zetec a long time ago.
    The fuel in pipe is in the centre underneath next to the idle adjust cable (if you was wondering what that does) . That is the only pipe you connect up, all others are left alone unless you use the fuel return/ overflow pipe.
    Setting them up is a bit of fun but first start by drilling the main Jets to about 1.6-1.8mm, this will get the motor running without stalling etc, next the needle plunger has a diaphragm which can be adjusted up or down by minor amounts by removing the tiny E clip (also known as Jesus clips!) and moving it down 1 step, this needs to be done to all 4x carbs as it meters the air fuel mix . Some Jets and are interchangable with Weber Jets. The angle the carbs work best on is to have the float chamber seal sit horizontal or to within 5deg tilted up or down. Mine were set low to clear the strut brace.
    I do not know if they have a vac port , but if there is it can be used for the dizzy advance if it's needed, bikes ran CDI ignition .

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    nortonnut
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    Re: Yamaha R1 carbs on a Pinto. 2020/01/06 06:57:37 (permalink)
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    Hi martymexico.
    Thanks for the reply and information. I can now proceed with confidence. I should be OK setting them up because my first love are classic motorbikes and, except for vacuum lifting the Slide and Needle, these appear to work the same as Amal carbs (Pilot Jet/Needle Jet and Needle/Main Jet). However, the jet size and needle position you have suggested as starting points will make this much easier.
     
    Your engine looks gorgeous. Something for me to aspire to in the future.
    Cheers. Mick.
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