1984 vf500 not starting

WTF - No props for me buddy??

 

The thing to understand is that there are 3 independent systems within each carb body. You have the low speed, the main, and the inrichment circuit (choke). Depending on pressure drop within the carb body based on the butterfly and the slider position is what allows fuel to be sucked into the airstream allowing a seamless transition from one system to another. In other words, as a rider, you don't notice the engine change from the slow speed to the main jet as the engine climbs thru the RPMs (at least when everything is working right).

So, the slow speed jet, along with the air mixture screw, controls idle to about 1/4 throttle. If you look in the carb body, where the butterfly is located, you should see a tiny orifice in the body at the bottom. I think there is a small orifice on each side of the butterfly. When you spray carb cleaner in the slow speed jet, you better be able to see spray coming out of these holes. Same with the air mixture screw on the side of the carb body. Follow the cast passagways along the outside of the body to see where these things go and make sure they are clear.

The main jet is the easiest because on this model carb (if memory serves me) it only connects to the slide needle. On some other carb models, the main jet can also feed the choke circuit. But on this one, you can see the main jet goes directly to the slide needle and no other. There is a vacuum orifice that goes from the carb body to the top of the vacuum diaphram, as pressure drops, the vacuum slider lifts and the tapered needle allows more fuel to pass thru the main jet.

Lastly, you have the choke or enrichment circuit. On these carbs it's technically called an enrichment circuit because there is no traditional choke butterfly valve. This circuit gets it's fuel from the third brass tube in the carb float bowl that doesn't unscrew. This one gives people the most trouble. There is another thread where this one was covered at length with ways to make sure it's properly clear so if I can find it I'll give you the link. The tube from the float bowl (going on a weak memory again) goes up to the plunger valve on the side and up to a little hole at the very top of the carb by the vacuum diaphram. It may also mix with an air orifice at the front of the carb air intake.

You also have to make sure the float level is set correctly. If it's too low or too high you can get a lean or rich mixture. There is a proceedure in the manual for how to check and set this. Above the fuel shuttoff needle/seat assembly you should find a little filter screen that must be clean.

oh yea, one more thing. Each jet has a number stamped into it. Make sure you take note of what slow speed and main jet is in each carb. Two reasons: some carbs used a different jet and emulsion tube (main jet holder) for the front vs. the rear cylinders; and secondly, if you have problems later (lack of horsepower at certian RPM ranges for example) it'll be important to know what jets are currently installed.

 

Here you go, this this thread should help you:

http://vfrworld.com/forums/1st-2nd-generation-1983-1989/27763-85-vf500-idle-choke-issues.html