Vacuum Petcock and CR's.

[Guest]

I searched but couldn't find a definitive answer.

So I've just realized that the old tank I removed and the new one I plan to use both have vacuum petcocks. I've replaced the stock carbs with a set of Keihin CR33's. What are my options for the petcock;

1). Run it in the prime position and switch it off each time I park (kind of used to this anyway).
2). Tap into a vacuum source somewhere (either fab a fitting in a spigot or use one of the synch. outlets).
3). Buy a non-vacuum petcock (assuming such a thing exists for my tank).

Any thoughts/advice? I guess option #2 would mirror the stock functionality best - if I go that route, where can I source a vaccum fitting? Any downside to that approach?

TIA.

[Billy Ricks]

I'm not familiar with CR's, I run RS flatslides myself. They don't have sync ports on them, mine do? If you have sync ports on the intake port or manifolds you could pull vacuum from there. With my RS carbs it seemed like the stock petcock wasn't flowing enough fuel so I picked up a Pingel. They have adapter plates with different bolt spacing for different bikes. The nice thing about them is when you turn them off the fuel is definitely shut off. They have them with dual outlets and some have a reserve function.

[pontiacstogo]

I'm not familiar with CR's, I run RS flatslides myself. They don't have sync ports on them, mine do? If you have sync ports on the intake port or manifolds you could pull vacuum from there. With my RS carbs it seemed like the stock petcock wasn't flowing enough fuel so I picked up a Pingel. They have adapter plates with different bolt spacing for different bikes. The nice thing about them is when you turn them off the fuel is definitely shut off. They have them with dual outlets and some have a reserve function.

I may look into a Pingel but it seems a shame when the petcock I have is near new (and seems to work fine). I don't believe the CR's have a vacuum port anywhere. I have seen folks tap a spigot for a vacuum source but I think that's kinda fugly.

Can I not use one of the 4 fittings in the head (intake side) used for synching the stock carbs? If yes, where would I pick up one fitting?

[Billy Ricks]

I may look into a Pingel but it seems a shame when the petcock I have is near new (and seems to work fine). I don't believe the CR's have a vacuum port anywhere. I have seen folks tap a spigot for a vacuum source but I think that's kinda fugly.

Can I not use one of the 4 fittings in the head (intake side) used for synching the stock carbs? If yes, where would I pick up one fitting?

That's what I meant by tapping into the sync ports on the head. You can pick up adapters for sync gauges that will fit the ports. Check with Motion Pro for the adapters. You'll just need to find out if you need 5 or 6mm adapters for your bike.

[donimo]

Only issue I can think of is that tapping into engine side vacuum is constant while the engine is running, while I think the vacuum source used for the petcock on the mikuni's is before the carbs, so it varies with throttle position. or am I wrong? I am still a newb with bikes...

I still cant see it being an issue as long as your float valve works.

[BassCliff]

Hi Mr. pontiacstogo,

If you really wanted to cheap out, leave the existing petcock on 'Prime' and fit a simple $3 on/off valve below it. But I think the Pingel would be a better solution. Just remember to turn it off when you're done riding.


Thank you for your indulgence,

BassCliff