no vacuum

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Feb 9, 2020 | 03:48 PM

#11

brownie4412

HDF Community Team

Joined: Apr 2018

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From: Ohio

Quote:

Originally Posted by nicsvert

Gas won't flow unless there is a vacuum caused by the carb.

vacuum isn’t caused by the carb. Maybe you should take it somewhere.

Feb 9, 2020 | 03:51 PM

#12

Jackie Paper

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From: Honah Lee

Pull the vacuum hose off petcock and attach vacuum gage to hose and crank motor. How much vacuum do you see on gage.

Feb 9, 2020 | 03:52 PM

#13

nicsvert

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Joined: Jan 2008

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From: mesa az

yes i put some started fluid in and it started up. I turned the throttle but no gas from the jet. I guess i could try to fill the bowl manually.It should fill though nwhen I crank it over.

Feb 9, 2020 | 03:53 PM

#14

cggorman

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From: NW Ohio

Got an alternate vacuum source, like a mityvac or whatever?

Most carbs have multiple vacuum ports, not all of which see manifold vacuum (which is what the petcock needs). Correct port must be chosen based on task. Unused ports must be capped tightly. All other gaskets and seals on carb body and intake must also be air tight.

Last edited by cggorman; Feb 9, 2020 at 04:00 PM.

Feb 9, 2020 | 03:53 PM

#15

Jackie Paper

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From: Honah Lee

I give up.

Feb 9, 2020 | 03:59 PM

#16

cggorman

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From: NW Ohio

Quote:

Originally Posted by nicsvert

yes i put some started fluid in and it started up. I turned the throttle but no gas from the jet. I guess i could try to fill the bowl manually.It should fill though nwhen I crank it over.

OK. So, the intake and carb body seals should be fine...or near enough. You just have a fuel delivery problem.

Carb bikes don't have fuel pumps so you can run it from any elevated fuel reservoir. A hose dipped into a gas can held above the level of the fuel bowl is sufficient. Even just a long hose held up and filled with fuel.

If it will run from that, or just the fuel in the bowl, you can rule out everything other than the tank, petcock, and associated bits and pieces.

Get fuel into the bowl first. Then, go from there.

Feb 9, 2020 | 04:01 PM

#17

nicsvert

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From: mesa az

well I don't have a gauge at home. One of my guys at work might have one. Isn't it odd that it was okay until i removed it?

Feb 9, 2020 | 04:03 PM

#18

cggorman

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From: NW Ohio

Vacuum during cranking is very low and may not provide sufficient pressure or volume to open the petcock. Normal day-to-day use would have fuel sitting in the line and bowl for the engine to start and run from for at least 30 seconds before it needs more fuel from the tank. This would give it enough time to build vacuum and open the petcock.