Carb vacuum/Fuel Flow issue - Advice Please? '84 Nighthawk

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Clu · #1 Unread post by **Clu** » Wed Apr 27, 2005 4:30 pm

Greets all!

I'm working on my Girlfriends 1984 Honda Nighthawk 700. There seems to be a vacuum problem with the carbs such that they do not produce enough suction to open the diaphram in the fuel valve to allow gas to flow. I recently replaced the diaphram and all the tubing to make sure there wasn't a leak and if I suck on the tubing, fuel does flow from the fuel valve like it should.

I cannot seem to get ANY vacuum at all from the carbs. can someone lend me some advice on what else I can do?

Thanks!

storminsince73 · Wed Apr 27, 2005 4:48 pm

my son is fixing up an 84 nighthawk as a first bike. he too had no fuel flow, until we rebuilt and synced the carbs. we had a torn diaphram, that we repaired... the new one was $124. once we rebuilt and synced, we had fuel flow. it appears that his were bad enough that they could not pull a vacuum to make the fuel flow.

norm

Clu · #3 Unread post by **Clu** » Wed Apr 27, 2005 5:14 pm

Ew..

Do you think just taking the diaphram out of the fuel valve altogether and just letting the gas flow is a good idea (Of course, turning the to OFF whenever its not running)?

Probably not but I just thought I'd throw that out there..

poppygene · #4 Unread post by **poppygene** » Thu Apr 28, 2005 3:52 am

Hey, Clu... I think Norm is talking about the vacuum diaphragms in the carbs. CV carbs have these inside them and they're usually accessed from the top. I'm pretty sure the Nighthawk has CV type carbs.

You could just let it free-flow, but that probably won't help the way it runs since there apparently is another issue.

You might also make sure the carb boots aren't cracked or damaged and that they seal well around both the intakes and the carbs. Re-check all the vacuum lines and fittings. It's gotta be there somewhere!

Good luck and keep us posted!

Clu · #5 Unread post by **Clu** » Thu Apr 28, 2005 9:07 am

Gotcha! I'm leary about tearing into the carb but I have my handy-dandy Chiltons-type manual so I should be able to give it a go.

One thing is that the bike actually runs just fine when I'm sucking on the vacuum tubes myself... lol! More than likely something may have gotten mucked up internally somewhere.

Thanks for the advice!

storminsince73 · Thu Apr 28, 2005 10:42 am

thanks for the assist there poppygene, you are correct in what i was referring to.

Norm