carb not shooting gas

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shovelhead63 · Tue Apr 21, 2009 3:38 pm

I have a honda 71cl450,I took the carbs off and sprayed carb cleaner on them and on the float part,put them back on,i have got gas in the bowl,but it does not spray gas when i twist the throttle.What is wrong with it?

#2 Unread post by **Wrider** » Tue Apr 21, 2009 3:56 pm

Well it probably won't spray gas when you twist unless there's an accelerator pump on the things. If there is one and it still isn't spraying, I'd check the pump rubber parts seeing as how old it is and how they have been submerged in gas for 38 years...

Fargo360 · #3 Unread post by **Fargo360** » Tue Apr 21, 2009 6:46 pm

I've got a '76 honda cb360t, and I was having the same problem on one of my carbs. I raised the float a bit and that fixed the problem. Those old kei hin's only run on air pressure so everything needs to be in check. It might take some fiddling, but when you get it right, you'll know it. It might take a few tries with different float settings, don't put everything back together until you check the remounted carbs out. If your float is too high you'll get gas coming out the overflow on the bottom. If it isn't high enough you're problem with persist. You might want to check to see if you have two tangs on the float, I had one that actuated the float needle and one that stopped the float from getting any higher. I ended up having to mess with both before I finally got it right. If that doesn't work and are looking for more resources, check out oldmanhonda.com, that guy helped me out a bunch.

shovelhead63 · Wed Apr 22, 2009 2:59 pm

On the round part that says kehin on top of the carb,that part on the inside of that keeps sliding down,i can see it when i look up in the carb.I push it back up in there but it eases back down.Is this a problem?If so how do i correct it.Thank you for the info you have given me.

#5 Unread post by **Wrider** » Wed Apr 22, 2009 4:42 pm

Do you mean this part???

If so then yes it's a problem because it's supposed to move freely and have a small, loose spring up above it.

shovelhead63 · Thu Apr 23, 2009 2:49 am

Yeah,Its the thing in there,but that dont look nothing like my carb and mine dont have a spring on that part

#7 Unread post by **Wrider** » Thu Apr 23, 2009 4:28 am

Alright. Well I'm not sure on your specific model but most have a spring in there. And it definitely needs to move freely. that thing is what basically controls the amount of air your engine gets based on vacuum and atmospheric pressure.

Fargo360 · #8 Unread post by **Fargo360** » Thu Apr 23, 2009 5:06 am

I think that needle piston is supposed to stay down until you start running the engine. If you took the carb apart, you would see that there is a spring pushing the piston down, holding the needle jet in place. When you rev the engine it would lower the pressure above the diaphram and raise the needle alowing for more fuel to come out. Even at idle speeds the needle should stay down (as the bike gets fuel from the slow jet at idle). If you're able to push the needle piston up and it comes right back down, that's what it is supposed to do. I'd start by adjusting your float heights and see if that helps, if not, you might need to clean or replace your jets.

shovelhead63 · Thu Apr 23, 2009 3:01 pm

Yeah i try that,Its got a big long brass needle that fits in a hole in middle of carb.You think i should push both cylinders up in carb before i try to start it.

Fargo360 · #10 Unread post by **Fargo360** » Thu Apr 23, 2009 6:50 pm

No, those needles are supposed to stay closed until you rev the engine. So if you push them up, the will come back down and are suppsed to be there. Don't move them. I am sure the floats down in the bowl aren't set high enough. There is a little metal flap on them that pushes a little valve up and down. You can bend this flap up and down to let in more or less fuel. If they aren't high enough, the jets aren't sitting in the fuel so there isn't really anything there for them to suck into the main barrel of the carb. Set the floats just a small bit higher and give that a whirl. But quit messing with the needles, if you bend them, they are shot.

If adjusting your floats doesn't do anything then your jets are plugged and need to be cleaned or replaced. You can get a carb rebuild kit for about $15/ea on ebay. You'll need 2 as you have a duel carb.

http://cgi.ebay.com/ebaymotors/Honda-CB ... ccessories