Author Topic: I hate these damn carbs (Read 2500 times)

TheFox · « **on:** September 28, 2008, 05:28:59 PM »

I've got a '71 CB500 with a 550 motor in it. I just finished rebuilding the carbs this morning and I can't get the bike to fire and idle. I did everything by the book and even ran a fresh tank of gas with some fuel system cleaner in it to help things move along. Now, I have removed the airbox and I have straight pipes on the bike. But I ran the bike up and down the street in the same condition before I rebuilt the carbs. So, I know it's possible to have it run just the way it is.

When I was putting the carbs back together, I set the float bowls to 22mm like my Clymer guide said but from what I've read on here, everyone is saying that they should be set to 12.5mm. I'm not sure what to think. Everything is clean and ready to go, but this tuning issue is really making me wish I would have never started this project. Any help would be great. Thanks.

Brad

low-side · « **Reply #1 on:** September 28, 2008, 06:36:58 PM »

I don't have a 500 or a book to look at, but I might try 12.5mm if it's not running on 22mm float height.

Honda_Nut · « **Reply #2 on:** September 28, 2008, 07:15:20 PM »

With that float height, it makes perfect sense that you aren't getting any fuel in the carbs. I think you set it about a cm to high.

TomC · « **Reply #3 on:** September 29, 2008, 08:05:49 AM »

Hi TheFox
On the Honda carburetors that I have done the float is square with the surface that the float bowl seals to when I have set the float level. I would think that if you set the float level off by 9.5mm the floats would just look odd.
TomC in Ohio

Johnie · « **Reply #4 on:** September 29, 2008, 10:07:45 AM »

Keep the faith fox...you will get it right. We have all been there and experienced the same let down. That is part of the entire project. Just look forward to when you get it right and you are driving down the road in envy of those looking at that bike. Good luck with it...

TheFox · « **Reply #5 on:** September 29, 2008, 12:18:39 PM »

thanks for the pickup guys. I just don't know what to think now that I'm hearing everything from 9mm to 22mm for the float setting.

TomC · « **Reply #6 on:** September 29, 2008, 04:04:53 PM »

Hi TheFox
That was off by 9.5mm. Not at 9.5mm. If 22mm is correct and you set the float level at 12.5mm. The float will just look wrong. And the other way around.
TomC in Ohio

TheFox · « **Reply #7 on:** September 29, 2008, 04:15:16 PM »

but I did set the floats at 22mm. Guess I'll try them at 12.5mm and see where that puts me. I have a surgery to remove some screws from my ankle this week. So, I probably won't have time to fart around on the bike.

Does anyone know of a good vintage bike mechanic in either orange county or the los angeles area? At this point I'd rather pay someone to work on it for me.

Frankenkit · « **Reply #8 on:** September 29, 2008, 06:32:00 PM »

I suspect what they're saying, Fox, is that at 'rest', the top of the floats should be roughly parallel with the part of the carb body where the bowl screws on, whatever the height. You should be able to look across and they should be roughly even all the way across, and all parallel to that connection.

TheFox · « **Reply #9 on:** September 29, 2008, 06:50:28 PM »

guess it's worth a shot. Anything would be better then what I'm getting right now.

TwoTired · « **Reply #10 on:** October 03, 2008, 11:00:57 AM »

The correct carb settings are in the carb FAQ. 22mm is correct for the float height.

Quote

I can't get the bike to fire and idle.

Pretty sketchy problem description. Are the plug wet with gas or dry? You certain all the spark plugs are, in fact, sparking? Are there soot deposits on the spark plugs?

Have you check each carb bowl to verify gas is getting to each one?

Have you synchronized the carbs?

Won't fire? Then why the complaint about idle? Dies at idle setting? Or, can't adjust it low enough?

Don't hate the carbs. Hate the mechanic that works them. Or, better yet, save the emotions for something that can actually care. What is the point of hating an inanimate object?

It's a puzzle. Work it out.

Cheers,

mystic_1 · « **Reply #11 on:** October 03, 2008, 01:27:21 PM »

Quote from: TwoTired on October 03, 2008, 11:00:57 AM

Don't hate the carbs. Hate the mechanic that works them. Or, better yet, save the emotions for something that can actually care. What is the point of hating an inanimate object?

I've known a couple of 'mechanics' who qualified as inanimate objects

Don't give up TheFox, take a step back, re-examine your base assumptions a bit, and then work through it methodically. The payoff will be well worth it.

cheers

mystic_1

TheFox · « **Reply #12 on:** October 03, 2008, 01:31:02 PM »

Thanks for all the support guys. Just getting sick of taking off these damn carbs.

mystic_1 · « **Reply #13 on:** October 03, 2008, 02:44:57 PM »

Heh, trust me, we feel your pain.

mystic_1

TheFox · « **Reply #14 on:** October 05, 2008, 10:58:45 PM »

I took a good long break from the bike and did some work on it tonight. I'm glad I did because I found out what was going on with my carbs. The main fuel feed line for 1&2 was almost completely clogged with old fuel deposits and buildup. I guess I just forgot to replace those old ass fuel lines.
Of course, that couldn't be the end of it there. All sorts of other problems had to pop up after that. It started spewing fuel from the splitter and I noticed some bungs that appeared to be vacuum lines or something. They are between the number 2&3 carbs. One of the barbs it broken off and fully exposed. The P/O just left them hanging. I'm assuming they are there to equalize the pressure between the carbs or something like that. I couldn't find anything on it in my Clymer guide. Some help on that would be great. Thanks.

Brad

mrbreeze · « **Reply #15 on:** October 05, 2008, 11:56:45 PM »

Sounds like you are talking about bowl vent lines. If you are new to these bikes/carbs.....you really need to get some manuals and read them to get an idea of what you are dealing with. If you are still stuck....there is plenty of help here.

TheFox · « **Reply #16 on:** October 06, 2008, 12:49:28 PM »

Thanks for the reply breeze, but I do have the original owners manual and a clymer guide I've been working out of. The vents are allfine and routed correctly. The part I'm confused about are the hose barbs on the outside of the carbs in between 2 and 3.

TwoTired · « **Reply #17 on:** October 06, 2008, 01:05:02 PM »

Quote from: TheFox on October 06, 2008, 12:49:28 PM

The part I'm confused about are the hose barbs on the outside of the carbs in between 2 and 3.

Those are bowl vents. Stock, they had hoses that routed behind the engine and in front of the swing arm.

They are the ONLY dedicated vents for the carbs.

The overflow stand pipes can also vent, but only when they aren't dealing with overflow.

You can always blow in them to see where they go. But, the other end is at the top of the bowl chamber.

Cheers,

dnewman417 · « **Reply #18 on:** October 06, 2008, 03:10:17 PM »

The proper float height for the 1978 CB550K is 12.5 mm. What year is yours?

TheFox · « **Reply #19 on:** October 06, 2008, 03:48:22 PM »

'76, which is 22mm

schneider419 · « **Reply #20 on:** October 07, 2008, 02:22:40 PM »

if the fuel comes out of the broken barb, it may be the line that supplies the carb.

Gregorymoto · « **Reply #21 on:** October 07, 2008, 03:08:50 PM »

Did you pull the spark plugs to see if they where wet with gas.

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Author Topic: I hate these damn carbs (Read 2500 times)

TheFox

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