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Author Topic: Carbs rebuilt, now won't run - Update  (Read 794 times)

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Offline stevenmgrr

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Carbs rebuilt, now won't run - Update
« on: August 01, 2008, 06:32:54 AM »
Ok.  I completed the rebuild of my carbs on my 71 CB500 last night and installed them.  Turned the gas on and I was able to get the motor started with the choke on, but I needed to open the throttle about half way to get it started.  Once started, it died after about 30 seconds of running and I was unable to get it going again.

I checked to make sure I was getting fuel to the carbs.  Valves checked; new plugs; ignition checked and set before rebuild; carbs benched sync'ed using the wire method.

I just want to get it running so that I can sync them with my Carbtune.

Am I missing something?
« Last Edit: August 02, 2008, 11:57:52 AM by stevenmgrr »
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'71 CB500 K0

martino1972

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Re: Carbs rebuilt, now won't run
« Reply #1 on: August 01, 2008, 09:15:52 AM »
did you set the float hight correctly???
now when you try to start her,do the sparkplugs get wet..??
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Offline stevenmgrr

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Re: Carbs rebuilt, now won't run
« Reply #2 on: August 01, 2008, 10:43:45 AM »
Float heights are set at 22mm.  The plugs don't appear to be wet.  I does start after sitting for 30 minutes or so, but it still dies shortly after starting.
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'71 CB500 K0

Offline TwoTired

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Re: Carbs rebuilt, now won't run
« Reply #3 on: August 01, 2008, 12:32:55 PM »
If you need to open the slides half way to get fuel to the cylinders, then perhaps the slow jets aren't clear and providing the fuel it needs to run with a more closed throttle.

The fuel delivery devices in these carbs are quite throttle position sensitive as to which metering device is prroviding delivery.

How confident are you that the slow jet were clean.  Counld you see light through them?

Do you have the air filter on?  Are you using choke and placing the lever in the proper postion?

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Gittfiddler

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Re: Carbs rebuilt, now won't run
« Reply #4 on: August 01, 2008, 02:42:50 PM »
What reference are you using for float height?  I had both haynes and clymer give different and wrong answers on various machines.  might want to call a honda service shop to double check their manuals. 
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Offline stevenmgrr

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Re: Carbs rebuilt, now won't run - Update
« Reply #5 on: August 02, 2008, 12:08:10 PM »
Well, I just wanted to thank you guys for your help.  Here is what I found.  Because I was taking the tank on and off, I only put a small amount of fuel in.  When I was doing my testing I had the petcock turned to 'ON'.  Further research on the forums found a post about the low idle circuit being fuel level sensitive and that 'Reserve' should be utilized for this type of testing.  I tried this and it worked.

Anyway, I was able to get the bike started and running.  It actually ran pretty well with just a bench syncing. I was then able to hook up my new Motion Pro sync gauge, which showed #1 was low and #4 was high.  Two minutes of tweaking later, I have a perfectly running, smooth idling '71 CB500. 

Thanks guys.

Steve
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martino1972

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Re: Carbs rebuilt, now won't run - Update
« Reply #6 on: August 02, 2008, 01:59:44 PM »
thats good news....so fill up your tank and ride that puppy....
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