Author Topic: 75 CB550F - Fuel not getting to carbs 2 & 3  (Read 110 times)

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Offline bamshackalacka

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75 CB550F - Fuel not getting to carbs 2 & 3
« on: October 11, 2018, 06:07:54 am »
I just finished a carb rebuild and finally put them back on the bike and when I cranked her over I found that the middle two cylinders were not firing. I checked ignition, changed spark plugs but still no life from cylinders 2 and 3. I finally got the bright idea to check if fuel is getting to them and the bowls were bone dry when a checked. Before pulling them off again is there anything I can do while they’re on the bike to try and get fuel running to them? I checked to make sure fuel was getting everywhere else so it’s just cylinders 2 and 3 that are not getting gas.

Offline flybox1

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Re: 75 CB550F - Fuel not getting to carbs 2 & 3
« Reply #1 on: October 11, 2018, 06:43:06 am »
Take them off for a proper cleaning.
Be thorough so you only have to do it once.
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
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Offline david 750F

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Re: 75 CB550F - Fuel not getting to carbs 2 & 3
« Reply #2 on: October 11, 2018, 07:05:08 am »
Give the float bowls a couple of hits with a rubber mallet. The floats may be hanging up on the gaskets.
« Last Edit: October 11, 2018, 07:07:00 am by david 750F »
1976 CB 750F

Offline Deltarider

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Re: 75 CB550F - Fuel not getting to carbs 2 & 3
« Reply #3 on: October 11, 2018, 07:28:05 am »
Give the float bowls a couple of hits with a rubber mallet. The floats may be hanging up on the gaskets.
+1, but gentle, NO hammer!
Floatneedles can stick. Remedy:
1) Tap the floatbowls (gently!) with the stub end of a screwdriver. If that doesn't help:
2) Remove the drainscrews and then open and close the petcock a few times. If you're lucky, in the combination with 1) you may free the floatneedles.
3. Add fuel additive to tank.
If that all doesn't help, remove the floatbowls for further inspection.
I have similar carbs and can do all maintenance with them in situ blindfolded. No need to pull the rack. Changing those awfull crossheads for Allen helps a lot.
« Last Edit: October 11, 2018, 12:10:55 pm by Deltarider »
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Offline bamshackalacka

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Re: 75 CB550F - Fuel not getting to carbs 2 & 3
« Reply #4 on: October 11, 2018, 07:46:42 am »
Thanks Deltarider!

The PO replaces the bowl bolts with Allens so that was nice. Can I assume that it’s a float issue and not a fuel line clogged at the very end issue?

Online Bodi

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Re: 75 CB550F - Fuel not getting to carbs 2 & 3
« Reply #5 on: October 11, 2018, 07:59:18 am »
Most likely a float valve hangup. The probability of both fuel tees blocking one end is not very high - if 1 & 4 get fuel, it's getting to those tees.
Nice to have Allen screws there!

 

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