Apexmaster40
New Member
Im trying to put back my 79bcb650 cafe racer back together after sitting for five years. I cant remember where this hose on the carburetors goes to ??
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79 cb650 carburetors install
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Apexmaster40
New Member
Anyone??
Agree with teazer. If the carbs have not been modified, the PD50AA used on the '79 CB650 have float bowl breathers that connect carbs 1 and 2 and then also 3 and 4 on the side of the carb body there will be two small nipples, those will connect to a small T with short pieces of fuel line. There is a sort of a fuel rail that runs between all of the carbs, but only has one inlet between carbs 3 and 4. My guess, because there appears to be two hoses starting between carbs 1 & 2 and also 3 & 4, is that those are the vent lines. They don't need to attach to anything.
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MathiasVogel
New Member
Yep, that sounds right. Those vent lines should just route downward and stay open to atmosphere — don’t cap them or hook them to vacuum. If they’re blocked, the bowls won’t vent properly and it can cause fuel starvation or weird running issues.
For reassembly, I’d also double-check the actual fuel inlet between 3 and 4 and make sure the hoses aren’t cracked after sitting five years. Old lines can look okay until fuel hits them.
Agree with you on all your observations and recommendations but want to point out one thing regarding the routing of the vent lines. From the factory, those vent lines were routed UP towards the top of the carbs. There were two binders attached to the carb tops. One attached to, I believe, carb #2 and one to carb #3 and the vent lines were routed UP through a large hole in the binder. I've attached a picture of a spare binder I have off a PD50AA carb rack.
