Topic: '76 550- rebuilt carbs, starting issues :(

[Ward]

Hey folks,

Looking for some insight on an issue i'm having... recently rebuild the carbs on one of my 550s. Checked all ports, redid the slides, gaskets, floats, jets, everything.. I started with the air bleeder screw 1.5 turns out. Bike will not start. I got it to fire up with the bleeders almost four turns out, but it will instantly stall when you touch the throttle. So seems like its running super rich... What else can i check out?

[Scott S]

 You didn't install the slides with the cut outs facing the wrong way, did you?
 Have you checked float height?

 Stock exhaust and air box?
 Have you done the 3K mile tune up: points, plugs, valve adjustment, timing, etc?

[Ward]

Slide cut outs facing the air filter side per a diagram i had, please correct me if i'm wrong about that! Float heights are correct. Stock exhaust, air box is not attached at the moment for troubleshooting purposes. Bike was purchased as a project, so hasn't been tuned up in a bit. Plugs are good though.. Even with some of that stuff being a little rough- i should still be able to fire up and at least rev a bit right?

[Scott S]

 Not necessarily.....not if your valve clearances and timing are way out whack.

[Stev-o]

I got it to fire up with the bleeders almost four turns out

Dont know what bleeders are but this is wrong.

[Bankerdanny]

Generally speaking it is best not to use the jets and needles from aftermarket carb kits. It is very likely that the jet sizes are not what they say they are and that the needle profile is not the same as stock.

Unless a needle was bent you should just clean everything completely and reinstall the stock brass with the new gaskets and o-rings.

You should hook the airbox up since it will affect air flow and fueling.

[DaveBarbier]

Is this the first time you're starting the bike? I mean did you try starting it before the carb rebuild or only after? During a rebuild you need to remove all jets, emulsion tubes and IMS and use wire, carb cleaner and compressed air to ensure passage ways are clear. Did you remove jets and emulsion tubes and clean all the tiny holes?

The "bleeders" you're referring to are probably the idle mixture screws (IMS) and stock setting from your bike is 1.5 turn out from lightly seated. If you're thinking rich is what you're experiencing then this could be the/a cause.



What you need to do first, and a lot of people over looks this, is the 3k mile service that's in the shop manual (which you can download on the site.)

[Ward]

I started the bike when i first picked it up. It ran, but not well as the carbs at that point were very dirty and gummed up.. So timing, valve clearance etc it somewhat right... Carbs were completely rebuilt, all passage ways are clear... and yes, i was referring to IMS. I started everything with those turned 1.5 turns out, but had to keep turning them out just to get it to start... The IMS on these is an air bleed setup, more you turn it out the leaner the mixture is.

I'm going to try the original jets and needles when i get back home. The only difference i'm seeing on those overhaul charts is that my needles were originally on the second notch down from the top.

Is this the first time you're starting the bike? I mean did you try starting it before the carb rebuild or only after? During a rebuild you need to remove all jets, emulsion tubes and IMS and use wire, carb cleaner and compressed air to ensure passage ways are clear. Did you remove jets and emulsion tubes and clean all the tiny holes?

The "bleeders" you're referring to are probably the idle mixture screws (IMS) and stock setting from your bike is 1.5 turn out from lightly seated. If you're thinking rich is what you're experiencing then this could be the/a cause.



What you need to do first, and a lot of people over looks this, is the 3k mile service that's in the shop manual (which you can download on the site.)

[DaveBarbier]

The IMS on these is an air bleed setup, more you turn it out the leaner the mixture is.

Oh ok, I'm used to my carbs

[Deltarider]

The only difference i'm seeing on those overhaul charts is that my needles were originally on the second notch down from the top.

By top you mean top, right? Not tip.
Can you inform us what the stamped on number is on your carbs. If you don't know where to look, it is in the blue circle in the pic