84 650 nighthawk richening system

[kiwiaudio]

This bike is hell to start, but runs fine when warm! I can easily foul out cyl #2 trying to get the choke in the right spot. I was told that there is a fairly simple "richening system" that is the "choke" on these carbs. I'm assuming the choke rod is lifting a needle in each carb.

My question is - Can the needles "seat" be replaced? I bet they are wasted and letting inconsistent amounts of gas through.

Do I have this right ?

Love to hear how this is done, and any other ideas anyone may have on the subject.

Kiwi.

[Wayward Son]

i think those have just a butterfly choke system.

i believe the seats are not replaceable.the needles could been worn or heavy float.

[kiwiaudio]

There are no butterflys in these carbs, main needle and jet are fine, floats have been set.

[Wayward Son]

float needles.

[kiwiaudio]

Nope, those are good too.

[Wayward Son]

define good?you replaced them?

obviously you have something thats not right as it has the flooding issue.

it is not normal.

it should withstand full choke no problem on cold start.

checked the tips of all the fuel screws?has stock pilot jets?

[kiwiaudio]

The float needle and seats are new. The carbs were overhauled before I aquired the bike a year ago, according to the previous owner. I pulled the carbs to inspect after this problem was immediately evident, and found everything I looked at in great shape. I obviously missed something though as the problem was still there when reassembled.

I would think if it had a float issue, it would be evident all the time? She runs great when warmed up !

[Wayward Son]

only has that issue on one cylinder?

[kiwiaudio]

yes, as far as I can tell, if i hold the choke on too far or too long, the one cylinder will foul the plug. Its running so rough at this stage that its hard to tell if 1 or more cyls are screwing up. I have pulled the plugs before it clears and found just the one fouled though. It finally comes around, but consequently I'm revving the old girl far more than I want to on a cold start. It will start great all day long when warm just so long as I don't touch the choke !

[kiwiaudio]

I have also traded spark plugs, interchanged plug wires, and coils trying to see if there is an electrical breakdown somewhere with a cold load start. Compressions are also good and uniform throughout all 4 cyls.

I remember now how I could feel the cold header pipe on the dead cylinder. The other three get hot instantaneously.

[Wayward Son]

its flooding that one cylinder while it sits.its a float valve issue.

[Who Whu]

Greetings:

Unless you replaced the parts yourself ......

I paid $23 for 1 needle for my 87 ZX 600 and

NEVER totally believe what the previous owner claims regarding repairs.

I've seen this kind thing do this to EVERY carb I go into for flooding issues.

1) Drop the float into water- if it starts to sink it has a hole. If no sink-o take it out of the water and shake to see if you hear anything. If you do, it has a hole. Super glue will withstand fuel but not ascetone. Super glue will fix the hole if you so select.

2) I've seen burrs on the float pin I didn't notice at first. I sand / file them. Sometimes varnish on the pin and inside the float pin housing will cause a sticky spot. B4 reassembly I rotate the pin in the float housing to make sure its smooth and always fill the carbs with fuel B4 assembling them back. If its going to leak, let them leak on the bench. The Night hawk air intake boots are a nightmare to take off and on.

If the seat is original, (problably is) take a Q tip and put it in a drill. Drop some rubbing compound in the seat area. With a medium speed burnish the seat. This will take out the resins stuck to the side wall that only super agressive cleaners get out. Resin residue may not be apparent and will cause the needle to stay open / flooding.

3) Caution: shops do a marginal job on old carbs because they cannot get the agressive cleaners banned by the Patriot Act. No shop / chemical dealer can get them. However, if you have a military or aviation source, the possiblity is there. And get some for me as this is the #1 problem with vintage projects! - I'll take 5 gallons.

Ultra sound cleaning does not work. Agitaion systems work for lighter duty jobs, not these old projects.

WW

[kiwiaudio]

Thanks Who Whu, You've given me something to think about. Its possible the one cylinder is flooding while sitting. The only reason I doubt this is that this bike has a vacuum controlled fuel petcock and I've checked that it works. Therefore there cannot be an endless supply of gravity fed fuel to a carb with a bad float valve !

But i'll definitely check the float system a lot closer. Sure wish I had an understanding of what is happening when I pull the choke. It has to be enabling more fuel into the venturi somehow.

Man - You are so right about those damn air intake boots. To get mine to fit at all, I have to leave the carbs out of the manifolds about a 1/4" ! They are so hard, I cannot hardly manipulate them at all. Almost went to pod filters !

Incidentally, motorcylecarbs.com,Inc , wanted me to send the carbs to them and they would take care of this for a cool $500. Right around what the old bike is worth !! They were talking ultrasound and a bunch of bull !

What is the cleaner/solvent called that I need to look for?