[Falconpunch]

Hello!

Bought a 85 450 Nighthawk for my sister as a wedding present. Past owner had the carbs cleaned and sync'd. It will run without choke but hiccups every once in awhile. 3/4- Full choke will ride nicely and idle great. Would this be the idle screw or something I need to take apart in the carb.

I looked in a few threads and didn't quite see what I wanted.

 

[83XLX]

When a bike runs better with the choke on, it means you're either not getting enough gas or you're getting too much air. Could be a carb adjustment, something clogging a jet or fuel passage, wrong size jets, defective/stopped up petcock, clogged tank vent, intake air leak, etc.

 

[J-T]

Or the choke linkage along with one of the above.

 

[Herb591]

Pilot jet is probably plugged.

 

[Falconpunch]

Checked the pilot and everything is clear. But look at the intake boots. One side is pretty well dry and cracking off.

 

[workdogz2]

Well there's your problem for sure massive air leaks.

 

[ScramblerCurtis]

^^^^^^ Too much air from leaky boots. Erratic idle will result.

 

[Falconpunch]

Replaced the insulators/boots. Checked the Pilot jet and main jet, those were clear. Bike will still only start and idle with full choke, any less and it dies. I hope I didn't clog the pilot with the silicone I put with the Oring. What else could I do? Buy a bigger jet for the bike? The intake boots are pretty secure, Airbox boots are on but tiny bit loose to the airbox. Carb looks good on the inside.

Before I was done for the night, I saw that the air host from the tank to the carb was crusty and old. I'm going to replace that today and hopefully something changes.

 

[J-T]

Silicone?

O-ring?

This wouldn't happen to be the O-ring on the mixture adjustment screw, would it?

 

[Falconpunch]

Silicone?

O-ring?

This wouldn't happen to be the O-ring on the mixture adjustment screw, would it?

No, O-ring on the intake boot to the head. The Mixture screw would be the little brass colored that sits under each intake port right?

 

[J-T]

Correct, that would have been a bad place for silicone. Should not be necessary on the intake boots but shouldn't hurt anything either.

 

[Falconpunch]

Well adjust the idle on the carbs, richen out a turn and bike seems to idle great without choke. Took a ride and does well. I like where it is.

Does anyone know the riding temp of the bike?

 

[Falconpunch]

450 nighthawk

 

[fxray]

You sound like you know what you are doing, but more than one person with the symptoms you describe (engine only runs with full choke) has misunderstood the choke's on/off positions. When they thought they were running full choke, the choke was fully off, and vice versa.

 

[blu3fan]

these carbs are a pig.
any air leaks will seriously create a bad time.
as well as them not being spotless inside.

 

[longdistancerider]

Good that's up and running now, operating temps are between really hot and hotter.