Finished the sync!

[Rein]

Okay, So, it seems like it's all done, but there's still something missing.

Carbs were cleaned, ultrasonic, came back spotless, new orings. Seats and valves are oem new, and float heights are set at 24mm.

Bought a secondhand set of carb to head boots. All the rubber is there, not as soft as the airbox boots, but I'm confident they seal very well. They look to be in great condition, no cracks. New orings there too.

Airbox boots seal great as well, no cracks in the airbox, filter is a UNI, and is oiled and cleaned.

Jets were replaced, got them from Bill (chef1366). 110's on the outside, 112.5 on the inner two. I was provided 160 air jets, as it's stated in the manual, but from a few pm's and research, I found that all 650g's actually have 150 airjets. the current ones in the bike are 155's.

I raised the needle by replacing the spacer with washers half the size. Didn't change much though.

Carbs synced with a Morgan Carbtune, screws set to 2.5 turns out. Haven't had time to mess with it, but I'd think 2.5 should be okay for now.


Symptoms: Starts up perfectly. Rev's up and down nicely. Ride for about 5 minutes and warm her up nicely, then she'll start to hang at 1500 before dropping to normal. Sometimes it'll drop slow to 2000, then 1500 then back down to normal. Cylinder #4 is not as hot as the others at idle. At idle, you can spray water on it, and it won't dry up. It's warm, but not hot. Open the throttle for a bit, or right after returning to idle, it's plenty hot, and will vaporize water like the other pipes.

Spark plugs are black and sooty, no indication that they are lean.

[Rein]

The only thing I can think of is bad exhaust gaskets. The current screws are mostly rusted, and two or three have been replaced with ss bolts.

[Nessism]

A hanging idle means the mixture is either too lean or the bike is sucking false air, typically from the intake boot and/or O-rings. I'd try 3 - 3.25 turns on the pilot screws and see if that helps.

Regarding #4, did you adjust the valves lately?

[Steve]

Actually, my guess is that it's still lean, most likely due to improper float setting.

You say they were set to 24 mm, spec calls for 22.4 mm.
Raising the measurement actually lowers the float, because they are set while upside down.
Also be sure that you are measuring from the bottom of the step on the float, not the top

.

[Rein]

A hanging idle means the mixture is either too lean or the bike is sucking false air, typically from the intake boot and/or O-rings. I'd try 3 - 3.25 turns on the pilot screws and see if that helps.

Regarding #4, did you adjust the valves lately?

I tried 3 turns out today, after I posted, went to 3.5. Helps a little, but still hangs. Boot o-rings are new, I just checked them last week after pulling off the carbs. I replaced them when I got the bike, and they're still nice and supple.

Should I try giving the boots a good torque down? I'm assuming, since it only runs lean when it's hot, the heat transferred from the head to the metal parts of the boots, and expands the rubber, creating a leak?

how soft are new intake boots? as soft as airbox boots?

[Rein]

Actually, my guess is that it's still lean, most likely due to improper float setting.

You say they were set to 24 mm, spec calls for 22.4 mm.
Raising the measurement actually lowers the float, because they are set while upside down.
Also be sure that you are measuring from the bottom of the step on the float, not the top

.

You know what? i'm not entirely sure. I may have set the floats to 22.4, or 24mm. I don't exactly remember.

If it's lean, why would my plugs read rich?

EDIT: Also, regarding the valves, I adjusted them a few months ago, before I left for training. Bike has practically not been ridden since then. Checked them last month, all are within spec, most on the loose side. I think the intake on # 2 and 4 were out of spec, but on the loose side. however, the other week, #4 was nice and hot at idle.

[Rein]

I'm suspecting the carb boots to the head. If it was a leak in the airbox boots or air ox itself, then wouldn't the hanging be present at all times? Not just when hot, right? Of course, when it gets hot, the boots expand and I guess create a leak that wasn't there before?

[SqDancerLynn1]

Re clean carb 3, turn the mixture screw out another 1/2 turn DO A CARB sync....

[Rein]

Re clean carb 3, turn the mixture screw out another 1/2 turn DO A CARB sync....

#3 or #4? Then re sync? Will do.

[Rein]

I'm guessing I might as well dip all the carbs anyways. The carbs were cleaned last december, but the bike sat in the garage with some stabil in the tank since then, while I was off at training. I just examined the carbs a little, and #4's choke circuit in the float bowl was clogged. Put it back on to check, but no difference. Gonna go back and check the fuel level with the tubing method, after I dip the carbs.

She'll start up perfectly, and idle like a clock all day. But once she's warmed up, she'll hang.

[1948man]

Is spraying carb cleaner to the seam where the carb boots mate up with the engine and listening for an idle change a worthwhile way to diagnose an air leak there?

[Rein]

I doubt it, the only thing that changes the idle speed is the propellant, not the carb cleaner itself. Spraying it on the carb boots would dry up the carb cleaner instantly, not to mention, if any liquid does make it on there, it would block air going in.

I think a better alternative would be to use another fluid, like oil in a spray bottle or chain lube, and hope that the oil will seal the seam for a bit, and prevent any hanging.

Disassembled the carbs, one pilot had some crust on it, one needle jet's top holes were blocked, crusty needle jet passages. I guess it's safe to say they needed a good cleaning. Sitting in the dip right now.

[Rein]

So, just put the carbs back together after dipping them for more than 24 hours, boiling them in hot water, and running them through an ultrasonic parts cleaner at my local tattoo shop for 4 hours.

They are spotless.

Assembled everything, and it still hangs when warm, hangs a little less, but still hangs. I'm beginning to think it's the 155 airjets when it should have 150's like everyone else. Not sure though. Carbs were synced, but color tune hasn't arrived yet. However, I would think if the screws were set at 3 turns out it should be bogging a bit like it's rich? Float heights were set with a digital caliper.

Plug chops for idle/quarter throttle reveal it's rich, turns tan with some soot at other throttle position.

I guess if it's running rich, it'll be fine? hanging is manageable, I can bog it down with the clutch.

[ozman]

Is spraying carb cleaner to the seam where the carb boots mate up with the engine and listening for an idle change a worthwhile way to diagnose an air leak there?

use a spray starter aid fluid like aerostart or similar ether will make the revs pic up if theres a leak
just spray it around the seams in small bursts and not near airbox intake
oz

[ddaniels]

Are all the pipes hot now? I was having that problem and turned out to be clogged choke circuits, but you fixed that.