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Finished the sync!

  • Thread starter Thread starter Rein
  • Start date Start date
R

Rein

Guest
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.
 
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.
 
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?
 
Actually, my guess is that it's still lean, most likely due to improper float setting. :-k

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. :o
Also be sure that you are measuring from the bottom of the step on the float, not the top

.
 
Nessism said:
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?
Click to expand...

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?
 
Steve said:
Actually, my guess is that it's still lean, most likely due to improper float setting. :-k

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. :o
Also be sure that you are measuring from the bottom of the step on the float, not the top

.
Click to expand...

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.
 
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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?
 
Re clean carb 3, turn the mixture screw out another 1/2 turn DO A CARB sync....
 
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.
 
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?
 
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.
 
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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.
 
1948man said:
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?
Click to expand...

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
 
Are all the pipes hot now? I was having that problem and turned out to be clogged choke circuits, but you fixed that.
 
Rein said:
I'm beginning to think it's the 155 airjets when it should have 150's like everyone else. Not sure though.
Click to expand...

650 carbs I have seen have had 155 or 160 air jets, where did you get the 150 spec?
 
Yes according to the manual, air jets are 160, but I pnd and did a big search on the forum, most of the 650g's have 150. However, if there are bikes out there running fine on 155, it's something else.

Well, #4 is hot again, like #1 and 2, but now # is not as hot. However, it's still too hot to touch, but it doesn't vaporize water. I'll chalk it up to the mix screws not being properly adjusted yet. Will give it another lookover
 
Anyways, went out to check one more time.

Idles fine and revs fine after start up. once she gets warm, all pipes are hot. #3 vaporizes water but not wd40 like the other pipes. still hot enough to burn though

... ask me how I know..

Once hot, she hangs when returning to idle. I sprayed carbcleaner around the boots, hoping to seal any leaks, and the idle would drop and the bike would nearly bog out. If I rev it when the idle drops, she acts perfectly fine. once the carb cleaner dried up, it was back to hanging.

I hooked up my voltmeter to verify that it wasn't the charging system dying intermittently. At charge, it seems the battery is only at 12.5-12.7 volts at idle. at 4000 rpm it's at 13.5V. When the bike bogs down after spraying the boots, voltage stays steady. With the bike off, voltage is at 13.2V. Although, this surprises me a bit, the bike passed stator papers before I left for training. I do have a new Honda R/R I've been meaning to get around to, maybe I'll change it out this weekend.

Boots look good, but then again, they might be some small but significant cracks on 3 and 4, which are the boots that I tested.
 
I sprayed carbcleaner around the boots, hoping to seal any leaks, and the idle would drop and the bike would nearly bog out. If I rev it when the idle drops, she acts perfectly fine. once the carb cleaner dried up, it was back to hanging.
Click to expand...
Sounds like you most certainly have an induction leak at the carb boots, I know you said the O Rings where new, but have you checked the mating surfaces of the boots, where they pull up against the head for straightness, they may be slightly warped or distorted.
Best way to ckeck this is with a known straight edge drawn across the surface and looking for any light coming through between the straight edge and the boot surface. What I like to do is lay a piece of fine 600 grit sand paper on a piece of glass pane, and rub the boot over the sand paper a few times, any high or low spots will show up straight away.
If they do, it is a simple matter od continuing to sand away on the glass pane until the surface is true again, it does not get straighter than that.

The same holds true for the mating surfaces on the head side, problem here, is if they are out, getting them fixed is much more difficult.

I know the O ring should compensate for it, to a point, but I have seen stranger things in my time, these are 30 year old machines and that area is subject to repeated heating and cooling cycles, I would be very surprised if they are 100% straight.
Hope this helps
 
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