BS38 Float Bowl Issues

[TwoManyXS1Bs]

Oh, yeah. A set of #61-#80 mini bits, with a good pin vise, is a welcome addition to the toolbox.
The #80 bit, at 0.0135" (0.34mm) comes very close to a #35 idle jet on Hondas.
Used that to fix many stumbling Goldwing carbs...

 

[Kgreenhaw]

I compared and inspected both sets of pilot jets. same pattern and same hole count...

I also took a closer look at the bowls and was thinking maybe the pilot was sitting so far down in its seat that it could be partially blocking the bleed air passage, but I shined a light through and could clearly see the air holes in the jet. It didn't appear that the threads of the pilot were entering/blocking the bleed air passage.

The only other difference I notice with the bowls is that there is crud in the very bottom of the pilot orifice. It seems I would have the opposite problem if fuel was being blocked. There is no airflow down there, correct?

 

[Kgreenhaw]

Oh, yeah. A set of #61-#80 mini bits, with a good pin vise, is a welcome addition to the toolbox.
The #80 bit, at 0.0135" (0.34mm) comes very close to a #35 idle jet on Hondas.
Used that to fix many stumbling Goldwing carbs...

Ok, so maybe not such a crazy idea! I would like to figure out whats going on with the bowl, but if I can get it to run nice with a modded pilot I guess I can live with it.

 

[TwoManyXS1Bs]

Correct, no air below the pilot's seat.
That area cross connects to the area above the mainjet, so the mainjet meters all fuel delivery.
It's possible to work a 90° probe/pick in there to dislodge crud, but that's about it.

Could try viewing down into the pilot well, check condition of the walls. That's where I'd try to cook up some sort of underwater bubble test, looking for leakage...

 

[Kgreenhaw]

I did some block sanding on the bowl I was having issues with and pretty much worked out any irregularities. I also sanded a bit on the other bowl even tough it didn't seem to be giving me any problems. It turns out the "good" bowl had worse pitting/gouging than the other. Good bowl is the last pic that is flipped the other way. I took the pic after a light sand to show imperfections, I continued to sand and flatten it out a little better..

 

[Kgreenhaw]

I cleaned out the bowls, reinstalled the pilot jets, put a light coat of oil on the gaskets and reassembled the way they came off (problem bowl on left) I just snugged the screws as I did every other time, trying not to over tighten.

I ran the bike and it behaved a lot differently. High idle, seemed to be running lean on both sides. I backed the mix screw out to 1 1/4 turns each side, adjusted idle and sync'd with manometer. Both cylinders ran good with consistent combustion, with the occasional hiccup.

One thing I did different this time was when I reinstalled the pilots, I used a different screwdriver and cranked down on the jets. I actually probably over tightened the one in the problem bowl, oops.. I kinda damaged the slot on the pilot, hopefully I can get it out if necessary, but maybe doing that sealed it up against its seat?? Idk.

Something else that showed up in the middle of all this is now the bike will stall out of nowhere at a stop. It never did it even when I was running rich and fouling the plug early on. It idles nice and seems better just off idle and all the way up to near WOT. not sure what's going on now..

I snapped a photo of each plug after a short ride this evening. the last time I ran it the left plug was covered in black soot.. Right plug looks white, but its closer to color of left (crappy picture) Am I too lean now? lol. Timing? Ugh.

 

[TwoManyXS1Bs]

I certainly applaud your sticktuitiveness. Be it better or worse, it's good you've got some changes now. Of course, 2 mods that may confuse things a little, flattening the bowl surfaces and firmer seating of that pilot jet. Certainly hope you can get it out later. There's some tips buried in here somewhere on removing stuck, stubborn pilot jets.

Couple things that helped my idle stability were:
Replacing throttle shaft bushings & seals, centering butterflys.
Retarding the timing a bit. Have to nudge the idle stops a tiny bit and gets the butterfly edges further away from the non-round carb throats.

You probably already saw that stuff in my album and threads.

I think you're doing a great job dogpaddling thru all this. These old bikes are definitely getting past the textbook maintenance and entering the bizarre world of having to re-engineer irreplaceable parts.

Might need new bowl gaskets. When they get old and hard, they can't compress/give/form to the surfaces. You still have the bowl swap option to diagnose further. You may also have air leakage now, because of the idle stumble and needing the mix screws out too far...

 

[grizld1]

Congrats!

Re. stalling at stop, that's often a symptom of high fuel level. To check, let the motor idle while you coast down a hill, and see if the motor stalls or revs drop sharply when you give the front brake a good squeeze.

 

[Kgreenhaw]

Thanks guys, I appreciate all the help. A couple things I should mention:

When monkeying with carbs a couple weeks ago, I adjusted the float in the right carb to try and lean it out, didn't help, but I never changed it back...

The stalling issue will occur even when bike is stationary on kickstand.

I'm also running a capacitor that I sourced myself from digikey. It has a higher farad rating than the "sparx" cap. Also I saw on mikesxs that they say not to use a cap with E-advance wondering if this could somehow be related. A week or two ago it died when I turned on the headlight, but now it doesn't.

Won't be back home til the weekend. I'll mess with it and give an update

 

[Kgreenhaw]

I was at the 100 mile mark on the engine so I went ahead and did a head re torque, checked cam chain, and reset valve lash. I also adjusted floats back where they were supposed to be (both set high), adjusted mix screw back to 3/4 turns, and sync'd. I was still experiencing the intermittent stall, so I played with the timing a bit. First I retarded it and it seemed to make it worse, so I advanced it and it seemed to like that.

I took it out for a spin around town and it didn't stall. It did have a little hiccup and one of the stoplights, but the engine didn't die.

Something I had neglected when installing my pamco came to mind. I remembered the part that replaces the advance unit was a little weird. The key ways weren't cut right and I had to "mill" them taller with a dremel so that pins would fit. Also, the key way for the pin on the cam looked to be offset and didn't line up with the axis of the advance rod. To me, this seems like it is retarding the ignition. To get the timing in the normal range I have to adjust the plate to nearly full advance. Is this normal?

I took the bike out again a couple hours later and went for a longer ride on some back country roads, it rode great! Maybe it was just me, but it seemed happier coming back through town at all the stops, no stumbling at stops, etc. I also had the headlight on and it didn't have any effect on how it ran.

One last thing. When I sync the carbs using my home-built manometer the left side always seems to pull harder, although very slowly. I backed the idle screw nearly all the way out and it didn't really do anything.. its like I have to turn them a lot to see any noticeable difference.

 

[TwoManyXS1Bs]

Pete will have to advise about that advancer replacement 'cup'.

The 'balance tube' between the inlets on our early heads may render manifold vacuum syncs difficult or meaningless. Good idea to check that thing anyway for leakage. I found a 1/2" crack on a hardened tube, close to the right inlet, on a used head. Would've never seen or found it without removing it. Must've given the previous owner fits.

Couple sync methods you could try:

1. Idle stops equal turns from full throttle plate closure. Mine are about 1/3 turn from full closed.
2. Equal pressure pulses felt at the exhaust.

 

[Kgreenhaw]

At second glance, the advance replacement cap would be putting my advance rod slightly ahead of the cam. That would advance timing and in theory would require the plate to be adjusted more towards the retarded position? I've verified the cam timing is correct.. I was almost worried I really was a tooth off, as I had thought a while back. Sorry, I know this thread is really starting to wander...

 

[TwoManyXS1Bs]

You could try a quick, impromptu cam timing test.

Remove plugs and both left valve covers. Rotate the engine so the left cylinder is at TDC of the overlap, where exhaust is closing and intake is opening. Watching the valve movements, and feeling for that position where the cam is trying to equalize the valve spring pressures, position the crank (without looking at the crank position), as best you can, so that both intake and exhaust are equally open.

Now look at the crank, and see how close the timing mark is aligned.
Misalignment of 20° is 1 tooth.
Or seriously stretched camchain.

Mine's stretched to about 10° retarded, so my points plate is set almost at full advance...

 

[TwoManyXS1Bs]

Re-reading your thread, found I overlooked this one:

...At one point I had tried a 42.5 pilot and it ran too lean. Wondering how this plays into the equation..

I'm running stock 42.5 pilots in my E3 carbs. If your carb was intended for 42.5 like mine, and it shows lean, then we're looking at the opposite problem, too much air...

 

[Kgreenhaw]

I can check cam timing again using the method you describe. The bike runs so well that I don't really suspect that it is off. I saw a video of how an xs650 will run with a tooth off and it looks like it would be pretty obvious. With the crank at TDC the pin on my camshaft is at 12:00.

My carbs are supposedly 1970's and from what I read on the carb guide they took a 45 pilot jet, so by putting in the 42.5 I would've expected it to run on the lean side. I only did this while trying to diagnose the rich condition, I wanted to see if there was any change.

The bike no longer runs rich at idle, so I guess I can call this one fixed! Still not totally sure whether it was the pilot jet seating or the irregular mating surface of the float bowl, but if I had to bet I would say it was the jets. I was using this little pocket screwdriver that didn't fit the slot well. When installing them the last time, I used a ratcheting T handle driver with interchangeable bits. Found one that fit well and got 'em nice and snug.

 

[5twins]

It's hard to find good fitting screwdrivers for the jets because the screw slots are metric sized. Many of us have taken to custom grinding 1/4" driver bits to fit. These are dirt cheap so no biggie if you screw some up in the process .....

I use a T-handled holder for removal and a stubby or knurled bit holder for install .....