Time for carb rebuild?

[Koboldwrangler]

Hello--

Been working on and riding my '78 gl1000. Fixed the charging and cooling issue, and I am still left with the popping issue from the exhaust, amongst a few other weird oddities. I am pretty sure the carbs need a rebuild, but just wanted to get confirmation on that.

• While riding, sometimes 1 or 2 (cant really tell) of the cylinders will occasionally drop out when mildly accelerating for a few seconds before rejoining the rest.
  
  When accelerating hard, after decel'ing a bit, 1 or 2 cylinders drop out for a few seconds before rejoining the rest.
  
  Sometimes the idle will be high (2k->2500-ish, tach is currently inop-ish) othertimes it will drop really low and stall.
  
  While keeping the rpms around 3k-ish for checking the stator, there will be a constant popping from the exhaust. I tried to take a video of it, but its harder to hear. In the video it just sounds like the engine is breaking up a bit. Very apparent in person.
  
  Sometimes when decelerating, the engine will sound normal for a bit, then ...Pop! ...popopopop...pop out the exhaust. I just rebuilt the ACV, and havent tested to see if that fixed this issue. PO rebuit it, but I think he forgot the small inlet o-ring as I didnt see one in there. Mounting o-rings were original though.
  
  Just adjusted the points (.016"), and adjusted valves (all i had was a .005 / .012mm feeler gauge). In the video, my points are sparking really bad. The condenser is new, cleaned the battery box connection, and added a secondary ground. I have new points I need to install, but I have to drill out one of the 1-2 backplate screws so I can properly adjust everything.
  
  When using the choke, it doesnt seem like its doing much of anything while starting. I can ride with it on as well and it may be a bit more hesitant at times.
  
  Checked spark plug cap resistors. None were corroded, all tested fine. Spark plugs are new as well.
  Carbs were synced when I first got it running. They could be better, but should be close enough to not cause issues.

Thoughts? Anything else I should check?

Should I do the rebuild myself, or send it out? I have done mild carb rebuilds before, but nothing to the extent of these.

Heres the video I took:
https://www.youtube.com/watch?v=iDyBzsK8_Ds

[gltriker]

Yes .

[Koboldwrangler]

For curiosity sake, See what effect setting all 4 pilot screws at 3 full rotations out from seated might provide

after re-reading the first post, again-
If you can ride with the choke on, that's extreme.

Yes. Removing the carburetors is required. Is the fuel tank de-rusted?

I will have to do a ride test tomorrow...but doing a center stand mid rpm hold, it still excessively popping from the exhaust. After holding the rpm around 3k-ish, if i give more throttle, rpm will dip before surging up, with cylinders dropping in and out as well as louder popping from the exhaust.

Maybe the popping is from the cylinders dropping in and out?

[cfairweather]

The symptoms you describe sound like your carbs are the issue. You have one or more float valves leaking or your plenum seals are leaking. Take the air filter off and shine a flashlight down into the plenum while the engine is running and wait for the problem to occur. You will probably see fuel run into the bottom of the plenum, which is what happens when the seals leak or the float valves fail to seal.

[Koboldwrangler]

Friday, May 27th edit- my suggestion is a waste of time! >>>>For curiosity sake, See what effect setting all 4 pilot screws at 3 full rotations out from seated might provide

after re-reading the first post, again-
If you can ride with the choke on, that's extreme.

Yes. Removing the carburetors is required. Is the fuel tank de-rusted?

After doing the screw adjustment, the choke did have a minor effect with it on the center stand.

Yes, I derusted the tank and coated it with the por15 tank kit.

[redglbx]

Just an FYI,,, the spark plug cap resistors should measure at less that 5k ohms, there are a number of issues that disappear with good plug caps, with that said I truly believe that’s probably not it. I currently am experiencing the same problem on my 76 and setting the 1100carb idle mix screws to 3 out from seated helped as did replacing 2 out of spec plug caps, but it still is popping, not nearly as bad but still there.

Myself I’m kinda thinking I have a problem with one of the Dyna modules but that doesn’t apply to you because you have points. Mine doesn’t start until the motor is completely up to temp , what about yours ?

The only other thing that experience has taught me about exhaust popping is from a sticking or bad exhaust valve, a compression test should show that.

[Koboldwrangler]

Just an FYI,,, the spark plug cap resistors should measure at less that 5k ohms, there are a number of issues that disappear with good plug caps, with that said I truly believe that’s probably not it. I currently am experiencing the same problem on my 76 and setting the 1100carb idle mix screws to 3 out from seated helped as did replacing 2 out of spec plug caps, but it still is popping, not nearly as bad but still there.

Myself I’m kinda thinking I have a problem with one of the Dyna modules but that doesn’t apply to you because you have points. Mine doesn’t start until the motor is completely up to temp , what about yours ?

The only other thing that experience has taught me about exhaust popping is from a sticking or bad exhaust valve, a compression test should show that.

when i checked my resistors, they were all around 5k-ish ohms. none were corroded whatsoever.

popping for me is immediate, cold or warm. I need to change my points as they are arcing really bad even though the condenser is new, and I have the secondary ground strap. I will probably pick up one of those no name dyna modules just to get rid of the points.

[Jonesz]

Not the same bike but I have just finished my resto on a 79 Suzuki GS850. Was chasing a popping condition and a couple of cylinders that seemed to "drop out occasionally at different throttle positions. Put in a set of new plugs and the condition cleared right up. I am assuming the old ones were at least 20 some odd years old as the bike had not been registered since 2000. One of the best tools I find to track cylinders firing/not firing is to check the headers while running with an IR temp sensor. Relatively inexpensive and at most major retailers. Just something you might try. Took the bike for her safety inspection yest, required here for registration and the shop owner commented that I had the bike running very nicely.

[pidjones]

A lot of the NGK plugs purchased online have been found to be counterfeit. I buy mine at NAPA. Really, ,if the points are arcing badly they need polished up (some 600 or 1200 grit) and run until not arcing before putting in new points. The connection between the condenser and the points in the triple joints needs to be good, too.

[Koboldwrangler]

(full disclosure, i dont know the proper names for the jets and whatnot in these carbs)

Welp, happy ending this time. Went to saber cycle and picked up a carb rebuild kit, and the plenum gasket. I wish I had known the kits didnt come with the plenum fuel donut o-rings...but oh well. Mine seemed to still be fine.

Got to work tearing into the carbs and...they werent all that bad. Bunch of silty rust in the bowls, and most of the brass wasnt clogged. The only clogs I found were in one of the middle jets in the bowl, and one of the air tubes had a couple of the holes plugged. Someone has been in the carbs as some of the rubber was still good, and there was a homemade holder for the brass piece that the float needle sits in. Aluminum pucks practically fell out of the carbs, and I only had to kinda fight one of the float pins.

I used plastic epoxy to cover the buttons on the carb hats. They were all showing signs of weather cracking, but one in particular had a crack leading under the button. Not sure if it made it all the way into the carb hat. Used deoxit gold on the inner brass sleeve to remove any oxidation, and to lubricate the slide to help things move freely.

My biggest complaint with the barracuda kit is the oring for the #60(?) jet in the fuel bowl is too small. On their own, the jet didnt have any resistance when pushing them into the towers. This will probably end up biting me later on, but I swelled the oring a bit with some acetone, and that seemed to help. Only time will tell I suppose.

I still need to check sync and do a dynamic timing set, but it runs waaaaay better now. It will start sputtering at high rpm in first gear, but seems to be fine in every other gear.