Mikuni CV BS34 lean but rich?

My 82 LTD 1000 has Mikuni CV carbs which I'm pretty sure are the BS34 type.
They have had basically the same symptom since I had the bike. From box stock, to header and uni foam dual throat pods, (122.5-127.7 mains, stock 37.5 non-bleed pilots) and the coil rewire job.

A bit hard to start, black smoke, fouling mew NGK plugs (not always the same one) on start up, popping, dead spot from 1100-2500rpm, had to run on half choke for a long time. When it's fully warmed up it ran pretty good.
Well it did. It has gotten progressively worse over a few hundred miles (in 3 years, used sta-bil and fresh gas as needed)
At this point(80+ deg) it won't run off full choke for several minutes and barely runs on half choke after that.
I didn't even bother to let it fully warm up this time.

I have had these carbs apart for the 4th time now. Even the first time they weren't dirty. That's the background. Now for the questions.
Could bad o-rings cause these problems? All the o-rings while not really hard are questionable as to a good seal. The slow speed screw o-rings are crap and likely not sealing much, the pilot jet plug o-rings are fair, and the float valve seat o-rings are so-so never seemed to overflow the bowls even running on prime due to bad petcock diaphragm. However the bowl vents are internal so maybe.
Here's a pic of carbs in question

Cycleorings.com has o-ring kits cheap. Did you put the rubber plugs back on the pilot jet holes ? I cant help you on the jetting, I dont like or run pods

Thanks for the link on o-rings.
The pilot jet plugs are brass with an o-ring and may have been the only ones that were sealing.

I think all I really need are the o-rings for the float needle seats, the idle screws, and the pilot jet plugs.

Ive never seen brass pilot jet plugs with o-rings before, are they stock ? The o-rings for the needle & seats may be your problem.

Yes they are stock. After further inspection they actually look like they aren't brass, but they are about 1/4" long metal plugs with an o-ring on 1 end. The plug o-ring looks the same size as the idle mixture screw o-ring.

I've got the big box of assorted generic nitrile o-rings that don't really have the perfectly exact sizes I need, but with a tad of grease they seem to fit in well without tearing up as they go in (a bit tight otherwise).
Will give them a try and see what happens.

Well it looks like I have been spinning my wheels here and not the wheels on the bike
All the carb work has changed nothing. While doing the rebuild I went ahead and put in the 127.5 main jets I had planned to put in before. Since it seemed rich I've waited til now thinking I've fixed the problem of leaky o-rings. I even changed plugs in case they got gas fouled one too many times.
It still is not even running on all 4. I am trying to run with tank off pouring gas into fuel line with a tiny funnel until it stops (bowls full, no overflow) then starting.
When I got it started I tried to determine which carb/cyl might be an issue. I shot a spurt of starter fluid in each carb, in 1,2 rpm down, 3,4 rpm up. After I shut it down exh pie on 1,2 were hot, 3,4 barely warm. Tried it with propane and couldn't tell any difference.
Put in the new plugs. No real difference from above except maybe #3 exh got a bit warmer.

It's still looking like a carb problem, but after totally going thru them this time I don't know. When I took the carbs apart AGAIN tonight I first checked fuel level and it looks like #1 might be a bit high, 3,4 ok #2 can't check because I can't get the drain screw out as it's stripped, but I dumped the bowl and it measured about the same as the others I drained into a cup. I noticed the the bearing grease I used to lube the orings on install in the pilot jet plugs looked like it might have "gelled" up, but I'm pretty sure that the grease will dissolve in the gas and not plug up anything.

I'm back to square one checking all the basics, compression, recheck ignition, wiring etc.
I did the coil rewire a long time ago, and checked original coils 2 days ago, 2.8 ohms on primary.
I've always thought that I might still have a weak spark even though it checks good. Used an inline spark tester light and it seemed fair on all cylinders. I need to check spark output by seeing how big a gap it will jump, but not sure how to do that.

I'm not a novice by any means having rebuilt 80-100 car carbs and did quite a few KZ carbs back in the 80's, but I'm about to throw up my hands for now on this bike. I don't have time to spend hours a day trying to get this figured out. My head is spinning, literally.

jga2z wrote: Well it looks like I have been spinning my wheels here and not the wheels on the bike
All the carb work has changed nothing. While doing the rebuild I went ahead and put in the 127.5 main jets I had planned to put in before. Since it seemed rich I've waited til now thinking I've fixed the problem of leaky o-rings. I even changed plugs in case they got gas fouled one too many times.
It still is not even running on all 4. I am trying to run with tank off pouring gas into fuel line with a tiny funnel until it stops (bowls full, no overflow) then starting.
When I got it started I tried to determine which carb/cyl might be an issue. I shot a spurt of starter fluid in each carb, in 1,2 rpm down, 3,4 rpm up. After I shut it down exh pie on 1,2 were hot, 3,4 barely warm. Tried it with propane and couldn't tell any difference.
Put in the new plugs. No real difference from above except maybe #3 exh got a bit warmer.

It's still looking like a carb problem, but after totally going thru them this time I don't know. When I took the carbs apart AGAIN tonight I first checked fuel level and it looks like #1 might be a bit high, 3,4 ok #2 can't check because I can't get the drain screw out as it's stripped, but I dumped the bowl and it measured about the same as the others I drained into a cup. I noticed the the bearing grease I used to lube the orings on install in the pilot jet plugs looked like it might have "gelled" up, but I'm pretty sure that the grease will dissolve in the gas and not plug up anything.

I'm back to square one checking all the basics, compression, recheck ignition, wiring etc.
I did the coil rewire a long time ago, and checked original coils 2 days ago, 2.8 ohms on primary.
I've always thought that I might still have a weak spark even though it checks good. Used an inline spark tester light and it seemed fair on all cylinders. I need to check spark output by seeing how big a gap it will jump, but not sure how to do that.

I'm not a novice by any means having rebuilt 80-100 car carbs and did quite a few KZ carbs back in the 80's, but I'm about to throw up my hands for now on this bike. I don't have time to spend hours a day trying to get this figured out. My head is spinning, literally.

Ohm test all four resistor caps, if any have a wandering reading problem solved.

I use these same carbs on my GPz1150 and can tell you that bad "O" rings ANYWHERE will give you a problem. Improperly adjusted pilot needles will also give you a problem. I run individual pod filters on my bike with no problems at all. When adjusting the pilot needles forget the "# of turns" method. Do the individual carb adjustment while the bike is running at idle method. The main jets only come into play in the last 15-20% of throttle setting. Did you ever check the "jet needles" to see if they are warn? after all they are only anodized aluminum and if the anodizing wares off they will ware very quickly. The pilot needle "O" rings must seal perfectly and so must the "O" rings on the pilot jet plugs. I have been building these carbs for decades and love them. They have the equivalent sweep area as a set of 31.5mm smooth bores would without loosing the fuel efficiency that smooth bore carbs would do. These carbs wont win you any drag-racing records but for everything else they can't be beat. you can check out my thread with the build of my bike.
kzrider.com/forum/11-projects/169462-bui...z1150-from-a-csr1000

CLICK----> Carb O'rings

You didnt mention if you blasted the pilot passage ways clean, verifying by looking in the carb bore for jetting (flow) of cleaner into the bore. If you plug the mixture screw hole and spray up through the pilot jet passage (no jet), then you should see a nice clean continuos spurt of cleaner out all three holes in the top of the bore.

Perfect air tight seal and accurate vacuum sync are crital to run these carbs successfully. Do you ahve a manometer? A bench sync is complete crap at best, and is usally 5 or more points off of a proper (spec) sync.

PS. Cylinders dont have to be firing for an accurate sync. If after syncing you discover that one or more of the throttles needs to be completely closed to match the sync of the others, that is because there is a vacuum leak.

Tune the mixture screws. Turn them out 1/4 turn at a time (waiting 3-4 seconds) till you hear a noticible drop in rpm (cleanness of idle), then turn them back in 1/2 turn (return to smooth idle). They should all be within 1/2 turn or less of eachother with pods. If not, then again you probly have air leaking in somewhere.

Good luck!

A good sync will only affect lo-idle. I have NEVER used a manometer to sync my carbs and have never had a problem. I just do mine mechanically.

Just a bit more background.
I have only put ~600 miles on this bike in 5 years riding at best 4-5 times a year. This has been a progressively worsening problem since I got it.
Last time it was ridden with decent performance was last fall. Next time was back in March when it ran 25 miles and would run like crap at low rpm's. Tried to run it a month ago and would only run smooth on full choke. got all blubbery on 1/2 choke like running on 3cyl which is about where I am now except it won't even run on all 4 smooth at any time.

In order of replies.
I have no resistor end caps. using MSD 8mm copper wires and MSD end boots, NGK B8ES (only 500 miles on them) and now Autolite 4054 plugs.
Idle jet needles, float valve seat, (both formerly crap o-rings) and pilot jet plugs now have new o-rings which while not perfect size should be sealing.
I've plugged all the vac ports on top of carbs, and tested for vac leaks at intake boots many times.
The main jet needles look like new.
While I didn't dunk the carbs in cleaner (they were never very dirty), I did blow cleaner/air thru every passage with no problems.
Don't have a manometer, but bench sync is, and was perfect. Never readjusted. Has run awesome on occasion.
The mixture screws were all at 1 1/2- 1 3/4 turns before last tear down, so that's were I started. I haven't changed them since it ran OK when I set them a couple years ago.
I'll try to readjust the idle jets, but I don't think they they are causing it to run this bad.