UPDATE

I replaced the old intake boots and my crazy out of control idle swing went away. But now I have another issue. Here's what happened.

Started the bike. It fired right up. Revs quickly climbed to 5k with the choke fully on. Backed off the choke a little and then the idle dropped nicely and bike held steady.

Took off, wow! Bike had great power and I ran through the gears no problem. It felt just like my old motorcycle I used to have did when it was working properly.

This only lasted about a minute. After that my idle dropped below 1k. Bike would stall and bog with throttle. Idle screw did not seem to change anything and putting full choke back on only brought the revs back up to around 2k.

Any thoughts? It was so sudden. Could it be that battery we know is on it's way out?

Try again without turning off the choke all the way until you've been underway for like 5 minutes. Otherwise this could still be w vacuum leak causing the petcock to not stay open, so try running on prime if it happens again and see if that fixes it. Could also be sticking float needle valves, float level too low, other fuel delivery problem.

My bet is you just got in too much of a hurry to turn the choke off. These bikes are very cold natured.

I tried prime, no luck. Tried restarting with choke full on. No luck. Nothing I did could recover the idle I had when I first fired it up. It just wanted to die with any throttle after that.

Such a tease because it felt really solid. I'm at least really happy to have solved the large vacuum leak causing it to go haywire. I think you're right that I'm dealing with a more straightforward fuel problem. Feels like I'm getting close.

I've got a clear tube lying around I'll do the float height test when I get home and maybe try bringing the mixture screws to 3 turns instead of 2 1/2. I'm most bewildered by why it started up so good then instantly wouldn't stay alive.

don't mess with the pilot needle adjustment. adjust it correctly, which means you need to ride it until it's fully warmed up and then adjust for fastest idle. don't guess with that. If it's too rich right now you will just make it worse. I can't remember if you replaced the o-rings on the pilot needles, but if you didn't, then they could be leaking causing it to always run way too rich at idle.

could be it's flooding, could be stuck open float needles. Mine usually won't start with full choke once it's been at least partly warmed up. Solve one thing at a time. Don't screw around with the idle mixture until you can get it running under load and get the bike to warm up correctly. You can always nurse the idle once you get the carbs working right in all other stages and then dial the idle in right once you fix everything else.

Good call checking the float height. It's either not getting enough fuel, getting a lot of extra air via a vacuum leak, or getting way too much fuel. The plugs can help you figure out what but the truth is you can set it up to be way too rich at idle and then it'll be lean under load if you have a vacuum leak. So you HAVE to fix all vacuum leaks before you can even assess mixture. And float level can affect dynamic mixture (that is, mixture changes over time dependent on load) so you HAVE to sort that before you can evaluate the mixture. Once you know that is 100%, and I mean by replacing o-rings and vacuum caps etc. not by spraying something on the carbs and guessing, only then can you begin to figure out the mixture. If you have stock airbox and exhaust then a 122.5 or 125 main jet and 40 pilot with 2 turns out on the pilot mixture will get it in the ballpark and then all there is to do is adjust idle mixture. If it's not running right under those conditions, then vacuum, slides/needles/diaphragms, carb assembly, float level, float needles are the likely causes.

Ok sounds good!

I'll check the float height first and if that doesn't show anything i'll go through that carburetor again.

That would be cool if it was just float height. Maybe that crazy vacuum leak I had before allowed fuel in and that minute I was running it last night just combusted anything I had left over in the engine and once it needed more the float height didn't allow it. That's my optimistic pipe dream. 

Glad I started this in the dead of winter and not in nice weather.

well the vacuum leak caused two problems:

1. insufficient vacuum pressure to pull the slides up
2. air getting in without going over the jet

so it winds up making it run really lean, and then barely at all.

A vac leak anywhere will have this same effect. top of the carbs, leaking in the vac line going to the petcock, seal of the diaphragm, throttle shafts, you name it. air gets sucked in and that air is not going past the jets so it has no extra fuel to match. thus, vacuum leak causes lean running. And then too often we skip the step of finding and fixing the vacuum leak and instead try to compensate by tuning it way too rich, but then it is only running correctly when under WOT and high revs, but it will be untuneable at idle or low throttle openings.

the theory on the float level is that you either had the floats too low, so you starved it of fuel before it could refill, or you had the floats too high, so it flooded once the choke is turned off and not consuming all the extra fuel.

So my tube didn't fit snugly around the drain hose like in the video I saw so I wasn't able to check the float height on the bike.

Tried to start it up just to see what would happen as it sat for a day. Just barely started, died, then wouldn't start, then lights started dimming. Hooked up the battery to the tender again, too low to charge.

Battery is toast like you guys were telling me. Not going to do anything until I get a new one. However I am a little over budget this month so i'm going to give it a slight pause. I could use a mental break as well.

I also forgot to mention previously I got the infamous oil leak underneath the side stand. I took off the cover to the front sprocket and HOLY JESUS there was about an inch thick layer of much and wax and dirt. Disgusting, but the "leak" went away instantly!

New battery, nothing changed. Bike didnt even want to start. New plugs and the bike roared to life. Old plugs were completely carbon fouled.

I let it warm up for a few minutes and got the idle nice and steady, everything sounded real good. Tried to take off and everything that happened before happened again. Checked the new plugs and they are completely black and smell like gas.

So obviously I am running super rich to the point where the sparks start to fail. Cant find too much on this other than a blocked air filter or a leaking needle valve seat. Next step may be to replace those seats...

Or more likely you need new rings and or valve guides.

Quote from: Joolstacho on February 20, 2020, 11:50:29 PM
Or more likely you need new rings and or valve guides.

Oh boy...would the compression test not have ruled that out?

black plugs and wet -> too rich. That's when you start the bike, not when it's warmed up, so we're not talking about a mixture problem likely.

Consider what would make it super too rich when first starting up regardless of throttle. Can't be the main jets because the needles are in the jets so (little or) no fuel coming in there. So whatever is happening, is happening on pilot.

- float level way too high, caused by it being adjusted wrong, leaking/bad needle valves, seats, o-rings, etc.
- incorrect pilot mixture, in this case most likely bad/missing pilot needle o-rings or incorrectly assembled pilot needle setup (spring/washer/o-ring wrong order, didn't pick out the old o-ring before installing a new one, etc.)

When my bike had bent valves and bad rings, it would only run when cold and then once warmed up, it would not run below about 5K rpm and required constant throttle to keep it running. It ran fine as long as you revved the crap out of it. Shop originally thought it was leaking float needle valves but they were wrong.

Ok thanks guys.

Pilot screws went through carefully, o rings replaced and I used the diagram to put it in the correct order.

I'm going to to replace the needle and seat and triple check the float height. Worth giving a shot and eliminating a carb problem before moving to the engine.

Quick question, should I be tapping the seat into place gently with a hammer or use strong finger pressure?

Update.

After checking the oil I saw a good amount of fuel had gotten inside. I decided to change my needle and seats, triple checked everything on the carb and made sure it was perfect.

Upon starting the bike again I had the same problem, except this time the plugs weren't fouling with fuel, they were being covered in what looked like oil. They were stinking like fuel before because I had fuel in my oil.

Decided to check the compression again to rule out a mistake there. I found my mistake. I did the test at the seller's house with one plug off at a time. With both plugs out and grounded I got barely more than 130 psi in each side. Compression tester also got some oil on it from the cranks just to do the test.

Wasnt sure what to do at first. I'm not terribly afraid of the job but with tools and parts it was going to be pricey. I have a mechanic friend I was talking to about this and he said itd be super easy. I said hey what if I just pull everything and hand you the head and pistons? So that's just what I did!

Removing everything turned out to be a piece of cake. I just followed the top end rebuild video on youtube step by step. Everything slides out nicely right in the frame.

Upon receiving the head he could tell right away the valves were leaking. He pulled the seals and said they just fell apart. Valves are still in good shape.He will also be doing a ring job.

I ordered new gaskets and orings (including copper washers) for when I reassemble so I think that just about rules out any oil leaks that could be occurring inside the engine.

I'm spending more than I hoped but this is turning out to be such a fun and rewarding experience.  I finally understand the basics of engines just by taking everything apart and seeing how it all works. It was a super cool experience taking everything apart. I used to think this kind of stuff was beyond me. I was cringing a bit just reading my posts at the beginning of this thread! I'll keep you guys updated.

I also forgot to mention when I could get it to rev I recorded the exhaust and could clearly see blue smoke. Here are some pics!

https://ibb.co/7W12shK
https://ibb.co/b1BGqVQ
https://ibb.co/4fJnTkR

My experience with compressions tests. I was worried when my gs only tested at 120 and 116, considering the min spec is 140, but hey guess what, it makes no freaking difference. The front right exhaust was a little bit loose and getting looser started at 06mm but gradually went to .1 however she has stayed there. The problem I was having was a faulty carb slide press fit piece that had come loose. New carb fixed that and she's been running really well ever since.

So seeing as I had the compression test kit, I tested an almost new S40 Suzuki and it too was testing 125 when it should have been 140 at the lowest,  and goes like the proverbial rocket.

Make of that what you will.

Quote from: user11235813 on May 13, 2020, 01:08:29 AM
My experience with compressions tests. I was worried when my gs only tested at 120 and 116, considering the min spec is 140, but hey guess what, it makes no freaking difference. The front right exhaust was a little bit loose and getting looser started at 06mm but gradually went to .1 however she has stayed there. The problem I was having was a faulty carb slide press fit piece that had come loose. New carb fixed that and she's been running really well ever since.

So seeing as I had the compression test kit, I tested an almost new S40 Suzuki and it too was testing 125 when it should have been 140 at the lowest,  and goes like the proverbial rocket.

Make of that what you will.

Noted, I'm not so worried about the compression as I am the plugs getting wet with oil and blue smoke coming out the back. Though I am resigned to the fact that maybe I'm overreacting but a fun project none the less and I need it right now.

Valve seals can be checked with engine in frame. In fact its best checked that way because by the time you take everything apart you've destroyed the evidence. Remove exhaust and carbs. Remove spark plugs. Turn over motor looking at valve stems. And for good measure clean them with a Q tip. Then turn it over a few times. Good seal = no oily stems.

Cool.
Buddha.

Quote from: The Buddha on May 13, 2020, 07:45:27 AM
Valve seals can be checked with engine in frame. In fact its best checked that way because by the time you take everything apart you've destroyed the evidence. Remove exhaust and carbs. Remove spark plugs. Turn over motor looking at valve stems. And for good measure clean them with a Q tip. Then turn it over a few times. Good seal = no oily stems.

Cool.
Buddha.

Yeah I realized I probably could have gotten away with a lot less but it's too late now. Everything is going to be gone through. The way I see it I can no bank on that engine lasting a long while and it can stay in the family.

IMHO diagnosing stuff is an art, a fast fast fast disappearing art.
Doing sheite is a lot easier.
Its easier to slap chit up and "weld it all together" That's why we have stupid retarded a$$$ stretched busas. and bobbers made from 1 and 2 cyl standards and café racers made out of GS850's ...

Pretty paint doesn't cover up retarded a$$ planning.
Slapping a side mount license plate on a 250K bike just screams we spend 1/4 mill and forgot it needs a license plate to ride on the street ... then when the dmv gave us the plate, we went omg omg omg where do we put it where do we put it, and slap it on the nearest bolt near the rear end and go ... whew, dodged a bullet.

Like some genius thinking genius in the ancient world said -
5% of people in the world think.
10% of the people in the world like to think they think.
The other 90% would rather die than think.

Cool.
Srinath.

UPDATE.

New piston rings, new valve seals. Had a pinhole issue in the top of my tank which sealed up beautifully with Casewell Tank Sealer. Got it all timed ,torqued and back together aaaaaaaand. Same issue. Went through the carbs again and found the issue. An incorrectly set Dynojet needle. It was set way too far down and had a washer underneath explaining my insanely rich mixture. Put it on the second notch down and now it runs and idles with no hangs or surges or anything!

I am overjoyed that I got it all back together and running, what an experience. You guys and youtube allowed me to go from zero mech experience to a whole top end job.

Now my last issue is this power loss I am getting at 4 to 5k. I did a search and I have seen this a lot. It sounds like it is bogging (engine note gets flat and lower and loses power.) I think a big issue is the fact that there is a dynojet needle being used with a 122.5 main jet. Doesnt the dynojet needle need to be used in conjunction with a different main jet? Im thinking about moving it up to the first notch to see if I can get it closer or just order OEM needles and be done with it.