So close....

[predator]

81 GS 850. Carbs rebuilt and syncd. Bought a new stock airbox to perform with the stock jets. Choke it and it fires up, 30 to 40 seconds and it'll idle off choke. Let it warm up for a minute or two and crack the throttle, no hesitation it lights right up. I sprayed ether on the head side of the carb ports into the head when its running and get a very very small rise in RPM (potential problem that I have a leak. BUT when I ride it its a whole different story. I hit second, usually 3rd and have the RPM but the bike won't move, I start to work the friction zone on the clutch. About 3 times in and out on the clutch and its flying like a rocket, so I think clutches slipping. Same thing in 4th and 5th.
I got a buddy that works alot on dirt bikes and he rode it, he says its in the carbs....I took this bike from the death bed and am baffled. I tightened the heads (not torqued cause I couldn't get in there but the movement was mininmal to say the least). My buddy wants to do a compression test which is next and that possible intake leak bothers me. But can the carbs cause this bike to have that much 'speed' loss running on a flat straight highway and yet feather your way up to good top speeds?
In the driveway, the clutch seems very resposive and will stall the bike easily. Basically i'm saying I can't feel any slip.
This bike is real clean but if the head gaskets are bad or valves, i'll part it out. Cause I know the value and am not gonna dump 500 to 600 into the engine if that need be.
Any experience or ideas if it sounds like the carbs or clutches if all else checks out. Basically from what I explained, which does it sound like to you?

[SqDancerLynn1]

I would remove the rear wheel and check the splined adapter on the wheel first, it could make you think the clutch is slipping..

[Nessism]

If the clutch is slipping you will see an increase in rpm but the bike will not increase in speed. If the rear hub spines are stripped, it may seem like the clutch is slipping along with noise from the rear end.

Question: When the carbs were "rebuilt" were they taken apart and dipped or did someone just take some Gumout to them?

[predator]

I got no noise in the rear end and that seems solid. The carbs were torn down completely and cleaned and whatever you need to do (I don't rebuild the carbs myself but I know the guy that did it and I was in his shop for a while and saw them torn down. That's all he does so i'm pretty confident in his work. He did my GoldWing and it runs like a clock. Back to my assumption. It all seems like the clutches but my friend who works on bikes like this says he's sure it isn't. I don't know what he felt compared to what I felt but I'm giving him more points than me because of experience. But its doing what Nessism says and in my mind playing the clutch in the friction zone is giving the gears a chance to catch up with the RPM's, works for me. Let me put it this way, if I play the clutch 3 or 4 times, will out of sync carbs come up to speed because the laden of weight is going off and on? (If that doesn't make sense, I explained it wrong)
So Assume its the clutches. The bike sat for a long time, I changed the oil and it ran rough. I added seafoam to the oil and things smoothed out. I was hoping the Seafoam would free any stuck clutches. So could clutch plates stuck together cause slipping if the Seafoam didn't help or is the another oil additive that I can put in to help condition the clutch faces after sitting a long time.

[rudy]

Sounds like carb problems to me. What do your plugs look like? Nice tan colour? Black? White? You say the carbs were synced. HOW were they synced? Did you do them yourself? Bench sync, or vacuum sync, or both? Has the mixtures been dialed in correctly?

You didn't mention anything about valve adjustment. Have you done this yet?

[TheCafeKid]

If the valves are out of adjustment THAT badly, the bike wouldnt start. I recommend you do the adjustment if you havent, but I doubt that is the source of your problem. When you get on the throttle in 3 4 and 5 whats the tach do? If IT rockets up, but the bike doesnt seem to respond, your clutch springs, and possibly, but probably not, fibres are shot. Springs are usually the first to go, and easy and cheap to change, so i suggest you get TWO clutch cover gaskets, and a set of springs and change them. Inspect the fibres and plates vs your manual specs to see if they are withing spec and if so, leave em be.

Your bike is an 81, so the crappy rear hub spline IS a possibilty depending on the date of manufacture (there were alot of bikes with 81 titles that should have been 82 models...) and Zook switched to that crappy spline material late in the 81 model year. Not having any noise from the area doesnt necessarily mean things are ok. Best to pull the wheel off and have a look. If the teeth on the wheel spline are at all worn, you're not far off from a total failure, if they arent already. There is just a bit of the teeth that doesnt always mesh in the final drive, and if it catches at low speed, you'll get going, but its not got enough surface area to take the torque at higher RPMs...Dig into it check that.

It IS possible that your carbs are simply poorly synched, but USUALLY that would rear its head down low in the gear set as well as up high. Remember, the throttle opening has NOTHING to do with what gear or speed you're going. Its about the amount of THROTTLE you are using. You can be doing 70mph and only be in the pilot circuit or just off it...