Maybe the problem is fuel flow being restricted. I would start with the fuel lines and pulling the petcocks to see if the filters are clogged. Fuel lines deteriorate over time, coming apart inside and creating loose flaps that will restrict flow.

Knowing the model and year would really help.

► A fuel issue, as per Jagarra, could do it. Along the same lines, another one would be...
If you run with a single petcock ON, the crossover tube could be blocked or crushed. My last bike had the cross over tubing crushed closed. It's easy to do.

► Torn carb diaphragms might also give you the same result.

Wobbly, Good point. 1993 R100RT .2 petcocks with a crossover lowered my suspicion for fuel supply. I will check today or tomorrow.
Thanks for the Star wheel post. I ran right out and checked my 1983 R65LS, Turns out i was gusseted appropriately.
Tim

A failure to develop power at RPM's above idle can sometimes be attributed to oil soaked intake air filters or other accumulated contaminates. These usually get worse over time. This is one more thing to rule out, or confirm. The test for this is to pull the intake tubes and run open carburetors for a distance.

will try, thanks

OK, Sorry this has dragged out, but work is interfering with my life terribly. I have now tried all suggestions received in this thread. The result was when disconnecting the air tubes into the carburetor . When ridden with the carbs open to the atmosphere the bike would rev to 4 or 5,000 before bogging down. As before flipping the choke on improved revs. So..... improved air flow and the resulting presumably leaner mixture improved performance. However so did increasing choke which should richen mixture. HHHMM. Still got to believe this is carb related.,but not sure how. High speed circuit blocked somewhere and idle circuit only giving so much gas ? I did check the Diaphrams. Intact. Any last thought before I send these off for a rebuild?
Thanks agian to all who reponded.
Tim

If it runs better with the choke in the ON position, then we can surmise that it's a leanness issue.... too little fuel.

Allow me to backtrack and double-check some details... The bike is a regular rider (more than once a month). You run standard high test fuel, which was purchased recently, and not some wacky racing fuel or other. You have removed both float bowls and 1) checked the contents of each for water, and then 2) turned ON the petcock simply to check the flow into each bowl. Your battery is in very good shape, and the electric starter has no issues cranking the bike. You have checked the carb diaphragms. You have installed new spark plugs.

If all that is true, then it is highly unlikely that the carbs need rebuilding. That is typically only needed after a long storage. Highly unlikely that that a regular rider got gummed up too. Much more likely that you gave the bike a bath OR filled up the fuel and introduced a slug of water, which is now resting in the very bottom of the float bowl and blocking the main and needle jets.

Other causes of lean running which you can check....
• Old, cracked, rubber intake tube between the head and carb. These need renewing every decade or so.
• Open carb balance port. My 1979 has screws in each carb port; my 1988 has the 2 ports connected by a balance tube. These ports cannot be open to the atmosphere. The port either has to be plugged with a screw, or the 2 ports need to be connected together with a hose. If you have a hose, it could be loose, fallen off, or have a hole in the tubing.

Hope this helps.

I did remove both bowls and emptied into a clear jar to look for water. I did not replace the spark plugs as this seems so fuel like. I will pull and check tomorrow. I had field recently but if it was contaminated, I expected to see in bowels. will check balance ports tomorrow. What tube between carb and head?
Tim

Thanks, Pulled the diaphragms again today because I liked the hold up to the sun idea. Still look perfect. Reassembled carbs. Did a compression test while i was at it. 135 Left, 130 Right seems to me that eliminates valves. Agreed? set within 1000 miles as was timing, but I will throw a light on it after I re-balance and adjust carbs. I ran a through copper wire through main jet while I was in there. Seems clear. I checked the balancing ports. Appropriately plugged. Tube connecting carb to head in good shape. I will replace plugs as soon as I can get some as I have seen rare ,bizare plug performance problems. these were a nice " toast brown".
And the beat goes on.
Tim

Thanks, Pulled the diaphragms again today because I liked the hold up to the sun idea. Still look perfect. Reassembled carbs. Did a compression test while i was at it. 135 Left, 130 Right. Seems to me that eliminates valves. Agreed?

Tim -
Sorry brother, it does not. It only means you have good compression. You need to at least check for adequate clearance in all 4 valves since Airhead valves are known to tighten up over time.

...set within 1000 miles as was timing, but I will throw a light on it after I re-balance and adjust carbs. I ran a copper wire through main jet while I was in there. Seems clear. I checked the balancing ports. Appropriately plugged. Tube connecting carb to head in good shape.

• Timed at idle or high RPM ? Using the "F" mark at full advance is highly favored.
•While running the bike observe the points. They should be sparking with a tiny yellow or white spark. Bright blue = bad ignition condenser.
• Why didn't you simply use a 10mm wrench and drop the jet stack and look for evidence of trapped water ?

I will replace plugs as soon as I can get some as I have seen rare, bizarre plug performance problems. These were a nice " toast brown".

"Bizarre plug" issues could translate easily into bad OEM plug wires, bad OEM plug caps, or even a bad coil. Spark plugs are generally either 1) run so long that they are burned out, or 2) encounter bad fuel and get fouled. The design of the plug is way too simple; it is very rare that anything else has an effect.

If you have not done so already, I highly recommend new metal-core plug wires and new 5K Ohm plug caps. Euro Motoelectric has a very nice set for $23 if you can't find them locally.

PS. If I may critique... you seem to assume way too much. There are at least 4 false assumptions in your last post alone. Slow down and thoroughly check details. The devil is in the details.

It certainly sounds fuel related. An easy way to tell is from the position of the throttle. There are 3 main parts, idle circuit, needle & main jet. Each one contributes to the whole. Idle circuit is involved up to about 1/3 throttle, needle - 1/3 to 3/4, and main jet -3/4 to wide open throttle. If you apply this to your bike it will give you a clue. Needle & main jet area are likely your culprit. As others have said, check for water or something similar in the main jet area. Also pull the idle jet and have a look.

Problems in the idle circuit can and do show up as misses etc at and around 1/3 to 1/2 throttle. Carb issues I'm sure account for 90 % of the problems with airheads. You need to develop a maintenance plan for them if the bike is being used as a daily rider and also a storage plan if they sit for long periods of time. Keeping up with replacing O rings in the carbs and replacing needles, replacing rubber intake boots, etc, draining tanks & carbs when bike is stored are all required. If you keep up with the carbs you will have a good running bike that won't let you down.

I believe we have an answer. I want to thank all of you who took the trouble to offer thoughts and advice. After doing and checking pretty much everything discussed here and more, I traile ed the bike to an airhead event and let others ride it. Consensus was carburetors. Then a beam of light came out of the sky and someone said, "the best thing would be to swap carbs and see if problem disappears". I can hardly believe I never though of that. Indeed not only does the R100RT run flawlessly, but the
R65LS that donated carbs for the test now has exactly same symptoms. Wobbly, thanks and I often do make too many assumptions. Full rebuild on the way. My current hypotheses is that the slide/diaphragm are still the issue despite looking OK and will not change the shape of the Venturi and revs go up.
Thanks again!
Tim

I'm truly glad that you've conclusively narrowed the issue down. Some last thoughts...

► The most common issue ethanol fuels cause is clogged jets. Obviously, the smaller the jet, the more probable it's clogged. Also, the smaller the jet the harder it is to clean without damage. So save yourself some aggravation and simply replace both the #45 idle jets.

Also replace both the needle AND needle jet. These both get banged up as the needle gets buffeted by the incoming air. You'll want to measure the exposed length of the old needle before removal. Install both new needles to that exact length.

The main jet and other larger flow control pieces can be soaked in carb cleaner and a wooden toothpick (soaked in carb cleaner) can be gingerly run around inside each. Use lots of compressed air, and NO wires or wire brushes.

You'll also want new floats, float needles, float bowl gaskets, and o-rings for all the jets.

► By rebuilding the carbs you are merely attacking the symptom of the problem. The root cause is typically that ethanol fuel has been left in the system for over 10 weeks. It really doesn't matter how you used to do it back in the 80's and 90's... it's a whole new ballgame now !! All you need to do in the future is snap the float bowls off after 8 weeks and allow all these jets to air dry. Drain the fuel tank into your car (which can't tell the difference) if the time goes over 10 weeks, and then leave the tank empty too.

► No matter how GOOD you are at cleaning carbs, they'll always need additional help and preventative maintenance. Use only high test fuels listed by Top Tier Gas ( http://www.toptiergas.com/ ), and then supplement that with a fuel conditioner, stabilizer and cleaner called StarTron ( http://www.starbrite.com/startron ). 1oz per tank fill-up should do it.

All the best and hope this gets you running smoothly again.