Yes those little buggers are soooo frustrating, have a good nights kip, what I found was that if you get a small electrical screw driver , you can push the screw end through the side of the spring which should hold it ,and place it in and compress at the same time

 

Thanks! I was going to ask for suggestions on getting those back in place that didn't require colorful language.

 

I have used a length of dental floss ran through the spring to act as a tether in the event one of those little suckers decides to take flight. They are crazy hard to find after they've flown several feet and rolled under a bench.

 

That's a really good idea. On my first reassembly of the carbs a month or two ago, that's exactly what happened.

 

Really had high hopes. Does the exact same thing. I officially give up. Time to take it somewhere.

One consolation is, I figured out a fairly easy way to get those little springs on. I first turn the carb sync adjustment screw on the 3 adjustable carbs almost all the way out which increases the gap between the carb throttle connections (where the spring sits) to almost the height of the uncompressed spring. That means the spring requires almost no compression to get it in place.

Then, I rotate the throttle cable 'wheel' (between carbs 2 & 3) and wedge a wooden dowel against the wheel and carb housing to keep the throttles full open. That positions the interconnection point of the carbs (where the spring sits) in an easy to get to place. I then used a precision tool (a large Sharpy pen) wedged against the butterfly of the higher # carb which keeps the gap where the spring is installed open.

The spring can then be easily slipped into place. The carb sync screw is then returned to its approximate previous number of turns (to be fine tuned during carb syncing.)

 

One side note on the ultrasonic cleaning... I noticed that after cleaning (this may have been the result of the long cleaning sessions.... I did four 30 minute cleaning cycles) that the butterflies would stick closed, requiring a little force to break them free (and open them). After closing the butterflies, they''d once again stick (a bit, not severely). Looking down the carb throat, I noticed a line where the butterfly contacts the inner bore of the throat when closed. The cleaning either caused a residue to form at the butterfly/throat contact point, or a mild erosion (couldn't tell what this 'line' consisted of. I used a bit of metal polish which cleaned away the line, and the butterflies no longer stick.

In future, should I ever undertake cleaning carbs again, I'll wedge a small piece of wood or plastic under the butterfly to open it slightly so it is not in contact with the carb throat during ultrasonic cleaning.

 

Hi matey just switched back on , what was the outcome did you get a start at all?

 

Does the exact same thing. Starts and runs with choke only. Choke off, engine dies. Open the throttle at all engine dies. If I let it run for 6-8 minutes, shut it off, and then restart a minute or so later, it runs off choke, and responds to throttle. However, it starts to rev up, so I reduce idle speed with the Idle set screw. After about 30 seconds, idle will start slowing down, and will die unless I increase the idle speed again. This cycle repeats ad infinitum. It looks like fuel is flowing unchecked.

During the times it runs only on choke, I see zero fuel entering the carb throats. After the long warm up (and the engine starts responding to throttle), I see a fuel bubbling out of the jet needles. If I then shut it down, fuel will continue to flow from the jet needle orifices, pooling on top of the butterflies (and if left unchecked, will eventually fill up the intake.)

The cleaning apparently had zero effect on this behavior, and I'm out of ideas.

 

Frustrating I know, it just seems to be getting too much fuel delivered at the carbs, but why ? we know carbs are really clean and the bike runs so air and spark , fuel should not be seeping into inlets (float needle } ,too much fuel when throttle (jet needle and jet) so maybe go down a size on those , pilot jet also , float height as well, read through the whole posts , what I did notice was that when you did the Sync with your unit, the bike was running good ,responding to throttle, could you put the Sync unit back on and try the sync again, just to placate an old trier

 

The symptoms are so specific and consistent. I laid awake last night thinking about what could cause this exact behavior, and I find my knowledge of the internals of this Keihin 38mm CV carb (I believe it's 38mm) is lacking. I'm usually decent at digging up tech docs on things, but haven't been able to find specifics about this carb. I'm going to list my outstanding questions. Not necessarily in the hopes of them being answered, but by stating the facts I'm trying to discover, I sometimes find it provokes new insights. (Warning, long post!)

Main assumption:
The orientation of jets when the carbs are installed on the intake are 'hanging' from the top of the float chamber at a slight angle. This requires either fuel pressure from the inlet side or negative pressure (vacuum) from the throat side for fuel to be pushed or drawn from the chamber.

My outstanding questions:
- From what inlet source does the enrichment circuit (choke) receive fuel ... main jet, pilot jet, other?
- Does the fuel enrichment circuit receive fuel before the level of the fuel in the float chamber reaches the main & pilot jet?
- what set of conditions would allow the fuel enrichment circuit to receive incoming fuel, but not the pilot, nor main jet?
- What variable could change (evidently affected by engine having run for 6+ minutes): Heat, pressure
+ How could this change cause fuel to flow through jets when it did not prior to warm up
- How can fuel continue to flow with no vacuum (engine off)? Does the vaporization of heated fuel in the float bowl pressurize the chamber causing it to push fuel out the jets? If so, what keeps all bikes from being flooded after they shutdown?

The advice I received from a local shop is "replace the carbs". My issue with that is:
1) it's giving up (which I've claimed to do on more than one occasion, but the engineer in me will not allow admission of defeat);
2) the used carbs available are worn/rusty/beat up/could be in worse condition than mine;
I need more knowledge, not more carbs.

You raised a good question. How did it run seemingly well during my first syncing? I do not have good enough recollection to remember if I had to continually readjust the idle speed (I don't think I did.) And, I don't remember it filling up the carbs with fuel after shutdown.

I am going to perform the float level test with some clear tubing. If that is not revealing, I will try syncing again (although it could prove challenging if I continually have to readjust the idle speed to keep it from stalling.

Last question is, how many nice riding days am I willing to let go by while I soldier on 'not admitting defeat'...