Youleftoutthe"y"..

OK... Whent bak en, en fouwned sompin..

His diaphragm does not just "lay" into its' "seat" (groove) in the carb body..
it will naturally sit just barely unseated and the lid/cap will NOT seat the thing when set in place and screwed on..

This sounds like a "DUH" but it is not. This "misalignment" is very subtle and not necessarily easily noticed - I didn't when I put the carb back together a few hours ago - producing a really bad consequence..

It is resinstalled and retested - My bike runs like a bat-outta-water, (a boat-outta-hell?) - It runs fantastic - now at DJ144 , 1N... PBnJ wants me to drag the neighbors dog behind the bike for additional loading - So I'll have to wait till late tonite for that..

So, could someone consistently mis-seat the diaphragm - I would have said "NO" before - Now I say "PERHAPS".. I don't know if this has anything to do with Snows' problem though.. The carb ran my bike fine straight outta the box he shipped it in..

 

Interesting developments Klxster. In my multiple attempts at messing with the Keihin, I had to deal with the swelling and contracting diaphragm each time. Removing the diaphragm usually meant it swelled up for a while. While it was swollen, it was impossible to get it to sit down in the grove and refit the cover. Very frustrating when trying to quickly make a change and then go for a test ride. I had to set it out in the sun for a while, or if it was dark, I actually put it in a low temp oven for a bit to speed along the shrinking process. I was always very careful when refitting the diaphragm, but that's not to say I never messed it up. Hope someone has a bright idea on where to go from here.

 

My diaphram was always consistently a touch to small. Placing it in the middle and setting the cap back on while twisting gently back and forth seemed to seat it properly...

perhaps not?

 

Yes, PWJM, "perhaps not" is correct. Snows diaphragm is just a tiny bit too small as well.. It will not seat by using the "cap" ..

The only help I can offer the membership is that the "Cap" will immediately go to direct contact with the carb body if the diaphragm is seated properly - then you can put in the bolts while holding the cap on with yer fingers.. Obviously, if the diaphragm is not seated correctly, the cap will not "hand" seat with direct, 360 degree, contact with the carb body..

 

The diaphragm on my '06 is never easy to seat. It always gets a soak in HOT water and dried before installing. I can see my way to imperfect installation.

 

So, assuming Snowdrifter and PWJM's carbs are not "possessed", "hexed", "enchanted", or "magical"... And assuming they cannot violate the laws of physics.. And have not achieved consciousness and/or self awareness.. How is this for a guess about the issue:

Consistent imperfection in reassembling/reseating the diaphragm which manifests in several scenarios -

1. Slide basically inoperative - a snap and hold to WOT produces only a pedestrian power ramp.

2. Aberrant slide operation at certain vacuum signalling strengths - resulting in "stumbling".

3. A combination of #1 and #2.

 

I might buy in to the consistent imperfection of reassembly theory except that as you stated, the carb ran fine on your bike as received. You received it in the exact same state that it was removed from mine, on which it produced the stumble. Therefore, it was "correctly" assembled at least at some point while I had it, yet it still produced the stumble on mine. Weird. Also, the issue was very consistent for me. So I was assembling it the same way (either right or wrong) every time. Symptoms were always present and severity varied with the jetting that was currently installed.

Is there any way to do further testing with a larger sample size? I.E. any way to further test pwjm's carb? Any other current forum members out there experiencing this issue?

 

Yep, it did run my bike perfectly well out of the box.. PWJM's ran 99% perfect at sea level.. I'll leave Snows carb on a while.. I'll cuss it and call it names some.. Maybe I can **** it off.. Still have to drag a farm animal behind it for a "biggy" load on the carb..

 

Could it be the rubber boot between carb and engine is not bolted down tight, 2 bolts. this may cause a small leak. Boot may have a hole in it.

 

Nah, that was one of the first things I checked. It was also re-checked later on while testing for carb leaks and whatnot as well.