Help diagnosing intermittent richness at idle

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acadian

acadian

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JS flatslides: bike runs well at throttle above idle, float height good, slides synced properly, single coil, plugs and wires pass resistance test, timing proper w/tri spark.

Problem: at idle I'm getting intermittent richness, causing a perceptible stumble (more noticeable on left jug), confirmed with a colortune test. The colortune chart says this could be caused by too high a float level, but any lower and she starts popping (float height set as per jim's suggestion)

any thoughts appreciated
 
Probably just vibration-related. I have the same issue with the left AMAL Mk I. With the right fuel tap ON, there's a little less hydraulic pressure on the left float and the vibes shake the carbs enough to slightly unseat the needle, causing fuel level to rise. At least that's my theory.
 
I have experience with JS flatslides 32 mm and 34 mm of my 750 short stroke. And I also had problems with bad idle.
In both my cases was cause by false air leakage. In my case the manifolds had poor surface quality. That led to air leakage (Especially 32 mm manifold was bad).The solution in my case was to grind the surface with sandpaper so I got smoother surface. There after I mounted new silicone hoses matched to the new diameter. These have worked well for two seasons now and it idel steady at 900 RPM.

Both carb type have standard idel jet from Jim.
 
I think pressure through a liquid remains constant ....
Craig
 
Kvinnhering said:
I have experience with JS flatslides 32 mm and 34 mm of my 750 short stroke. And I also had problems with bad idle.
In both my cases was cause by false air leakage. In my case the manifolds had poor surface quality. That led to air leakage (Especially 32 mm manifold was bad).The solution in my case was to grind the surface with sandpaper so I got smoother surface. There after I mounted new silicone hoses matched to the new diameter. These have worked well for two seasons now and it idel steady at 900 RPM.

Both carb type have standard idel jet from Jim.
Click to expand...

Interesting, I'll investigate this, though I'm not using the manifolds sent by jim as they had no balance tube provision, I source a pair of manifolds with the balance tube stubs.
 
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