Hallo World !!

Denmark is calling. And thanks letting me in the groupe.

Issue: Suzuki 1400 Intruder idle popping back into the inletchanal when hot, only back cyl.. WPS 500 S and ign. waveform shows late ign. Ign. have to be 2 dg. BTDC. Any idears ?? Pic 1 shows cyl. pres and ign., Pic 2 shows vacum in inlet with popping back.

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Hi Franke,

Unsure about the waveforms we dont see many of this model here but there are a few things that i have found that can cause the popping in the inlet particularly when hot. Given the apparent late ignition timing on only the one cylinder i would start with the crank sensor for the cylinder giving the fault, according to the manual/ wiring diagram there are 2 sensors one for each cylinder and its not uncommon for them to fail or get bad signals when they get hot. Could be the cause of the 1 cylinder having issues. Also depending on milage and history of bike either rich or lean carburation can give similar popping in inlet manifold. Worn carb, anyhting above 25000 miles is common to find symptoms from wear particularly on angled mounted carbs? or blocked carb if having been sat for a period of say 3 months or more.

Franke...........bottom of compression form looks whacked.  I don't see any normalization with the exhaust valve open which should be barometric pressure.

Don't know but obviously timing is a problem but would appear there is a cam issue here possible a leaking valve being pulled from vacuum of the other cylinder.

Once exhaust opens we should have a fairly stable plateau until intake opens and then falls again on the inhale.

Might post it over in the general discussion asking for some help with an interpretations.  State that it is a motorcycle but somebody should help.

Stitch