SOHC.co.uk Forums > CB500/550

PD46 Idle Jet

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Laverdaroo:
Currently in the US if anyone needs any bringing back. Back late December.


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K2-K6:

--- Quote from: McCabe-Thiele (Ted) on November 17, 2024, 01:07:02 PM ---The jets in my 400 & 500 were clear right through.
There is an optical illusion imho that makes some folk think there is a fine mesh inside.

I used a long wire taken out of a wire brush to make sure it's unobstructed - I then pop it in the Ultrasound bath again for an extra clean.

--- End quote ---

I remember discussing that Ted, and thought I could see something of that order.

I researched that further (but forgot to post anything about it) with this link  https://www.telescope-optics.net/diffraction_pattern_and_aberrations.htm I think, explaining more about it.

If you go approximately halfway down that page, there's illustration of "primary astigmatism " with attendant longitudinal cross section, accompanied by end on optical effect, this i believe accounts for that effect in the viewer's visual interpretation.
It seems to produce a cross from light diffraction through that tube type view you instigate by looking through the idle jets in the scale they are.

That's quite deep into optical theory, phew  ;D

Sesman:
Heat them over a flame that give them a light tap. Most of the resin comes out as ash. Then clear with the E string. Or give Superbike Surgery a nudge. He has a super duper carb cleaning formula…he say.

deltarider:
The design of the PD46 carbs differs fundamentally from the oldstyle carbs on previous CB500/550 models. The idle jets of the PD carbs see less fuel passing than the slow jets in the oldstyle carbs. Gasoline (petrol) has changed also. Best advice I can give: either use your bike regularly or add a maintenance dose of a socalled fuel system cleaner additive at every tankfill and hope the best of it.

Johnny4428:
I replaced my pilot jets with 45’s. Just give a little extra fuel to improve starting and running. I have had a reasonable success so far and to compensate have been tweaking the mixture screws ((closing about an eighth of a turn at a time). Unfortunately the bike is now in hibernation until next spring. But the last run I had there was still some adjusting to do on two of the cylinders. I do work an addative too (Frost Ethomix) longer periods between runs.

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