[F500] Mikuni round slide throttle stick warning

[Lindsey, Mark]

I had that happen on a set up/adjustment last week.  Fortunately I caught it
as I was syncing the carbs.  I found out the spring in the carb got under
the little brass plate as I reinstalled and lifted the pin just enough to
fall out of the hole.

-----Original Message-----
From: John Whitling [mailto:alliancemillsoft at worldnet.att.net]
Sent: Tuesday, July 09, 2002 11:20 AM
To: f500 at www.f500.org
Subject: [F500] Mikuni round slide throttle stick warning


This last weekend I was at the Peru National Tour and had a very
disconcerting event occur. The throttle stuck wide open in one of my
Mikuni round slide carbs. The slide itself rotated in the bore, out of
alignment with the pin and jammed in the bore. This is on a clean carb
without any visible signs of wear.

I called my most knowledgeable Mikuni guy and this is what he told me
occurred. My needle valve was lifted completely out of the needle jet
and the needle then held the throttle open because the needle was
misaligned with the jet. The slide then rotated in the bore as the
spring tried to force the slide down. This is what happened, as I could
see some light scratching in the bottom of the throttle bore, presumably
from the tip of the pin.

*The lesson here* ... always make sure sure that your needle is long
enough to stay fully engaged with the needle jet. Otherwise you can have
the same problem. I had never had this problem before and I have not
changed my needle groove settings in years ... literally. Please make
sure that your needles stay engaged in the needle jet or the same thing
can happen to you.

John Whitling