Subject: Phase sensor shimming Tue Mar 19, 2024 12:27 pm
A few months ago I replaced the phase sensor and found that it was running two shims, .9 and .3 mm. I measured (roughly) and removed the .3. The bike ran well for the remainder of the season but the surging and bucking symptoms returned on the first long ride of the Spring. A quick experiment revealed that a .3 shim put it too close. I am now looking for a "Goldilocks" shim of .5-ish Any help would be appreciated. I will cross-post to the FB group. TIA DW
Edit: RTFM! A trip to AF1 Racing revealed that they sell individual shims (gaskets in their parlance) in a variety of sizes. I will post my findings after I get a few. DW
Got the exact situation with mine. Removed old sensor with 2 shims. Measured and installed new sensor with 1 shim. Ran well till last month. Measuring is not that easy. Thinking about measuring with a soft substance at the top of the sensor. When removed it should be pressed till 0.00 mm. from there you should know what thickness shim to use. (I gues)
Top left hand side of the timing chest at the front of the engine. It's an inductive coil device that picks up a signal from a toothed wheel on the front of the camshaft/idler shaft to trigger the injectors and ignition. It is very sensitive to clearance.
To Guzziowner? Have you replaced the sensor? They aren't usually *That* sensitive. Maybe yours is breaking down somehow?
guzziownr Nibbio
Posts : 634 Join date : 2013-12-23
Subject: Re: Phase sensor shimming Wed Mar 20, 2024 4:35 am
Pete Roper wrote:
To Guzziowner? Have you replaced the sensor? They aren't usually *That* sensitive. Maybe yours is breaking down somehow?
I replaced the original sensor last year and it ran OK for a while before symptoms returning.
My theory is that as the engine case heats up it expands and takes the sensor out of its happy zone.
Symptoms always appear after the bike has been run for a while, parked and then restarted while still hot.
I tried a .3 shim but it left a trace of oil on the sensor when I spun the engine by hand. I think .5 should do the trick and AF1 had a couple in stock.
guzziownr Nibbio
Posts : 634 Join date : 2013-12-23
Subject: Re: Phase sensor shimming Wed Mar 20, 2024 7:04 am
Deepdive wrote:
Got the exact situation with mine. Removed old sensor with 2 shims. Measured and installed new sensor with 1 shim. Ran well till last month. Measuring is not that easy. Thinking about measuring with a soft substance at the top of the sensor. When removed it should be pressed till 0.00 mm. from there you should know what thickness shim to use. (I gues)
Aha, a fellow sufferer, Did you get the same symptoms? Starts and runs from cold, shudders and bucks when hot after a stop?
I am just going to put a smear of grease on it to see if it is touching then clean it off and run it with the .5 shim to see if it's a fix.
New .5 shim from AF-1 is in replacing the .9. Started and looped around the neighborhood without issues but the real test will be running hard on a hot day and then restarting hot. .9 and .3 shims pictured.[You must be registered and logged in to see this image.]
Subject: Phase sensor shimming 
Tue Mar 19, 2024 12:27 pm
