Topic: Fast Idle Cam Problems

[starf]

Hello all,

I'm in the process of troubleshooting why I don't get a consistent (or sometimes any) fast idle on my K7 750 with the PD41 carbs.

When I pull the choke, the fast idle cam moves and contacts the pin on the throttle shaft. The throttle shaft then moves slightly, but the pin "rides" up the cam - its spring compressing as it goes, causing no more movement of the throttle linkage. Put another way, the pin moves somewhat independently of the throttle linkage instead of being firmly attached.

The attached picture hopefully explains a little more clearly. Note that this is not a picture of my actual carb, it was taken from an eBay listing.

So my question is: how is it supposed to be attached? Is the metal tab supposed to hold it steady and mine is just bent enough to make it loose? Is the yellow stuff in the image some kind of glue?

Many thanks!

[majorzozo]

Hi Starf,

No expert here but on my 78F I played with that for a while.  I followed the manual which I believe (not with me) states to pull the choke and adjust the pin until it just touches the cam, close the choke then adjust the pin 2 more turns.  So when the choke is fully pulled it rotates the throttle shaft a little, which mine does.  I also believe the yellow is just slippage mark paint which indicates if the setting was disturbed.  Again, no expert here but my 78F does indeed raise the RPM.s when choked.  I get home in a couple of weeks and could possibly take a video of it moving if you haven't resolved by then , good luck.

[starf]

Thanks majorzozo.

This problem came about as I checked the adjustment following the manual, but it didn't have any effect. Then I saw that the entire mechanism (pin and nut it threads through) was moving relative to the throttle linkage.

My guess is that the tab is supposed to keep the nut captive, and mine has come loose for some reason. I'll probably end up tweaking it back (or dabbing a little glue there), just wanted to see if there were better ideas.

[starf]

After a closer look, I think I misunderstood how it was attached. The nut is not captive, the pin is held in place by spring tension. If I pull the choke, all that happens is the spring compresses. If I take the throttle return spring off, it seems to operate as normal.

So either the fast idle cam spring is too weak or the throttle return spring is too strong.

[starf]

Another update to this. After going through the carbs a few more times, it turns out that the bike was running really rich.

Once the carbs were sorted and the idle screw property adjusted, the fast idle cam started working as expected. The issue being that the idle screw was already very far in and the fast idle cam could barely contact the throttle linkage.