Question about hot start circuit - 39 Keihin

Would anyone know the ‘state’ of a Keihin 39 mm (2005 WR 450F) with the hot start plunger removed from the carburetor? Since the hot start plunger is spring loaded and moves up when the level is depressed I’m trying to figure out if with the cable removed from the carburetor whether the hot start circuit would be open or closed.

While changing jets by first rotating the carburetor to access the float bowl I accidentally disconnected the hot start cable/plunger. I was left with the spring and end of cable only. Apparently there is a plunger that fits on the end of the cable and holds the spring in tension. I may have lost that end piece – I’ve not removed the carburetor to see if the end piece is still in the opening at the top but I assume it’s not.

So I could check to see if my 45 to 48 pilot jetting changes had any affect on my air screw setting I put a cork in opening and screwed the cork in. The bike started right up and seems to idle and run fine.

I will of course be fixing (maybe trying to find a new cable or plunger end piece) but I’m left wondering if the hot start circuit is affected by the removal of the hot start cable.

The issue would be if the hot start circuit was ‘on’ with the cable removed the engine might be running lean, a bit, all the time.

I found out from Eddie that with the cable out the hot start circuit would be open. Big problem. So I fixed it. Here a post I sent to someone with the same issue.

I've just finished going over the hot circuit after the cable came out and I was left with the spring and little else. I then discovered that the plunger was indeed still in the hole and it was easy to use a very small pair of needle nose pliers and removed it. The plunger is easy to affix to the end of the cable. You might be helped by adjusting the hot start circuit (at the lever) all the way in. That will get you a bit more cable to be able to put the spring on then attach the plunger.

The hot start circuit needs to be 'off'. You can tell if it's working right if you press the level the bike picks up rpms a bit thus the leaning of the mixture is working as it should.

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