Fast Idle

[Bob_Irwin]

I have a bugeye with a 1098 engine and HS-2 carburetors. For some reason, I can't get the idle below about 1500 rpm. I've backed off the idle adjustment screws completely, and taken off the accelerator cable, and it stays up. The idle will go down after the car warms up. Any ideas. Thanks

 

[Gerard]

First thing to do is look for a vacuum leak. This could be at any of the gaskets between the carbs and cylinder head. Also check for any cracked or disconnected hoses. All manifold ports should either be closed off (plugged) or have hoses connected (i.e. crankcase ventilation) If all of this is right, the most likely cause is worn throttle shafts. This is common on HS2's. The only remedy for that is new throttle shafts and retrofit bushings. Repair requires a specialized oversize reamer (which I have). You can also check shafts by disconnecting linkage and seeing how much play/wobble you can feel in the shaft.

You can check for a vacuum leak at the gaskets and throttle shafts with a spray like WD40 or starting fluid. Spray suspect areas long enough to see if the idle changes. If it drops, you've found your problem.

Adjusting the jets will affect idle too, but if you can back off the idle screws all the way and it doesn't help, it probably still a vacuum leak.

 

[Rut]

Bob, generally speaking HS2s don't wear much where the shaft fits, but the shaft does since it's softer brass. This is a very easy R&R, but you want to do one at a time and make sure the butterfly goes in the way if came out. It's easier to pull the manifold with the carbs attached since you can adjust the linkage before they go back on. Take pictures with you digital camera so you will have a good reference for assembly.
Good luck, Rut

 

[JPSmit]

Before you do all that check and see if the butterfly valve is closing properly. Some grit, or, more likely, a misaligned valve will do that. Easy adjustent too. Slack off the screws, adjust and tighten.

 

[drooartz]

Before you do all that check and see if the butterfly valve is closing properly.

Had this very thing happen with my old MGB earlier this summer -- one of the butterflies was not closing all the way. A little re-seat and all was good. Wasn't that hard to pull the carbs and give them a look over.

 

[nomad]

I'm with Gerard for a first test with WD 40. I'm betting vacuum leak!

Kurt.

 

[smaceng]

Make sure the choke fast idle cam is not touching the fast idle screws also.

 

[Guest]

I'm with Gerard for a first test with WD 40. I'm betting vacuum leak!

Kurt.

I like using a propane torch (unlit of course). I caught one on fire before with carb cleaner.:eeek: