Can't get idle low enough to stop clutch engaging

[Striikar]

While you have it apart you might as well replace the clutch with a new one.
Consider it maintenance and peace of mind. So that potential issue is eliminated.?

 

[KevTrem]

would an air leak between the carb and isolator block cause it too run lean thus increasing rev's?? Might be worth intake gasket set as well as clutch kit.

 

[EdwardSimpson]

Hey guys, so this isn't really a huge issue, but it's annoying and since I have time, might as well figure it out. I bought a used original HPI Baja last summer and it needed some TLC. Runs great now except for the issue I have listed in the title. No matter how low I set the idle, I cannot get the clutch to disengage. When I do eventually get the idle low enough to stop the clutch from engaging, the motor dies after a few seconds. Is there something wrong with my clutch? If the spring is broken, the clutch would fail to engage correct? I was thinking maybe it had a very low RPM spring and a higher RPM clutch spring would fix this issue? I've played around with carb settings to try to bring down the idle, but that doesn't work either. I've just been living with it, because it only rolls away slowly on flat ground. If I lightly tap the brakes or the thing sits on a slight incline, it won't move. Any ideas? It's a purple chassis, so I guess it's an older Baja. The thing has DDM stickers all over the motor, has an MSD ignition wire and the piston doesn't look like the stock CY. I know the housings at least are CY. The thing blows my DBXL CY30cc out of the water, so I feel like the motor might be upgraded.

Why do manual transmission cars stall if you let go of the clutch completely without applying a bit of throttle? Why don't they just move forward with the idle power?

Because suddenly engaging the clutch rather than gently, loads the engine rapidly with the rolling mass of the entire vehicle and its contents. This load is greater than the power the engine is outputting as it is at low rpm (idle), the combustion in the cylinders isn't happening often enough, or forcefully enough to produce enough power to overcome this so the engine is forced to stop. The piston can't move down when the fuel ignites there is too much load. Once a few cylinders fail to fire the engine doesn't have any momentum left to keep turning so it stops.
Let the clutch out very, very gently and you can pull away at idle rpm. Obviously give it a little more revs and you can be much less gentle and pull away faster.
In an auto (the more traditional type) which has a torque converter, a fluid coupled device which connects the engine and gearbox, the idling engine is always connected to the wheels by the fluid. This fluid drags the car along which is why you have to keep your foot on the brake when stopped. It also means the engine doesn't stall, as the slip in the torque converter prevents the engine ever feeling the entire rolling mass over a very short period of time.

 

[Striikar]

would an air leak between the carb and isolator block cause it too run lean thus increasing rev's?? Might be worth intake gasket set as well as clutch kit.

Yes!?
Check if manifold is cracked,that would cause idle and surging issues.?

 

[Z.hb71]

If the idle is getting low enough but the clutch isn't disengaging, then it's not an air leak or the throttle link. It's the clutch not disengaging

 

[atom3624]

It sounds like the mixture is lean, causing a high idle.

This can be caused by a leak, mentioned above, or simply poor adjustment of the carb.

Check for leaks, give it a good clean, then tune it.

Petrol R/C's don't need tuning much.

Spring would be unusual, but not unknown - worth a punt if the others don't work.

Al.

 

[Bryan K.]

Just an update. I swapped in an 8000RPM clutch and while I really like this clutch better than the stock one, it didn't fix the fluctuating high idle issue. It still stalls when I try to lower the idle screw. However, with the higher RPM clutch, the rig stopped driving away on it's own at idle speed. I love how I can give it enough power to do controlled drifts instead of the earlier engaging clutch just bogging the engine down and spinning it out when I try to counter steer a drift. 8K is definitely the way to go and much more controllable and suits my driving style. The stock clutch felt like I had turbo lag. lol.

How soft is the stock clutch spring supposed to be? I can twist the stock clutch with my fingers easily and remove the spring. Near impossible with the 8K clutch. Is that normal or was my stock spring stretched?

Anyways, I guess my fluctuating idle is a carb issue. Time to crack it open and clean it or replace it. It's from an original purple chassis Baja, who knows how many miles it has on it.

 

[Seandonato73]

Stock should have been 6k. So not really a lot softer then the 8k.