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How can the idle speed on a 2000 70 HP Johnson be adjusted? This is a pre-mix model running 50:1. It is idling between 1200 and 1400 RPM. Carbs just rebuilt - was idling too high before rebuild. Butterflies fully closed and carb linkage adjusted so all butterflies synked and close together. The carb follower is against cam and not advanced.
The motor runs out great, just idles too high.
Edited by jfortson on 05/27/12 - 12:34 PM
15' Striper 1987, 70 hp 2000 Johnson
The carbs have nothing to do with the idle speed - it's controlled by the timing. The idle timing setting is pretty simple but then you need to readjust the rest afterwards. Get the factory service manual and go through the link and sync process. It's pretty simple and should take you less than an hour. Skip adjusting the WOT timing setting - sounds like you're fine there.
Tim, Thanks for the input. I do have a service manual which as many manuals, seems to make a simple process sound overwhelming. After spending some time with the manual, the process is fairly simple as you stated.
Realizing I was going to have to check/adjust the timeing, I made some timing adjustments (counting turns) both ways and it had minimal effect on the RPM. I have ordered a light so I can set the timing where it needs to be. I made the adjustments with a horizontal screw directly under the starboard side of the flywheel - is that the correct adjustment?
I am a little concerned that the adjustments I made had little effect. From what I have read, the next suggestion is that there could be an intake air leak. I have double checked what I can see - hoses, gaskets, etc. and cannot fing a leak. Any suggestions there?
I will wait on the timing light and hope that fixes it, but still a little concerned since the adjustments I made had little effect.
If what you adjusted was right up at the top of the motor, just below the flywheel, then that is not correct. That's the advance stop which controls the maximum spark advance, and unfortunately that's the one thing you dont want to mess with as too much advance and you will fry the motor. And as you have found it has no effect on the idle timing.
I no longer have the motor and I don't remember where the idle advance setting is. Since you are having trouble, I am guessing you have an aftermarket manual - you need the factory service manual.
Tim, First, it was the idle timing screw I was adjusting. On this model, the spark advance stop is on the port side and not as easy to get to.
However, I did solve the problem. The problem was staring me in the face and I did not recognize it. The throttle cable (from the remote to the motor) was adjusted so the the throttle control arm could not return anywhere near the idle stop - probably an inch away. I can only imagine that the previous owner did this to increase the idle RPM to overcome dirty carbs that needed rebuilding - which I have done.
I adjusted the throtle cable so the arm is against the idle stop and the RPM came down. Right now it is at 950 with muffs on. As mentioned, I ordered a timing light, so when that comes in I will set the timing and go from there.
