I had some quality time last night rebuilding the 'ol Carter 1 YFA. I've done motorcycle carbs before, so this was a new experience. Kind of zen, like cleaning a gun. And nope, that's not footage from the Mars Rover....thats my bowl. Anyway, she did start, so that was great to see. I tried my best to do all my initial adjustments before reinstall it. The rebuild kit shows fast idle on a '74 200 as 2000 RPM. It was definitely high. How long should that last before it kicks down a little bit? She was howling! Definitely sounded 1500-2000 RPM to my ear. Is that normal? I'm open to suggestions too.
I have a 72 with the same engine/ carb. After starting when I blip the throttle RPM will drop a bit right away and engine runs fine. If I understand correctly, engine vacuum will open the choke a bit( there is a piston as part of the choke mechanism) even before the choke spring starts to heat up. Some carbs may have an external choke pull off. This should cause the fast idle screw to drop down a notch on the associated cam. Make sure your choke isn’t sticking. Check the piston and the choke shaft. On mine I had to remove the shaft and “ polish” it a bit as it was sticking. The choke butterfly needs to be removed to do this. The butterfly screws may be staked to keep them from falling out. I don’t know what my starting fast idle rpm is, but I would not describe it as howling. I did set my curb idle with tach/ dwell meter.
I adjusted the fast idle cam to inspect and ensured the choke isn't binding or somehow failing. My wife said it started a lot easier today, but there's still a hesitation when applying the throttle whether in park or in gear. This was rebuild with a new accelerator pump, so I'm at a loss as to the issue.
Here's a video from me testing the choke. Works great, but the idle will not come down. It only drops a bit if you restrict the intake or open the throttle. https://www.facebook.com/messenger_...message_id=mid.$cAAAAAAsHBJ2DHEprFV86wUbeCIJu And here's a couple pieces that came off my old accelerator pump. They weren't shown in the parts diagram or in the rebuild video, so I would assume that they're not something to swap over.
Hesitation at off idle is usually not enough accelerator pump shot. Can also be caused by low float level. If there is no pump shot action when throttle first moves, you need to find cause. Automatic chokes do not automatically release, working correctly, once started idle can be reduced with a quick blip or two on throttle. May be necessary to run a few seconds. If still running away, reduce the thermostatic setting(be sure vacuum is operating/pulling hot air from manifold). I all but never set to factory spec, that usually leads to long run times on high idle. Ignore marks, set so choke plate is just barely closed around 75*. I usually set high idle at no more than 1500 RPM. Main thing, be sure there is still enough throttle opening on the mid step that engine idles maybe 850 rpms. Some increase in idle is necessary for first few minutes engine is warming up.
Thanks for all the great feedback, Tom. I had tried messing around with some of the settings last night but decided I just had to pull the carb off again and make sure everything was right. I re-cleaned all the jets and passages, verified everything was in place, and used my newly acquired shop manual to (correctly, I think) adjust the metering rod again. I put it back on and finally got a normal-ish idle I could make adjustments on, so I must've missed cleaning something out. Can't quite tell if there's a miss, but I do have new points and a condenser I can put on. Right now I have the indexing mark on the choke set to "one mark Rich" per the sticker on the valve cover. I used the 9/64 drill bit to check the gap between the throttle plate and bore and I think it's a little wide (lean). Should I simply adjust that gap with the rotation of the choke housing or bend the choke rod?
you're saying the 9/64 is amount throttle plate is open when choke is fully closed? Choke pull off should open plate slightly when engine starts. Unless there's something about your choke I'm not familiar with(possible), sounds like bending rod would be the remedy. AFAIK rotation of choke housing only determines length of time choke is activated.
I might have to take a closer look, but I believe the FSM I've been using says that with the throttle cable disconnected, the choke plate and bore should have a clearance of 9/64" at the rear. To me, that seems perhaps a little "too open" but I'll re-read that section. It's certainly possible I may have to adjust the fast idle rod, which should help narrow that clearance.
