jwerty1 Posted April 20, 2011 Report Share Posted April 20, 2011 Just bought my 620... Wonderful little truck for what it is. It idles about 2500-3000, lacks power bad. Of course I don't know what these trucks are supposed to drive like, but I assume they should pick up a little better than this. I played with the idle screw and mixture screw last night, to no avail. Changing timing affected the idle greatly, however the lowest idle was about 2000 and the timing was waaaaay off. I'm not the most familiar with carbs at all, but I am mechanical. Just wondering if there is anything common to cause this issue. I didn't get much time to read up on it yet, so I figured I'd ask. Also wanted to ask, what vacuum lines and emissions items can be deleted or blocked off? thanks Quote Link to comment
datzenmike Posted April 20, 2011 Report Share Posted April 20, 2011 Choke may be on or stuck on or the fast idle cam stuck. The choke may be on because the choke heater is not hooked up. This is the choke heater. It will have a Blue wire coming from it that should have 12 volts when the motor is running. Just below the lettering you can see the ivory colored fast idle cam. Here's another look at the fast idle cam. It has steps and a set screw that holds the throttle open to speed warm up. Get some carb cleaner and spray this area while holding the throttle open and working the linkages to free them up. When working properly the fast idle is set when the choke comes on on a cold motor. As the choke heater warms the choke it releases the fast idle cam and the motor slows to a lower warm idle. Quote Link to comment
620doof Posted April 21, 2011 Report Share Posted April 21, 2011 Hey Mike is it normal to have the choke adjusted that far to the left(rich)? Like in that picture, mine was centered on the dot. Or is that just an example pic for the OP? Quote Link to comment
datzenmike Posted April 22, 2011 Report Share Posted April 22, 2011 Colder climate might require richer choke settings. It's just a picture. Quote Link to comment
jwerty1 Posted April 25, 2011 Author Report Share Posted April 25, 2011 well, after a week of messing around, I have come a long way. I managed to count my auto choke as bad. It has power to it, but never adjusts, so I adjusted it to full open and just let the truck warm up a lil longer. I managed to get the idle down to normal levels and I'm hoping I got the mixture screw close. Truck still didn't run good. I messed with it another night or 2 and still won't run right. Turns out since I work at a dealer and work on 2000+ MY vehicles all the time my gut instincts have been thrown out the window with this truck. I said to myself tonight that it seems like a misfire, but with as noisy as this engine is it is hard to tell and I'm not used to it yet. I adjusted the valves and spark plug gaps last night to no avail. So for fun, I set up the timing light on all 4 wires tonight, turns out #4 had no spark. Ok, check dist cap, no evidence of missing. Swap wires 3 and 4, no change, check plug on #4, seems ok. Swapped 4 plug to 3. Now 3 is missing. So this whole time I had a bad plug. Previous owner included old parts that have been replaced, so I had a spare plug to swap in. Now all 4 cylinders are firing and I can't wait to drive to work tomorrow and see how this thing runs on 4 cylinders. Quote Link to comment
Steve - AF1 Racing Posted August 4, 2011 Report Share Posted August 4, 2011 Choke may be on or stuck on or the fast idle cam stuck. The choke may be on because the choke heater is not hooked up. This is the choke heater. It will have a Blue wire coming from it that should have 12 volts when the motor is running. Just below the lettering you can see the ivory colored fast idle cam. Here's another look at the fast idle cam. It has steps and a set screw that holds the throttle open to speed warm up. Get some carb cleaner and spray this area while holding the throttle open and working the linkages to free them up. When working properly the fast idle is set when the choke comes on on a cold motor. As the choke heater warms the choke it releases the fast idle cam and the motor slows to a lower warm idle. Awesome post. Thank you. I think my 620 has a sticking choke as well. Interesting that the choke doesn't work like the anti-dieseling solenoid, but apparently acts like a stepper on the throttle plates. When I think choke, I think open fuel passage irrespective of throttle position (more common in motorcycles, I guess). Though this one seems to be more of a "fast idle." Very enlightening, thank you. Quote Link to comment
ggzilla Posted August 4, 2011 Report Share Posted August 4, 2011 The fast idle cam and the choke effect (starting enrichment) are two separate things. But are combined in most butterfly carbs. In slide carbs/SU type - as most motorcycles use -- they are opening the jet instead of using a choke. The british call a butterfly choke a "strangler". Quote Link to comment
herculesinwyoming Posted August 5, 2011 Report Share Posted August 5, 2011 i fought the same issue, mine was timing, and tune up parts Quote Link to comment
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