Box Stock

SA predator will only idle on choke "help"

C

Champ2014

New member
I need some help figuring this one out. I built a SA predator. It is on methanol. .650 methanol carb. The motor will only idle on full choke. If you take the choke off it revs up higher and dies. U can work the throttle and keep it running with the choke off but you have to keep the rpms up to around 3500 rpms. The slightest drop in rpm makes it want to die. I have talked to the company and the individual that done the work on the carb. I have changed all gaskets, changed the insulator, cleaned the carb. Nothing seems to fix the problem. It idles fine on full choke. I was able to take the choke off and cup my hand over the breather and get it to idle but I had to choke the air way down with only about a dime size hole allowing air in. It has a .059 main jet and a .036 idle jet. Any suggestions besides what I have already tried? I've tried everything I can think of.
 
Air Leak.. could be on carb or fuel line connections
Weak Fuel Pump
Trash in a jet or passage
Fuel strainer bowl could have trash (Not the Big Carb Bowl)

Jets are roughly ok... if you have extra jets and bits make a .038 lo speed and a .063 hi speed
 
I have checked for leaks in the carb. Changed gaskets. can't find anything there. I will check the fuel lines. Also will get those jets and try them. And no the carb does not have epoxy.
 
Is the throttle bore also bored out? If the butterfly is too small for the bore, it will rev up like that when you turn the choke off and will only idle right with choke on, i have had that happen before
 
Your problem is probably in the low speed circuit, the engine relies on it when the throttle is closed. When the choke is closed the passage just to the left is supplying the majority of the air needed by the engine, as it flows in it picks the fuel up at the lo speed jet, and delivers it after the throttle plate. By playing with the throttle when the choke is off you are transitioning to the main jet. You need to remove the pilot jet, check the oring(s) blow air through the passages to ensure they are clear. You may have an adjustment screw left side close to engine set it 1.5 to 2 turns to start off. These screws have been to fall out also that will cause your problems.
 
I have had the oring on the low spead jet fail due to cleaning with certain carb cleaners and allow air into the carb and affect the idle like you have described. Basically the oring desintegrated and fell apart in my hand after I took it back out to check for air leaks.
 
Is the filter cup covering holes? I had to cut the cup a little to get air in all the passages.
 
Ok today I have checked and tried everything. I drilled out low speed jets, took the carb completely apart and cleaned and inspected everything, made sure all of the gaskets were sealing. I checked my oil and noticed it was milky. I recently changed it. I'm thinking methanol has got in my oil from running it on choke so much trying to figure out the problem? Also I am wondering if perhaps my head gasket could be leaking. Would that cause this problem? It is not leaking oil but perhaps it's sucking air? I don't know. What do u guys think? I am pretty confident it's not a jetting or carb gasket issue at this point. I have checked everything over and over. The milky oil has now thrown me for another loop.
 
The milky oil is because your running it with the choke on so much, dumping a ton of alky into your crank case....which will also wash the oil off the cylender walls. You need to figure out the issue without running the engine with choke on, or change your oil alot more often when your trying to fix the problem and are running the engine with the choke on like that. Try a different carb and see if problem goes away
 
Ok thanks. I changed the oil. Still havnt figured out the problem. Will try another carb and see what happens. Thanks for the help
 
You must log in or register to reply here.
Back
Top