Predator carb low speed jet issue, i think

[jamyers]

Got this bone-stock Predator engine that I've had sitting around for years, with not a lot of hours on it. Changed the oil, new spark plug, cleaned the carb (which was pretty funky with dead gas). It's a RuiXing 128, with no idle mixture screw - just a brass plug where other model carbs have screws.

Engine ran pretty well for about 2 hours total over the course of a week. Now it only starts and runs with the choke at 80% on. At that setting it's got tons of power right off idle, but of course won't rev up very much.

I've pulled the carb several times, each time sprayed cleaner through every passage, pulled the (stock .016) low-speed jet, blown cleaner and air through it, even ran a single copper wire strand through to absolutely confirm that it's clear. I've blown cleaner and compressed air forwards and backwards through the idle mixture hole, the transition holes, the main jet, the emulsion tube holes, the air bleeds at the front of the carb, everywhere I can find. I've replaced the gaskets on both sides of the plastic spacer, and looked for cracks or anything that could leak vacuum. With the carb and spacer off, the engine pulls a decent vacuum when cranking.

Still no joy.

I removed the low speed jet entirely and plugged the hole with my finger, and the engine started, idled, and revved (no load) like it's supposed to - without the choke on! Of course, that ain't right, and I'm sure if I capped it off permanently it wouldn't keep working properly.

Every thing I read says "clean the idle passages and the low-speed jet", but for the life of me I can't imagine them being any cleaner...

Ideas?

 

[itsid]

sometimes it's just bewitched..
I've heard people cooking their carbs in ctric acid for hours.. twice w/o luck..
then a puff of air and it's good..
and some -as you - blow each and all orifices and stick fishing line (better than copper wire strand.. less likely to scratch )
w/o much of an improvement..
and one quick bath in an ultrasonic cleaner and it's as new again...

You can't tell what removes that miniscule spec of dirt that's clogging the one air bleed until it's removed.

Now... we can tell it worked properly before,
and we can tell it doesn't as of now.
And unless you find a crack that adds air somehow where it shouldn't,
the guess remains a clogged passage.

IDK what to suggest tbh, sounds like you tried most already..
maybe give the lemon juice boil a chance.. maybe get an ultrasonic cleaner for christmas and give that a chance.
And at one point time's more expensive than parts and you may call it done and get a new one.

I think since since you narrowed on in on the low speed jet.. I'd try once more to poke around there.
boil in lemon juice rinse then reinstall the jet, cap the hole and give it a go..
and if that didn't help I might order a new one just to save time.

I found the Honda carb check sheet helpful more often than not,
so just to be sure

Maybe it helps you find the one tiny hole you haven't so far

'sid

 

[chimmike]

My predator after sitting a month needed the idle jet cleared out. I had to strip the plastic off a bread bag twist tie to poke thru the orifice. Once I did that, good to go. That doesn't fix the other odd issue you have, though.

 

[65ShelbyClone]

no idle mixture screw - just a brass plug where other model carbs have screws.

Often times carburetors like that have an idle screw under the plug. The plug is there for emissions purposes to keep people from tampering with the adjustment. It also keeps you from removing the screw to clean out the passage.

They are a common and unwelcome sight here in CA.

 

[jamyers]

Update: Tried boiling it and another round of cleaning - no joy, so I got a new carb via amazon. It'll run without the choke on now, and the idle mixture screw is awesome, but it's still not making power like it ought to.

Taking a deep dive into the ignition is next, i suppose.