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Old 03-19-2020, 09:02 AM
DeeLad DeeLad is offline
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Default Predator 212 Carb Jet: Is it worth the trouble

So i in the process of building my kids a mini bike and purchased a Predator 212 motor. So far we have upgraded the intake and spark plug. I am awaiting header pipe and 18lbs valve springs.

My question is while still using the stock Carb (temporarily)is it worth change the jet out to a .036 /7. will this have any added HP or RPM. or should i just save money and change the carb out to a racing one.
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Old 03-19-2020, 09:14 AM
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Racing ones, unless you're talking about a Mikuni, are sometimes bored or other things done to them. Don't mess around with racing carbs if you're not sure.

If you should jet the carb is completely up to you to figure out. Due to people living in different climates and elevations, and other factors, some people may need to drastically upjet to make their engine run right, but some may need no jetting. Put the header on first and see how it runs. If it's lacking on power, most likely it needs a bigger jet.

PLEASE, DO NOT INSTALL 18 lb valve springs! Unless you have installed an ARC billet connecting rod and flywheel(or a PVL 'wheel, which is a bit cheaper).
The stock internals are NOT up to the task of spinning higher than what the stock valve springs will allow(about 5200 RPM).
Have you completely removed the governor gear in the engine, or have you just bypassed the external linkage?

If you haven't installed an upgraded con rod and flywheel, and the governor gear is still in, DO NOT install the 18 lb valve springs. There would be a VERY high chance of blowing up your engine. And maybe punching a hole in your engine block and causing other carnage, completely ruining your engine.

Please note: I tell this to other people, too, no one here is trying to be mean or single you out, it's just unsafe to upgrade valve springs without doing the internals.

BTW -
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Old 03-19-2020, 09:25 AM
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"Is it worth the trouble"

Well, there's no trouble at all really. All you need is a 10mm wrench and a skinny flat tip screwdriver. Doing a jet alone won't give anything, but like you said, you're doing other engine upgrades. So that's a yes from me. Upgrade your jet.

And when it comes to racing carbs, the only one I would consider for a lightly modified Predator is the Mikuni.

And please do consider the above message, as tampering with governors and modding stock engines can lead to messes. Better off to build it internally and be safer and faster.
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Old 03-19-2020, 09:28 AM
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Thanks. Everything I read says 18 work with the stock motor. I had planned on removing the gov before changing the springs. And he internals down the road. But I’m take ur advice and hold off on the springs till I do the internals but I will be removing the gov.
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Old 03-19-2020, 09:36 AM
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Phew! Glad to hear it! Some people do say that they've run 18 lb springs in an otherwise stock engine with no issues, but SO many people have blown up their engines. Also heavier springs rob power at low RPM since the engine has to work harder to open the valves. Heavier springs go best with an upgraded cam, so you get more power AND more RPM.

Removing the governor is a wonderful mod, it frees the engine, and makes it way more fun!

Have fun!
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Old 03-19-2020, 10:26 AM
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The predator is lean from the factory to meet epa regulations. If you modify it fo more airflow, then it is a must to rejet in my opinion. The best way to go about it is to get an assortment of jets, and find a good spark plug reading chart and study it closely.
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Old 03-20-2020, 10:40 AM
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I re-drilled and did plug tests, when I did an upgrade on my exhaust and intake...
I went to the tool rental shop nearby, asked if I could take a look into the junk box of carb bits... Buddy gave me a bunch of E-tubes and jets for $5.....He used to be a Kart racer.. so he understood what I was doing...

Try a tool rental or lawnmowershop... see if they have a junk box they will be able to part bits out...
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