Predator 212cc 7hp and ar3910x issues

[realfast89gt]

I bought they newest 212cc engine from hf and one of the first things i did was get a new spark plug(ar3910x). Everything i have read online shows nothing but good things with this combination but my engine never seemed to run right with this plug.

From the first time i installed it i felt a loss in low end power. Then after about 20 minutes the engine started misfiring. I removed the plug and installed the original plug and it ran fine. I figured i would try again once i installed my header and air filter so i put a new ar3910x in. Ran ok, but soon after same thing....misfiring and loss of power.

Any ideas? I have put a few hrs on this motor and it continues to run perfect with the original plug. Is it possible to get 2 defective plugs back to back?

 

[smgs92]

The spark gap could be wrong with that plug or maybe timing.

 

[realfast89gt]

The spark gap could be wrong with that plug or maybe timing.

It is a 4 electrode non-gappable plug.......Timing is not adjustable as well.

 

[minichoper]

Jet the carb. Is it popping?

 

[realfast89gt]

Jet the carb. Is it popping?

Yes after a few minutes it would , not to mention i couldnt restart it witout it popping out the exhuast.

 

[jamyers]

If it's popping out the exhaust (especially when revving down), it's lean.

It is a 4 electrode non-gappable plug.......Timing is not adjustable as well.

Except in engines designed for them (like aircraft), I HATE multiple-electrode plugs! The spark will follow the path of least resistance, which means that it's typically going to "pick a favorite" electrode and go to it 99% of the time - which means that the other 3 electrodes are shielding the spark. Your engine is leaning out because of this shrouding, and I'll bet the plug is trying to foul out as well. Re-jetting the carb is putting a bandaid on the real problem, and will only cost you time, effort, and more fuel out the tailpipe.

Throw the fancy/expensive plug as far away as you can, put the stocker back in and chalk it up as a learning experience.

If you want to help a basic sparkplug, bend the grounding electrode back to where the very tip of the end is centered above the center electrode, instead of covering the entire thing. This tends to expose more of the spark to the fuel/air, an old nitrous racer's trick - but I'll bet still not worth half a %, which means practically nothing on our small engines.

There are lots of better ways to get more power out of any engine, fancy sparkplugs are just a way to separate you from your money.

 

[jamyers]

Did some investigating...from the ARC Racing site;

This is the spark plug you want for the clone or the Animal. Gasoline or Methanol. This plug greatly outperforms the stock plug that comes with a clone engine. We have seen as much as a 3/4 HP gain simply by changing to this plug from the stock clone plug.

HINT...run the engine hot...at least 425°F

Yup, as I suspected, that plug is intended for a (probably highly) modified racing engine that's going to run WAY hotter than stock to keep the plug from fouling. It's not something you'd just stick in a stock engine and expect 3/4 hp... even though that's what they're claiming, they're talking about a modified high-rpm engine - it's a racing part, sold for racers, and if it was that simple to get 3/4 hp out of a stock engine then every OEM would be using them and boosting their hp claims.

If you're planning on modifying your engine, you might keep it - otherwise I'd lose it and move on.

 

[Doc Sprocket]

Well said, Jammy!

 

[realfast89gt]

Did some investigating...from the ARC Racing site;


Yup, as I suspected, that plug is intended for a (probably highly) modified racing engine that's going to run WAY hotter than stock to keep the plug from fouling. It's not something you'd just stick in a stock engine and expect 3/4 hp... even though that's what they're claiming, they're talking about a modified high-rpm engine - it's a racing part, sold for racers, and if it was that simple to get 3/4 hp out of a stock engine then every OEM would be using them and boosting their hp claims.

If you're planning on modifying your engine, you might keep it - otherwise I'd lose it and move on.

Yes i already have a cam, header, air filter, and trick springs, but i think i may need to wait to put it back in until i remove governor and install a billet flywheel/rod. I will try this plug again at that point, after runnng with the stock plug for a bit.

 

[smgs92]

Yes i already have a cam, header, air filter, and trick springs, but i think i may need to wait to put it back in until i remove governor and install a billet flywheel/rod. I will try this plug again at that point, after runnng with the stock plug for a bit.

Just curious why would you upgrade the cam before upgrading flywheel/rod so you can pull the governor? The springs are also unnecessary as they're purpose is so you can rev higher. I'm sure the plug would work fine once it is running in the proper RPM range. It's going to want to be ran hot.

 

[realfast89gt]

Just curious why would you upgrade the cam before upgrading flywheel/rod so you can pull the governor? The springs are also unnecessary as they're purpose is so you can rev higher. I'm sure the plug would work fine once it is running in the proper RPM range. It's going to want to be ran hot.

Just curious why you would ask why i upgraded the cam before pulling the governor/upgraded flywheel and rod? Have you ever installed a cam in an engine? It makes a HUGE difference even up to when the governor kicks in. Cams do not only help at higher rpms.....I noticed alot more low end torque/hp and it was only $30. This applies for any engine, big small....it doesnt matter, just depends on the make-up of the cam.

As far as the trick springs, they are the stock pressure until they compress then there is a little more than stock. I upgraded simply because i was ordering other things and the springs were $9 and this way i didnt have to pay shipping again for the springs.

 

[smgs92]

I am aware that the cam will make a difference with or without governor. However it's just going to rev up to 3600rpm faster and then the engine cuts out I would've gotten a flywheel or a rod first.
I understand what all these parts do but the springs are just going to get unnecessary wear installing them before you pull the governor. There is no benefit to currently having them installed.

 

[realfast89gt]

Really?.........Oh you mean besides having a better quality part inside the engine which is less likely to fail.

When it comes down to it, my kart with 18x11.5-8 tires on it doesnt even hit the 3800rpm max until i am about 35mph. Doesnt really seem to be any negatives if it revs faster. It also spins the tires from a stop and drifts like crazy so please explain the negatives to installing the cam? It feels like a completely different motor.

I am not trying to be out of line, just informative.

 

[smgs92]

I'm not saying that it's bad to upgrade that first just most people upgrade the other stuff first. The springs are pointless to be in though the only benefit is you won't have to later.

 

[OzFab]

He only said he has the springs, which he bought to save on shipping; nowhere does he say he installed them yet.

Besides, heavier springs will be benificial with a low end cam; not much point having a trick cam if the valves don't work properly...

 

[realfast89gt]

I'm not saying that it's bad to upgrade that first just most people upgrade the other stuff first. The springs are pointless to be in though the only benefit is you won't have to later.

Well at my age i have come to realize that if you follow what "most people" do you will never get ahead in life.

If i waited to put a cam in i would never have known i could spend a mere $30 and have a governed 212cc engine that has this much low end torque and hp and is still a "safe" engine. If you think about it, $200 later for the rod/flywheel and how much benefit would it be compared to $30 for the cam? For racers yes, but for me I dont need it(although i still plan on getting them to see the difference eventually).

And as far as the springs go, it is never "pointless" to replace valvetrain parts with a known higher quality part regardless of wht you think.

 

[jamyers]

I bought they newest 212cc engine from hf and one of the first things i did was get a new spark plug(ar3910x).

Aha, I didn't know you'd swapped cam, etc. yeah, keep the plug for if/when you start running higher rpms.

I see nothing wrong with upgrading cam and springs - while you've got it apart you might as well...


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