212cc predator

[paz]

Im needing advice for which type of aftrmarket fly wheel would work for my engine. I have an older pay to ride kart, kinda heavy(for parking lot and small dirt track fun.I purchased a gx200 carburetor w a pulse adapter, mikuni fuel pump and k and n type filter. I want to remove the governor, add 18 lb springs.maybe a better push rod(stock)?and better rocker arms.eventually I plan on getting gx160 heads,and beefing that up when I get more money.my question is.what fly wheel will work well for my stock engine and hold up for when I get the new gx 160 head? Will a stock coil work? Advanced timing flywheels.don't know much about advanced timing.any advice is appreciated.

 

[Doc Sprocket]

I'm not even sure a GX head will fit that engine. Perhaps some of the folks here have had a chance to find out more about these engines, as they are relatively new.

 

[paz]

Thx

 

[Justin9]

the ARC Box Stock / Clone / GX200 billet flwheel will work on the new predator engine, and the gx200 heads should also fit so I don't see why the gx160 head would go on there... with the k&n style air filter, you want to run either a 36 or 37 jet, if you got a blueprinted carb from ARC or some race shop, then it will already have a good jet in it. Also the stock coil will work just fine.... I probably wouldn't worry about getting the springs until some cams start being produce for the engine.. I know some are out there like Nr Racing, but they are pricey. The GX200 cams will not work in the predator, the cam bosses are bigger in the predator. I wouldn't think you need new lifters or rockers with just 18 pound springs and a mild cam...

I race the clone Gx200 engines and they are a good package, and have many hopup parts avaible unlike the new predator (however, ARC did just release a billet rod for it), you can buy the box stock racing kit packages from many places, like ARC, EC Birt, etc and have a good engine that will make around 9.5 to 10 hp and turn 6,000 rpm.... let me know if there are some more questions about those engines, like I said, I also race karts (running a 100 lapper on a dirt oval this weekend paying $3,000 to win) and other than needing a fuel tank, I can get you a complete package with a cam, springs, fuel pump, exhaust....

 

[paz]

Cool Thx alot for the info.I bought a gx 200 carburetor , blueprinted from nr racing plus filter.I meant to say eventually im going to try the gx140 head.I hear it adds alot of power.but if I choose to do that,will I need to get a fly wheel w advanced timing?I don't know much about timing advancement and its benefits.eventually im going to get an oval kart.my brother has a big ranch and tractors to make a track.I wish I was racing 100 laps.so kewl and fun.and I definitely appreciate the offer on the parts set up advice.kick some ***.n have some fun

 

[paz]

Also.when I take the governor off.I was told that 18 lb springs is better than the stock ones so the valves wont float at higher rpm's? Do you think I should re check valve lash after my engine is broke in?and what is it for stock.? Intake and exhaust? Thx alot.!!

 

[Justin9]

Here's the theory I have on valve float and the springs...

If you take the governor out, you have no way to limit the engine rpms, in the racing engines, for Box Stock rules, we use a 10.8 pound spring that limits the rpms to around 6,000 before the power band drops off and the valve begin to float. Using 6,000 rpms, allows us to run for the most part safely without a billet flywheel or a billet rod. If you want to turn more RPMs than that, you need the 18 pound springs, a better cam, and you will need the billet rod and flywheel. So bascially, in our case, using the weaker springs will cost the valves to float sooner, but, they will also keep us from over revving the engine and breaking a rod or flywheel... That being said, you really won't notice much difference until you start making serious mods like either putting on a smaller head or cutting the one you have... I don't know what head gasket comes on the predator, but if it is a thick head gasket (like .040 thick), you can swap it to a .009 head gasket or .010 over and gain around 3/4 of a CC just right there, which will increase your compression...

If you want to simply advance the timing, you can buy a offset key for the flywheel, in the box stock classes, we can not exceed 18 degrees, which is usually a #2 or #3 key, but the ARC flywheel is set at 24 degrees from their shop on the standard key. Depending upon the changes you make to the engine, will determine the amount of advancement you need... for building something like we race, 17-18 degrees is fine, with a #2 or #3 key... I wouldn't be concerned about getting to 24 degrees until I got a high lift cam and stronger springs and I cut the compression some.

For the valves, if you want to keep top performance, they should be checked fairly often... for a play kart, you can probably just set them around .003 on both the intake and exhuast and let them eat for a while. If you run the 18 pound springs, you will probably need to check it less often, as those springs don't give up as much and as quickly as the 10.8 springs... It would not be a bad idea to check the lash again however after a good bring in period, just so everything can get worn in a bit.

 

[Doc Sprocket]

Here's the theory I have on valve float and the springs...

If you take the governor out, you have no way to limit the engine rpms, in the racing engines, for Box Stock rules, we use a 10.8 pound spring that limits the rpms to around 6,000 before the power band drops off and the valve begin to float. Using 6,000 rpms, allows us to run for the most part safely without a billet flywheel or a billet rod. If you want to turn more RPMs than that, you need the 18 pound springs, a better cam, and you will need the billet rod and flywheel. So bascially, in our case, using the weaker springs will cost the valves to float sooner, but, they will also keep us from over revving the engine and breaking a rod or flywheel... That being said, you really won't notice much difference until you start making serious mods like either putting on a smaller head or cutting the one you have... .

That's what I have been suggesting on here for quite some time. It's nice to have someone with experience in racing ungoverned clones chime in. Thanks!

 

[speedshopmike]

i know it's common practice with these little motors, but using valvefloat as a rev limiter in automotive racing is unheard of and very unwise.
it kills the v'springs, pounds valveseats out, etc.
does anyone market either lighter gov weights or some kinda ignition rev limiter?
if there's 12 volts available it wouldn't be hard to adapt a car unit; set it for 4 cylinders and quarter the desired rpm setting.
i'm gonna see if i have any rpm activated switchboxes left.
using one to ground the coil could be the rev limiter, even if it has to run off a little 12V battery...

 

[Doc Sprocket]

For the record- I don't suggest "using valve float as a rev limiter". Allow me to clarify. When people want to defeat the governor and continue to use a stock flywheel and rod, I advise them to stay with the stock valvesprings as a failsafe. I do not suggest constantly and deliberately running the engine into that RPM range. Rather, in case the load is suddenly lost, or other short-duration circumstance were to cause excessively high RPM, this will hopefully save the guts.

As far as what they do in racing, or to what extent, I have absolutely no idea.

 

[speedshopmike]

toystory, that wasnt directed at you at all - again, it's seemingly what *everyone* does.
sorry if it sounded bad.
i haven't found a part or a post anywhere yet saying anyone does anything else but bury their foot and let it rev till it won't (relative to the "real kart" racers, the pavement guys, not us offroaders)

http://karting.4cycle.com/

 

[Doc Sprocket]

That's okay, I didn't take it as a personal attack. I just decided it was a good time to clarify my position on the topic.

Without getting into the whole flywheel bomb thing (yet again), there is a clear line (in my mind, anyways) between using your head, and just being an idiot.

 

[speedshopmike]

the problem there is idiots also have heads.....

 

[devino246]

does anyone market either lighter gov weights or some kinda ignition rev limiter?.

Someone on here had started creating something of the sort. It measured the number of sparks per minute and grounded the coil when the number became to high.

 

[Doc Sprocket]

Here's the thread- http://diygokarts.com/vb/showthread.php?t=10006&highlight=limiter
Kibble hasn't been around much lately, must be busy.

 

[Justin9]

Like Toystory said, I'm not saying he should buzz around all day floating the valves, because you will eventually drop a valve... but... if you know whne you start vlave float, then you know you need to back it down... I have two of those baja mini bikes running no governor and use the 10 pound springs, if i ever twist one up enough to hear valve float, which is rare since I don't just go tearing down the road or anything for long periods at WOT, then I know I need to easy back a little bit. But bumping the float limit until you learn where to turn the motor by feel shouldn't be a problem... we twist these little motors on the dyno until the valve floats to get a complete pull on the engine and see how far we can take them...

BTW... the Briggs Lo206 motor does have a rev limiter built into the coil.. the lo206 motor is a spec racing engine that is modeled after a animal... they have a rev limiter for junior classes set at 4200 rpms, and the adult class limiter around 6,000... if someone developed a plate to adapte the animal flywheel and coil to the gx200, you would have a solution.... plus, it is a pvl ignition, which has a spark curve that doesn't change at a given rpm, it remains the same at idle to WOT.

 

[speedshopmike]

ok, great info on the Lo206, thank you.
btw, wasnt aiming any sort of valve floating insult at anyone; i'm just trying to find the right path.
so....
are these flywheels neutral balance?
i assume they are but i dunno squat about little engines.
since the limiter's built into the coil itself perhaps the flywheel wouldn't need to be swapped.
a flying magnet's a flying magnet long as it's got adequate gauss and the gap and curvature are correct....my tecumseh flattie snowblower motor has one (i know because the coil came loose and encouraged the flywheel not to turn), clones have them.....am i missing something?
like perhaps the length of the magnet is an issue?

also, what's a pvl ignition?
seems to me the fixed coil and magnet are going to deliver fixed timing regardless of rpm, yes?
i'm not understanding what you mean about the curve not changing w/ a pvl.
thank you for the education.

 

[speedshopmike]

toystory, just cked out that thread.
interesting..we think in a similar way.
be afraid.
sidewinder beat me to my own idea, lol.

 

[paz]

Thx.really good advice.dig this site

 

[Justin9]

For some reason, when I researched using a pvl coil from a 206, I want to say you would need the flywheel because the position of the magnet on the pvl flywheel was moved further in or out on the crank and to get a good signal, you coil needed that as well to get the full spark, maybe not... I know when we raced animals and the pvl can out, you had to get the wheel and coil for it to work because the position of the magnet shifted....

As far as what the pvl does.... I'm not the expert on this, I'm only relating what I was told, the regular coils will move around as far where the timing is set, it idle it could be 20, but at Wot, it could be 22..... the pvl would actually help keep the timing at 20 throughout the rpm hand because the circuitry is better in it. That's kind of a rough explanation, the animal forum at 4cycle will have all the details.