IKF 4-cycle CC maximum?

[Ryan Knowlton]

Our local track runs under IKF rules and insurance, any idea of the CC maximum for a 4-cycle?
We've got a circle track guy wanting to try a built Honda GX390 on a sprint chassis in with the tag guys to see what it can do....
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03 Italkart Supersonic V
420cc Predator Clone

[John Matthews]

He's gonna need to be a pretty skinny guy that's good at chassis set-up to be competitive. A lot will depend on the track but power to weight won't be in his favor. Still you should encourage him to try, on the right track a good driver in a World Formula can give the TaG guys trouble.

Don't have the IKF rulebook in front of me but I think the biggest they every ran was the Star (Mike Clements?)....

There should be a "local option" clause that would cover if your track decided to let him do this. Let us know how it works out.

Cheers,
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John Matthews
Heartbeat Power, LLC.

[Roger Miller]

There isn't really an answer to your question from the IKF rulebook. The 390 isn't an engine in the book. So, any rules around the 390 would be developed and submitted to IKF as an "option" class for approval.

Typical IKF engine rules would keep bore/stroke stock, but that isn't to say that a option class couldn't be created that opened this up if that is what the folks in the area want.

[mike clements]

The Tecumseh Star motors were 358cc's. IKF and WKA never put a cc limit on anything that I remember except for when they said the open-unlimited enduro and sprint karts could run C-Open. That was twin 135cc engines for a total of 270cc.
We build a lot of the modified GX-390s and in enduro racing it's not difficult at all to drive by an entire field of Ratax Max karts. So racing heads up with the TaG class in general, I would think you should do well. Be prepared though. The first time you beat them they will start crying foul. Too many cc's, etc.
Funny thing, "Before" the race, they will be laughing at you
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Began kart racing 1959. Made many friends along the way.

[mike clements]

edited
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Began kart racing 1959. Made many friends along the way.

[Ryan Knowlton]

Well I'm going to be trying a 420cc myself. My BP build sped me up a bit but still wasn't fast enough for my weight to keep me in the hunt, then a broken rod bolt grenaded the whole engine in my warm up lap of heat #2 and I had to mount my prior motor to finish the day.
I've started with a 420cc predator which I'm modifying very little, bascially following the OVKA big block program , remove governor, filter and adapter, header, and trick progressive springs inside the stock ones. Rejet carb with jets and e-tube open.
I'm very curious to see how I'll rate with ~15HP and ~20#'s of torque at 450#'s to the others at 360#'s with small clones/GX200's.
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03 Italkart Supersonic V
420cc Predator Clone

[John Matthews]

[Ryan Knowlton]

Got an update from my first SIMA race in Sumas, WA with the big block.
I had a misfire issue.....not sure if it's a bad coil or carb issue....wouldn't rev over 4000 rpm and was cutting out a lot like the spark was intermittent.
Despite this I ran only 1/10th of a second slower than my small clone for lap times @ 464#'s with all the electrics stripped(pull start only) compared to the others at 360#'s. The torque on this thing is incredible, it wheel hops coming out of grid and you need to ease the clutch into lockup. I fully expect this to get me in the hunt when I get this issue figured out. On a 15* mount I was able to keep 46oz of oil in the engine which really seemed to help. My oil stayed golden and was very clean for a new clone which usually sheds a fair amount of metal.
I think If this class grows, we'll set a gear rule to keep RPM's down and should be able to use the stock rod and flywheel at that rate. I ran 16/54 gears myself. Beware, you need a GOOD chain, I stretched the heck out of mine and ended up installing a new gold/gold RLV on it, which still stretched a bit then stayed consistent after my 2nd heat.
I'm 265#'s and I was able to fit my seat and the engine on my kart but it was close. I ended up about 5#'s heavy on the left rear due to the huge motor, but the difference in handling wasn't enough to be an issue(barely noticeable) as the track is RH turn prominent.
I've been in touch with one of the OVKA guys who says their class has grown to 10 big blocks this year. If you're on the sidelines as a spectator or pit dad for a bean pole kid because your too big, this may be what you've been waiting for.
The important thing is, if you push for this class at your track, do not let the bean pole drivers invade the class and vote in lighter weights. It's time for the fatties to have a place in karting:)
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03 Italkart Supersonic V
420cc Predator Clone

[Ryan Knowlton]

Just an FYI for exactly what I did for a motor:

$305 out the door for a Harbor Freight 420cc predator. Get help it's 78#'s in the box!
$150 Noram Star Clutch 16T
$40 Burris Big Block top plate for Burris's mount(changes it from small clone to big). I would get PFM's mount instead as the motor sits up a little too high on the 15* mount.
$6 "trick" small clone valve springs inside the stock 420cc springs
$12 Lash cap and exhaust retainer for intake valve(my preference-not req'd)
$15 grade 10.9 black flange bolts for sidecover. Stock ones are junk and stretch like crazy.
$5 solid side cover dowels. Same as the small clones.
Flywheel is stock, rod is stock, balance shaft stays in. I toothpick'd a little Loctite into the female threads on the rod and tightened the rod cap bolts to 140 in/lbs.
Took engine to my dad's place and we honed some extra clearance into the bore. Was .002" overall, bore vs. piston skirt, took it out to just under .0035".
I made my own header, top plate, and throttle linkage cannibalizing some parts from my small clones ARC top plate kit and using the 420's longer throttle rod.
PFM(performance from modification) offers all these parts ready to go for those without the fab skills and a bigger budget than mine lol.
Lifan head gaskets and side cover gaskets fit great. Watch your gasket thickness however, my piston was only .010" in the hole and you may have piston/head contact if less than .030" clearance. I had to use two of the thin Lifan head gaskets.
Still playing with jets but took the idle jet to .021" and the main at .044" with the bottom row of holes plugged in the stock e-tube. It's a bit rich I suspect.
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03 Italkart Supersonic V
420cc Predator Clone

[John Matthews]

Hi Ryan,

Sounds like a fun ride for not a lot of money, I built one similar a while back but did a little porting and more carb mods.

I'll be interested in how it holds up and how close you get to the TaG drivers so keep us updated.

Cheers,
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John Matthews
Heartbeat Power, LLC.

[Ryan Knowlton]

It was fun not even running right. I don't think it will get with the tag guys as it sits now, but it should get me into the pack if not in front of them in our mixed 4-cycle class. We've got WF's, ASN GX200's, stock and modified clones and are currently playing with weights to get everyone close.
I'm sure if I did a build on it, it would hang with the 2-smokers thanks to all the torque on demand x 18 turns.
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03 Italkart Supersonic V
420cc Predator Clone

[Ryan Knowlton]

I found my problem.
My dad came over to see the kart and help me find the issue, and after warm up and a few minutes running on the stand it got worse and worse and then died and wouldn't start. No spark and a very weak zap when you ground the plug into your hand. Coil is junk, easy fix:)
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03 Italkart Supersonic V
420cc Predator Clone

[Ryan Knowlton]

Just another update. Replaced the coil with a Honda version and still having some issues.
Turned out I was having fuel flow problems. The pulse signal was going away and above 3500rpm my fuel flow was just a trickle.
Moved the pulse fitting to the carb isolator and have plenty of flow now.
Next race June 22nd we'll see how it does.
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03 Italkart Supersonic V
420cc Predator Clone