Predator 212 Engine - Collected Info

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I'm collecting Predator 212 info and thought I'd make a thread on it.

The easiest things to do are to replace the stock intake and exhaust. The intake is designed to do a couple things, one is to be compact, and another is to keep the intake noise down. Unfortunately it is also restrictive, and restrictions cause a loss in power, so it's a good idea to ditch it.
The exhaust is supposed to be a spark arresting type. that, plus the baffles to keep it quiet, also is restrictive. Actually, the quieter the muffler, the more restrictive it is.
Here is a webpage where the 212 was ungoverned, with a new intake and exhaust. According to the article, the motor is rated at 6.5 hp (but we knew that) and with these mods it put out nearly 9 hp at 3600 rpm (governed speed) and 9.8 at 4700 rpm. It goes on with a few more mods to pull a max of 12.13 hp.
http://www.kartpartsdepot.com/help_answer.asp?ID=11


You might read something about the Hemi head motor. I don't know the specific differences, I can only find that the hemi head motors are better, they came on motors built after June 2013, and have a cast aluminum valve cover. Here's a thread about how the hemi head flows.
http://www.oldminibikes.com/forum/engines-modifications/86535-flowing-hemi-head.html
According to this post http://karting.4cycle.com/showthread.php?4851-3-Inch-Predator&p=42607&viewfull=1#post42607 it sounds like you can use a head from a GX160 (5.5 hp) on a Predator with a stock piston and decent cam, and get 17 hp. I wouldn't try it unless I had money to burn.


Here is a debate on ethanol vs methanol. It sounds like E85 is a cheaper alternative to methanol. I would think that if you were going to run methanol you'd want to bump up the compression and build a motor for the fuel. Since I can't get E85 where I live, I'll just stick to regular.
http://www.oldminibikes.com/forum/759098-post33.html


Here is a thread on an all out Predator build. It was at 15 page when I linked it here. (He had just over $1000 in it too) http://www.oldminibikes.com/forum/h...ines/86170-predator-212cc-hemi-upgrade-s.html

Parts websites
Cams and valvetrain http://www.smallenginecams.com
Predator engine parts http://www.parsonsracingengines.com/harbor freight predator performance go kart parts
"Hop up kits" (cheap way to get a bunch of parts) http://www.nrracing.com/category-s/1819.htm

Torque specs http://brainlubeonline.com/clone/

Fuel injection? Heck yes! http://www.brainlubeonline.com/clone/fuelinjection.html

Video time! I don't know this guy and have nothing to do with him, I just thought he has some good videos.

http://www.youtube.com/watch?v=1xLelRrEVwk
http://www.youtube.com/watch?v=0yqxjnU1O1g
http://www.youtube.com/watch?v=xmuDNc-Zx4Q
http://www.youtube.com/watch?v=rXvHIq7z0J0
http://www.youtube.com/watch?v=13NssmZJi00
http://www.youtube.com/watch?v=_fL1xTZnI_I
I highly discourage this. It is no way to accurately lighten a spring. With all the money this guy spent on his engine, he should have just bought the right springs.
http://www.youtube.com/watch?v=25ME0YxoW2Y
http://www.youtube.com/watch?v=dGzGiWqGsug
http://www.youtube.com/watch?v=PAetNvvR3bo
http://www.youtube.com/watch?v=tfc_hAzf5ow
 
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I tripped over the "8000 RPM" test video last week; I thought it was just a one off thing. So this guy's legit? Based on the way he presented that video, I wasn't real interested.....

If you think the info is legit, I'll give it a good look (the video's, I mean; oldminibikes.com usually doesn't mess around). Anyone else?
 
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Only real prob I see is he making the intake as smoth as possible which is a no no. Pretty much any engine builder will tel you its best to leave intake a little rough to help with fuel atomization. Exhaust port wants to be as smooth as silk. That long duration cam is nice. wonder which is better to gain lift, from cam or higher ratio rockers. Im thinking cam.
 
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It appears legit, but I don't remember him having a tach of any sort to verify 8k.
After all that time and money spent, I'd like to see it on a dyno.


There were some other things I found, like stud kits, roller rockers, billet side plates, etc, but I didn't think that sort of stuff is necessary for a yard kart. My personal plan is to change the air filter and exhaust, yank the gov, and leave the rest alone. If that gets me 9+ hp like that article says, I'll be happy.
 
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212 Carb flow data

Thanks for all the info so far.
It looks to me that the stock carb is pretty restrictive, I don't know how people are getting 12 HP with this carb or the bored out versions.
Does anybody have flow data for these, or a Honda GX390 carb?
I even thought of a Tilly as used on some 1/4 midgets, but it looks like its too big. I think it might work but would take an air horn about the size of trombone bell and about that long. It would be ugly as **** but might play some sweet notes!
I don't want a big bog at 3500 RPM. I think a Tilly flows about 50 CFM, maybe something between 30 and 50.
Been thinking of building a dyno, maybe I should build a flow bench.
I like to tune for best average torque.
 
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;1Ok i just watched ALL videos of this guy........ for a yard kart......this would be perfect....for the average guy that can read a txtbook.......and use a piece of sandpaper....never smooth the ports......fuel atomization is key..........never seen him go for advanced timing!? .....race engine? however i did agree that he did buy all of the proper parts (except for valve springs and correct size head dowels). what was up with the valve spring lightning!? why eve;1n do that if your building a race engine correct springs WILL be needed for tech........if your using a fuel pump.....why mount the tank above the carb?..... he stated racing engine!.... he hit maybe 6500 ..... however a S/A gas carb?.....most ive gotten is 7650 was with a custom top end cam grind from tim isky ( www.smallenginecams.com ) and 26 lb springs, billet lifters, loose bearings and low tension rings....only one engine we built made it that high and at that didnt really make enough power curve like claimed until we switched to alky.......you know when your mashing the pedal on the straights of greenville (J&J's)and hittin 8k trust me...better have good tires.... overall....the man did build a pretty snappy engine but FOR A YARD KART....not a racing engine...no carb work noted.....no real actual time dyno testing, no secrets to be learned.... id like to see the engine in action....every engine is snappy with no load....even stock flatheads (6.1:1 comp. ratio)
 
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I've done a little more research, while I don't have a flow bench I found that a GX390 carb measures about 22 mm and should flow about 30 CFM. Someone makes an intake for this swap. (To a predator). This looks to be a viable setup for milder cams and should really perk these engines up in the 4000 to 5000 RPM range. Also would be less money than a similar sized Mikuni style which would flow a little better.
Based on what I've seen in our local club, this should be a good setup on our tight turns and long straights. Now I wouldn't say that a bigger carb and more cam won't make more "putty" but there is a limit to traction, I would rather have a flatter torque curve and an easier driving kart at this stage of the game. Some of our guys have went to bigger cams (than say a CL 1 or 2) and have had no performance gain if not a negative gain because of the restricted carbs (even though bored).

Thanks for this forum, it has been a real help.
 
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