Helpful Information For Beginner Predator Engine Builders

TLDR: Don't even bother with the Predator 212s unless you have to, just skip right to the Predator 224 non-hemi, AKA Ducar DH225. Only buy the Ghost if it is mandated for your racing class, and never buy the hemi head 224. 

All three of the 212cc Predators and the Predator 224 non-hemi engines are actually designed and produced in China by different companies and then rebadged by HF for their stores. They get most of their dimensions from the Honda GX200 engine, but for legal reasons, they can't actually be "clones" like the older Greyhound series of engines.

Predator 212cc non-hemi = Rato R210 = weird crank, weird cam and side cover, weird head dowels. Castings are NOT shot peened for extra strength. That shiny finish makes it a bit weaker.

Predator 212cc hemi = Loncin G210FA = weird crank, short cylinder.

Predator 212cc Ghost = Ducar PR212 (Ducar DH212 with a different head) = too expensive and not faster.

Predator 224cc non-hemi = Ducar DH225 = weird stock piston pin, but otherwise awesome. This the one to get.

Predator 224cc hemi head = Loncin H225 = weird everything, do not attempt.

All of the above engines can be fitted with a standard GX200 clone crank in 54mm, 55mm, 56mm, 58mm, 59mm, 60mm, and even 62mm strokes if you just want avoid having to have special "Predator" sized rods and weird taper flywheels. They cost about $45 (a little more for the 59, 60, and 62mm) and can help you use flywheels and rods that you might already have, or want to reuse later. If you want to reuse GX200 clone cams or billet side covers, then you'll need to stay away from the Predator 212 non-hemi.  

Be careful of the stock 196cc engines on Coleman and other minibikes with 5/8" output shafts, they aren't worth building. There are no clutches that fit the 5/8" output shaft, and those cranks are cast, not forged, so they are weak. Best place for these engines is your nearest dumpster.

Here are some quick specs for the original Honda GX200, as far as I know: 

Bore: 68mm

Stroke: 54mm

Deck Height: 135.5mm

Rod Length: 3.303" (Piston sits 0.020" down from zero deck at TDC)

Piston Pin Diameter: 18mm

Piston Compression Height: 23.5mm/0.925"

Piston Crown: Dish

Ring Thickness: 1.5mm

Rod Journal Diameter: 30mm 

Cam Core Diameter: 14mm/0.550"

Intake Valve Face Diameter: 25mm

Exhaust Valve Face Diameter: 24mm

Stem Diameter: 5.5mm (both)

Valve Length: 63mm/2.480" (both) 

Rocker Arm Ratio: 1:1

Output Shaft Diameter: 3/4" 

Head Dowel Pin Diameter: 10mm

Flywheel Taper: Honda

Pushrod Length and Diameter: 5.260" x 3/16" 

Combustion Chamber Shape: Inline (non-hemi, zero valve inclination)

 

Predator 212 non-hemi (Rato R210): head dowels are 11mm, cam core is 14.2mm/ 0.560", rod journal is 30.2mm, flywheel taper is Rato, pushrods are 5.190". This is the only one of these engines that needs our stepped dowel pins. 

Predator 212 hemi head (Loncin G210FA): Rod journal is 30.2mm, flywheel taper is Loncin, piston compression height is 23mm/0.906", piston crown is flat, combustion chamber is hemispherical, pushrods are 5.340", block deck is 135mm.

Predator 224 non-hemi (Ducar DH225): Piston pin bore is 18.2mm, lifters are slightly longer than GX200, lower exhaust bolt hole sits slightly lower (just oval the hole in the flange and gasket)

Predator Ghost 212 (Ducar PR212): Piston pin bore is 18.2mm, hemi head is just as useless as the Loncin's. Ignition coil is limited to 5600rpms. There is no reason to buy this engine unless you are racing in a Ghost only series.

Predator 224 hemi head (Loncin H225) This engine is designed to be super compact and produce very low exhaust emissions, and it does not make a good performance engine. Check the specs and manufacturer part number on the box. If it has a wide and flattish rectangular valve cover instead of a tall octagonal valve cover, put that box down immediately because you don't want that one. Both the Loncin H225 and the Ducar DH225 have black valve covers, but the shape and size are different.

So if you go with our high compression option for the Predator 224 kit, you get a piston and rod that use standard GX200 pin and journal diameters with the shorter compression height of the Loncin G210FA piston and everything else fits just like it was designed to. With the Predator 224 you get a taller block and a longer stroke crank, so it's a 224cc instead of a 212cc, but everything else is GX200 sized. I feel it's the best value out there, and the most compatible of the aftermarket engines. You won't be building a stroker 212 for the extra $30 the 224 costs, but when you buy parts for your 212s, you'll spend more than that on upgrades that you won't need with the Predator 224/Ducar DH225. If you ever decide to build a 236cc engine, you can buy our 72mm block and flat top piston and reuse all of your other stuff from the Predator 224 engine, but if you buy a 212 you'll be replacing everything because you can't get a 58mm stroke crank with a Predator sized rod journal or the Loncin or Rato flywheel tapers. Also you'll have to fit it into a lower deck block with less reinforcement with a different cam core size and larger head dowel pin bores.  

Check the boxes for the manufacturer's part number on a white stick on the outside. If it starts with "DH225" with the bore and stroke specs of 70mm x 58mm you've got the right one baby. The MPN label will look like this: 

And the specs should look like this: 

BUT, If it has this longer number that starts with "TE" on it, it's the one you don't want: 

And the one you don't want will have these specs: 

Here is what to get: 

Harbor Freight Predator 224 (non-hemi version): 
https://www.harborfreight.com/66-hp-224cc-max-performance-ohv-horizontal-shaft-gas-engine-epa-71415.html

Remember to check the box that you are going to buy to verify that it has the correct specs and manufacturer part number. The non-hemi Predator 224 has the 70mm bore and 58mm stroke, the hemi Predator 224 that you don't want has a 74.5mm bore with the 51.5mm stroke. Both engines have black valve covers, but one will be shaped like a stop sign, and that is the one you want. The wider and shorter rectangular valve cover is on the hemi head 224 engine.

There are several options for non-stock type carburetors out there, we happen to be fond of the Keihin PWK replicas, so that is what we sell. There are also Mikuni VM22 replicas and PE22 replicas, but we don't sell them. Nibbi carburetors are nothing special, just more expensive Chinese copies of the original Mikuni and Keihin designs. I wouldn't get too hung up on carburetors because they all work in similar ways. Clear fuel bowls crack, weird jets are hard to tune, and wild colors only tell you that the company building those carburetors isn't trying to make replicas, and you want replicas of the original Japanese carburetors because they were designed by engineers who understood carburetion. That is why we sell the carbs that we sell. They might not be flashy, but they work like the originals did and they are consistent.

The stock carburetors on these engines are VERY small and made to run a generator or log splitter at wide open throttle being controlled by the internal engine speed governor. If you are removing the governor and you aren't forced to use these stock carburetors by a racing class, best to move on to the above discussed types. 

Ignition timing advance is when the coil fires the spark plug, described in degrees of crankshaft rotation, before the piston reaches top dead center, or zero degrees. Because the flame front generated by the combustion of fuel and air inside the engine takes a set amount of time to move out from the spark plug, where it should be initiating from, if you want to make more power at higher and higher engine speeds you will need to light the fire earlier and earlier. It doesn't matter how fast the engine is spinning, each fuel has a set rate of burn, and it always burns at that rate, so the flame front always moves at a set speed across the chamber. Speeds vary for different types of fuel (gasoline, alcohols, specialty fuels like hydrazine and nitromethane are all different) but NOT with RPMs, so as the engine spins faster and piston speeds increase, you have to fire earlier and earlier while the piston is on its way up the bore for the hot gas front to hit the piston at the right time for effective power transfer. 

So, if you are trying to spin your engine to 9,000rpms and your lawnmower flywheel is giving you 18 degrees of ignition timing, the piston will be outrunning the flame front and giving you very little power indeed. You need at least 32 degrees to spin up to 7500rpms and more for higher engine speeds. If you are burning alcohols like E85 or methanols like M1 or M5 you will need even more ignition timing because either corn or petroleum based alcohols burn super cool and super slow. It's not uncommon for big V8 race cars running methanol to use 40+ degrees of ignition advance, and nitromethane burning Top Fuel dragsters and Funny Cars can see 60 degrees of ignition advance. This is why we sell billet flywheels in our kits that start with 32 degrees of ignition advance. They're just easier to set up, and they work better too. 

Exhaust Pipes: 

Use a 1" primary pipe with as many steps as you like, but do not use a "weenie" pipe or a restrictive muffler like the screw-on style or an RLV. They are loud and restrictive, and there are cheaper options on Amazon with removable baffles for stealth operators. Better to be like Spec Ops and get the job done without being noticed than being loud and flashy and ending up with a nasty ticket. Also always brace the exhaust pipe to the engine and not the chassis.

Oils:  

Modern passenger car oils have been formulated for ridiculously long service intervals and are super thin for tricking the EPA mileage tests. You don't care about that stuff, but you do care about your cam lobes and lifter faces, and these will wear quickly with an oil that is made for passenger cars. For these engines you want to use a 10w-30 grade high ZDDP oil made for older cars with flat tappet lifters like these engines have. It doesn't matter with a stock engine, but when you start moving serious air, spinning at 7,000rpms, and mashing big cam lobes into 40lbs of spring pressure on the seat you'll need the protection of a high pressure additive package in "hotrod" oils. The easiest one to get is Valvoline VR-1 in 10w-30 grade and can be found at your local Walmart. You can use either synthetic or conventional types once the rings have seated into the bore, but not during the break-in when you first start a fresh engine.  

Clutches: 

There are two main types of power transmission on minibikes and go karts that use these engines, and those are the centrifugal clutch and the torque converter. Centrifugal clutches work by pressing shoes or discs into a corresponding drum or basket that is attached to the final drive sprocket. Shoe type clutches usually have lower clamping power and don't shed heat as fast or stall as high as the racier disc type clutches. Both types can be had with removable drivers for different final drive ratios and both types can have their stall adjusted, but the disc clutches are usually able to stall much higher, dissipate more heat, and have greater clamping force for higher horsepower and heavier applications. The more friction discs and steels a disc clutch has, the more power and heat it can handle. Clutch "stall" describes when the clutch begins to grab, and for street and hobby type applications where you may be going offroad and don't need every ounce of take off power you can setup your drive clutch to stall until just above your idle speed, or you can bump it up to 3,000rpms for better take off. If you are racing, then you want a disc clutch and you'll want to set it up to stall until your engine is reving above its torque peak, which could be as high as 5,000 or 6,000rpms depending on your cam and head. For this type of application you will want a three or four disc "Bully" style clutch, and for drag racing you'll want an aluminum basket. 

The other power transmission technology used with these engines are torque converters, which work like a CVT transmission, except for the a belt instead of chains. These setups can usually achieve up to a 7:1 ratio split before the final drive gear and consist of a drive clutch, a driven clutch, and the belt between the two. The most popular style for these small block sized engines is the Comet 30 Series, and its hotrodded version is the Super 30 Series which includes the famous "Juggernaut" drive clutch. This is probably the way to go for must users, and it is nicely adjustable with many spring and weight kits out there to get them to stall until the engine is at around 4,000rpms. The same thing that applies to disc and shoe clutches also applies to torque converter clutches with regards to stall, but it is harder to get them to stall as high as a disc clutch will. Since the torque converter acts kind of like a CVT, you get more top speed with less RPM out of them, but they also limit your top speed a bit more than a disc clutch because they are heavier and not as efficient as locking and transferring power. 

Helpful Links: 

Here is good tuning guide for Keihin PWK carburetors: 
http://www.shiny-red.net/guides/keihin-carburetor-jetting/

Here is link to gearing calculator so that you can estimate your top speed with different gearing and tire diameters: 
https://www.bmikarts.com/Go-Kart-Gear-Ratio-Speed-Calculator?srsltid=AfmBOoqJRF7Gn-GT-RmzmzWhfOybHev2uRRnnQhJyrb0GCK2j3GYcVps

Engine Displacement Calculator: 

Compression Ratio Calculator: 
https://www.uempistons.com/p-27-compression-ratio-calculator