New engine build questions

[Coverfire]

I'm currently about to start my second engine build and wanted some input from more experienced karters. Over the last year I have been slowly modifying a Predator 212 non Hemi on a murray explorer yard kart. This has been my first build ever and I've learned a lot from this forum, carsandcameras, Redbeards garage, and loads of other youtube videos. I wanted to get some input on what parts I can reuse and what I should do different this time.

The kart does around 50mph at top speed with a 60 tooth sprocket on the axle (original size but upgraded to a split sprocket). I feel that the top speed is fine for what what I like doing with the kart so I don't necessarily want more top speed although if that is a byproduct of more mods then let her rip! The torque is pretty powerful but who doesn't want more power? I guess what I'm saying is that in general I'm looking to add more torque, faster acceleration, and more overall power vs top end speed. Here is a list of my current modifications:

1. Governor/oil sensor delete
2. 18 lb valve springs
3. ARC billet flywheel
4. ARC billet rod (stock length)
5. MOD2 camshaft
6. Genuine 22mm Mikuni carb
7. Header pipe and muffler
8. Juggernaut 30 series driver


Here is what I was thinking to further upgrade the new engine so far:

1. Go with a Billet rod +.020 for better compression
2. Use a thinner .012 head gasket to further increase compression
3. Port and polish the head
4. Adding a .570 compression height flat top piston https://www.gopowersports.com/flat-top-piston-for-212cc-predator-70mm-570-compression-height/
Does anyone see a problem with these mods? Clearance issues with the head/spark plug or anything?


Here are some of my questions:

1. What internals can I reuse? I've been told by another member that I can reuse the billet rod (although I want to go with the +.020 next time) as long as there is no excessive wear or play it the wrist pin and that I replace the bearings and rod bolts. I assume I can also reuse the cam as long as it is not damaged?
2. Is there a better/different cam than the mod2 cam from DynoCams that I should use to get more torque and acceleration vs top speed?
3. Should I upgrade the push rods? How do I know what length to use on my build?

Thanks for any help and guidance in advance.

 

[txluke]

The cam you use dictates the springs. Look at the Banzai 265 from EC. The cam and 26lb springs will only set you back $50. Are you running a gen 1 or gen III non hemi? The gen III has bigger valves and better keepers.

 

[Coverfire]

The cam you use dictates the springs. Look at the Banzai 265 from EC. The cam and 26lb springs will only set you back $50. Are you running a gen 1 or gen III non hemi? The gen III has bigger valves and better keepers.

Thanks for the information I'll check out that cam for sure. I'm not sure which generation of Predator I am running. Is there an easy way to tell? Also, should I upgrade the push rods?

 

[txluke]

I just remembered that you are running a non-hemi and that cam is only made for clones/hemi-predators. The gen III has the split automotive style valve keepers. Gen I has the 1 piece. I run a hemi block and non hemi crank and head. I can use clone cams and flywheels.

 

[txluke]

Also either get a good cam and champion rockers (best bulletproof option for cheap), or find the rockers off a 79cc predator. They are 1.2:1 stamped ratio rockers.

 

[Coverfire]

Thanks, in that case I have a gen 3 non-hemi because I have the split valve keepers. Too bad that cam is for a Hemi it sounded like just what I was looking for when I was reading about it online.

 

[txluke]

Thanks, in that case I have a gen 3 non-hemi because I have the split valve keepers. Too bad that cam is for a Hemi it sounded like just what I was looking for when I was reading about it online.

Find a hemi block and sidecover. Swap everything over.

 

[OPmini]

Pauls Karts

 

[Coverfire]

Pauls Karts

Oh, wow! some of those engines look amazing!

 

[65ShelbyClone]

That's because he polishes turds. We roasted one of his videos on another site for all the rank amateur work he was showcasing in it to get work as an "engine builder." Horrible advice, misuse of tools, spitting on the valve guides, hideously porous welding, and he didn't even have a straight edge at the time. That was two years ago, so maybe things are different now, but none of the established engine builders seem to take him seriously. They also charge a lot less than he does for parts with a track record.

Billet rod +.020 for better compression
thinner .012 head gasket to further increase compression
Adding a .570 compression height flat top piston https://www.gopowersports.com/flat-top-piston-for-212cc-predator-70mm-570-compression-height/
Does anyone see a problem with these mods? Clearance issues with the head/spark plug or anything?

All of those parts are going to reduce piston-to-head clearance. You'll need to measure the parts you have and how much clearance they provide in order to know how much more you can reduce it.

 

[OPmini]

That's because he polishes turds. We roasted one of his videos on another site for all the rank amateur work he was showcasing in it to get work as an "engine builder." Horrible advice, misuse of tools, spitting on the valve guides, hideously porous welding, and he didn't even have a straight edge at the time. That was two years ago, so maybe things are different now, but none of the established engine builders seem to take him seriously. They also charge a lot less than he does for parts with a track record.



All of those parts are going to reduce piston-to-head clearance. You'll need to measure the parts you have and how much clearance they provide in order to know how much more you can reduce it.

Link to video? I've bought from Paul before.

 

[65ShelbyClone]

Around the same time he went on 4cycle claiming his engines make over 100% VE which wasn't supported with any evidence. The rest of his post didn't show a thorough understanding of how that actually is done with a four-stroke engine.

 

[Coverfire]

That's because he polishes turds. We roasted one of his videos on another site for all the rank amateur work he was showcasing in it to get work as an "engine builder." Horrible advice, misuse of tools, spitting on the valve guides, hideously porous welding, and he didn't even have a straight edge at the time. That was two years ago, so maybe things are different now, but none of the established engine builders seem to take him seriously. They also charge a lot less than he does for parts with a track record.



All of those parts are going to reduce piston-to-head clearance. You'll need to measure the parts you have and how much clearance they provide in order to know how much more you can reduce it.

Hmm . I've never seen any of his videos or anything about him. I just saw the main page with some shiny motors on the table. Doesn't sound good if he is passing off as a professional and isn't though.
As far as for the modifications I guess I'll have to just so some measuring and experimenting. It's part of the fun and learning experience anyways.

 

[65ShelbyClone]

I don't want to rag on Paul if he has improved since then. I just know I saw a lot of things back then from a third-person view that I didn't like. I see some things now that I don't like.

I don't recommend them for stuff that really matters, but if you want to get your feet wet measuring rod lengths and piston compression heights and things like that, pick up some cheap digital calipers for $20. I inherited a Harbor freight 6" caliper that I use as a beater if I need "closer enough" than a 6" machinist scale. For everything else I use Mitutoyo calipers/micrometers/indicators/etc and actually prefer dial types over digital.