Build my engine

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Azuslow

New Member
#1
#1
Ok, this may not be possible due to too many opinions but maybe we can all come to an agreement for the most part.

My goal is to stay under $600 in aftermarket parts. What I'm starting with is a predator 212 with exhaust and air filter.

The plan: high revving hp. I don't have the drag racing scene popular in other cities and states. It just me. So my goal is to make a top speed mini. With a single gear my thoughts were to build something that can rev, maybe I should just build torque and keep gearing up? I'm a good fabricator and can work on anything. But when it comes to what parts work together to make the power you're intending. That's out of my hands.

Any thoughts and suggestions to get me going?
Thanks, Todd
 
OND

OND

#2
#2
Is this the Hemi Head Engine 60363 or the 69730 non Hemi engine ?

Black Mamba Cam ! from Tim Isky . :wink:
 
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D

davidlamb78

Member
#3
#3
22 or 24mm carb, Black Mamba cam, shave down the hemi head, ARC rod and flywheel, 26lb springs, SS valves, and open exhaust. If you can flow a head, you might consider the 18cc head with big valves. I have no idea what that will cost, but it would be what I would build given the opportunity.
 
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Azuslow

New Member
#6
#6
I tried searching those black mamba cams on that small engine cams website. It kept freezing and crashing before I could fully browse the site. But I did get a min to look. First off I saw a cam good for 8k rpms. I would definitely upgrade the springs and valves. I guess I would go ahead and replace the pushrods while I'm there. I also saw roller rockers. Are these expensive? I would imagine at 8k these would be helpful.

Now that I'm on a dream wish list for a 8k rpm engine. I would imagine I would need to balance my rotating assembly for such high rpms? I don't have a clue where to look for something like that or how much that cost. Now that I'm this far I'm imagining I'm close to the $1000 range? Am I getting in over my head wanting to build a high rpm motor? Or is $1000 closer to the budget i should be setting for myself. I guess I'm limiting myself by adding a budget but I hate the fact of limiting what I can build just because of a few dollars.

Thanks again for your help guys.
 
vwfan79

vwfan79

Active Member
#7
#7
Here is the predator build I did that would spin 8000+ in the 1/8 and spun it over 9500 once on accident.
14cc head milled .030
27/25mm stainless valves
Black mamba cam
37# springs
3/16 cut to length push rods
Billet lifters
Champion rockers
Billet flywheel
Billet rod
Flat top piston (out of a hemi)
22mm mikuni carb
Bike ran 10.89 seconds at 63 mph in the 1/8
 
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davidlamb78

Member
#8
#8
Roller rockers are crazy nice, but they're expensive. Champion rockers are nice if you can find them. Yep, you're getting up there in price. Flywheel and rod will be $160. Isky cam and springs around $60. FT piston and rings around $20 (Honda). Prices for valve train will vary. You can get that stuff on Isky's site for a good price. Probably around $100 once you buy valves, keepers, and push rods. The open header will be between $40 and $50. A Mikuni 22mm carb, filter, and manifold will be around $100 as well. That will still be under your $600 if you already have the motor and you do the work yourself. The key to getting the most out of this motor will be how well your head flows. I'd consider having someone open it up to help it breathe.
 
vwfan79

vwfan79

Active Member
#9
#9
Yes the head is very important, mine was ported and polished. Not as good as this but it worked, this is my new motor build head.
 
A

Azuslow

New Member
#10
#10
Once I can get to a proper computer I will send Isky an email and have him get my valve train in line. Maybe set me up with a whole package deal.
I will also make a few calls to some somewhat local kart racing shops for head work.

Thanks all for your helpful insight, hopefully I can get to this soon and I will let you all know how its working out.

Todd
 
David wulf

David wulf

#11
#11
Look A-slow what predator do you have ? The hemi is not all that , the flat top piston is what makes it good . If you have a 69730 predator they come with one of the best heads around . To check there look on the bottom back side to see if it is marked RTC-6 . That head is a big valve 25 intake, 27 exhaust with automotive type keepers and locks . You won't find a better head , maybe a Honda 18cc but that's it . You also need a flat top piston , and look at OldMiniBikes warehouse at the dyno cams . The F 275 is close to a black mamba and also the 308 is a good cam .
 
Full Throttle

Full Throttle

Member
#13
#13
VW, what did you use to get your ports to a mirror like finish. I been working on a hemi head and been polishing on my ports and combustion chamber but can't quite get the finish that you have got ?
 
David wulf

David wulf

#14
#14
Full throttle use only want to do the exhaust port like that . The intake side needs to be left kinda rough , to smooth and the air fuel mixture won't atomize or mix properly .
 
Full Throttle

Full Throttle

Member
#15
#15
Got cha, David. Thanks for info on polishing ports , i always thought the smoother the better but seems i was wrong. Still i would like to get my exhaust port to shine like VW's does.
 
A

Azuslow

New Member
#18
#18
So that head in that eBay link is good parts and value for a 8k engine build? Sorry for all the question but this is all very new to me. Myself like many others just want to make sure I'm spending my money wisely.

Another thing I was thinking about. You guys are using 22mm mikuni carbs on these engines, I have a 125cc honda z50 and it has one of those carbs on it and that is nearly 80% smaller engine. It's the carb that came with the engine.
 
vwfan79

vwfan79

Active Member
#19
#19
I would say that's a good deal on that head as long as it's ported well. I paid about 200 for my first one with 27/25 valves and 37# springs. A 22mm carb will work just fine or you can up grade to a 24mm flat slide, the price is also much higher about $120 for just the carb. My new build is getting a 24 flat slide. I have a thread going on it called stroker motor.
 
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