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ajkirton

New Member
#1
#1
Let me start by saying that i have spent some time researching and reading your site (and reading the rules).

My kids kart that I got them through some recent bartering a while back has finally died. The stock subaru / robin 169cc 6.5hp motor was done.

I know it would have been really easy to rebuild that motor, but the mods were few and far between for that motor. I insted purchased a Predator 212 hemi. The kart that I am putting it on is relatively heavy being a full suspension, two-seater kart. It wasnt bad before with the stock 6.5 motor on it, but i wanted to make it a little faster and more fun for my kids. i decided to order some modifications for the predator, and have reached the point where i dont know if I should be done, or continue with the mods. As a car guy, I always want to modify everything. As a father I want to make sure my kids are safe, and the kart is reliable so I see lots of future smiles.

Mods that I have purchased:
New Predator 212 Hemi
Arc billet flywheel
Arc billet rod
Mikuni vm22 carb.
billet aluminum intake manifold
k&n filter
long 3 stage race header
comet 20/30 series hybrid
removed governor

before I put everything together and get it running and dirty i want to know if this setup would be pretty good on a kart setup as i mentioned earlier. i am not concerned with this kart having a high top speed, I just want quick and reliable.

Please let me know if you have any recommendations.

BTW: The kart is a Manco Silver Fox
 
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ajkirton

New Member
#4
#4
Yeah. They are super excited. I hope its alot faster. I am usually chasing them down on my z400. That was my daddy project a while ago. That was afyer the wife made me stop modifying my wrx.

The z400 has a 522 race motor running on 110 race gas.

The wrx is a 2014 with about every bolt on you can get. It dynoed 361 wheel on pump gas.
 
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ajkirton

New Member
#5
#5
Im also big in mountain bikes so thats a whole other story.

Has anyone tried lightening the crank and doing a full balance on one of these motors. It looks to me like there is alot of potential in machining some of the stock parts.

I think i might buy another motor and start making stuff for it. Figure out how to make a girdle. Maybe some welding in some week spots.

I know when i built my sr20 motors for customers i made custom girdles, welded the heads and re-machined them. I would also have to weld transmission cases and machine output rings to hold them together better.

I never knew this small engine world existed and i am really excited about the possibilities.
 
J

jbrocks

New Member
#7
#7
Welcome to OldMiniBikes ajkirton! Sounds like you're on the right track with your engine mods. I don't think you'll have to worry about going faster, I did HALF the mods you're doing and my minibike is totally faster. Stopping the dang thing is your new issue, hope the brakes are good on that kart! We like pics here, so as soon as you figure that out, love to see what your doing. Enjoy the site.:thumbsup:
 
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ajkirton

New Member
#8
#8
Yeah. I never take pictures. I am pretty bad about that. I will have to take some pictures.

Wish my wife had taken pictures of me today. I had all of the kids sitting around the dining table with me building the motor. I tought them what everything does, and why it is there. I also taught them why we are replacing the certain parts that we are.

I was a little surprised when i pulled the side cover off of the motor. All of the pictures i have seen show a plastic cam gear, as soon as i opened the side cover there was a bright metal cam gear. I also noticed that the crankshaft had been toleranced with machining. Both features i hadnt seen in my previous research.

I did run across quite a few bolts that were under/over torqued. Because of this i verified the torque on every other critical piece of the motor. One of the head bolts wasnt torqued properly as well.

I also noticed that the motor had a semi-phenolic spacer between the head and the carb. I was expecting one of the carb bolts to be shorter than the other, but both studs were equal length.

When i removed the oil sensor i didnt have a plug that was the correct size. I ended up cutting the wire off of the stock wire pass through hardware. I then threaded a small drywall screw into the rubber grommet that the wire exited the engine through. Doing this allowed me to remove the rubber from the threaded piece. I then tapped the now hollow part with a 1/4 20 and cleaned it and lock tighted it.

For the governor removal i followed the typical steps, and filled the holes with 1/4 20 hardware as well. I used red loctite 267.

When putting everything back together i used copper gasket spray to heavily coat the stock gasket that i removed. I started doing this years ago on my race motors.

I also realized for the firat time why everyone keeps the stupid ugly side cover over the flywheel. I had never realized that that is used to directbair to cool the motor. After looking at it a while today i feel i can make some modifications to the shape of it to allowbfor better cooling. I may also do some cross cuts in the stock head to offer more surface area for heat transfer.

I am having more fun building this than i ever have before. It is wuch a great motor to teach my kids on.

I did also examine the head for any excessive flashing or port protrusions. The casting also looked much better than what i was expecting. I did grind down a few small areas, but by no means ported the head. I believe i will port match to the intake and exhaust manifold once good old ups delivers them. I also think i am going to make a new valve cover as i am having a little heartburn with the location of the vent.

I am going to spend the rest of the night looking tor pictures of failed blocks to find any patterns to indicate a weakness.

After building the motor today we went outside and ran two tanks of 110 octane tgrough my 4wheeler. I tought the older two kids how to drive it on their own, but i dont want them to leave first gear. My 10 year old son never stalled it. Not even his first try. My 13 year old daughter ob the other hand took like 20 timesvto get it going the first time. But she finally got it. I am so proud of these kids. My 5 year old girl was just wanting to ride around with me. She loves sitting in front of me and holding the bars.

I might really get into the small motors. It really is fun. I might be able to make some new deigns or modifications that are far from the norm as i have a pretty extensive race engine development background.

Hopefully i can become a regular on here.
 
Commonrail

Commonrail

New Member
#9
#9
I did the OldMiniBikes stage 4 kit on my hemi (on my DB30 original mini bike) and the only regret is it doesn't start up on the 1st or 2nd pull. It keeps fouling out the plug. The 1 time I got to ride it around the neighborhood yesterday after upgrading to 26 lb valve springs, it pulled hard as heck BUT it will not start back up! I pulled the plug and it was black as coal. The kit with the CNC 615 carb said its pretty close to a direct bolt up and only have to remove an o-ring after 20-30 min break in, in which I did. I just need to set the idle but that's hard to do on an engine that won't start!
 
fistfullabar

fistfullabar

Well-Known Member
#10
#10
I am also a avid mtb rider. Single speed only. It is good your kids are learning about engines. Me and my son work on our mini bikes all the time:thumbsup: Glad you found the site.
 
A

ajkirton

New Member
#11
#11
I had to sell my single speed about a yeqr and a half ago. It was an all carbon 29er.

On One lurcher with horizontal dropouts.
Dt swiss carbon wheels
Fsa team carbon cranks
Fsa carbon bars
Fsa carbon seatpost
Well you get the picture. I had to sell it because i got sick and wasnt expected to survive. I fought through it and am short one lung and a few other not so important organs.

No i cant ride far at all, but i have a little play bike. Its pretty setup too.

I really hope that their kart doesnt have starting issues. We will see.
 
A

ajkirton

New Member
#16
#16
I am going to take the tc backplate off. I dont like it and it touches the oil fill plug. Hopefull we will be breaking it in this weekend.

You can almost see the billet flywheel poking through on that first picture.

Its a shame that all of the pretty parts get covered.
 
A

ajkirton

New Member
#17
#17
Well I will revive this old thread. I have been gone for a LONG time...

The kart sat for a while as I picked up a KTM to build and a yerf dog that had better suspension. The yerf dog was just a pain and everything broke so I am done with it.

The manco Silverton is getting built back up now as I am bored.

I am rebuilding the motor with a few new parts.
Arc billet rod +.020
Arc billet flywheel
Weisco flat top piston (stock spec)
Mod 2 cam
22# valve springs
Stainless flat bottom valves
Port matched and cleaned up hemi head
Mikuni vm22 carb
Short intake manifold
3 stage race header
Billet side cover
Welded bracing on the block (.25" aluminum stock)
Have a custom made 1" adapter and will be running a Polaris torque converter setup.

Added blaster shocks for the rear, but will be redesigning the suspension. Kfx shocks mounted on the front. 16" (I think) tire in the front.

I will be adding many gussets to the frame. I will also be looking to add a twin hydraulic disc setup.

Ready to get this thing going for the summer. I also want to find a way to quiet the exhaust down a little without hurting performance. It was loud how it was, but will be at a higher compression now and I am trying to keep it at the 7500rpm range.

Any suggestions would be appreciated.

I will post up more pictures once I really get into the build more. I have since acquired a large shop to build more projects.
 
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