Turning an ebay CNC 12cc head into a 7cc powerhouse.

[Jayraye39]

Im on a quest to find my lost power.

The motor im running has hit 50mph in the past and on an even heavier bike. However on this lighter boardtracker i hit a wall at mid 40s. So I disassymbled the top end. And right off the bat I found a mistake I should have never made.

I used a rubber O-ring to seal my carb because their was a small gap in between the joining portion of the intake tube and the carb. So thought it was a good idea to take up that space with the O ring. NOPE. dumb move on my part.

After riding awile the carb loosened a bit as they normally do. The O ring got sucked into the motor and melted all over the piston crown along with head chamber and plug.

DO NOT USE AN Oring unless your intake tube has a trench made for an O ring to sit. You do not wanna clean that mess up Trust me.

Basically i sanded down more of the intake tube where it is thick and made it the same size as the part your able to stick in the carb. That allowed me to push my carb all the way back on the intake tube. Now there is no gap where they join.

While cleaning my retarded mess. I decided to take my ebay head off and do a proper cc measurement on the chamber. Ive done this once before but i used a longer plug and only had teaspoons to measure the water i put in. After converting the numbers i found the head to be around 7cc.

Without using a pressure gauge This lead me to believe that my compression was in the ball park of 130 or more since I have a .8 squish and a decked jug. Well I was wrong again folks. Just did a proper volume measurment of my head using the correct plug and a syringe. This ebay head is 11 almost 12 cc's. Holy cow was I off.

Seemingly though, this motor with all the port work and mods this little bas**rd still gets after it. Even with the low compression I have, which i'm guessing, cant be more than 95 to 100psi. Thats also why im guessing my engine temps are so surprisingly low. Running at around 260 degrees F without my cooling system.

So my new project today is reworking this 12cc ebay head by hand using hand tools only and making it at least an 8 maybe 7cc head. This will give me the compression I need to get back in the 50mph club. Which I miss greatly. Tired of being passed by cars on a 40mph street.

This is gonna take all my skills to be this percise because if I slip or im off just a hair this head will be trash. Gonna document this project start to finish. Hear is the head I bought on ebay its my starting point.


Moderators Note:

Once again, I have had to break up a solid wall of text to even make this readable, I will not be doing this forever because I just know that you folks will eventually take the hint and break things up into paragraphs to make things readable...A solid wall of text is not exceptable in any forum when it is done time and time again...Thank-you all for reading this note, just please apply what I am talking about in future posts...DAMIEN

 

[Street Ryderz]

Your guessing at stuff isn't helping you or anyone that reads your post's, firstly the o-ring used to seal the carb is used by most that use a stock carb and intake without issue because your carb should not come lose, if it does it will go lean and cause the over heat issues your experiencing.

Next, squish clearance has nothing to do with the compression, compression is the trapped volume above the exhaust port to the top of the stroke, this is why a compression tester is needed to find the actual value not guessing at it! If you had 100 p.s.i. with your 11cc head the compression ratio would be 4.94:1 and barely able to run!

Compression makes torque not rpm/speed, the higher the compression the more the piston has to fight to complete the up stroke hence why two strokes are low compression engines!

Your video running around the block should never produce the heat shown even if the engine was all ready at running temp! Out of the over 1k engines I've put out there so far none of them have ever seen over 300f even after prolonged periods of wot, I can run my engine for over an hour and never see over 240f, proper jetting and setup ensures this!

 

[Jayraye39]

Your guessing at stuff isn't helping you or anyone that reads your post's, firstly the o-ring used to seal the carb is used by most that use a stock carb and intake without issue because your carb should not come lose, if it does it will go lean and cause the over heat issues your experiencing.

Next, squish clearance has nothing to do with the compression, compression is the trapped volume above the exhaust port to the top of the stroke, this is why a compression tester is needed to find the actual value not guessing at it! If you had 100 p.s.i. with your 11cc head the compression ratio would be 4.94:1 and barely able to run!

Compression makes torque not rpm/speed, the higher the compression the more the piston has to fight to complete the up stroke hence why two strokes are low compression engines!

Your video running around the block should never produce the heat shown even if the engine was all ready at running temp! Out of the over 1k engines I've put out there so far none of them have ever seen over 300f even after prolonged periods of wot, I can run my engine for over an hour and never see over 240f, proper jetting and setup ensures this!

When you have no money you guess at stuff using logic and science. You build things from nothing and turn it into something. You learn from trying and failing. Not knowing the exact amount of volume or even the right compression matters to me. What matters is me getting my already good running motor to run even better.

Im a different builder with a different type of skill. I dont rely on math equations, computers, or even acurate tools. Nothing I do is exact or precise. But at the end of the day what im have is something I have built relying only on my self and nothing else. Thats why you see alot of do it yourself post from me.

I dont buy parts I make them only using primitive hand tools. I am an innovator and an innovator does not have a set of guideline to follow you do it. it don't work. you do it again. Guessing is a big part of innovating. Because it leaves with a foundation to work off of. That's why you see a lot of post documented that I do because I want people to see there is another way to do it. Just because it's the accepted way doesn't necessarily make it the right way

 

[Jayraye39]

Yes I know people run the O ring in their intake. I was basically stating if your carb is not secured or it is loose you will suck that b****** right into the motor.

As for my motor running hot, 250 seems like a good running temperature all around. I see plenty of post with people at that temperature the high 3 hundreds is what kills them.

Not really sure how my post does't help anybody when you can obviously see the point of my test was my motor runs cooler with the system that I guessed at just what can you do by yourself when there's nothing that tells you it's right or wrong.

 

[Jayraye39]

Go ahead and take all the trash in your garage And add that with a pocket of $200 create 2 bad a** bikes That are Beautiful and completely different than anybody else's. Guessing is a big part of building every scientist you've ever known has started with a guess Or theory

 

[Jayraye39]

Got it down to 9cc using these tools and guessing. I'm going to smooth everything out and install it at this point and video document my run in my neighborhood I have a digital speed clock at the end of my neighborhood that will tell me my exact mile per hour.

The most I got previously On the speed clock was 37 miles an hour I bet you a $1000 I will hit 39 miles per hour at least. (SPEED IN MY NEIGHBORHOOD IS 25MPH. LMAO), Still going to take it down the head a bit more but I want to show people That doing it yourself and
guessing every now and then Is beneficial.

 

[Street Ryderz]

Got it down to 9cc using these tools and guessing. I'm going to smooth everything out and install it at this point and video document my run in my neighborhood I have a digital speed clock at the end of my neighborhood that will tell me my exact mile per hour.

The most I got previously On the speed clock was 37 miles an hour I bet you a $1000 I will hit 39 miles per hour at least. (SPEED IN MY NEIGHBORHOOD IS 25MPH. LMAO), Still going to take it down the head a bit more but I want to show people That doing it yourself and
guessing every now and then Is beneficial.

View attachment 191784

View attachment 191785

So if your dying and need help it's ok that your doctor just guesses at what might help, then guesses at and jury rigs some contraption to do that!
Learning is one thing but when you are told or shown how things work and still chose to do it your own way is just a waist of time and effort!

 

[DAMIEN1307]

And I think we really need to leave it at that.

The back and forth with different opinions on the right or wrong way of doing things in this thread is not going to change his mind or your mind from what I can see...It is a waste of time on both your parts to continue this.

To each his own...Lets just put an end to this now so I do not have to lock yet another thread for the never ending tit for tat dissertations...Thank-You.

 

[Deleted member 33388]

Got it down to 9cc using these tools and guessing. I'm going to smooth everything out and install it at this point and video document my run in my neighborhood I have a digital speed clock at the end of my neighborhood that will tell me my exact mile per hour.

The most I got previously On the speed clock was 37 miles an hour I bet you a $1000 I will hit 39 miles per hour at least. (SPEED IN MY NEIGHBORHOOD IS 25MPH. LMAO), Still going to take it down the head a bit more but I want to show people That doing it yourself and
guessing every now and then Is beneficial.

View attachment 191784

View attachment 191785

I hope it turns out like you hope. I have a head like that, but i think it was already at 8 or 9cc. And it did cross my mind on what ur doing to it. All i`ve did to mine so far was take the squish down to 1.0 I just recently i put my stock head back on cause i`m trying to tune a 21mm carb on top end. And something ain`t right. The head and the f2 pipe perhaps. That digital speed clock at the end of your neighborhood dont have a camera?

 

[Jayraye39]

I hope it turns out like you hope. I have a head like that, but i think it was already at 8 or 9cc. And it did cross my mind on what ur doing to it. All i`ve did to mine so far was take the squish down to 1.0 I just recently i put my stock head back on cause i`m trying to tune a 21mm carb on top end. And something ain`t right. The head and the f2 pipe perhaps. That digital speed clock at the end of your neighborhood dont have a camera?

Nope no camera just a flashing warning light if your speeding you wil see. Lol.