Ht Performance Porting Success

[Quenton Guenther]

Hi 210061741.

When you raised the cylinder with the gaskets, you raised both ports in the process. Raising the exhaust usually helps the top end a little, but the intake port needs to be lowered [or raise the back of the piston]. Adding a second gasket also changed the compression slightly [lowered it] and could have easily changed the balance from the crankcase to the cylinder volume.

Sure is fun playing with different ideas on such a simple motor design.

Good luck, and have fun,

 

[210061741]

I cut the piston skirt .090 inches on the intake side last night.
That leveled it just about perfect with the intake port at TDC.

I have tried about everything now.

I swear i have dismantled that motor so many times now i could take it apart and put it together like a soldier and his gun.

The motor really ran great with no base gasket at all.
I'm gonna go back to that.
See what happens.

Got my new 66cc PK today.
But i want to get this 48cc running good again.

If i can.

Hopefully it goes back to the way it was when i pull the base gaskets.
It was really rockin.

Now it feels like my timing is off.
It wants to hit but hesitates.

I know one thing for sure, if it runs good when i pull that gasket i definatly will know which way not to move the intake.

Really had hoped to get er runnung perfect so i could replicate my mods on the new PK.

O well i aint givin up.

 

[210061741]

Got rid of the base gaskets and shes cooking again.
Even better than before.

So the grubee is back in buisness and running soo strong i cant even get myself to hold it full throttle for very long.

And i like to go fast.
Just not that fast.

Revs high and quickly reaches top speed.

Anyway time to concentrate on the new 66cc i got.
The 48 is now better than it needs to be.

 

[AussieJester]

time to make a more suitable frame for these higher powered motors buddy!longer and lower is the ticket to high speed stability buyild in some adequate rake and your in business ;-)

KiM

 

[AussieSteve]

You're on the ball with that, Jester. I had a good long ride today, much of it on gravel at WOT, (38kph today), and these things ARE a bit unstable. I've ridden dirt bikes all my life, but this is a different feel, almost like one tyre is flat, sometimes. I think it's a side effect of the rag joint.
My electric bike is 10" longer in the wheelbase and as stable as you could want. It feels like it was built to coast downhill no hands.
(I don't have the nerve to take my hands off the bars long on my HT bike. Two hands everywhere, hanging on tight.)
... Steve

 

[210061741]

Aussie folks

I agree 100% about stronger.
And the configuration of the Frame is an important factor to stability.

Right now my motor is mounted to a Schwin High Timber 2.4 FS.
Pretty nice All Terrain Bike.

My rear sprocket is mounted to a disk brake hub.
A custom setup i built myself.

The rim is a double wall and made for Downhill and the hub is a nice Cannondale.
I use kevlar lined tires with slime tubes.
With the rag joint i was ripping apart wheels to no end.
With the disk brake hub i've had not a single problem.

This bike handles great and i've had no problem with stability.
Never wiped it out or laid it down Ever.
There is a nice s - curved road i love to ride. Nice sharp curves.
I can roll at 30 mph and lean down to the point of scraping peddles on the road and this bike will glide like an angel.

-------------------------------------------------------------------------------------
The 66 install will be very clean and tight.
I expect much higher torque to be had here.
Obviously putting higher strain on the frame.

I am not one to start off from a stand still.
I peddle hard and get that bike movin good before i ever throttle it.
Then i peddle as much as i can until i can't keep up with the motor.
This helps dramatically reduce the torque strain on the bike.

I have installed an extra seat post into the Downtube from the seat.
The seat post is aluminum but the wall thickness is about 3/8" per side.
The bike frame itself is steel.

I am in process of making new mounts for the 66.
1/8" thick X 4" long high strength steel plate that will be formed to wrap around the downtube and the seattube.
Then 2 exhaust clamps will be used to clamp these plates to the bike frame.
The motor will mount with the studs to each plate.
Also note the 66 has the new 40 MM front mount spacing "better from the start".
The mounting will be solid cause i'm adding 1/8" of steel to the tubes at the high stress areas. Frame cracking will not be an issue and neither will motor movement.

With the 48 i run BMX chain and have had some stretching issues.
With the 66 i will be using the 415 chain " we will see what happens."

------------------------------------------------------------------------------------

It is getting close to snowing here soon ( YES I PLAN TO RIDE )
So i will soon be going to a large gear 48 / 50 tooth in place of the 36T i run now.
It will be slow travels most of the winter ( Perfect for breakin in the new motor )

------------------------------------------------------------------------------------
On a final note if you check out my Jackshaft / Shiftkit Thread ( still not completed )

You will find that i am going to get a Shurly Instagator.
Titanium Alloy Frame / Gussets / made for stunt riding jumping and all the abuse you can dish out.

Basically a very high quality 26" BMX guarenteed not to break, designed for thoose guys you see on tv flying down hills and doing flips in the air.

In my opinion the best MB Frame you could buy for a reasonable price. ( $400 )

So by spring when it's time to TUNE UP THE JUICE AGAIN

I'll be ok.

MOST DEFINATLY AN IMPORTANT POINT TO BRING UP THOUGH GUYS.
iF YOU MAKE YOUR MOTOR HIGH PERFORMANCE.
YOUR BIKE BETTER BE BUILT TO MATCH.

Someday i'll have the cash to get some welding and bending equip.
You guys that can make your own frames are awsem.
You have the advantage from the gate.
I would love to build my own frame.

 

[PaulFlorida]

I love this thread! I thought I was the only one grinding away searching for power. WhatWith my 66, i took it out of the package, inspected it and tore it down immediatly. I've had it a week now. Until I get speed parts, I'm running "maximum Stock-modified". Ported everything on the jug and milled the head- now its time to dig in to the cases hehehe. Real snappy motor, no top end power though

 

[PaulFlorida]

210061741- Is the case mod a real noticeable change in power? Could you post more pic- I'm replacing my social life with two-stroke education and love to see other people hacking away and butchering it up.

 

[210061741]

Yes it did make a big difference.
I have a brand new PK80 Slant and tore it apart.
The crankcase transfers were ground this way stock.
I only matches the transfer ports ground it out a little more and polished it up pretty good.
I also ground the ports good enough to produce sommothe surfaces.
Made them a little wider and took about .030 off the bottom intake port.
And about .030 off the Top of the exhaust.
Milled the head and the jug plus installed ultra thin Aluminum base gasket.

The pk ports were pretty large to start i'm gonna do a port map and see where it is at.

The most work was blending the edge of the tranfer on the bore side of the jug.
Thin that web out real good.

 

[andrew88rmz]

Man this thread is sweet. I ve been trying to figure out how to port mine, put you have already done the work and figured it out. THANK YOU! I was goening to lower the intake and raise the exhaust but i had no idea how much on such a small engine. I am wanting to do it but i might be wasteing my time without an expansion chamber. I just like the way my bike looks with the stock pipe. Since you seem to be an expert with these little motors do you thing i would be wasteing my time with this mod if i kept the stock pipe? I did cut the cat converter apart remove the guts, and weld it back up. I dont know you tell me please.