Choosing Power Enhancing Parts

But that would add 1mm to the squish clearance, and the cost with two rings, omg! It would be cool if there was a flat topped piston (with the same wrist pin to crown height) so it just adds the volume taken up by the dome shape.. Wouldn't be much but it seems simpler.

Saying that I have no idea what the cranking pressure will turn out to be when I get a chance to test.
 
If you've ever had a motorcycle or scooter and then you noticed the power lessening more and more as time went on and then you found out the rings were worn and the gap too big, then replaced them and the power was back to normal then you'd know how important that ring gap is.
Grubee engines probably vary a lot from engine to engine due to sloppy tolerances but on mine the gap was 3 times what is considered normal for a small engine!
Replacing the stock crap with quality piston/rings takes care of that problem. It is a true power boost which a good squish band does not give. The squish band exists to keep the piston temp down with high revs but even modified Grubees usually don't rev more than 9000rpm so the squish band isn't necessary. Just use your rotary tool to eliminate the band which will also help to bring down the excessively high compression the aftermarket heads give.
 
If you've ever had a motorcycle or scooter and then you noticed the power lessening more and more as time went on and then you found out the rings were worn and the gap too big, then replaced them and the power was back to normal then you'd know how important that ring gap is.
Grubee engines probably vary a lot from engine to engine due to sloppy tolerances but on mine the gap was 3 times what is considered normal for a small engine!
Replacing the stock crap with quality piston/rings takes care of that problem. It is a true power boost which a good squish band does not give. The squish band exists to keep the piston temp down with high revs but even modified Grubees usually don't rev more than 9000rpm so the squish band isn't necessary. Just use your rotary tool to eliminate the band which will also help to bring down the excessively high compression the aftermarket heads give.


HEY GUYS, I am back..away for few hospital fun days ....anyways back to bikes,,, still havent tried my new RM 85 pipe,, i got it on there nice and welded up and positioning was crucial,,between pedal clearance, front tire swing clearance for hitting,, frame and fuel line and PET COCK, going to put in metal MESH tube just for safety and looks,, had to do some bending on ending stinger pipe and got a cool silencer...well back to work

just trying one thing at a time so i can see the full range of that modification or part...i still got my 44 tooth on,,, want to put my nicely painted flat 36 tooth on but want to see if new pipe and timing woodruff magneto key and jetting would break that 7,560rpm and 34.7mph first......let you now later buddies
 
I came up with a better way to measure the cylinder head volume.
Use modeling clay (PlayDooh, etc).
With the spark plug screwed in press in the clay to fill in the head area.
Use a ruler or anything with a straight edge to cut off all the clay sticking above the head mating surface.
Pull out the clay and roll it into a ball and measure its diameter and then use an online sphere area calculator to figure out its volume in ml which is equal to cc.
My two 55cc modified heads (for higher compression but not too high) gave 5.6 and 6cc.
(69/55)x6=7.5 so if that is the correct way to estimate for a 69cc engine then it should be 7.5cc and as you know they are all 7cc or less which gives too much compression.
 
I do wonder how/why the expansion chamber pipe ever got that name in the first place. It seems it's primary function is to act as an echo chamber and calling it that would have given more of a clue about how it works (or doesn't) at RPMs that sync up (or don't) with the returning pressure wave.


because of the useage of incorrect terms.

a tuned pipe is tuned. why we call em tuned pipes. if they arent tuned, theyre useless.

an expansion chamber is an expansion chamber. it allows gas to expand. its not tuned, it isnt for adding performance. its just for expanding, therefore cooling, exhaust gas. an expansion chamber is actually a muffler. but people keep calling tuned pipes expansion chambers.

and i keep calling them turkeys :)
 
well then if they are to be named by what they do then they should be called expansion/contraction chambers because the exhaust first expands and the contracts (since the stinger is smaller in diameter than the header). Contracting the pulse is the reason they are so loud. It causes the pulse to have more pressure before its released into the free air. The greater the pressure difference between the pulse and the air, the greater the sound level.
 
expansion of exhaust gas. not the pressure wave. the pulse travels down the pipe a hell of a lot faster than the exhaust gases do.

you dont really seem to understand how tuned pipes work at all. or how gas flows into low pressure zones and away from high pressure zones, and how changes in the diameter of a pipe causes sound waves to react. and definitely get sound waves confused with, for want of a better term, the "exhaust gas front"

take the reversion cone off a "tuned pipe" and tell me that that is QUIETER than a standard pipe with stinger, please do :)

then ill show you my new design for a megaphone, with a reversion cone because obviously, a megaphone should be louder if it closes up again at the end.

i wonder why trumpets flare out at the end when obviously, they would be louder if they closed up at the end.

silly bastards, theyve been using megaphones back to front all these years!

images
 
as usual your medicine is distorting your ability to perceive reality.
the megaphone is a smaller outlet diameter than his voice entering free air without any device to direct it.
like a smaller stinger
 
Back
Top