Basics of Boosting Engine Power

[Fletch]

Yes, the piston/wrist-pin is heavier than those of a 48cc engine and the crank is balanced for the 48cc (somewhat). You can just drill a bigger hole in the wrist pin to see if that takes care of most of the vibration.

Thanks!

 

[Fletch]

25psi seems very low to me. i havent done a true reading yet on my "65.9"cc sd stinger. but with just a couple slow peddles mine was at about 80 psi. i had my bike in the basement and i didnt have any room to really peddle the bike. im sure when outside and if i get going, it would be at about 100-115 psi. and thats just a stock engine with about 20 miles on it.

125 psi is what I meant to type.

 

[happyjourney]

which is the head mating surface and the top of the cylinder? i'm guessing we're talking about sanding a mm off the flat end of a piston (the end that faces the spark plug and entrances for gas and air) when you say top of the cylinder or is that the head mating surface. where can i get a top connecting rod needle bearing and what other parts should be replaced. I'm still planning a build and want to get it right the first time. sorry for my noobness. i'm about to go search on top connecting rod needle bearings. i have a 66cc motor to clarify

 

[Deleted member 12676]

C'mon man why would you ask something so obvious? If I asked you to touch the top of your head would you go to the college to ask advice?
Ask me a decent question and I'll answer.

 

[Fletch]

Haha.... The head mating surface is the part of the head that touches the cylinder. The cylinder is the part the head touches. You sand 1mm off the head mating surface (bottom of the head). Bearings and other parts are sold by many of the vendors who's ads are on the left. A Google search for "thatsdax" will probably get you there too.

 

[Neon]

You can also take your existing bearings and seals to a local bearing and seal shop. They can usually match up much better replacements and there is no wait time or shipping charges.

 

[TimmyD]

The thick glass is perfectly flat. No ridges or wavy surface to bugger up your sanding job.
The mm thing I have no answer for.

i took off 2 mm and had to put in a gasket because i thought i could hear knocking . a friend just said it was the massive compression but it works well . mine was lathed so i know it was 2 mm for sure . 1.5 it optimum stock

 

[Deleted member 12676]

most important is the cranking pressure.
for a non-squish-band head make sure it's not over 135psi.
for a squish band head with .8mm clearance make sure it's not over 155psi.

 

[Frankenstein]

most important is the cranking pressure.
for a non-squish-band head make sure it's not over 135psi.
for a squish band head with .8mm clearance make sure it's not over 155psi.

What about a cylinder with open transfer walls? I know you don't think they are good for the standard happy time but these are a different motor. Is there even a practical way to adjust that on a one piece head?

 

[Deleted member 12676]

that doesn't affect the cranking pressure or head temps