boosting compression? ideas?

GoldenMotor.com

Thunderhead289

New Member
Jul 2, 2013
49
0
0
an iowa corn field
so I shaved my head down a bit and was curious on everyones opinion on doing so.

I also drilled a few extra holes in the baffling of the exhaust due to the higher compression.

can anyone tell me the adverse effects of lessoning the back pressure. what negative effects will it have? obviously with less back pressure there will be more heat in the chamber, but is there anything more than that?

bear with the video a bit as I made it to get views on youtube since I get paid through ads.
https://www.youtube.com/watch?v=ZMMbWtStkTY
 

Thunderhead289

New Member
Jul 2, 2013
49
0
0
an iowa corn field
explain that too me, where is the back pressure needed?

I cant bring myself to get one over a shift kit, I just do not care for the look of them even if they are such an improvement. id love to build a motor for best power, though I seriously doubt the bottom end integrity of these motors.
 
Last edited:

Nashville Kat

Well-Known Member
Apr 20, 2009
1,501
55
48
Jacksonville, Florida
I file the head down flat- I take all the ridge away that fits down onto the head gasket-
the normal ridge actually makes the head gasket have a smaller area of contact, and usually bends the head gasket onto two different planes

anyway, filing that ridge away takes a little bit of top cylinder space away, and with the same bore and stroke otherwise, increases compression- I could really feel the pop when I first did it

the head gasket is not compromised either in volume or squashed into two different planes, so in theory and probability at least, it should last longer and seal better.

I just got an odd extra 50 cc engine dirt cheap on ebay- the straight verticle plug head is ALREADY flat with no ridge- so I'm curious as to when it could have been made, and have no way to find out.
 
Last edited:

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
explain that too me, where is the back pressure needed?

I cant bring myself to get one over a shift kit, I just do not care for the look of them even if they are such an improvement. id love to build a motor for best power, though I seriously doubt the bottom end integrity of these motors.
Actually the bottom of these engines does pretty good, the wrist pin/upper bearing is normally the weak spot on these engines when bearing fails its usually that one, sanding the head down flush wont hurt a thing, I've done it multiple times, it will increase compression and give your engine a bit more grunt power and help power even on top end, a well tuned carb and a free flowing exhaust is where to biggest improvement is on a basically stock engine, I will include links to upper bearing which is very good quality.

http://www.pocketbikeparts.com/Piston_Wrist_Pin_Bearing_p/cgpr302450.htm

https://www.treatland.tv/malossi-needle-bearing-p/malossi-needle-bearing-663209b.htm

Map
 
Last edited:

Thunderhead289

New Member
Jul 2, 2013
49
0
0
an iowa corn field
so if I run it richer to keep the combustion temps down I should be alright with less back pressure? im sure it will use more fuel due to better flow, but im not all too worried about fuel mileage with what these get!
 

Huffydavidson

STREETRACER/MANUFACTURER
Jan 29, 2012
1,076
4
38
st.louis,mo.
So, what saying is, that if I shoot some holes in the can I'll have higher compression ?
Dang , after all the money and machine work I've done and spent , NOW you tell me.
LMAO