Sanded stock head VS aftermarket



FNTPuck

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Is there a difference other than heat? Mr killa joule wonder
Heat is the whole point. Assuming you are running the correct plug and its not shrouded, on a 2stroke there is no real performance difference from a head besides the compression benefit, which you can get from a stock head by sanding it down. Total opposite of a 4stroke, in which all the power is made in the head and cam.

With high compression, especially if jetted on the lean side for power and with a restrictive exhaust, the engine can overheat after running it hard which will kill your power, make it bog, and damage your engine.
 

gary55

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Respectfully disagree. The heat reduction is great in after market heads, as is the increased compression, but that isn't where their superiority over a sanded stock head ends. You also see performance benefits through improved chamber design, hemi burn chamber for even spread of fire wall with squish band designed to reduce chance of detonation allowing higher comp. ratios and creates charge swirl for better combustion.
Add this to the fact that once the AM head is torqued it doesn't require constant re torquing, doesn't warp, lasts forever, and the crush ring extends to the chamber wall and the improvements over stock sanded heads are huge.
 
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FNTPuck

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Respectfully disagree. The heat reduction is great in after market heads, as is the increased compression, but that isn't where their superiority over a sanded stock head ends. You also see performance benefits through improved chamber design, hemi burn chamber for even spread of fire wall with squish band designed to reduce chance of detonation allowing higher comp. ratios and creates charge swirl for better combustion.
Add this to the fact that once the AM head is torqued it doesn't require constant re torquing, doesn't warp, lasts forever, and the crush ring extends to the chamber wall and the improvements over stock sanded heads are huge.
Not sure I agree either, but no worries - to each his own :). IMO none of that is anything you would find on a chinagirl head, which is what I was limiting the thread to lol. All the chinagirl advertised heads are the same simple dome, tapered squish band with no performance benefit besides heat transfer and compression. There is no real R&D done on our parts because you would never recoup it selling them for $30 on ebay lol. Bet if you dyno'd a stock head and a fred head with the same cc's they would make identical power (unless it was on a combo that caused the stock head engine to overheat). I went with a Tomos head and shaped the squish band myself with an old piston and decked the head to proper squish distance and compression but none of that is a bolt-on thing you would get with an off the shelf chinagirl head...I don't have a dyno but I have personally tested CNC heads, stock heads, and moped heads and until compression and squish are changed there is no noticable performance difference IMO.

Tons of killer aftermarket 2stroke heads for motors like the AM6 and dirt bike motors with orings, better plug location, and proper squish bands but they won't just bolt to a chinagirl head.

Stock head is a warping prone piece of junk that runs hot, but from my experience makes the same power as a CNC head until you have enough compression and exhaust setup to cause overheating...the jug is still where 99% of the power is made :)
 

gary55

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Not sure I agree either, but no worries - to each his own :). IMO none of that is anything you would find on a chinagirl head, which is what I was limiting the thread to lol. All the chinagirl advertised heads are the same simple dome, tapered squish band with no performance benefit besides heat transfer and compression. There is no real R&D done on our parts because you would never recoup it selling them for $30 on ebay lol. Bet if you dyno'd a stock head and a fred head with the same cc's they would make identical power (unless it was on a combo that caused the stock head engine to overheat). I went with a Tomos head and shaped the squish band myself with an old piston and decked the head to proper squish distance and compression but none of that is a bolt-on thing you would get with an off the shelf chinagirl head...I don't have a dyno but I have personally tested CNC heads, stock heads, and moped heads and until compression and squish are changed there is no noticable performance difference IMO.

Tons of killer aftermarket 2stroke heads for motors like the AM6 and dirt bike motors with orings, better plug location, and proper squish bands but they won't just bolt to a chinagirl head.

Stock head is a warping prone piece of junk that runs hot, but from my experience makes the same power as a CNC head until you have enough compression and exhaust setup to cause overheating...the jug is still where 99% of the power is made :)
Agree to disagree. While there is most likely no R$D done for china girl there has been enough done on head design in general to make one superior in design to the stock crappers they come with. I agree that most of them have either to large of a squish ring or are improperly angled/shaped and it's a crap shoot getting one that does and shaping it yourself along with adjusting gap is the only way to optimize them. Also agree 99% is in pipe, jug, and carburetion. After all this I still believe in the Aftermarket VS sanded the aftremarket is the way to go. To reduce a stock head to the volume of a 6 cc head you would need to remove roughly .045" to .068" depending on the head you have as they come in quite a variety, and that is a lot of sanding along with moving the crush ring a lot farther into the cylinder.
 

Karl Snarl

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Sep 20, 2019
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Is there a difference other than heat? Mr killa joule wonder
high compression is best on lower rpm machines. the stock head un touched will give you higher rpms ( especially the flat piston style) over a higher compression aftermarket head. you can use the modded stock head, but they are poor at removing heat on modded engines. if you go to high on compression, you will have to change your timing and octane rating. i've got one bike i have to run race fuel in because even the highest pump gas cause it to ping. the compression on tht one is around 235psi. it last for about 3-6 hours of racing, and then needs completely rebuilt from the torture. tht engine took awhile to get right, it was cracking jugs and throwing rings till i figured out the race fuel idea. it has so much power the bearings shell out if i dont rebuild it often. if i was you, i'd just drop the 50 bucks on an after market head, and save a ton of hassle and blown jugs. even the cheapo top hat heads provide better cooling than a stock head. those top hats are great for tooling around town and add quite a punch to a stock machine when the squish is set right.
 
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