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post #14 of (permalink) Old 03-20-2019
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Join Date: Mar 2008
Posts: 20,796
Re: Cag port timing

Originally Posted by edek91 View Post
I currently have .5mm gasket with .65mm squish

Cam2 are you talking 40 thou e.g. 1mm squish or .40 of a mm ?

Doesn't removing the base gasket effet your blow down time ?

Have you ever tried building up the bottom of the exhaust port ?
I quote my squishbands in inches or thousandths of an inch...

I realized now you used mm's but didnt add the mm's...I thought you forgot the zero because the 2 and 3pc headkits Ive built they started in the .054-.058" of squish without basegasket and standard copper ring with varying thicknesses so I assumed you meant inches.....

It seems your on the right track and yes Ive built up the bottom bases on engines....

Youre getting a lil critical of a tool based engine and blowdown timing...If we were talking Polini, Blata and BZM or IAME it would be a different perspective...

These engines are built in a retarded state to maintain a descent amount of torque to get the job done and also get the longest life longevity possible out of it...In tool engines its about how hmuch fuel and air you can pack into the whole engine and do it with as much velocity possible...Euro engines start their life out in the 16.5/17:1 range as a comparison and have a short lifespan,,

Racing engines are built in reverse of these Chinese tool engines....Theyre ported aggressively with tight and exacting squishes to compression ratios and also deliver the power packed goods for a much shorter period of time..

Once you start exerting that type of cylinder pressure through a cylinder where the transfers are open and exposed controlling blowdown timing is virtually just a number with zero meaning and operates on a principal of size to design......

Once you upset that happy medium it comes with consequences like erratic powerband,,overheating and being really hard to start ,tune and keep running..

In a euro engine choking out as much empty space delivers power because the intake is designed to be smack dab in front of the transfer ports also to mention fed by a big honking azz carburetor....

In a tool engine having a crankcase that can handle excessive fuel is needed to flow the fuel into the transfers so the more fuel compacted into the crankcase the better the upward push of power adding mix gets into the cylinder...

Seeings the mix has to pass through the crankcase the crankcase must become a storage vessel.. Eliminating the internal area eliminates the fuel that feeds it per stroke...the more it can inhale per stroke the more power it puts out...

3/4 of the stuff they claim is HP stuff for these tool based engines are actually just bolt-on bling bling with very minimal to no increases in overall performance without causing other types of problems .

When you look at the 2 stroke building websites these two stroke masters n such you can really get a lot of valuable info but also the wrong info as the engines theyre using as examples are Japanese made MX dirtbike or snowmobile engines....

If you want the right info on how to hop up tool engines go back to the race kart days when they converted chainsaw engines into performance engines....

That's where youll get all your pertinent info from......There were no full circle cranks for them either but they belted out the goods regardless......LOL


Last edited by CAM2; 03-20-2019 at 02:23 PM.
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