Mild Piston Trimming Without Reeds

Go right ahead Dodge lift up your Skirt and lets see whach ya got !!!
This aot be good.
LMOA

Ya not gonna hurt a thing -scribe Piston skirt @ TDC- Drum sander in a drill press, you'll be glad you did!

i cut a whole 1/4 in off the entire intake side of my piston skirt, then rounded the cuts.

my bike rev's a whole lot quiker and seems to have a lot more mid range after the mod. i will do this to all motors i get after the port and polish and head decking of course !

you also want to cut ramps in the piston. i did this also. just cut ramps for the exhaust and transfer ports you will be glad you did !!!!!!!

a lot more power everywhere and no loss of bottom end, in fact i gained bottom end !

Keep it simple. Raise your skirt DD then tell us all about it!

dodge dude94 said:

As some know, I'm thinking about pulling my engine this winter and doing a tear down with porting work. Among which I am considering a mild piston skirt trim.

Now I know that for big trims you need reeds, but what about a few thousandths of material from the skirt? I will be getting a Dax RT carb in the near future so I would hope that would fix my jetting issue I'll have, but any thoughts?

Click to expand...

DAX RT Excellent choice. You're a CNS guy. Same Jet size 6mm. You'll need to jet down. Expect to.

Leaner
http://www.sickbikeparts.com/catalo...ucts_id=154&osCsid=ql7ngl7lacavm2ee5315c4jgc1

smaller the number the leaner they are (or at at least here)

I'm at 65 ft above sea level - and very happy with lw end grunt and top end speed with size 63 and 64 jets in NT, CNSv3 and DAX. I must also tell you not only do I do the piston skirt mods but also adapt pocket bike xpansion pipes to all bikes. Use your own better judgement. Stock mufflers will be better with richer jets (66-72) my exp. for what it's worth.

I have never considered that.

Higher compression won't really affect jetting much unless you go nuts. Just crisper power and more of it everywhere.
Running things just a tad rich is always a good idea for any two-stroke.
Especially one built with such questionable materials. I'm convinced ht's are cast from recycled beer can pull tabs and gum wrapper tinfoil.

Thanks mani

dodge dude94 said:

Alright. I don't have an x-pipe at the moment, so how much can I get away with before I start blowing gas out the exhaust? lol

And how steep of a ramp should I grind into the piston for the ports?

@allen: jet down? Richer or leaner?

Click to expand...

your piston ramps should go down the side of the piston enoght to effect timing but not go to close to the rings . i went 3/4 the way down and ramped it nice and smooth tword the middle .

google pics of piston ramp mods for 2 strokes and you will see what to do clearly

as you can see there are many ways to do it ... it all depends on what you want for rpms and a power band . i do big exhaust port ramps and steap transfer ramps aimed at the middle of the chamber

i woud say to go for pic 3 and you can take more of if you feel you want more rpms and a higher power band later.

pic 1 is exacty how i do my transfers and my exhaust is even bigger !

this along with a high comp head and a tunned exhaust and good carb and intake all port matched and good flowing on a dax motor ported wide open (intake lowered 1.5mm and exhaust raised 1.5mm bolth widend .5 mm each side) will give you a street ripper motor !!! i am runnning a grubee gt5 bottom end stock and have the same mods with a cns carb and i hit 37 with a 44t rear !!!! this is on a single speed cruiser bike ! with the 16mm cns carb, it will keep reving till it blows !!!! lol i have no rpm limit !!! i have a vibration limit due to the grubee gt5 bottom end !!! if i had a nice balanced bottom end and great bearings it would rev to the fr%ggin moon !!!! this is all without reeds or a 3rd transfer ! though next time pull my jug i wil ad a 3rd transfer lol


ohh and ps..... lucas oil upper cylinder lube will help with high rpm driving ! i add 1-1.5 oz to a half gallon of 40:1 mix gas and i ride my bike like i am trying to blow it !!!! cause i am lol !!! i have been trying to blow my motor wile driving to and from work (5 miles) every day by reving it as far as she will go and taking her to her very top speed and holing it there for the whole ride !!!! she vibes like a damn earth quake but she is still going strong after 3 weeks of this abuse and i suspect the lucas oil cyclinder lube has a lot to do with it . i srsly do not expect her to last much longer but who knows lol

i want to see what the china can REALY TAKE for punnishment ! that and i plan on doing a 212cc preddy swap and i have most every thing i need for the swap so i want to see what she will take before she blows lol !!! so far 3 weeks in reving the crap out of it and holding top rpms for 5 miles gritting and bearing the vibration and its still going strong !! no over heating ether !!! my mind is blown !!!!!!!! srsy i thought she would go first ride at top speed wide open throttle all the way for 5 miles non stop . i was shure of it lol and i still am ready for the bang every ride but she just wont quit !!!

been running true fuel 40:1 pre mix 92 oct with 1.5 oz lucas oil cylinder lube added to a half gallon or 2 cans of true fuel.

pss ... crmachineman and jakes sell the pre cut piston, its well thought out for broad power but not cut enough for real high top end rev's.

that upper cyl lube is heavy thick and slippery !!! good stuff !!