strong

Can someone tell me how to take the piston off of a sikk engine.....................I want to try to make it lighter.............................And will this give me more RPM"S.

Dekman

It should have clips on each side of the wrist pin off of the connecting rod. Not trying to be a dik but if your not sure how to remove the piston I don't think you should be lightening it yourself. But it is your engine and I may be completely wrong.

BILLIUM

My Feedback: (40)

You got to start somewhere!! Live & learn!! Dekman is right thiers more envoled than just grindin off metal .. You really sould reconcider .
Later Bill

strong

Thank's for the reply bekman...................The only way to learn is to try......................I'm going to send my zen off to have it modded...............But in the mean time I can try to lighten a piston...........................Others have did it on this forum so why can't I.

MrMikeG

Dig the C clip out, cover it with something so you don't loose it. It is best to put a new one back in but if your careful you can reuse the old one. If you twist it in any way replace it as it will tear up your engine if it comes out. Slide the pin out and the piston comes right off, make note of how the bearing and spacers go in so you can put it back on the same way.
Dremel the inside of the piston away, take most of the meat out of the dome. Stay away from the little nub in the center. The pistons are cast for two rings, you can take a lot of weight off where the second ring would go. I measure from the outside down to the ring and set my carbide bit in the dremel to just short of that height, that way I can't go too far. Don't go too thin on the wall, there is no advantage and your piston could go egg shaped.

Dekman

Hey like I said not trying to be a dik, i like experimenting as much as the next guy, but I also like seeing money spent in the right places. Good luck on your mod let us know how it works out.
love bekman

strong

Can you get the clips from like a small engine repair shop or do I need to order them from say...... davemotors or a zen dealer.

MrMikeG

If you show them any small engine shop should be able to match them up.

strong

Thank's MrMikeG...............................That what I love about this forum....................Lots of good Information and people who don't mind sharing it............

rickburnout666

lightening the piston can can be done by yourself , i have done it on my zenoah weedwacker engine , it will rev up faster and you will get more rpm out of your engine , but make sure the piston remains balanced after lightening it ,i tune 2 stroke motorycles, most of the stuff i know i learned from making mistakes, and watching others,
Shops that sell garden tools sell the clips to fit a zenoah piston (UK), i think the sikk piston is the same but i might be wrong on that point ( someone tell me if i`m wrong)

strong

[8D].................Going to make sure I can get the clips first and then get a carbine tip for my dremel and give it a try.......................Also might try some port timing with the degree wheel I down loaded off this forum....................just minor stuff to be safe.

MrMikeG

Which Sikk do you have?

45deepvee

why not just get a piston on ebay cheap and mod that one, rather then tryign to modify the only one you have.

take it to a machine shop and have them lighten it. will be cheap. then they can balance it also, which is a big part it has to be balanced.

strong

Sikk 25.................yes 45deepvee that a thought..[sm=idea.gif]

MrMikeG

That Sikk has pretty good port timing already, lighten the piston and give it a go.

45deepvee

if you dont balance the piston it wont rev up as fast and wont reach full rpm at all. will hurt the performance of the engine greatly. better to just take it to a machine shop and tell them to weight it then figure otu how much to take off. they can drill the bottom, take some out of the skirting, just dont let them touch the dome as it will hurt compression. then just have them balance it.


friend of mine did a 468 ci chevy big block and had then pistons drilled and fly cut and lightened. pistons were balanced and the motor rev'd out to 8500rpm. they drilled 4 holes in the bottom of the pistons next to the skirting and fly cut the domes to fit the heads.

just make sure there balanced and there enough weight taken off for your liking and you should be good to go.

MrMikeG

You can't balance a single cylinder 2 stroke engine. The Sikk pistons are too heavy, it is a well known fact amongst RCBoat racers, reduce the riciprocating weight you will get more RPM.

45deepvee

you cant get them perfect btu you can get them close, if you take off al the skirting on the one side it will be way off balance and will hurt rpm badly. every piston in any motor is balanced to a certain degree.

if you lighten it it will gain you rpm, but if its way way otu of balance the piston will react different to the ignition and the force the rod will be putting on it in the upward motion, this will make the piston move upwards in a akward position and it will create wear on the one side or whereever its not riding smoothly.

they will be able to balance it to a certain point, just not perfectly.

rickburnout666

The balancing is of the piston after it has been lightened, if the sikk piston is too heavy surely thats more reason to lighten it therefor enabling more revs from the engine , I still dont know if the sikk and zenoah pistons are the same ?? If the piston is not balanced this can cause premature wear of the piston ring and of the bore lining

MrMikeG

Here's a piston and sleave from a CMB 45, these engines will turn in excess of 30,000 rpm, does it look balanced to you?
The Zenoah and Sikk have a hard chrome bore, the pistons are aluminium, the rings are Steel, which parts are going to wear first? Ring yes, piston skirt (maybe) both are cheap replacements to go fast, both will last more than a year of hard racing!

45deepvee

depends on if its counter balanced underneath instead of up top. its still an internal combustion engine. there has to be some sort of balancing effect in that motor to get it to work correctly

rickburnout666

You are right that does not look balanced, and i dont think it has a ring and i dont think its anywhere near the weight of a modded zenoah piston ,which is about 20 grams. I have run 2 stroke engines with chrome liners and nikosil liners and probably others and i always balance the pistons, as for which wears first, its always the ring and then liner as the aluminium piston barely touches the liner(unlike a nitro engine piston) unless its very off balance, and if it touches the bore it will cause the piston to become more unbalanced over time . The piston in my weedwacker has done 15 years, its balance was checked before i lightened it and suprise suprise it was still balanced and i balanced it after i lightened it ,in my opinion(and fact)balance the piston, if not unessassery wear will be caused to the engine

MrMikeG

Rick, I'm happy for you to do what ever you want but it is not neccessary, if you think about it the rod pushes the piston to one side on the upstroke and the other side on the down stroke, no matter where the balance is. The piston is never being pushed straight down. Further in the Zenoah engine the bore is slightly off-set to increase power. The best thing to combat wear is good oil which I'm sure your using. I have a 5 year old Zenoah 2 port that will turn close to 17k in a boat with the original piston and ring, I'm sure your weed wacker is no where near 17k and probably doesn't get held flat out for 5 minutes at a time ether.

strong

Good stuff guys...........

patriktegelberg

Info on why lightening a piston increases the rpm.