Questions: Arrow on piston, Milling cylinder head, stock washers

Discussion in '2-Stroke Engines' started by mikedabomb, Jan 28, 2016.

  1. mikedabomb

    mikedabomb Member

    Opened my 66cc and the arrow on the piston is pointing towards the intake? Also, how far to mill the head? I'm guessing I have to mill it until it has a consistent surface, and no more.

    On my mounting hardware and the head nuts I have split washers and I do not know what the order is for the nuts, flat washers, and split washers.

  2. crassius

    crassius Well-Known Member

    read more

    I have never, in close to 1000 motors, had to mill a head. Never look at arrow (or lack thereof) for direction of piston - only important thing is that the ring locating pins are on the intake side. Several flat washers, split washer, nut. Add enough flat washers to keep stud from binding inside the acorn nut (just one washer if you use a normal open nut).
    mikedabomb likes this.
  3. HeadSmess

    HeadSmess Well-Known Member

    ditto that. have never milled a head, but do remove the stock gasket and use teflon tape instead, works so much better.

    the spring/split washer should be in contact with the nut.

    use as many or few flat, plain washers as required.

    ignore the arrow, locate the piston by the pins in the ring grooves. place them towards the intake.
  4. mikedabomb

    mikedabomb Member

    Thanks for the responses. You guys saved hours of time that I used to seal up the wiring hole

    I came across something weird...when I put the head back on, I noticed that I had 10 flat washers instead of the 8 which I expected. This concerns me, I don't know if my organization is wrong and they came from a different part sitting nearby or if the manufacturer is sloppy and put a few extra on...I'll use 2 on each stud to stay consistent

    How do you make a Teflon tape gasket?

    What do y'all think of packing snow on the cylinder to keep it cool during break in, where I can't resist WOT?

    Thanks, Mike
  5. butre

    butre Well-Known Member

    take some teflon tape, twist it up, and coil it around the mating surface and don't overlap anywhere. it'll compress to a hair under 1 thou. teflon gaskets aren't reusable so they'll need to be replaced if you ever disassemble the engine, but they cost all of a quarter to make so no biggie.

    putting snow on the cylinder is a good way to crack it. think of what happens when you try to boil water in a drinking glass, or put cheap dollar store glassware into a sink of hot water. same mechanism, just less extreme.

    WOT is good for break in, just don't hold it at top speed. that's how you glaze rings. as long as the loads are kept high (ie. accelerate only, no cruising) you'll have the best possible break in. that whole "baby it for break in" thing you get with new cars and bikes and such is just lawyers talking, not the engine builders. hard break in gets you the most power and the longest engine life.
  6. KenM

    KenM Member

    Hi Mr. Butre. You have me interested it your Teflon tape gasket now too. This is a head gasket you are talking about?
    I can see it working for the side covers. But I thought their would be to much compression at the head for it to work there . Thanks for the tip!
    Keep looking up! Ken.
  7. mikedabomb

    mikedabomb Member

    I'm struggling with "twist it up," "coil it" and "don't overlap anywhere". When I think twist it up and coil, I think of the structure of a rope.

    I think I get what you mean by coil, lay each piece next to each other in progressing circles, but "twist it up" the end of a joint?

    Thanks ahead of time
  8. sbest

    sbest Active Member

    As mentioned, ring ends go toward the intake. How does this match up with the arrow now?

    The head as it comes is probably fine.
    Mine did warp, but as a result of heat and detonation.
    New sheet of 150-250grit sandpaper on a flat surface and rub.You will see when it is good.

    I am not a fan of the Acorn nuts or stacks of washers. Buy good nuts and use one flat washer is my choice.

  9. crassius

    crassius Well-Known Member

    the assembler at the factory will usually try to get the right amount of washers needed (they do sometimes fail tho) - having two extra washers tells me that you have two studs that are a bit taller than the other two (or one stud way taller than the other three) and that's where the extra washers are needed - you could measure how tall they are, but I usually just sight across them to spot the high ones
  10. butre

    butre Well-Known Member

    you got it.
  11. HeadSmess

    HeadSmess Well-Known Member

    teflon gasket jointing material...

    it is the engineers choice of material for high temperatures and high pressures... non reactive, doesnt stick, easily dismantled, squishes to minute clearances...

    from memory...300C+ at about 4000psi.

    your (worked, high compression, high performance racing) engine will be lucky to get a peak pressure of 1000psi ;)

    there is a "special" teflon string available, but as mentioned..teflon tape, twisted into a string works fine. and is a lot cheaper.

    if you want pink or yellow, go for it, ive always just had white stuff on hand. its still teflon.

    it may take a few goes to get the technique down pat. dont worry about popping the head off again to make sure, practice makes perfect!

    they (?) also recommend very minute grooves cut into the sealing surfaces...a dead smooth, flat surface has no "grip" so to speak. think of an LP record sorta thing. as the head comes stock, is fine. unless there are any obvious gouges in it...leave it alone.
    KenM likes this.
  12. Neufcruz

    Neufcruz Member

    Just got my windowed piston so ready to put that in and head on. So I remove the metal gasket and replace with Teflon. And pics of how to? Even a sketch would work for us slow
    I bought the heavy duty bolt kit. There's 4 large Allen head bolts the size of the studs. Do these replace the studs? I don't see where else they would go. Never seen a head go on with bolts and not have studs. If so, every time you pull the head the entire jug comes lose?!!!
    Do I use Teflon on the jug Tom case?
    I'm getting close!
  13. HeadSmess

    HeadSmess Well-Known Member

    pic...tures? what eez zis peec-ture?

    sheesh, you only gotta make it into a donut sort of shape...not that hard! as long as its a few mm in diameter bigger than the piston/bore, she'll be good. the trick is to not move it out of line when installing the head! personally i couldnt care less if its overlapping anywhere...

    dont even contemplate doing it for the lower gasket...unless you have a LOT of patience ;) that spot, good old cardboard from a cereal box, the standard gasket as supplied, expensive gasket paper from an auto spares shop, or if youre into experimenting with port timings and compression ratios, alloy shims, all do the job :)

    bolts? no studs? no comment... i have seen it but i cant say id ever design it that way... definitely more likely to strip the threads in the case if you plan on dismantling it fairly often.

    there should be a spigot on the base of the cylinder that keeps it lined up anyway... just doesnt keep the holes and gaskets lined up but hey, just a little wiggle will cure that.
  14. Neufcruz

    Neufcruz Member

    Thanks Headsmess.
    Just making sure I do it right.
    You answere a bunch of question regarding the bolts and lower gasket as well that I just posted.
    Appreciate the clearing up.
    I'm very new to this and don't plan to have apart that often. I hope!
  15. canalcat

    canalcat Member

    Tore my cylinder apart , pins for rings were on exhaust side!! Well that's how I reassembled it ( new rings and honed cylinder. ) , now she fly's about 32 mph!!! GO BIKE!!!!!!!!
  16. Neufcruz

    Neufcruz Member

    So now we have 3 on here that say ring pins on intake and 1 says exhaust side.
    I'm assuming the intake side unless corrected! My windowed piston was the wrong one so now going to drill myself.
  17. sbest

    sbest Active Member

    Luckily Mike, due to my Army experience my vision of you drilling yourself involves a lot of fancy marching.
    I hear others have different interpretations... :)

    Canalcat: These engines have small intake and exhaust ports so no danger of snagging the ring end on the exhaust port with the piston backwards (on these engines only). There are 2 other possible problems. The piston pin is slightly offset in most pistons, not it is on the wrong side. This may or may not be the case, many cheap pistons have the pin centered. The worst worry is the end of the rings and their locating pins are subject to the exhaust heat and may fail early.

  18. crassius

    crassius Well-Known Member

    any mention of port mapping on these should be considered 'rude humor' - not sure if I've ever seen two barrels with exact same dimensions of port machining - I have seen kids put pins at exhaust side & snag a ring in the port
  19. butre

    butre Well-Known Member

    yeah ring pins go on intake side. I've seen plenty of engines destroyed by putting the ring ends on the exhaust side
  20. Neufcruz

    Neufcruz Member

    Thanks butre.
    Going intake side.