NRG spark plug damage question

Discussion in 'The Workshop' started by fula28, Nov 23, 2009.

  1. fula28

    fula28 Member

    Messages:
    72
    WEll ive rebuilt the top end today rebored iron cylinder honed,matched with .50mm oversized piston new gaskets new little end gap,d the rings as per. Still only getting 60psi compression with full open throttle and oil in cyclinder WTF? Been on to most of my two stroke racing buddys and were stumped? wheres it gone fook knows :confused:cratch: It starts on the button so pretty sure crank case seals are good its 2007 a-c so fecked if i know i get 150psi everyday out my gsxr but thats a four stroke( deisl) in two stroke world Lol. So why so low on the Nrg,50
     
  2. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    LOL you cant compare an nrg 50 to a gsxr 1000 man.

    if you know its got a new piston and rebore its not gonna be anything to do with that anymore.

    if it rides i would just leave it, or if its still not running properly it must be something to do with setup
     
  3. fula28

    fula28 Member

    Messages:
    72
    Tell me about it!!! Gsxr is easyier to work trust me no plastic covers no feckin Variators i am beging to hate scoots dare i say :confused:ick: . Well if its setup how come it ran ok before i took the variator off to change the rollers? They were goosed all squared off badly so i slung some 6grms in.It was 5.5 before but rev,s were soo high about 11k screeming @ 45mph, so though the 6grms would bring the top end rpms down, Any ways since then ive done belt, rollers plug top end rebore/hone new piston Its a std scoot really only has arrow exhaust std carb ect,ect still only 60psi comp ain,t riden it today as theres too much snow for an ole' duffer like me to go out in, Will try in the am tomorow IF THERES NO SNOW lol.
    Reports forthwith. :beg:
     
  4. fula28

    fula28 Member

    Messages:
    72
    Well latest update have run it up the road for few miles very slowly 30 mph no more 7 k revs, Still bog,s around 5,5 k so must be speed control rollers i fitted 6 grms because when
    it was running before @ flat out its reving 11.5k too high really, So the compression issue is a weird one still only getting 60-65 psi even with fresh bored barrel and oversized piston? Anyway it runs @ moment, Just pulled rollers out again and machined centres out to get 5.5 grams per roller and it runs much better still slight hesitation around 5.5 k revs but im happy enough with it. So deliverd it back to Bosses son last night made his christmas i recon just HOPE :pale: he runs it in ok??? Sure he will AS have told him if it comes to me again its getting a box,a matches and can of petrol this time :lol: .
    Im glad thats done feck me!!!!

    Happy Christmas Fella,s
     
  5. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

    Messages:
    14,276
    Rides:
    et2 monster
    yes your seals are gone... or its the wrong head (silly low compression) they DONT alwayts have a "head gasget" as you put it.. you DONT always need one on an ac ether way, the squish is set via the base gasget ONLY. the fact it didnt have a head gasget simply means it didnt have one. its an ac, skim of heatproof silicone and your away (both machined faces so will bearly need that) ether way if they do come with one (not that im aware) ive never used a top end gasget wiht a 50 ac engine. theres dick all point, the compression is bearly running wihtout a gasget so further reducing this is a waste of time if its machined flat to 0.02mm (wich it is as its a lapped surface on botht eh head and barrel) this alone wont cause THAT much of a loss... your not telling me 90psi of air is pissing out the top of the cylinder, between 2 machined faces (wich youve checked for flatness im assuming?) without an OBVIOUS hissing noise.

    all oil seals, this wont last long. if it killed the cylinder its probably DUE to the fucked oil seals leaning hou what little mixture is getting into the barrel.

    there NEVER made from 7074 aswell... dont know who youve been chatting to but 7074 is high tensile hardend pure aliminum (well, pure is a lapse term, it has 1% zink) .. not soft ATALL (trust me, just chunked an entire engine casing out of 7072/7075) 7074 (seem's is ether made up/rare) i cant find anywhere that stocks the stuff.. all i can find is poorly written explinations of what people make outr of what they think is 7074 when it is infact 7072/7075...

    the metal's usually used for gasgets are as follows...
    Copper 600 oxidizing agents.
    Brass 500
    GHL 212
    Grafoil 800
    Titanium 1000
    Soft Iron, Low Carbon Steel 1000
    Stainless Steel,
    Type 304 1000
    Stainless Steel,
    Type 316 1000
    Stainless Steel,
    Type 321 1600
    Stainless Steel,
    Type 347 1600
    Stainless Steel,
    Type 410 1200
    Stainless Steel
    Type 430 1400
    Nickel 1400
    Hastelloy 2000

    all pulled from a gasket manufactor, no ali anywhere... theres even brands in there (company's own names for specific alloys)
     

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