155z top end rebuild

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LEO DPRO 037

LEO DPRO 037

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My bikes been blowing heaps of smoke and by a process of elimination ive put it down to piston rings.
Is it possible to change to a 165 big bore kit without changing the head?
is this a good or bad idea?
Ive spent days and hours reading tutorials on miniriders.com and it seems too easy to just change the piston.
but I dont have the money right now to do the 4 valve head etc..
any help would be great thanks.
 
Cheap as for the new rings.. thanks.
cheaper is better I guess. Couldnt possibly be anything wrong with the piston???
 
i havent seen it before, i'm only a new 155Z owner though.
is the barrel long enough it says to suit a GPX/YX150?
 
Will I definately need to get new gaskets? They look to be metal from the outside are they likely to **** themself when I pull the bits apart or can I expect them to be ok??
 
depends on how many hours are on it.
pistons do wear, but not as fast as rings.
 
I dont know the difference between yx/gpx/z.
I thaught 155z may of been gpx? Am I incorrect?
 
Thats unreal. Thanks again!
What would be the best carbie to go with it?
I assume mines standard but I baught it secondhand so who knows.. works fine as is tho.
 
yeah good price, and it's from a site sponsor too.


the top link kit i posted comes with a Keihin 28mm carby
what do you have now ?
 
Im gunna say 28 or 30mm mikuni I think.. takes approx a 42mm air filter if that helps. But yeah mikuni
 
oh yeah, probably like the china 30mm Mikuni on my new/used 155 engine.
have a look at the last post on my Atomik Fuse thread, there is a pic of the carby
 
yeah thanks, the 155Z is my first YX style engine,
i have got a few things i want to do to the engine, and a few mods to do the the bike.
my tight budget makes things hard though.


i don't think you'd have too many problems rejetting/tuning it to suit the bigger cc's
make a thread for the conversion if you end up doing it, and post it as you go.
i think the stock carby runs a 100 Main jet in it, i'm guessing it may need a Main jet around a 110 or possibly larger ?
somewhere around the number 8 or 9 kit here, DHZ will be your cheapest option
http://www.dhz.com.au/buy/mikuni-carburetor-slow-main-jet-kit/CARB-012-MIKUNI-KIT

otherwise Show and Go Motorcycles on Brighton rd sell the jets too, but are dearer.
 
Tell me about it 1 boy, girl on the way in january, fresh 1st mortgage. Spare money is like hens teeth around here thats why Im going to attempt the rebuild myself.. like I said earlier. It just seems to easy to just fix the standard piston. Whats a realistic lifespan of the big bore kits are they fragile and do they break easy
 
it will put a bit more strain on your gearbox, making a bit more power, so could cause premature failures there.

someone else thats done the big bore will probably chip in their thoughts too
 
"Brain ticks over" food for thaught. Leave it with me and thanks HEAPS for your help
 
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