What size jets for a .080 bore?

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gavicc

New Member
Jan 22, 2010
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I just bought a 00' blaster. I am replacing the piston because it melted a hole through the middle of it. I'm guessing its running too lean. I am going to refresh the top end with a piston kit and gaskets. It has a .080 bore. What do I need to check or adjust in the carb to make sure it is set up right for this bore? What size jets or needle valves.I want to make sure the guy who bored it before did all the right things to the engine to make it run correctly with this bore.

Thanks!
 
Well just putting an overbore piston doesn't meen anything, leave it as it was.
But since you were way too lean before it would be a good idea to go richer.
Give us some more info. What mods do you have and what jetting were you running before?
 
I dont know what size reeds or jets it has. It has a FMF Gold Series pipe and silencer.

Thanks
 
Could running the .080 over bore, with an FMF gold series pipe on a stock carb with a stock needle and jet be what caused the engine to run too lean and melt the piston? I have no idea what the guy who previously owned has done to it other that what I have stated. I'm lucky I measured the bore before I bought the new piston. I just don't want to install the new piston and have the same thing happen again.

So on my set up....what needle and jet do I need? Or do you still need more info?

Thanks
 
we need to know what size jet is in it now??? pull the carb, then the fuel bowl, then use a 6mm socket to take out the main jet, it's in the center, its brass and hex shaped, the size will be written on the side, use a magnifyin glass if your old like me, haha and report back to us, i'm thinkin it should be around a 270 main and possibly the needle clip in the 3rd or 4th slot
down with that pipe and an a/m air filter,
but you'll need to read and learn how to do plug chops <<< use the search to find this and learn how to do it, and also search for "jetting 101"
read and learn grasshopper
 
Last edited:
I took the carb apart and got some numbers.
Jet - 250
Needle - 5J22

I couldnt tell what ring the clip was on the needle but it looked like the second one as it kind of fell off as I was taking it out. What one should it be on? I measured the ID of both sides of the carb. One was 23mm and the other was 35mm. Is this a stock carb? It looks like it has Boyesen pro series reeds on the stock reed frame. Looks like the stock air filter. Im in WI for elevation by the way.

Thanks again!
 
the 250 is too lean for a a/m pipe, to start try a 270 main jet , or possibly a 290 during these cold winter months, needle clip on the middle (3rd) slot down, airscrew 1 1/2 turns out,
32:1 gas/oil mix using a good synthetic oil, no cheap weedeater sh*t, factory yamaha, honda, maxima, klotz ect. ect,.........
and read, understand, and do, the "plug chop" and "jetting 101" articles found on here, re-read, then read again, till you understand how to do these, or you're gonna get real good at doing top end rebuilds
 
exactly shawn /\, search for "how to break in a 2 stroke" also, very important to do those heat cycles, as is warming it up properly and completely every time you ride it
 
Sweet. Now I'm on track. Now.....where is a good place to get one or a kit of jets to work with that is a decent price? Maybe a carb kit with them.

Thanks
 
i run a 300 main with the same pipe in florida... you have to see if you messed the jug up if so it will need to be bored if thats the case the new piston you just bought is worthless.. jetting 101 is a good thread to read and learn..
 
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