Suggestions on main jetting for current mods

Mtbcam

New Member
Aug 23, 2019
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BC, Canada
Hey folks, new to the forum,

I’d like to start by saying thanks to everyone who contributes to this community, it’s been a big help for me so far when looking up upgrades and sourcing compatible parts. I know that there are loads of threads on jetting, but I bought a blaster with a few mods and I’m hoping someone with more experience can help with getting a jetting baseline with those specific mods in mind.

I just recently found a blaster for a pretty good price, I had one back when I was in my teens and it was too good of a price to pass up. (2006 for $600) small price to pay for the nostalgia this simple little machine gives me!

It came with the air box cover removed, k&n air filter and had a Fmf gold exhaust system/silencer and booysen reeds. When I took it for a test ride it really ripped, but it sounded on the lean side.

I pulled the carb and gave it a good cleaning, deleted the oil injection system (not because I’m worried about it failing, I just find it easier for carb tuning) and I noticed the main is only a 230. I believe (correct me if I’m wrong) that is the stock jet size? I’m new to blaster tuning but even I thought this was a bit small for the mods it is running.

Any thoughts/ballpark ideas on which jets I should start with for baseline jetting before I start plug chopping?

My elevation is 2200ft, and the temp is on the chilly side up here in Canada.

Compression is on the low side.. 115psi, I’m hoping to put off doing the top end till sledding season.

Thanks! If I’ve left any useful info out please just let me know!
 
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Don't run it again with that stock 230 main.

115psi is still acceptable, and may stay in that range for quite a while with the proper jetting and good oil

buy 270, 290, 300 & 310 mains, start large and plug chop down
https://www.blasterforum.com/threads/how-to-plug-chop.53237/

you will need to increase the main as temps drop further, like maybe 1 size per every 20-30 degree drops depending on how close to the edge you originally jet it < there's no formula for this, just what has worked for me.
the manual may cover some of this, my original new '96 came with an extra 240 main to be used "under 30 degrees" (?) but that's for a stock engine, start modding these engines and they get way more finicky to jetting
if plug chops determine a 290 works now in "chilly" temps, it will fry in "cold" temps

you blocked off the oil injection port on the carb right ?
 
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Right on thanks for the tips and info!
I kinda figured it ran dangerously lean by the sound of it, (plus it ran way too *well*... as they always seem to right before they go boom lol) I didn’t ride it much because I wanted to tear everything down before I took the last owner’s word for anything.
I just ordered all the jet increments from 320-270 and will go from there.
Thanks again!
 
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