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  #1  
Old 08-01-2003, 03:50 PM
OLDMXRACER 393's Avatar
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Question Jetting Question: Need Help Tonight

     

I'm swinging by the shop tomorrow morning before me and the nephew go riding. I need to clean up a low-end, into the mid-range rich condition. 1993 YZ125. Flat slide Mikuni. The needle is lowered all the way to leanest position. This bike runs great on top end. I checked my air screw and is 4 turns out. This is too many, should be 1.2-2.5, right? The pilot jet has what looks like 17.5 stamped on it. I have no clue what the next size down is and my question is will the next size down be about right? Will 2 sizes down put me in a dangerous lean condition?
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  #2  
Old 08-01-2003, 04:19 PM
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Default Re: Jetting Question: Need Help Tonight

Lowering the pilot shouldnt put you in a dangerous lean condition, but you should pay attention to it. Usually bikes will only lean seize when the throttle is near wide open.
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Old 08-01-2003, 04:41 PM
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Default Re: Jetting Question: Need Help Tonight

bingo, dell nailed it.
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Old 08-01-2003, 04:47 PM
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Default Re: Jetting Question: Need Help Tonight

Ok. But do I drop one size or two?
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Old 08-01-2003, 05:00 PM
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Default Re: Jetting Question: Need Help Tonight

i say go for both, then at least you have an extra one in case you go into higher elevations or something.... they aren't THAT expensive, maybe 5 bucks apeice or so?

hope all goes well!

Rob
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Old 08-02-2003, 02:30 AM
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Default Re: Jetting Question: Need Help Tonight

I just picked up some here and i paid $2 each
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Old 08-02-2003, 05:20 AM
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Default Re: Jetting Question: Need Help Tonight

extra jets are always good to have. i have a nice collection now. i will rejet people's bikes for them and they never want the old jet. they go into my toolbox.
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Old 08-02-2003, 05:29 AM
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Default Re: Jetting Question: Need Help Tonight

Right on... I'll have to start doing that. I need a collection.
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  #9  
Old 08-02-2003, 05:33 AM
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Default Re: Jetting Question: Need Help Tonight

i have all kinds of stuff off of peoples bikes (not the infamous "leftover part"). new perches come with new bolts, so i get the old ones, etc.
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Old 08-02-2003, 03:58 PM
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Default Re: Jetting Question: Need Help Tonight

Hit 2 shops this morning. A HUGE Yamaha/Honda dealer and a mom and pop KTM/Kawasaki dealer. NO JETS ANYWHERE! Sigh.....
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  #11  
Old 08-02-2003, 04:08 PM
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Default Re: Jetting Question: Need Help Tonight

that's a bunch of BS... dang that sucks. if you are really good with a toothpic and JB weld, you can make "custom" jets a drill helps too.... LOL
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Old 08-02-2003, 06:02 PM
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Default Re: Jetting Question: Need Help Tonight

Warning:

Do not listen to Blitz. He is only trying to make your bike run like crap.
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Old 08-02-2003, 06:09 PM
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Default Re: Jetting Question: Need Help Tonight

hey, that's how the old farts used to do it.
they would buy a solid brass jet and drill thier own. they used wire size drill bits.
now we pay $5.00 for a $.05 piece of brass
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  #14  
Old 08-02-2003, 06:31 PM
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Default Re: Jetting Question: Need Help Tonight

Quote:
Originally posted by yardpro
hey, that's how the old farts used to do it.
they would buy a solid brass jet and drill thier own. they used wire size drill bits.
LOL! OK you guys. I am from the indoor plumbing era. Never had to make my own jets! Oh wait......I DID help a guy running alcohol in a mini sprint one time......
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  #15  
Old 08-02-2003, 06:43 PM
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Default Re: Jetting Question: Need Help Tonight

Quote:
Originally posted by OLDMXRACER
LOL! OK you guys. I am from the indoor plumbing era. Never had to make my own jets! Oh wait......I DID help a guy running alcohol in a mini sprint one time......
i'll bet the main jet was 5/8" thick too : those alcahol-runners REALLY need a HUGE jet... from what i hear, it is near twice the original gas jets ::
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  #16  
Old 08-02-2003, 09:16 PM
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Default Re: Jetting Question: Need Help Tonight

17.5 is REALLY small. Just a thought but I am going to bet on the needle jet being worn. The bike is 10 years old and vibration has a way with brass. If it were me, I would do what I do with all my restorations. Buy new brass so you have a good baseline. Best place to find Mikuni jets is Carburetor Warehouse. www.carbparts.com
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  #17  
Old 08-02-2003, 10:25 PM
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Default Re: Jetting Question: Need Help Tonight

wow man you are an info-monster. you sure you arent a vintage-info computer mainframe?
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  #18  
Old 08-03-2003, 07:37 AM
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Default Re: Jetting Question: Need Help Tonight

Thanks VintageDave. I've had this problem before and my memory is'nt good enough to remember what to do! I'll try it.
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