atc3434`

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Nov 1, 2001
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Did the jetting on my friends wifes TTR 125L last night... wow! I mean WOW WOW WOW! What a different. Went to a 110 main and a 17.5 pilot, did a little airscrew work and adjusted the idle, and its almost perfect. I might have to go back and move the needle up one clip position, still got that annoying stumble. I thought the pilot would have cleaned that up completely, but I guess not. But its running amazing... warms up quicker, and pulls much stronger, especially on the top. If you have a TTR125, and you want the biggest gain in preformance with the least investment, jet it! Really, $5 and 15 minutes work, and yes, anybody can do the work, is deffinatly worth you time and money. Hardest part is finding somebody with those litte itty bitty jets. Going to ride it this weekend... I no longer have a bike I can call my own... :ugg: Mabye again some day...
 

Unit74

Member
Dec 16, 2001
494
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What did you adjust the airscrew to(and where is it located)? Also, I can't seem to find the idle adjustment. How the heck do I do it?
 

atc3434`

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Nov 1, 2001
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Ok, as far as the air screw, its on the underside of the carb... on the front closestest to the engine. There's a cutaway on that side of the carb where the screw is up in. I have no idea how many turn in or out I'm at.... basically I just fiddle till the idle was the smoothest, if anything a tad on the rich side. You'll need one of those dinky screwdrivers... there isn't lots of room between the carb and the cases.

Now for the idle speed, on the left side of the carb (As you sit on the bike facing foward) there is a bronze screw right in the center of the top half of the carb. Its small, but its pretty much the only thing there. Getting at it is quite a pain, again a small screwdriver works best.

For tuning in the airscrew and the idle I basically got the airscrew set where I thought the idle was the smoothest and there was the least amount of bog when snapping the throttle wide open. Then the idle was quite a bit higher, so I turned it down some.

The main jet is easier to do that either of those two... and it will make the most difference. Thing pulls as hard as it can now at higher rpms. Changing that just involves first dropping the bowl of the carberator. To do that you have to lossen the clamps, take of the hose from the air box, and slid it around so you can get a screwdriver on all the screws. Yamaha reccomends in the maneul that you disconnect the throttle and choke and pull it all the way out, but I think thats a waste of time, worked fine doing it this way. Then you just take out the old 105 main, and slip in you 110 (For a stock TTR125 anyways) with a pair of pliers to hold the main jet nozzle, and a screwdriver to turn the jet. There's a little pink float that was stuck to the main jet that was in there, just pressed on. It wouldn't stick to the new main jet, but there is a spot for it to rest in the bowl of the carb, lines it up right were it should be during reassembally.

I hope this helps ya with your jetting a little. ITs really worth you time. The maneul is decently helpful too, (at least the pictures) especailly if your like me and want to see how it works BEFORE you rip it apart. ;) Have a good one.
 
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Unit74

Member
Dec 16, 2001
494
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I need to find a manual. If you could make photo copies and send it to me, I will take care of your expenses. Please let me know.

Also, which way do you turn the idle screw to increase the idle?Right now, it won't even stay running.
 

atc3434`

~SPONSOR~
Nov 1, 2001
579
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I think you want to go clockwise to up the idle. So it runs, but won't idle? Yeah, that sounds like idle speed and air screw. That carb acts really funny at very small throttle openings unless its right on. You may need to fiddle with the air screw, I'm not sure how much out it should be. I guess I would start at 1 and 1/2 turns out and work from there. And on the idle screw, a little turn makes a big adjustment. I'd have somebody keep it running by blipping the throttle, just little revs enough to keep it alive. Then start turning out the idle screw untill you can tell its idlling up high, then back it off to where you want it. If it gets rough as you back it down, get it in a spot where it will stay running, but roughly, and then start opening and closing the airscrew to find a sweet spot. Then bring the idle down the rest of the way. Just don't set it too low.

I don't have the manuel at the moment, but I'll grab it Sunday (I hope) and make a few copies of the carb stuff. Anything else in there you want? Don't worry about expenses, I'll just e-mail them to you as jpegs or something.
 

Unit74

Member
Dec 16, 2001
494
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Hey, I used the info you gave me and got it running pretty awesome. The airscrew was way out of whack and the idle screw was about 7-8 turns out from fully seated. Now it starts on the 4-5th kick and no problems with the idle. I installed the 112.5 as well. It did have the 110, but there is an FMF turbine core system on it so I figured it would be better to run it richer.

As for the manual....I would really like to have the whole thing if it is not too much trouble to scan it all. Otherwise, I'll take whatever you can send me.

Thanks a million for your help. Now I can take my wifes early X-Mas/Late B-day present out and teach her how to ride it today! She has been prodding me to go, but I did not want to take it out in that condition.
 

cr25096er

Member
Apr 16, 2002
707
0
sounds pretty lean on the pilot. it should start on the 1st kick unit74. also run a plug chop to check to see if the main isnt too rich or lean.
 

fourjs

Member
Dec 1, 2001
21
0
When you go order the the next size jet (stock is 105, I would like to get a 110) do you order by a small round jet or large round jet? Do you have a part number? If so, please send me a reply, thanks.... .. ;)
 

KLRay

Member
Apr 9, 2002
61
0
I just changed the jet on my wifes ttr and it took me an hour and a half and it cost me twenty bucks to get the jet from BBR motorsports, 6.95 for the jet and 13.05 for shipping and handling. Just ask for the round Mikuni 110 main.
 

kdxtaz

~SPONSOR~
Mar 29, 2002
385
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I found the same pot of gold. I cut the whole top off the airbox, rejetted w/ a 112.5 main & 17.5 pilot. I tried moving the needle clip up one position but it bogged slightly so I moved it back. I would guess at about a 20 percent increase in power & it starts 1st kick hot or cold, something it never did before.
BTW - You want the LARGE round mikuni main.
 
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atc3434`

~SPONSOR~
Nov 1, 2001
579
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Isn't it amazing how much it wakes the little bike up. It went from being a dawgy dawg to being a fun dawg :-) Still slow, but a good time. ;) I'm going to ruin that rear fender for sure one of these days. Working on my wheelies. Gotta get a good balance point.
 

bluerider125

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Feb 23, 2002
598
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the "air screw" you are talking about is actually a fuel screw. out for richer, in for leaner.

i live at 4300 ft. above sea level, and the engine is stock. does anyone have an idea about jetting? i fiddled with the fuel screw a little and got it to run better, but i think it could run better. there isnt a "flat spot" anywhere, but i think it could do better overall. any suggestions?
thanks
 

atc3434`

~SPONSOR~
Nov 1, 2001
579
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125 more cc's :) First off, you are correct on the fuel screw, I originally thought it was an air screw as on other carberators I've worked on, and it sure didn't richen up when I turned it in, so I figured it was fuel. Checked it with the book. Good correction. For more performance at altitude, maybe take care of the airbox mod.... your going to need all the air you can get. Doing the main jet might help too, although your probably not too lean at that altitude. Just work on fine tuning the jetting. I think BBR makes some cool mods for the ttr also, if you want performance and have money to spend! ;)
 

atc3434`

~SPONSOR~
Nov 1, 2001
579
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Stock Pilots a 15. Most recomend a 17.5. I stuck with the 15, mainly because they couldn't find a 17.5 at the store ;) Started up on the third kick today at 45 degrees out. Quit right away, and they stayed running on the second kick. Ran beautiful all day. Took her out into a sand bed with a bunch of quad guys. They were impressed with what I'd try on that little bike. She did dig into the sand a lot, I see why all the desert guys ride CR 500's. I did manage to run out of steam on a tall hill too, shoulda caught second half way up, or wasted the clutch. 3rd just wasn't enough ;) Fun day though.
 
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