Jetting on TTR125

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#1
I just pulled the snorkle and cut a great big hole in the top of my airbox.The bike breaths good but now it is a little too lean. Can anyone suggest any jetting changes. I've already heard 110-115 main but what about the others? I'm at sea level and 70 deg year round.
 

stormer94

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#2
I put the BBR pipe on ours, it's got the 112.5 jet now, did the aribox mod's I'm happy as a clam.:)

Bob
 

ACS

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#3
With an openeded up exhaust 112 or 115 would be about right. I would go the 115 as you are at a low level and warm.
 
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#4
I am about the same level and temp as you here in N. CA and started with the 110... but was a bit lean. I recently put the 112.5 in and she is running like a champ now, although still a hair lean. I will try the 115, but I'm affraid it will be a bit rich.

I have opened up the airbox, and have the BBR pipe installed, btw.
 
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#5
Thanks, I'll grab a 112.5 today. Has anyone messed with the pilot jet,needle jet or the pilot air screw?
 
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#6
I am no wrench so I have been following BBR's recomendations. They have not been able to dial it in right with the stock carb if you change pilot or needle position, so I have left well enough alone. I know they have gone up to a 120, depending on the riders style. If you are running wide open 90% of the time then you do want a larger main. But I want to be able to put around at the same time without fouling plugs constantly.
 

ACS

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#7
The standard carb is pretty small but works good. I tried adjusting the needle etc and it made the bike run not as well. This was on stock bike with airbox opened and standard exhaust unplugged. If you go with pipe, lightened flywheel and other engine stuff a bigger carb works really well but then you find the limits of the CDI and head design.:(

A side note is that I talked to the development guys at Wolf ignitions which are sold in USA as FMF (orange box ones) about new cdi. They would probably be willing to build them but is there any interest?
 
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#8
I put in the 112.5 main today and it runs great. My hand is currently in a cast so the bike will see a lot of use next week when the pins come out. The little thumper should help my timing before I hit the track again. Thanks for your help.
 
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#9
112.5?

Hello,

I have the air box mods, bbr exhaust, airbox mods, and flywheel done and am still finding it running cold blooded.

I called the dealer and he had 110, 115, 120 size jets, but no 112.5 Where are you finding the 112.5? Is it a stock type of jet I can find at parts stores???

thanks,

Mike
 
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#10
most shops can order the half sizes mike. I never did find anyone with them in stock tho. BBR sent one to me. but anyone should be able to order it for you. Are you going to ClubMoto tonight? I will be there around 5:30-6:00 depending on traffic, but not riding tonight.
 

LocoCD

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#11
Most of the shops around here cary them, go to any shop - not just the Yamaha Dealer and ask for a large round Mikuni 112.5, they are fairly prevelant.

We have 2 TTR 125's, one with an FMF pipe and the other with a Pro Circuit T-4, the 112.5 jets seem to be spot-on.
 
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#12
My 2001 TT-R has the stock pipe with the PowRoll Thrust Chamber extension. I've also drilled six quarter-inch holes around the outlet into the spark arrestor so she'll push a larger volume of exhaust, while keeping the spark arrestor functional. I've removed the airbox snorkel and drilled 2 one-and-a-half inch holes in the airbox. This allows me to run a small sheet of foam filter at the top of the airbox, without it getting sucked in.

Anyway... Every dealer I've been in (I check Yamaha parts places whenever I travel on business) asks me for a part number. I don't have one, so they ask me if it's slotted or hexed. I haven't actually taken the main jet out yet to show them--I don't feel like taking the carb apart only to be told they don't have what I want in stock.

Can one of you tell me what the part number for the 110 is? I take it a "large round Mikuni..." as posted by LocoCD indicates it's slotted.

Thanks.

deadhead
 
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#13
I do not know a part number but stopped at my local aftermarket shop and asked for a "large Round Mikuni, 112.5" and they pulled out a small box and had a whole selection. Aparently the Large is the key, they make small also.

mike
 
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#14
air screw

I have changed jets, but am new to this "tuning thing".

what are you running the air screw at?

Mine has all the mods, BBR exhaust, air box, flywheel, etc, but it still runs supper cold and can be tempermental to start. I tried the needle one step richer but when my daughter putt-putted around it fouled a plug.

I am back to stock on the needle, running a 110 main. will the 112.5 help the cold starts?

Any tips appreciated.

ps. my yz400 is a one kick wonder, hoping to get the ttr as dialed in too!
 
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#15
I didnt even check to see where the mixture was... I simply left it alone. Mine has gotten easier to start over time and when I put in the 112.5 main , it did start a little easier... but ran a lot better on the top end.