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The TTR250 FAQ web pages -> TTR250 -> Modifications -> Doing mods. Need jetting advise.
Post Info TOPIC: Doing mods. Need jetting advise.
Terrence R


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Doing mods. Need jetting advise.
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I'm in Canada. I'm riding at sea level mostly. Just ordered the tusk DS kit, sprockets and chain kit ( my chain is fine, just wanted the gearing and a spair chain), and an FMF PC4 with spark arrestor. I ordered it all on ebay. I'm pretty pumped!

 

   I'll have to obviously do some jetting to accommodate for the pipe. I also trimmed the snorkel down a bit on both ends last night. I may eventually remove the snorkel as I don't usually ride in mud and deep water. My air filter is in great shape. But, should I get a twin air to help the flow of the new pipe? Or will removing the snorkel be enough to make the difference.

 

   The jets in my carb look a little different than most jets that I've ever delt with. What brand jets should I be replacing them with ( remember, I'm in Canada. ). Also, what sizes do u think I should start with? I'm at sea level.

 

   Also, the plug that was in my bike was some weird looking thing that was a #7. Yikes! So I had an extra cr8e that was laying around from a WRF that I put in it. Should I run the cr8e? Or go with the recommended cr9e? Or iridium? Any help is greatly appreciated. Thanx.



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TT-R250M


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First of all- trimming down the snorkel is not a good thing IMO. It will make it run rich. Trimming the snorkel only made it run so rich that full throttle was not reachable at all! I suggest that you remove it and/or fit a larger snorkel. See here for more details- http://ttr250.activeboard.com/t53318498/air-box-snorkel-modification/

If you upgrade the air flow (i.e. high flow exhaust), you should now upgrade the air filter to allow more air to be pushed through. If you do not upgrade the air filter, you will not get any decent improvement. It will also cause a rich condition from the greater air flow not being able to suck enough air, the result is that it sucks more fuel. The words ''Twin Air'' does not mean anything other than it has a dual stage foam layer. I would suggest either a Twin air or GYT-R air filter.

A good start would be to upgrade your main jet and pilot jet 2~3 sizes. Just remember that the small round Mikuni jets are not numbered the same as Teikei jets. It has been said that a Mikuni small round #140 is the same as a Teikei #150, it is yet to be confirmed by myself though. You can buy a Sigma jetting kit if you don't mind spending the cash. You get main jets x3, a pilot jet, a wood drill bit?, washers for the main jet (not needed) and basic instructions. The good thing is that the Sigma jets are made with the same numbering system and taper as the Teikei jets.

You can use either CR7E, CR8E, CR9E or CR9EIX iridium spark plug. The lower the number, the hotter the plug. So if the weather is very cold and you find it hard to start your bike, use a CR7E. If the weather is a little warmer but not hot, use a CR8E for a little more power and better starting. The CR9E is the standard plug that should be used in warm~hot weather. The iridium obviously giving you slightly better response, better starting and durability beyond the standard plugs. 

Jarrah



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Terrence R


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Ok. I'll remove the snorkel. I just ordered the jet kit and a Twin air dual later filter. Thanx.

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