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Ttr230X top end sputter

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I just bought a 2008 ttr230 with no baffle. I purchased a powertip with a spark arrester, it runs well but has an issue of sputtering at 90-100% throttle. Do I need to jet the carb to account for the exhaust being open or do I have a lack of fuel issue?

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I just bought a 2008 ttr230 with no baffle. I purchased a powertip with a spark arrester, it runs well but has an issue of sputtering at 90-100% throttle. Do I need to jet the carb to account for the exhaust being open or do I have a lack of fuel issue?

 

This is usually due to a rich condition.  Check the float level and valve lash and then use Mikuni's Roll-Of method to check the main jet:

 

"This method is a good way to get the main jet either correct or within one size of correct. It is based on the fact that that as the throttle is closed, the air/fuel mixture richens momentarily. This normal enrichening can be used as a diagnostic tool. The test is started with the engine running at an rpm high enough to ensure that it is “on the cam.” Open the throttle fully and let the engine pull for several seconds. Then, quickly close the throttle to about the 7/8ths position. If the engine seems to gain power, the main jet is too small (lean). Fit a larger jet. If the engine hesitates as the throttle is rolled off, the main jet is too large. Fit a smaller one. When the main jet is correct,  the engine will continue to run smoothly and evenly as the throttle is closed. Note that a main jet that is far too rich or lean may cause the engine to misfire at full throttle."

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Thanks VortecCPI. I will investigate these setting this weekend.

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I just bought a 2008 ttr230 with no baffle. I purchased a powertip with a spark arrester, it runs well but has an issue of sputtering at 90-100% throttle. Do I need to jet the carb to account for the exhaust being open or do I have a lack of fuel issue?

definite rejet. When I took out my baffle and opened the airbox up it popped at the low end like popcorn, especially going downhill. Rejected it but now, (this is also a question if anyone would know why) I upped the main and middle jet, but left the pilot alone as the bike shop near me didn't have any to fit my carb and now it won't idle unless really hot. I have to start it full choke even on 100 degree days and run it a bit then turn off the choke. Even if I let it sit for ten minutes I have to choke it again.

This is usually due to a rich condition. Check the float level and valve lash and then use Mikuni's Roll-Of method to check the main jet:

"This method is a good way to get the main jet either correct or within one size of correct. It is based on the fact that that as the throttle is closed, the air/fuel mixture richens momentarily. This normal enrichening can be used as a diagnostic tool. The test is started with the engine running at an rpm high enough to ensure that it is “on the cam.” Open the throttle fully and let the engine pull for several seconds. Then, quickly close the throttle to about the 7/8ths position. If the engine seems to gain power, the main jet is too small (lean). Fit a larger jet. If the engine hesitates as the throttle is rolled off, the main jet is too large. Fit a smaller one. When the main jet is correct, the engine will continue to run smoothly and evenly as the throttle is closed. Note that a main jet that is far too rich or lean may cause the engine to misfire at full throttle."

generally (mine is) a 230 carb is a TK, not Mikuni. Newer models may be but mines an 05 and has a TK.

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definite rejet. When I took out my baffle and opened the airbox up it popped at the low end like popcorn, especially going downhill. Rejected it but now, (this is also a question if anyone would know why) I upped the main and middle jet, but left the pilot alone as the bike shop near me didn't have any to fit my carb and now it won't idle unless really hot. I have to start it full choke even on 100 degree days and run it a bit then turn off the choke. Even if I let it sit for ten minutes I have to choke it again.

generally (mine is) a 230 carb is a TK, not Mikuni. Newer models may be but mines an 05 and has a TK.

 

 You've answered your own question, order a pilot jet and adjust the idle mixture screw. You can get the part # and directions in the sticky at the top of this page.

  You might want to figure out your own jetting issues before giving jetting advice to others.

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