250r jetting - Honda ATV Forum
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post #1 of 14 (permalink) Old 08-06-2011, 08:58 PM Thread Starter
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250r jetting

anyone know the stock jet sizes for a 1987 trx 250r and what would be recommended for one with a fmf pipe and silencer uni filter and no airbox lid thanks for the help
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post #2 of 14 (permalink) Old 08-06-2011, 10:11 PM
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I dont remember what the stock jet is . i cant seem to find my clymer manual. Im guessing the stock jet is around 152 or 155. I have a 250r with the same pipe and filter and i ran around a 170 to a 180 jet
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post #3 of 14 (permalink) Old 08-06-2011, 10:30 PM
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152 main 48 slow agree on the jetting^^^^ but a plug chop would be better

"MOOSE WAGON "
00 TRX400EX aka "MOOSE ROCKET"
91 TRX250X aka "MOOSE WAGON" RETIRED
96 Polaris 400L sport (Mrs. Moose Ride)
07 Suzuki LTZ250 (Sons)
96 Polaris 250 Trail Blazer (daughters)
06 TRX450ER aka === Under construction

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post #4 of 14 (permalink) Old 08-06-2011, 10:35 PM
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As Deeper would say, Deja Vu, again.

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post #5 of 14 (permalink) Old 08-06-2011, 10:46 PM
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Stock is a 152 mj, and a 48 pilot jet. You will probably have to change both jets to compensate for the extra airflow. I would buy several larger sized keihin PJ carb pilot jets, as well as your main jets for your stock 34mm carb. If your air screw is turned in all the way to idle correctly it is a good indicator that you need a larger pilot jet. You should end up around 1 to 1 1/2 turns out on the air screw and have a good throttle response off the low end, and you have the correct pilot jet. Then turn the weird choke/idle adjustment to get your correct idle speed. (if I remember correctly thats how you adjust the idle on these is with the choke knob)
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post #6 of 14 (permalink) Old 08-07-2011, 06:45 AM Thread Starter
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what do you mean [a plug chop] so if i try around a 170 180 main what about pilot jet keep in mind it idles perfectly but almost acts like it has a rev limiter when i try to get on it thanks guys

Last edited by woodcock27; 08-07-2011 at 06:47 AM.
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post #7 of 14 (permalink) Old 08-07-2011, 07:26 AM
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A plug chop is to go balls out down a straight stretch and let it scream then immediatly pull in the clutch and hit the kill switch then check your plug.
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post #8 of 14 (permalink) Old 09-22-2011, 12:11 PM
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Bumpp!!

My buddy has a 250R that I somehow get to work on for free (no clue how that happened) that does not enter the powerband. Pretty sure it has an FMF pipe and definitely an aftermarket silencer, but the jetting is 155 and 48. What should I be around? I'm also at 1600ft elevation if that matters a whole lot..
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post #9 of 14 (permalink) Old 09-22-2011, 03:08 PM
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may not be the jetting, check the fuel mix ratio check for exhaust leaks and check the reeds for cracks or improper sealing

"MOOSE WAGON "
00 TRX400EX aka "MOOSE ROCKET"
91 TRX250X aka "MOOSE WAGON" RETIRED
96 Polaris 400L sport (Mrs. Moose Ride)
07 Suzuki LTZ250 (Sons)
96 Polaris 250 Trail Blazer (daughters)
06 TRX450ER aka === Under construction

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PM FOR MANUAL HELP
JETTING
Service_Manual_Downloads
2000_400EX_Build
400EX_Pivot_Bolt_
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post #10 of 14 (permalink) Old 09-22-2011, 03:41 PM
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The needle clip is in the middle position, idle screw is about 2 1/2 turns out. If I screw it in, the bike will die. No exhaust leaks on the engine, the only leak that is there is coming off of the stinger into the silencer. Don't think that would make it run the way it's running?

Reeds are all perfectly fine, and they are sealing nicely. Fuel is mixed at 32:1. The bike don't start with the choke on, hot or cold.

EDITS:

The idle screw is 8 1/4 turns out. Any farther in and the bike won't idle. Definitely think it's lean correct?

Last edited by Xpress; 09-22-2011 at 04:38 PM.
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