300ex quitting problem - Honda ATV Forum
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post #1 of 29 (permalink) Old 01-26-2013, 08:22 PM Thread Starter
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300ex quitting problem

hello, i am new to the forums and i have been having a problem with my machine just dieing on me on the trail for no reason (bogging and backfiring then dieing) prior to this i installed a fmf power core 4 full exhaust and a uni air filter along with a umi stage 1 jet kit witch came with a paper saying witch jets to put in, what to set the fuel mixture screw at and where to set the clip on the needle for my elevation. so i cleaned the carb and jets and still acting the same. so i started reading on here about it and no one seams to have this problem but some guys said to swap the recomended 118 main jet for a 128 main so i did and still no luck, the only thing i found is that if i run the machine with the choke on it seems to run fine, so i pulled the plug and it looks good, not sure what else to look at any help would be greatly appreciated thanks

2008 honda 300ex
(got a couple little mods)
-fmf power core 4
-protaper bars
-stage 1 jet kit
-powermadds
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post #2 of 29 (permalink) Old 01-26-2013, 08:40 PM
jdp
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if its bogging and back firing, that's telling me that your not getting enough fuel. Might even be to lean. Try cleaning your tank and petcock, also clean the carb really good. (You might wanna go with the stock set up if it was me). Another thing you can do is check the float and needle. I think the fmf power core is your problem cause most of the time all you need is an aftermarket exhaust and jet kit, with High flow filter.



1993 Honda 300

Seafoam "In every tank"

Mobil1 4T 10w-40 (great stuff)

Superwinch Terra 35/synthetic rope, KFI winch Mount.

AMS Swampfox front 23x8x11, GBC dirt devils 25x12x9 rear.

Diehard Gold lawn tractor battery in rear storage box.

"Go prepared even if you think you don't need it".
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post #3 of 29 (permalink) Old 01-26-2013, 09:03 PM Thread Starter
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ok i will try these things out tomorrow and let you know what happens thanks alot

2008 honda 300ex
(got a couple little mods)
-fmf power core 4
-protaper bars
-stage 1 jet kit
-powermadds
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post #4 of 29 (permalink) Old 01-26-2013, 09:12 PM
jdp
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sure thing



1993 Honda 300

Seafoam "In every tank"

Mobil1 4T 10w-40 (great stuff)

Superwinch Terra 35/synthetic rope, KFI winch Mount.

AMS Swampfox front 23x8x11, GBC dirt devils 25x12x9 rear.

Diehard Gold lawn tractor battery in rear storage box.

"Go prepared even if you think you don't need it".
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post #5 of 29 (permalink) Old 01-26-2013, 09:56 PM
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Hello and welcome, Im new around here too and just got a 300 ex. Im curious if the UNI jets are actual Kehein jets? Anyway you can look at one ? Im currently running a 128 jet in mine with a HMF slip on. Seems a bigger main jet is in order if your is an actual Kehein jet and that size. Im sure the others will chime in and offer up some suggestion. I did end up with a 40 pilot jet, 2 1/2 turns out on the screw and did a valve adjustment too which seemed to help a LOT.

2007 TRX 300 Ex
HMF Slip On
Jetted
Uni Filter
Holeshot Tires
Tag Mini CR Bars
Work in Progress !!
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post #6 of 29 (permalink) Old 01-27-2013, 05:52 AM
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Garage
I would put a 125 main in and give that a whirl Whats your elevation???

"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

Progress and Help
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JETTING
Service_Manual_Downloads
2000_400EX_Build
400EX_Pivot_Bolt_
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post #7 of 29 (permalink) Old 01-27-2013, 07:07 AM Thread Starter
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About 1200ft thanks for all the help guys all try it out today and let ya know

2008 honda 300ex
(got a couple little mods)
-fmf power core 4
-protaper bars
-stage 1 jet kit
-powermadds
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post #8 of 29 (permalink) Old 01-27-2013, 07:11 AM
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1200 ft then jump to a 130 and on your muffler remove the rear end cap and take that darn restrictor plate out.( it will have a hole about the size of a quarter) . . . put the cap and spark screen back on though

"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

Progress and Help
PM FOR MANUAL HELP
JETTING
Service_Manual_Downloads
2000_400EX_Build
400EX_Pivot_Bolt_

Last edited by TRX2fiveO; 01-27-2013 at 07:13 AM.
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post #9 of 29 (permalink) Old 01-27-2013, 09:30 AM Thread Starter
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ok i just got in i put in the 128 main (its a 128 or a 140 no 130) and i put the f/mix screw to 2 1/2 out and i looked at the pilot jet and it has a 38 on it and the kit did not come with a 40 oh and i cleaned all the carb and now im just going to put it back together and try it thanks

2008 honda 300ex
(got a couple little mods)
-fmf power core 4
-protaper bars
-stage 1 jet kit
-powermadds
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post #10 of 29 (permalink) Old 01-27-2013, 09:32 AM Thread Starter
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and the fmf did not have a restricter plate but i did remove the spark arrester when i got the pipe a couple months ago

2008 honda 300ex
(got a couple little mods)
-fmf power core 4
-protaper bars
-stage 1 jet kit
-powermadds
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